Action Of Ultraviolet Radiation Research Articles

Tratamento fotoquímico de percolado de aterro sanitário visando reuso na agricultura

No presente trabalho, estudou-se o tratamento de percolado de aterro sanitário (chorume) visando avaliar seu potencial de reuso na agricultura. Para o tratamento, foi escolhido o processo fotoquímico baseado na ação de radiação ultravioleta (UV) sobre o H2O2.O tratamento foi realizado em um reator de vidro borossilicato com capacidade volumétrica de 2,5 litros, com controle de temperatura através de refrigeração aágua e sistema interno para controle de vazão de recirculação do chorume. As condições experimentais otimizadas ocorreram à temperatura de 45°C, vazão de recirculação 400 mL min-1, volume de H2O240 mL, empregando uma lâmpada de mercúrio de alta pressão, de 400 W, sem o invólucro externo. O tratamento foi realizado durante 120 minutos e apresentou redução de cor da ordem de 97%, de 50% na turbidez e de 72% na demanda química de oxigênio. Em análise de identificação de toxicidade aguda utilizando as espécies: Lactuca sativa L. (alface); Solanum gilo (jiló);Abelmoschus esculentus L. (quiabo), verificou-se que a toxicidade poderia ser decorrente da elevada alcalinidade (5100 mgCaCO3L-1) persistente após o tratamento fotoquímico.

Transformation of porous structure under vacuum ultraviolet irradiation of the films based on silicon dioxide

Transformation of the films with the pores of different radii under the action of vacuum ultraviolet radiation was studied experimentally and theoretically. Simulation results showed that Si–O–Si angle depends on pore size. Fourier Transform infrared spectra provide indirect confirmation of this statement. The experimental data and calculation results suggest that methyl group decreases π bonding, which causes a decrease in Si–O–Si angle. The action of ultraviolet radiation is to be considered as a photochemical reaction; the fragments formed in this reaction (СН3⁎, CH2⁎) can participate in polymerization, which leads to pore sealing.

Growth Control of Microbial in Miscible Cutting Fluids Using Ultraviolet Radiation

Considering the issues involved in industrial cutting and machining systems, and, in particular, the problems arising from the use of cutting fluids in these systems, this study presents the results of an analysis that points to a safe and efficient way to reduce contaminated microbial cutting fluids using ultraviolet radiation. The study proposes a transmitter system of simple ultraviolet radiation, safe and easy to obtain. The results of this study showed that the action of ultraviolet radiation on microorganisms in metalworking fluids is very effective and leads to a significant reduction of the load of microorganisms. In addition, no changes were observed during the experimental period that would lead to impairments in the performance of the activities of the cutting fluid used. Given the results, we can conclude that the use of ultraviolet radiation in the prevention and control of contamination is an important contribution to the durability of cutting fluids in machining and grinding operations.

Damage to Skin Extracellular Matrix Induced by UV Exposure

Chronic exposure to environmental ultraviolet radiation (UVR) plays a key role in both photocarcinogenesis and induction of accelerated skin aging. Although the spatiotemporal consequences of UVR exposure for the composition and architecture of the dermal extracellular matrix (ECM) are well characterized, the pathogenesis of photoaging remains poorly defined. Given the compelling evidence for the role of reactive oxygen species (ROS) as mediators of photoaging, UVR-exposed human skin may be an accessible model system in which to characterize the role of oxidative damage in both internal and external tissues. Although the cell-mediated degradation of dermal components via UVR-induced expression of ECM proteases has long been identified as an integral part of the photoaging pathway, the relative importance and identity of cellular and extracellular photosensitizers (direct hit and bystanders models, respectively) in initiating this enzymatic activity is unclear. Recently, both age-related protein glycation and relative amino-acid composition have been identified as potential risk factors for photo-ionization and/or photo-sensitization. Here, we propose a selective multi-hit model of photoaging. Bioinformatic analyses can be employed to identify candidate UVR targets/photosensitizers, but the action of UVR on protein structure and/or ROS production should be verified experimentally. Crucially, in the case of biochemically active ECM components such as fibronectin and fibrillin, the downstream effects of photo-degradation on tissue homeostasis remain to be confirmed. Both topical antioxidants and inhibitors of detrimental cell signaling may be effective in abrogating the effects of specific UVR-mediated protein degradation in the dermis.

Effect of the solar wind on the formation of a photoinduced dusty plasma layer near the surface of the Moon

A dusty plasma layer formed near the illuminated part of the surface of the Moon under the action of ultraviolet radiation, as well as fast and slow solar wind, has been numerically simulated. The numerical calculations including the photoemission properties of lunar regolith samples delivered to the Earth have been compared to estimates within known theoretical models. It has been shown that the flux of solar wind particles plays an important role in the formation of the surface photoelectron layer. The conditions of the charging and stable levitation of dust particles in the surface plasma layer of the Moon have been analyzed.

