Wavelength UV Radiation Research Articles

Influence of UV radiation wavelength on conversion and temperature distribution profiles within dimethacrylate thick material during photopolymerization

UV-light initiation is now commonly used to induce polymerization of multifunctional monomers. The highly crosslinked networks obtained have a wide variety of applications. The thermal effects which take place during polymerization can be the cause of non-homogeneity and defects in the final material. These defects greatly alter the physical properties of the final products, particularly the optical ones, which causes problems in the design of thick and optically perfect materials. To better control the homogeneity of photocured materials and to determine the influence of different experimental parameters on them, conversion and temperature distribution profiles within a material during photopolymerization were simulated numerically, using the general heat equation applied to one-dimensional system. To describe the true conditions of kinetic experiments, some necessary parameters were measured, like conversion, reaction rate, spectral irradiance of the Hg vapor lamp and dimethacrylate spectral absorbance. We focused our attention more particularly on the influence of the irradiation wavelength. Indeed, the high values of the spectral absorbance coefficient cause a great decrease in light intensity in the depth of the material and lead in turn to a sharp drop in conversion.

Effect of increased intracellular melanin concentration on survival of human melanoma cells exposed to different wavelengths of UV radiation

Purpose: To investigate the effect of intracellular melanin content on cell survival of G361 human melanoma cells following exposure to UV radiation. Materials and methods: Cells were cultured in medium containing elevated concentrations of L tyrosine phosphate and L glutamine to increase their melanin content. Cell survival was assessed by colony-forming ability in treated and untreated cells following exposure to 254nm germicidal UVC radiation (0-60 J m -2) , 311nm UVB radiation (0-5 kJ m -2) , or broadband UVA radiation (Sellamed 4000, maximum output between 350 and 450nm) (0-1.2 MJ m -2) . Results: Treated cells, with a 2-fold increase in total melanin concentration and an increased ratio of eumelanin to pheomelanin, were marginally more resistant than untreated control cells to cell killing by 311nm UVB radiation, but treatment had no effect on killing by germicidal UVC or broadband UVA radiation. Conclusions: There was no evidence of any photosensitizing effect of increased melanin on human melanoma cell survival following exposure to UVC, UVB or broadband UVA radiation. The slight protective effect seen following exposure to UVB radiation may have been due to increased scavenging of reactive-oxygen species, particularly by eumelanin, at this wavelength.

Photoluminescence of open-framework phosphates and germanates.

Upon excitation by long wavelength UV radiation, strong room temperature luminescence is observed in a family of metal-activator-free zeolite-type materials; the luminescent output from the large cage UCSB-8Mg structure is independent of temperature from 298 K until at least 77 K.

Differential sensitivity to natural ultraviolet radiation among phytoplankton species in Arctic lakes (Spitsbergen, Norway)

Incubation experiments demonstrated a differential sensitivity to natural UV-radiation among the dominant phytoplankton species from three Arctic lakes, situated near Ny-Alesund, Spitsbergen (79° N). The growth of small chlorophytes, diatoms and picocyanobacteria from two oligotrophic lakes was inhibited primarily by the shorter wavelength UV components, while the growth of the larger colony-forming species (cyanobacteria, Planktothrix sp., Woronichinia sp. and the chrysophyte, Uroglena americana Calkins) apparently was stimulated. These colonies (not easily eaten by daphnids) dominated at the end of the experiment in those treatments where the short wavelength UV components were not excluded. For the two oligotrophic localities, 70 and 61%, respectively, of total phytoplankton biovolume were edible in the treatments excluding short wavelength UV, compared to only 13 and 19%, respectively, in the treatments including such radiation. For the third, more productive and less transparent lake, the percentage of edible species in the treatments with and without short wavelength UV radiation did not differ (ca. 75% for both treatments).

The spinning disc reactor – studies on a novel TiO 2 photocatalytic reactor

A new type of photocatalytic reactor, the spinning disc reactor (SDR), was used to degrade aqueous solutions of 4-chlorophenol and salicylic acid. The efficiency of the photocatalytic process depends on the type of UV source used. Lamps supplying shorter wavelength UV radiation are more efficient than those whose emissions lay mainly in the near UV region. The method used to coat the disc of the SDR does not meet its operational requirements. The characteristics of the turbulent liquid films produced in the SDR reduce the influence of mass transfer over the overall photocatalytic process.

