Ultraviolet radiation, influence

Gallar. j. et al. (1995) Irritation of the anterior segment of the eye by ultraviolet radiation Influence of nerve blockade and calcium antagonists. Curr Eye Res.. 14.827-835. 

M.L. Bothwell, D.M.J. Sherbot, C.M. Pollock (1994). Ecosystem response to solar ultraviolet radiation Influence of trophic level interactions. Science, 265,97-100. 

Patsayeva, S.V., Fadeev, V.V., Filippova, E.M., Chubarov, V.V., and Yuzhakov, V.I. (1991). Temperature and laser ultraviolet radiation influence on luminescence spectra of dissolved organic matter. Vest. Moskov. Universit. Ser. 3 Fizik. Astronom., 32(6), 71-75. 

In Section 17.13 reference has been made to the influence of various substituents in the benzene ring on the absorption of ultraviolet radiation, and the purpose of this exercise is to examine the effect in the case of benzoic acid by comparing the absorption spectrum of benzoic acid with those given by 4-hydroxybenzoic acid and 4-aminobenzoic acid. 

Possibilities exist for the involvement of halo-genated species such as CCI2F2 (CFC-12) or CCI3F (CFC-11) inasmuch as they can influence the column amounts of stratospheric O3 which is both a strong absorber of solar ultraviolet radiation and an absorber and emitter of infrared radiation. (Refer back to Fig. 7-11 for a survey of the chemical reactions that are involved.)... 

The last-mentioned compound has been chosen in preference to benzoyl peroxide in many of the more recent kinetic investigations on account primarily of the freedom of its decomposition from side reactions such as radical-induced decomposition (see p. 113). It may also serve as a photoinitiator under the influence of near ultraviolet radiation, which... 

Ultraviolet radiation (UVR) is a natural fraction of the solar radiation, and therefore has always influenced life in aquatic ecosystems. The development of oxygenic photosynthesis 2.5-2 J billion years ago (Holland 1984) led to drastic chemical changes in the Earth s oceans and atmosphere. The gradual increase in photosyn-thetically produced oxygen over millions of years was accompanied by a strong enrichment of it in the atmosphere, which ultimately acted as precursor for the ozone (03) layer in the stratosphere. 

Silver azide (AgN3) is a white-colored crystalline explosive. It requires less energy for initiation than lead azide, and fires with a shorter time delay. This primary explosive decomposes under the influence of ultraviolet radiation. If the ultraviolet... 

Environmental influences (e.g., the autosomal recessive disease xeroderma pigmento-siun will be expressed more severely in individuals who are exposed more frequently to ultraviolet radiation)... 

Particle mobility and zeta potential can now be measured by more sophisticated techniques. With photoelectrophoresis, particle mobility is measured as a function of pH under the influence of ultraviolet radiation. At pH < 8, the electrophoretic mobility of irradiated hematite particles (A = 520 nm) was markedly different from that measured in the absence of UV irradiation. This was attributed to the development of a positive surface charge induced by photo-oxidation of the surface Fe-OH° sites to (Fe-OH) sites (Zhang et al., 1993). The electroacoustic technique involves generation of sound waves by the particles in the colloidal dispersion and from this data. 

Tretinoin or retinoic acid is the acid form of vitamin A. Actually it is the all-trans isomer of retinoic acid. It is an effective topical agent for acne vulgaris. Its mechanism of action is believed to be associated with increased epidermal cell turnover. Some 10% of the topically applied dose is absorbed, metabolized by the liver and excreted in the urine and bile. To be effective tretinoin should be applied in a concentration that results in mild irritation and erythema. Patients should be advised to avoid or minimize sun exposure and use a protective sun screen as animal studies have raised some concern about possible carcinogenic effects under the influence of ultraviolet radiation. There are no indications that topical tretinoin is associated with an increased risk for birth defects. 

Zerefos C.S., Factors influencing the transmission of solar ultraviolet irradiance through the Earth s atmosphere, in Solar Ultraviolet Radiation, Modelling, Measurements and Effects, edited by C.S. Zerefos and A.F. Bais, pp. 133-142, NATO-ASI Series, vol.52, Springer Verlag, 1997. 

Ortho photocycloaddition was first reported in a U.S. patent [1] dated September 3, 1957. Irradiation of benzonitrile in the presence of various alkenes resulted in the formation of derivatives of l-cyanobicyclo[4.2.0]octa-2,4-diene. The first ortho photocycloaddition to benzene was reported in 1959 by Angus and Bryce-Smith [2], who discovered that benzene and maleic anhydride react to form a stable adduct at 60°C under the influence of ultraviolet radiation. This 1 2 adduct was formed from one molecule of benzene and two molecules of maleic anhydride. Two years later, Bryce-Smith and Lodge [3] found that acetylenes could also be photoadded to benzene. The isolated products were cyclooctatetraenes, formed by ring opening of the primarily formed bicyclo[4.2.0]octa-2,4,7-trienes. Since those early years, hundreds of examples of ortho photocycloadditions of alkenes to the benzene ring and many mechanistic investigations have been reported and they will be discussed in this chapter. 