Are dark-skinned people really protected from ultraviolet radiation?

Premature ageing of the skin (photoageing) results from the action of ultraviolet radiation (UVR) on skin. One of the histopathological findings of photoageing is the presence of solar elastosis in the dermis. Skin pigmentation is protective against UVR. To evaluate the presence of solar elastosis in dark-skinned people. Normal facial skin biopsies of 147 dark-skinned and 140 light-skinned people were examined histopathologically for solar elastosis. The degree of solar elastosis was graded on a five-point scale by a panel of dermatopathologists blinded to patient demographics. There were 112 of 140 (80%) light-skinned and 50 of 147 (34%) dark-skinned patients with high-grade solar elastosis. In the dark-skinned patient group, high-grade solar elastosis was seen in 29 of 61 (47.5%) Hispanic and 5 of 49 (10.2%) African American subjects. Dark-skinned people are not completely protected from the effects of UVR.

Synthesis of chitosan-stabilized Au nanoparticles with controllable sizes

Au nanoparticles stabilized by chitosan have been prepared under the combined action of ultraviolet radiation and thermal exposure of its solutions doped with HAuCl4. With the use of absorption spectrophotometry and small-angle X-ray scattering, it has been shown that the use of chitosan of different molecular masses allows one to control both the sizes of Au particles and their aggregative stability in nanodispersions.

Study of micro and nano surface structures from UV irradiated urethane/urea elastomers

In this work we address new results obtained with a thin free standing flexible film (∼120 μm) of a urethane/urea copolymer related to the formation of micro and nano size structures [M.H. Godinho, A.C. Trindade, J.L. Figueirinhas, L.V. Melo, P. Brogueira, Synthetic Metals, 147(1-3), 209 (2004); M.H. Godinho, A.C. Trindade, J.L. Figueirinhas, L.V. Melo, P. Brogueira, Molecular Crystals and Liquid Crystals (2005)]. The copolymer was synthesized from a polypropylene oxide-based prepolymer with three isocyanate terminal groups (PU) and polybutadienediol (PBDO) with PBDO content of 40% wt. After casting and curing the film was cut into different samples and each exposed to UV radiation for different periods of time; 23, 25, 26, 31 and 49 h ( λ = 254 nm) and later extracted with toluene and dried. The dried films were then studied by polarising optical microscopy (POM), small angle light scattering (SALS) and the surfaces exposed to UV radiation analyzed by means of atomic force microscopy (AFM). Before extraction with toluene a nanometer-flat surface, characterized by a mean roughness value Ra = 0.59 nm, was obtained. Depending on exposure time to UV radiation and after extraction with toluene a corrugated surface, with features μm-sized in all axes, resulting in an increase of the overall mean roughness value to Ra = 50.7 nm, starts to develop after 25 h of exposure time. This work gives evidence of the non-monotonous time behavior of the wrinkled surface growth that develops under the action of ultraviolet radiation. As the exposure time increases the free-standing films directly exposed surfaces show a decreasing density of the structures observed and an increasing characteristic peak-to-valley height. The peak-to-valley height measured for samples exposed for 23, 25, 26, 31 and 49 h, respectively 193, 383, 381, 1550 and 2039 nm and the corresponding mean roughness values are Ra = 50.7 nm, 105.4, 116.8, 438.3 and 515.4 nm, respectively. Between 26 and 31 h exposure time a leap in both values, peak-to-valley and Ra, was observed. The sudden increase in these values is correlated to fabrication of wrinkles by uniaxially stretching PU/PBDO elastomer films.

Abiogenic synthesis of nucleotides on the surface of small space bodies with high energy particles

Abiotic formation of such complex biochemical compounds as nucleotides and oligopeptides on the surface of interstellar and interplanetary dust particles (IDP) by cosmic radiation was examined. In order to study the formation of organic compounds on IDPs, solid films prepared from nucleososide and inorganic phosphate were irradiated with high energy protons. Irradiated products were analyzed with HPLC. The natural nucleotides were detected. The main products were 5′ AMP (3.2%) and 2′3′ cAMP (2.7%). The results were compared with others experiments on the action of ultraviolet radiation with different wavelengths, γ-radiation and heat on solid mixtures of biologically significant compounds. The experiment on abiogenic synthesis of nucleotides on board of space satellite “BION-11” was compared also. The present results suggest that a considerable amount of complex biochemical compounds formed in extraterrestrial environments could have been supplied to the primitive earth before the origin of life.