Decolorization of water for domestic supply employing UV radiation and hydrogen peroxide

A kinetic study concerning water decolorization using a combination of low wavelength UV radiation (253.7 nm) and hydrogen peroxide has been performed. Kinetic studies were carried out in a specially designed flat plate reactor, made in such a way that almost “isoactinic” conditions are achieved. Results were analyzed in terms of a very simple kinetics expression. Absorbed radiation effects were duly quantified by means of a one-dimensional radiation field model. With experimental degradation rates, a kinetics expression relating the initial color (expressed in terms of initial total organic carbon) with the most important process variables was proposed and the decolorization kinetics parameters were obtained. The initial decolorization rates at 25°C can be properly represented with an equation of the following form: R TOC 0=− kC TOC 0 e a( z).

FT‐IR spectroscopic studies on degradation of lac resin – part II: ageing and UV irradiation

Applies FT‐IR spectroscopic techniques to study the degradative process occurring on ageing/UV irradiation of lac resin. Unequivocally concludes that hydroperoxidation and inter‐etherification reactions are more likely to occur during the degradative process. MS(FAB) and solubility studies also support FT‐IR studies. Establishes that lac resin is remarkably stable to long wavelength UV radiation but tends to undergo prominent degradation on exposure to short wavelength UV irradiation.

UV Transmission Measurements of Small Skin Specimens with Special Quartz Cuvettes

Background: The penetration of different wavelengths of UV radiation through human skin is of major importance, especially for the determination of photoprotective properties of sunscreens and UV-protective clothes. Objective: In this study we present a new method for the measurement of UV transmission through small skin specimens. Methods: The transmission measurements were performed by using a UV spectrophotometer with an integrating sphere operating in the wavelength range of 280–390 nm. For the skin samples, special quartz glass cuvettes were developed which allowed measurements for very thin and small skin specimens. Furthermore, the cuvettes prevented dehydration of the specimens and guaranteed, by using an additional diaphragm, that the transmission data were derived solely from the small skin specimen examined. Specimens measuring 8 × 3 mm² with a thickness of 0.3 mm (histometric and sonographic control) were taken from the thighs of 10 subjects via shave biopsy. Results: In the UVA range (315–390 nm) we obtained a mean transmission of 4.6% and for the UVB range (280–315 nm) of 0.9%. No significant (p >0.14) difference of UV transmission was found between the individual skin specimens. Conclusion: This new method seems to be well suitable for UV transmission measurements of small skin specimens. As UVA radiation has a much deeper penetration depth and in in vivo situations dermal hemoglobin could have an effect on UV penetration, the present method is better suitable for the investigation of UVB-induced biological adaptation mechanisms and the impact of topical agents on UVB transmission of the epidermis.

Degradation of Polymer Coating Systems Studied by Positron Annihilation Spectroscopy. 3. Wavelength Dependence of UV Irradiation Effect

Photodegradation of a polyurethane coating induced by accelerated UV irradiation is studied using three different light sources: 340 nm UVA, 313 nm UVB, and Xe lamps. Doppler-broadened energy spectra (DBES) and positron annihilation lifetime (PAL) are measured as a function of incident positron energy (0−30 keV) and of irradiation time (0−800 h). The photodegradation of the coating is characterized in terms of subnanometer defect changes. Significant variations of S parameter, orthopositronium lifetime, intensity, and lifetime distribution are observed as a function of depth and of exposure time. These results indicate a decrease of free volume and holes at the atomic level during the degradation process. The UV irradiation at 313 nm shows a significant effect compared with that at 340 nm on the photodegradation: (1) the magnitude of S reduction increases a factor of 2 near the surface; (2) the photodegradation rate increases ∼25 times near the surface; (3) the irradiation effect attenuates with depth, and a larger extinction coefficient is observed with shorter wavelength UV irradiation. The observed effect by Xe light irradiation is the strongest among these three light sources. Enhanced degradation at shorter wavelengths is also indicated by increased free radical production, as observed by electron spin resonance spectroscopy.

