Ultraviolet radiation and

Hydroxybenzophenones represent the largest and most versatile class of ulbaviolet stabilizers that are used to protect materials from the degradative effects of ulbaviolet radiation. They function by absorbing ultraviolet radiation and by quenching elecbonically excited states. 

Seek alternatives to chlorine for water treatment and disinfecting applications. For example, sodium hypochlorite has been used both in industrial and municipal water treatment applications (Somerville, 1990). Other alternatives include calcium hypochlorite, ozone, ultraviolet radiation and heat treatment (Negron, 1994 Mizerek, 1996). 

This is to be used only for buried pipework or in ducts, as it is adversely affected by ultraviolet radiation and its use inside buildings is prohibited by the Gas Safety (Installation and Use) Regulations. For pressures up to 4 bar. 

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. 

For nineteenth-century scientists, the obvious way to account for the laws of black-body radiation was to use classical physics to derive its characteristics. However, much to their dismay, they found that the characteristics they deduced did not match their observations. Worst of all was the ultraviolet catastrophe classical physics predicted that any hot body should emit intense ultraviolet radiation and even x-rays and y-rays According to classical physics, a hot object would devastate the countryside with high-frequency radiation. Even a human body at 37°C would glow in the dark. There would, in fact, be no darkness. 

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.)... 

SASPs comprise about 10-20% of the protein in the dormant spore, exist in two forms alfi and y) d are degraded during germination. They are essential for expression of spore resistance to ultraviolet radiation and also appear to be involved in resistance to some biocides, e.g. hydrogen peroxide. Spores (a /3 ) deficient in a//3-type SASPs are much more peroxide-sensitive than are wild-type (normal) spores. It has been proposed that in wild-type spores DNA is saturated with a/j3-type SASPs and is thus protected from free radical damage. 

Chemical fixation for transmission electron microscopy prepares cells for the preservation of damage due to subsequent washing with aqueous solvents, dehydration with organic solvents such as ethanol or acetone, embedding in plastic resins, polymerization of the resins by heat, exothermic catalysts, or ultraviolet radiation, and imaging with high-energy electron beams in an electron microscope. 

Shick, J.M., M.P. Lesser, and W.R. Stochaj. 1991. Ultraviolet radiation and photooxidative stress in zooxan-thellate anthozoa the sea anemone Phyllodiscus semoni and the octocoral Clavularia sp. Symbiosis 10 145-173. 

Ponsonby, A.L., McMichael, A., and van derMei, I., Ultraviolet radiation and autoimmune disease insights from epidemiological research, Toxicology, 181-182, 71, 2002. 

Karsten U, Franklin LA, Liming K, Wiencke C (1998) Natural ultraviolet radiation and photosyn-thetically active radiation induce formation of mycosporine-like amino acids in the marine macroalga Chondrus crispus (Rhodophyta). Planta 205 257-262 Karsten U, Bischof K, Hanelt D, Tug H, Wiencke C (1999) The effect of ultraviolet radiation on photosynthesis and ultraviolet-absorbing substances in the endemic Arctic macroalga Devaleraea ramentacea (Rhodophyta). Physiol Plant 105 58-66 Kessler A, Baldwin IT (2002) Plant responses to insect herbivory the emerging molecular analysis. Ann Rev Plant Biol 53 299-328... 

Smith RC, Prezelin BB, Baker KS, Bidigare RR, Boucher NP, Coley T, Karentz D, MacIntyre S, Matlick HA, Menzies D, Ondrusek M, Wan Z, Waters KJ (1992) Ozone depletion ultraviolet radiation and phytoplankton biology in Antarctic waters. Science 255 952-959 Sommaruga R, Psenner R (1997) Ultraviolet radiation in a high mountain lake of the Austrian Alps air and underwater measurements. Photochem Photobiol 65 957-963 Swanson AK, Druehl LD (2002) Induction, exudation and the UV protective role of kelp phlorotannins. Aquat Bot 73 241-253... 

By a method similar to that described in the last section phenylazide in cyclohexene was irradiated with ultraviolet radiation and unreacted cyclohexene was distilled off with evaporation. The residue was extracted with n-hexane. The extract was separated into several products by gas and liquid chromatography. The gas chromatogram and the liquid chromatogram are shown in Figures 7 and 8, which give five peaks from A to E, and four peaks from A to D, respectively in addition to the peak due to the solvent. Peaks A and A were determined to be aniline by their retention times. Peaks B and C are due to 3,3 -bicyclohexenyl. Peaks C and D are those of aziridine[9] and the product which was formed by the insertion of phenylnitrene to C-H bond of cyclohexene. ... 

Giese, A. C., H. L. Leighton, and R. Bailey. Changes in the absorption spectra of proteins and representative amino acids induced by ultraviolet radiations and ozone. Arch. Biochem. Biophys. 40 71-84, 1952. 

Uses/Sources. Used as a disinfectant for air and water for bleaching textiles in organic synthesis produced in welding arcs, corona discharges by ultraviolet radiation, and around high-voltage electric equipment... 

Acrylic and modacrylic fibers have a wool-like appearance and feel, and excellent resistance to heat, ultraviolet radiation, and chemicals [Bajaj and Kumari, 1987]. These fibers have replaced wool in many applications, such as socks, pullovers, sweaters, and craft yams. Other applications include tenting, awning fabric, and sandbags for rivershore stabilization. The use of acrylic and modacrylic fibers in carpets is low since these materials do not hold up well to recycling through hot-humid conditions. This also prevents its use in the easy-care garment market. 

Neamtu M., I. Siminiceanu, and A. Kettrup (2000). Kinetics of nitromusk compounds degradation in water by ultraviolet radiation and hydrogen peroxide. Chemosphere 40 1407-1410. 

Stapleton, A.E., Ultraviolet radiation and plants burning questions, Plant Cell, 4, 1353, 1992. 

The presence of proflavine protects some viruses against inactivation by ultraviolet radiation and proflavine has been shown to inhibit formation of thymine dimers in DNA.86 (6) The sensitivity of microorganisms to ultraviolet light increases with, but is not proportional to the square of, the thymine content of the DNA.86 (7) Substitution of... 

The activity that characterizes a comet is driven by solar heating. As the comet approaches the Sun, jets of dust and gas erupt from active areas (Fig. 12.1), as they periodically rotate into the sunlight. The nucleus becomes surrounded by a spherical coma formed by the emitted gas and dust. Emitted gas becomes ionized due to interaction with solar ultraviolet radiation, and the ions are swept outward by the solar wind to form the comet s ion tail. A separate dust tail commonly has a different orientation, reflecting variations in the velocities of solid particles and ions. A popular term describing comets is dirty snowballs , although that description probably understates the proportion of rock and dust relative to ices. 

Ultraviolet radiation and cancer Pyrimidine dimers can be formed in the skin cells of humans exposed to unfiltered sunlight. 

The temperature of the upper atmosphere, and hence its density, varies with the intensity of solar ultraviolet radiation and this, in turn, varies with the sunspot cycle and with solar activity in general. The solar radionoise flux is a convenient index of solar activity, since it can be monitored at the earth s surface. The minimum nighttime temperature of the upper atmosphere above 300 kilometers has been expressed in terms of the 27-day average of the solar radio-noise flux at 8-ccntimctcr wavelength. This varies from about 600 K near the minimum of the sunspot cycle to about 1400 K near the maximum of file cycle. The maximum daytime temperature is about one-third larger than tile nighttime minimum. 

Modulation of Solar Ultraviolet Radiation and Photochemistry by Stratospheric Ozone, aerosols and tropospheric ozone... 

---