Variation in the Opacity of the Intergalactic Medium During its Reionization

It is now assumed that reionization of the intergalactic medium occurred under the action of ultraviolet radiation from hot stars contained in galaxies that formed early. Regions of ionized hydrogen (“H II zones”) were formed around such galaxies. The effects of hydrogen recombination and of the simultaneous cosmological expansion of such regions on their opacity are considered. It is shown that regions formed at zi < 6 are opaque to Lc radiation, while for zi ≲ 5 the intergalactic medium should be transparent at 0 < z < 5. This conclusion is in accord with recent observational data.

The influence of heating on the spectral characteristics of pure alkali halide NaCl crystals

The influence of high-temperature heating on the spectral characteristics of pure natural NaCl crystals is studied. It is shown that defects changing spectral characteristics of crystals are formed in them when heated. Temperature dependences of the luminescence intensity growth for these defects are described by the hyperbolic function. The action of X-rays on heated crystals results in the formation of new defects luminescent in regions of 435 and 570–585 nm. The efficiency of formation of these defects is obtained as a function of the temperature of heat pretreatment. Regularities in variations of the location and the intensity of luminescence of the defects obtained under the action of ultraviolet radiation and on long storage are determined.

Immunocorrecting action of ultraviolet irradiation of blood in patients with different types of pathology

The results of immunologic examination of 68 patients with different types of pathology are presented. The immunologic deficiency is revealed in 4050% of the cases. The seances of autotransfusion of the blood irradiated on the Nadezhda-100 device promote the normalization of the changed immune status in patients of these categories.

Irreversible reactions in the photochemistry of provitamin D under optically dense layer conditions

IRREVERSIBLE REACTIONS IN THE PHOTOCHEMISTRY OF PROVITAMIN D UNDER OPTICALLY DENSE LAYER CONDITIONS I. P. Terenetskaya, O. M. Galkin, and N. A. Bogoslavskii UDC 543.422:541.143 The stage of photoisomerization of provitamin D (Pro), in the course of which a direct precursor of vitamin D, the previtamin (P), is formed by the action of ultraviolet radiation is a key stage in the technology of the synthesis of vitamin D (see scheme). The main prob- lem.at the stage of photosynthesis is to achieve the maximal yield of P. However, this is hindered by its side-reactions, among which the cis-trans-isomerization reaction is the most effective, in which a toxic photoisomer tachysterol (T) is formed. Since in the vast majority of papers the photoisomerization scheme of Pro is used, which includes only the reversible photoreactions of P [2, 5, 7-9, 12-15], the main attention at the photosynthesis stage customarily is devoted to the prevention of the accumulation of T. It was found [I0] that in the photostationary state, the concentrational composition of the mixture of the photoisomers formed with the progressing irradiation of the initial Pro, is dependent on the irradiation wavelength, and with its shift to the long-wave region of the absorption spectrum of Pro, the amount of the accumulating T decreases [12]. These are the prerequisites on which in the technology of the synthesis of vitamin D the use of the erythematous lamp is the basis as the source of irradiation, the radiation spectrum of which is in the range of 290-350 nm [5]. Despite the fact that irreversible photoreactions of P giving toxisterols (Tox) have long been known, it is customary to assume that because of the low quantum yield of formation of these so called "overirradiation products," their accumulation "does not lead to serious complications, takes place slowly, thus ensuring a constant concentration of the main photo- isomers in the course of a considerably long period of time" [12]. However the investigations of the photoisomerization of vitamin D by means of a returned laser revealed the inaccuracy of the accepted concepts on the second-degree role of the ir-

Ammonia and ammonium fluxes between photolithotrophs and the environment in relation to the global nitrogen cycle

summaryAmmonium (used here to signify NH4+ plus NH3) is the immediate inorganic precursor of organic nitrogen in photolithotrophs. In marine habitats ammonium is also the major exogenous nitrogen source, and the same is probably true of terrestrial habitats. In addition to this major role of ammonium as exogenous nitrogen source, it is also quantitatively very important as an endogenous nitrogen source with nitrate or N2 as exogenous nitrogen source, and as a recycled nitrogen compound in photorespiration and in phenylpropanoid synthesis. The shoots of terrestrial plants have higher NH3 compensation partial pressures than most natural soils, and especially higher than that of the sea. However, long‐distance transport of gaseous NH3 (e.g. from continents to oceans) is a negligible component of the ‘natural’ global nitrogen cycle. Current concepts of evolution of the atmosphere and biosphere do not involve high partial pressure of NH3 in the atmosphere: any ammonium produced in inorganic or biological processes is removed from the atmosphere by rain‐out, or, over larger time‐scales, by the action of ultraviolet radiation (especially before the ozone screen came into being) and of hydroxyl radicals (especially after oxygenation of the atmosphere). In addition to posing problems for the origin of life and arguing for an early rather than a late evolution of diazotrophy, a low NH3 partial pressure renders implausible arguments that phenylpropanoid synthesis was restricted early in evolution by the effect of high ammonia in reversing phenylalanine ammonia‐lyase.