Detection of DNA in Agarose Gels Using Berberine and Mordant Yellow 3R

A nontoxic and simple staining method for the detection of DNA in agarose gels is described. After eletrophoretic separation, the gels were stained with 5 μg/ml of berberine (BB) prepared in distilled water and then the gels were soaked in 20 μg/ml of aqueous Mordant Yellow 3R (MY3R) solution. Employment of MY3R as a counterion dye efficiently quenched unwanted background fluorescence of BB. This method can detect as little as 10 ng of plasma membrane H+-ATPase cDNA obtained from Arabidopsis thaliana L. (AHA1, 3.2 kb) under a long wavelength of UV irradiation (366 nm) within 1 h.

Photocatalytic Oxidation of Chlorophenols in Single-Component and Multicomponent Systems

The photocatalytic oxidation of single-component and multicomponent systems consisting of chlorophenols in aqueous TiO2 suspension was investigated using long, medium, and short wavelength UV radiation. In the single-component experiments, 2-chlorophenol (2-CP), 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, and 4-chloro-3-methylphenol (4-Cl-3-MP) were found to degrade at the same rate. The rate of mineralization of 4-Cl-3-MP was higher than that of the others. Power law kinetic models for the temporal prediction of the degradation and mineralization profiles fitted the experimental results well for the single-component systems. The application of these models to represent the simultaneous oxidation of a binary mixture of 2-CP and 4-Cl-3-MP was examined for several equimolar and nonequimolar mixtures. Competitive inhibition kinetics were observed. Under equimolar feed conditions the rates of degradation of the total mixture were comparable to those for single-component systems and could be ...

Elucidating the mechanism of the photochemical Pauson–Khand reaction: matrix photochemistry of phenylacetylenehexacarbonyldicobalt

Short wavelength UV irradiation of (phenylacetylene)Co 2(CO) 6 ( 3) in argon matrices at 12 K results in loss of CO to form (phenylacetylene)Co 2(CO) 5 ( 4). Reversal of this reaction occurs on longer wavelength irradiation. When the reaction is instead carried out in mixed argon/nitrogen matrices (phenylacetylene)Co 2(CO) 5(N 2) ( 5) is formed as an additional product. Irradiation at λ=390 nm allows selective reversal of photoproduct 4 to the parent species, leaving photoproduct 5 unaffected. When 3 is irradiated in pure nitrogen matrices photoproduct 4 is not formed, but two photoproducts containing coordinated dinitrogen are observed. One of these may confidently be assigned as 5, but the identity of the second cannot at present be specified with certainty. The results gained are discussed in the light of the much more widely studied and better understood thermal chemistry of such complexes.

Photocarcinogenesis: an overview

Photocarcinogenesis represents the sum of a complex of simultaneous and sequential biochemical events that ultimately lead to the occurrence of skin cancer. These events, initiated by UV radiation of appropriate wavelength, include the formation of DNA photoproducts: DNA repair, mutation of proto-oncogenes and tumor suppressor genes; UV-production of radical species with subsequent effects on mutation and extra-nuclear function; and other epigenetic events that influence the course of carcinogenesis. The epigenetic influences may include immunological responses, antioxidant defenses, and dietary factors. This review represents an effort to provide current research results in the aforementioned areas and an attempt to meld these events into a comprehensive overview of photocarcinogenesis. If effective prevention and intervention strategies for skin cancer are to be developed, a more thorough understanding of the disease process is imperative.

A small-scale outdoor plant growth chamber with modulated enhancement of solar UV-B radiation.