Bryce-Smith [2] in 1959. They found that benzene and maleic anhydride react to form a stable 1 2 adduct under the influence of ultraviolet radiation. The authors proposed that initially an ortho adduct is formed which could normally be expected to revert rapidly to the starting materials, but which would be stabilized by rapid addition of a further molecule of maleic anhydride to the bicyclic diene system. The stereochemistry of the 1 2 adduct was established by Grovenstein et al. [23] (who reported that they had independently discovered the same reaction) and, more firmly, by Bryce-Smith et al. [24] and Pettit et al. [25], The structure is depicted in Scheme 4. 

Helbling, E. W., Villafane, V., and Holm-Hansen, O., Effects of ultraviolet radiation on Antarctic marine phytoplankton photosynthesis with particular attention to the influence of mixing, in Ultraviolet Radiation and Biological Research in Antarctica, Weiler, C. S. and Penhale, P. A., Eds., American Geophysical Union, Washington, D.C., 1994, 207. 

Oregno, I.F., Black, H.S., Kettler, A.H., and Wolf, J.E., Influence of dietary menhaden oil upon carcinogenesis and various cutaneous responses to ultraviolet radiation, Photochem. Photobiol., 49, 71, 1989. 

By far, the most detrimental factors influencing adhesives aged in a nonseacoast environment are heat and humidity. The reasons why warm, moist climates degrade many adhesive joints were presented in the last section. Near the seacoast, corrosion due to salt water and salt spray must also be considered when one is designing an adhesive joint. Thermal cycling due to weather, oxygen, ultraviolet radiation, and cold are relatively minor factors with most structural adhesives. 

It has been reported151 that, under the influence of ultraviolet radiation, aqueous solutions of formaldehyde and ammonium salts produce imidazole products. It is possible that the irradiation catalyzes... 

The future of the mathematical modeling techniques is linked to cooperative activity between the theoretical and experimental arts in the field of air pollution. Important phenomena are yet to be added to any of the mathematical schemes. The formation of aerosol and its extinction of ultraviolet radiation has not been explicitly treated in the computations. Moreover, the whole area of heterogeneous reactions on either particulate surfaces or urban surfaces remains obscure. The reacting flow problem of mixedness and its influence on kinetics has not been reduced to an engineering procedure for calculational purposes. 

When an explosive slowly decomposes, the products may not follow the previously described hierarchy or be at the maximum oxidation states. The nitro, nitrate, nitramines, acids, etc., in an explosive molecule can break down slowly. This is due to low-temperature kinetics as well as the influence of light, infrared, and ultraviolet radiation, and any other mechanism that feeds energy into the molecule. Upon decomposition, products such as NO, NO2, H2O, N2, acids, aldehydes, ketones, etc., are formed. Large radicals of the parent explosive molecule are left, and these react with their neighbors. As long as the explosive is at a temperature above absolute zero, decomposition occurs. At lower temperatures the rate of decomposition is infinitesimally small. As the temperature increases, the decomposition rate increases. Although we do not always, and in fact seldom do, know the exact chemical mechanism, we do know that most explosives, in the use range of temperatures, decompose with a zero-order reaction rate. This means that the rate of decomposition is usually independent of... 

Under the influence of ultraviolet radiation (X = 365 nm), the reaction between CO and OFj proceeds, even at 15-35 C [1056a]. However, in addition to COF and COj, comparable quantities of FC(0)0F and (FCO)jOj are also formed. The rate of reaction is proportional to the light intensity, and is barely affected by the reaction temperature, the CO partial pressure, or the system s total pressure. The following elementary reactions contribute... 

Gjessing, E. T. and Gjerdahl, T. G. (1970). Influence of ultraviolet radiation on aquatic humus. Vatten 26, 144-145. 

When the fluorescence method becomes more generally adopted, it will be necessary to study not only those factors (neutral salt, temperature) which alter the equilibrium relationships, but also those which influence fluorescence (deformation effect, influence of solvent, etc. cf. P. W. Danckwortt, Luminescence Analysis, 2 Ed., Leipzig 1929 F. Weigebt, Optical Methods in Chemistry, 1927). The interesting publication of L. J. Desha should be consulted regarding the quantitative aspects of fluorometry. In quantitative work it is best to use the filtered monochromatic ultraviolet radiation (X = 366 mm) from a quartz lamp. Con-... 

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