Direct observation of UV induced bleaching of 240 nm absorption band in photosensitive germanosilicate glass fibres

Ultraviolet loss measurements on germanosilicate fibre samples showing an intense absorption, centred at 242 nm, with an associated fluorescence at 413 nm are presented. The first direct observation is reported of the bleaching of this 240 nm band under the action of ultraviolet irradiation, evidence which is consistent with the Kramers-Kronig model for the photosensitive refractive index change in these glasses.

Effect of ultraviolet irradiation on the retention of physicomechanical properties in fabrics made of pneumatically texturized yarns

-- Ultraviolet irradiation very sharply reduces such properties of fabrics as resistance to abrasion and resistance to double bending. To a smaller extent, the breaking characteristics and crease resistance of fabrics are reduced, depending on the duration of exposure. -- The results obtained make it possible to give recommendations on a fabric structure which ensures high resistance to the action of ultraviolet radiation. The basis for this is development on the fabric surface of a light-resistant system of yarns in such an amount that it covers the weaker yarn system.

Zelluläre Wirkungen der ultravioletten Komponente des Sonnenlichts

The discussion on the possible increase of solar UV on earth due to the destruction of the stratospheric ozone has led to a renewed interest in the action of ultraviolet radiation on biological systems. The paper deals with changes at the cellular level stressing particularly molecular alterations in deoxyribonucleic acid, the carrier of genetic information. The most important repair processes by which lesions are removed or bypassed are described. It is also discussed whether the effectivity of a complex spectrum can be predicted on the basis of measurements with monochromatic radiation. Furthermore, possible consequences on human health are outlined which may be derived from cellular studies.

Abiogenic synthesis of oligonucleotides on kaolinite under the action of ultraviolet radiation

The present work deals with the processes involved in the abiogenic polycondensation of nucleotides adsorbed on the clay mineral kaolinite under the action of ultraviolet (UV) radiation. The dependence of the yield of synthesis products on irradiation dose was studied. The maximum yield corresponds to a 6-h exposure. The newly synthesized substances were analyzed by ion-exchange chromatography. Some fractions were studied for the type of bonds they contained by venom phosphodiesterase and RNase T2 enzymatic hydrolysis. It was determined that some of the products synthesized by exposure of AMP adsorbed on the surface of clay particles to UV radiation may be looked upon as oligonucleotides in which some fragments have 2'-5'-bonded and others 3'-5'-bonded nucleotides.

Action of ultraviolet radiation (UV-B) upon cuticular waxes in some crop plants

The surface structure and composition of surface lipids were examined in leaves of barley, bean, and cucumber seedlings grown in a growth chamber under white light and low levels of ultraviolet (UV-B; 280-320 nm) radiation. The cuticular wax of cucumber cotyledons and bean leaves appeared as a thin homogeneous layer, whereas on barley leaves crystal-like structures could be observed under these irradiation conditions. Principally, the amount of cuticular wax found in barley leaves was five times greater than in bean or cucumber leaves. The prediominant wax components were primary alcohols in barley, primary alcohols and monoesters in bean, and alkanes in cucumber cotyledons. Irradiation with enhanced UV-B levels caused an increase of total wax by about 25% in all plant species investigated. Aldehydes, detected as a minor constituent of cucumber and barley wax, increased twofold. Distribution patterns of the homologs within some wax classes were different at low and enhanced UV-B levels. In general, the distribution of the homologs was shifted to shorter acyl chain lengths in wax of leaves exposed to enhanced UV-B levels. This was most apparent in cucumber wax, less in bean or barley wax. The UV-B-caused effects upon cucumber wax were mainly due to a response by the adaxial surface of the leaf.

Photoresponsive polymeric systems: 1. Mixed monomolecular films of some synthetic polymers and indolinospiropyrans

The properties of mixed monolayer films of photochromic indolinospiropyrans and poly(methylmethacrylate) (PMMA), poly(vinyl stearate) (PVSt), and poly(2-vinyl pyridine) (P2VP) have been studied. It was found that reversible photoinduced changes in monolayer surface-pressure with time occurred in collapsed systems and in mixed films in which the photochrome had been forced out of the polymer monolayer. Mixed films of P2VP and a spiropyran of particular structure could have their inherent stability increased under the action of ultraviolet irradiation on aqueous subphases. This effect appeared to be related to the formation of a physically crosslinked photomerocyanine-polymer two-dimensional network.