An outdoor, solar illuminated growth chamber with modulated UV-B enhancement, is described and its performance characterized. The chamber was clad with Teflon film that transmitted both UV-A and UV-B with little absorption and whose transmission did not change significantly over 1 yr. An array of UV-B emitting fluorescent tubes with cellulose diacetate filters provided additional UV-B radiation inside the chamber with little additional UV-A, while a similar chamber with unenergized tubes provided an ambient control. Ambient and enhanced UV-B levels were measured using a pair of integrating broad band radiometers, and it was found that frequency modulation allowed control of lamp intensity over a range in excess of 100:1. Within the UV-B chamber, enhanced levels of integrated UV-B could be maintained at a constant ratio over ambient throughout the day. However, it was not sufficient simply to maintain a constant ratio of radiometer output voltages: the angular responses of the two radiometers had to be well matched. The shape of the UV-B portion of the enhanced spectrum closely followed that expected under ozone depleted skies, while the enhancement of UV-A was insignificant. The spectral profile obtained in the UV-B depended on the thickness of the cellulose diacetate filters used to block short wavelength UV radiation emitted by the fluorescent tubes. The number (thickness) of cellulose diacetate filters required to achieve this match varied with season. Although the filters did degrade with exposure to UV-B it was not necessary to replace them for several months. This was due to: (i) low rate of filter degradation because the lamps were rarely required to be run at full brilliance except at midsummer midday; and (ii) increased tube intensity compensated for reduced filter transmission.

CREB is activated by UVC through a p38/HOG-1-dependent protein kinase.

Changes in environmental conditions such as the addition of growth factors or irradiation of cells in culture first affect immediate response genes. We have shown previously that short wavelength UV irradiation (UVC) elicits massive activation of several growth factor receptor-dependent pathways. At the level of the immediate response gene c-fos, these pathways activate the transcription factor complex serum response factor (SRF)-p62TCF which mediates part of the UV-induced transcriptional response. These studies have, however, suggested that more that one pathway is required for full UV responsiveness of c-fos. Using appropriate promoter mutations and dominant-negative cAMP response element (CRE)-binding protein (CREB), we now find that UVC-induced transcriptional activation depends also on the CRE at position -60 of the c-fos promoter and on the functionality of a CREB. Upon UV irradiation, CREB and ATF-1 are phosphorylated at serines 133 and 63, respectively, preceded by and dependent on activation of p38/RK/HOG-1 and of a p38/RK/HOG-1-dependent p108 CREB kinase. Although p90RSK1 and MAPKAP kinase 2 are also activated by UV, p90RSK1 does not, at least not decisively, participate in this signalling pathway to CREB and ATF-1 as it is not p38/RK/HOG-1 dependent, and CREB is a poor substrate for MAPKAP kinase 2 in vitro. On the basis of resistance to the growth factor receptor inhibitor suramin and of several types of cross-refractoriness experiments, the UVC-induced CREB/ATF-1 phosphorylation represents an as yet unrecognized route of UVC-induced signal transduction, independent of suramin-inhibitable growth factor receptors and different from the Erk 1,2-p62TCF pathway.

RecA-dependence of the response of Pseudomonas aeruginosa to UVA and UVB irradiation.

The responses of the autochthonous soil and aquatic organism, Pseudomonas aeruginosa to UV radiation wavelengths (UVA, 320-400 nm, and UVB, 280-320 nm) has been investigated in this study. P. aeruginosa recA mutants were found to be more sensitive to both UVA and UVB radiation than were their isogenic RecA+ parents. Introduction of a low-copy-number plasmid containing the cloned wild-type P. aeruginosa recA gene restored UVA and UVB resistance to recA mutants. The concentration of RecA protein increased twofold 120 min after exposure to either UVA or UVB radiation, suggesting induction of expression of the recA gene by these wavelengths. In this study, we found that a functional RecA protein is required for activation of D3 prophage in lysogenic cells following exposure to UVB radiation. Prophage were not induced by exposure of their hosts to UVA radiation. Induction of damage-inducible (din) genes in response to UVA or UVB irradiation was also shown to be RecA dependent. These data indicate that the recA gene plays a role in the response of P. aeruginosa to exposure to wavelengths of UV radiation found in the solar spectrum.

