UV = ultraviolet irradiation

UV = ultraviolet irradiation ORD = optical rotatory dispersion CD = circular dichroism. 

UV—Ultraviolet irradiation X—X-ray irradiation 7—7-ray irradiation A—annealing D—doping RT—room temperature. For example UV77KA195K means Ultraviolet irradiation at 77°K followed by annealing at 195°K. 

UV (ultraviolet) irradiation of PDMS surfaces has been described and compared to the results from water-plasma treatments and plasma polymerization. These treatments affect cracking of thin coatings of PDMS during stretching. 

Ultraviolet (UV) spectroscopy (Section 14.7) An optical spectroscopy employing ultraviolet irradiation. UV spectroscopy provides structural information about the extent of 7r electron conjugation in organic molecules. 

UTP Uridine triphosphate UV Ultraviolet UVA Ultraviolet A UVB Ultraviolet B UVR Ultraviolet irradiation UW University of Wisconsin (preserving solution)... 

Fig. 14.11 Reaction yields in the rearrangement of 2-benzoyloxyaceto-phenone induced by microwave heating ( ), ultraviolet irradiation (0)> or simultaneous UV and MW irradiation (A). Adapted from Ref. [92].

UV-C technology is widely used as an alternative to chemical sterilization and microorganism reduction in food products (Lamikanra 2002 Fan and others 2008). Ultraviolet light also induces biological stress in plants and defense mechanisms in plant tissues with the consequent production of phytochemical compounds (Lee and Kader 2000). Phytoalexin accumulation could be accompanied by other inducible defenses such as cell-wall modifications, defense enzymes, and antioxidant activity, which have been reported with health benefits (Gonzalez-Aguilar and others 2007). It is well documented that UV-C irradiation has an effect in secondary metabolism. 

A typical photochemical isomerization of the azobenzene amphiphile was found in an ethanol solution. A trans isomer converted to a cis isomer with ultraviolet irradiation. Back reaction from cis to trans was accelerated when a weak n-n absorption band of the cis isomer at ca.450nm was excited (Figure 21a). An alternative irradiation of uv and visible light to the ethanol solution gave reversible changes of the ji-ji transition between 355nm and 325nm attributed to the trans and cis isomers, respectively. 

Sies H (1991) Oxidative stress oxidants and antioxidants. Academic Press, San Diego Shick JM (2004) The continuity and intensity of ultraviolet irradiation affect the kinetics of biosynthesis, accumulation, and conversion of mycosporine-like amino acids (MAAs) in the coral Stylophora pistillata. Limnol Oceanogr49 223-262 Shick JM, Dunlap WC (2002) Mycosporine-like amino acids and related gadusols biosynthesis, accumulation, and UV-protective functions in aquatic organisms. Annu Rev Physiol 64 223-262... 

Haas Company (Philadelphia, PA), (2) reverse osmosis (RO), (3) adsorption/oxidation with PAC and copper, and (4) ultraviolet irradiation/ozonation (UV/O3). 

Measured total column ozone has fallen between about 1970 and 1994. Ultraviolet irradiation increases at the surface of the earth due to ozone depletion should peak at about 15% in midlatitudes. The incidence of harmful health effects of UV radiation can be expected to rise, eventually, at midlatitudes. Public health action is still necessary to reduce sun exposure, increase protection against the sun, and develop clear policies on the action that should be taken on early detection and treatment of skin cancers (Armstrong, 1997). 

The solutions of the corresponding diazonium fluorides must be heated to a high temperature which also favors tar formation. Recently, it has been shown that fluorodediazoniation can be performed under ultraviolet irradiation (300-500-W high-pressure Hg lamp) at room temperature or below, even with ortAo-substituted anilines.45,89,96,98 101 Byproducts are thus dramatically minimized.99 Illustrative results are listed in Table 3. Except in the case of aniline itself, which gives fluorobenzene in 31 % yield at 20 C in the dark, no fluorination occurs with other substrates at this temperature in the absence of UV light.5 Comparative results in hydrogen fluoride/ pyridine mixtures at higher temperatures can be found in Table 2 vide supra). 

The phase separation temperature shift by photo-isomerization implies that in the temperature range between 19.4 and 26.0 °C, ultraviolet irradiation solubilizes the polymer or expands the polymer chain, while visible irradiation decreases the solubility, or shrinks the chain. Figure 3 shows the photo-stimulated phase separation at 19.5 °C accompanied by the conformation change of the polymer chain. Upon exposure to UV light (350 <%< 410 nm), the opaque solution became transparent, while visible irradiation (>. > 470 nm) again decreased the transmittance of the solution. The polymer chain conformation changed concomitantly with the phase separation. 

Job and Littlehailes [127] have irradiated a 1 1 molar mixture of benzene and acrylonitrile under nitrogen at 0°C and obtained 7-cyanobicyclo[4.2.0] octa-2,4-diene. The reaction did not proceed in the absence of ultraviolet irradiation or in a Pyrex apparatus. The yield of photoadduct is little affected by the presence of air, which, according to the authors, strongly supports the intermediacy of a singlet excited complex. They were, however, unable to detect a UV absorption band of a ground-state complex. However, the yields of adduct were low and the possibility is considered that a low-intensity absorption band is hidden by the benzene spectrum. 

Khan, S.U. and M. Schnitzer (1978). UV irradiation of atrazine in aqueous fulvic acid solution. J. Environ. Sci. Health B, 13 299-310. Khan, S.U. and D.S. Gamble (1983). Ultraviolet irradiation of an aqueous solution prometryn in the presence of humic materials. J. Agric. Food Chem., 31 1099-1104. 

Similar reactions with Cr and W carbonyls require ultraviolet irradiation to give (r/=-Cp)2SnM(CO)5 (M = Cr, Mo, W) and (PhCOCHCOMe)2SnCr(CO)5 The UV irradiation gives M(CO)5THF, which then reacts with the tin compound ... 

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