Advanced Oxidation Processes Against Phenolic Compounds In Wastewater Treatment

Abstract Experimental research into the oxidative treatment of aqueous solutions and wastewaters containing phenolic compounds was undertaken. Ozone, supported by short wavelength UV-irradiation, hydrogen peroxide and titanium dioxide catalyst, was selected as an oxidant in the following combinations: O3, O3/H2O2, O3/UV, O3/TiO2, O3/UV/H2O2 and O3/UV/TiO2. 5-Methylresorcinol was chosen as a model compound for the experiments with synthetic phenolic solutions. The results obtained from these experiments were compared with the results of oxidative purification of wastewaters produced from the thermal treatment of oil shale in Estonia.

Synthesis of 8-Bromo- and 8-Azido-2′-deoxyadenosine-5′-O-(1-thiotriphosphate)

Abstract Treatment of 3′-O-methoxyacetylated 8-bromo-2′-deoxyadenosine (5), with a twofold excess of salicyl phosphorochloridite (6), and subsequent reaction with bis(tri-n-butylammonium) pyrophosphate and oxidation with sulfur followed by removal of the protecting group gives predominantly 8-bromo-2′-deoxyadenosine-5′-O-(1-thiotriphosphate) (7), and minor amounts of the corresponding brominated monothiophosphate. Alternatively, the photoreactive dATP analog 8-azido-2′-deoxyadenosine-5′-O-(1-thiotriphosphate) (11), is obtained by phosphorylation of unprotected 8-azido-2′-deoxyadenosine (9) with a 1.8 molar equivalent excess of thiophosphoryl chloride and bis(tri-n-butylammonium) pyrophosphate. A protection of the nucleobase 6-amino group is not required. The photoaffinity labeling reagent 11, was characterized by 31P-NMR and ion-spray mass spectroscopy and its photolysis upon long wavelength UV irradiation was studied. Both α-thioderivatives of 2′-deoxyadenosine triphosphates can be incorporated into plas...

Immunosuppression by Factors Released from UV-Irradiated Epidermal Cells: Selective Effects on the Generation of Contact and Delayed Hypersensitivity After Exposure to UVA or UVB Radiation

Exposure of murine epidermal cells to UV radiation in vitro causes the release of immunoregulatory factors that mimic some of the immunosuppressive effects of in vivo UV irradiation. The purpose of this study was to investigate the spectrum of immune responses affected following i.v. injection of supernatants obtained from cultures of epidermal cells exposed in vitro to UV radiation. Treatment of primary epidermal cell cultures or transformed keratinocytes (Pam 212 cells) with UVB (280-320 nm) radiation caused the release of factors that suppressed the induction of delayed hypersensitivity to alloantigen and trinitrophenyl-modified self-antigens in syngeneic and allogeneic mice. Contrary to expectations, however, the injection of supernatants from UVB-irradiated epidermal cells had no effect on the induction of contact hypersensitivity to trinitrochlorobenzene. On the other hand, treatment of the keratinocytes with UVA radiation (320-400 nm, filtered to remove wavelengths in the UVB region) resulted in the release of a factor that suppressed contact but not delayed hypersensitivity. Neither the UVA-induced nor the UVB-induced suppressive factor inhibited the generation of an antibody response to sheep erythrocytes, indicating that, like the suppression that occurs after in vivo exposure to UV radiation, the suppression induced by factors from UV-irradiated keratinocytes is selective in nature. These data support the hypothesis that soluble keratinocyte-derived suppressive factors are involved in the induction of systemic immune suppression by UV radiation. In addition, they suggest that multiple suppressive factors, having different immunosuppressive properties, are produced by different wavelengths of UV radiation.

Effects of Solar Radiation on Photoorientation, Motility and Pigmentation in a Freshwater Cryptomonas

AbstractThe effects of solar radiation on motility, photoorientation and pigmentation have been studied in a freshwater Cryptomonas species. The diaphototactic orientation performed by the cells is impaired within about 90 min of solar radiation. Likewise, the percentage of motile cells within the population and the average velocity of the swimming cells decreases within about the same exposure time. This effect is not due to a thermal stress but rather seems to be caused by the solar UV‐B component, since decreasing short wavelength UV radiation by means of an artificial ozone filter or UV cut‐off filters increased the tolerated exposure time. Solar radiation also bleached the photosynthetic pigments of the cells as shown by absorption difference spectra.