Effect of sunlight

The effect of sunlight, ie, the sunstmck flavor in beer, is caused by the formation of mercaptans. The portion of sunlight that is photochemicaHy active is the blue-green region of the visible spectmm (420—520 nm). 

Thus, Staphylococcus aureus produces a golden yellow pigment, Serratia marcescens a bright red pigment. There appears to be no valid function for these pigments but they may afford the cell some protection from the toxic effects of sunlight. 

As somewhat of a side note on the exposure of these materials, it was also reported that there was a distinct difference in the coloration and impact properties of the UV-stabilized PECT, depending strongly on an exposure variable not often reported in the literature, that of the effect of sunlight reaching the back side of... 

Miller GC, Hebert VR, Miller WW. 1989. Effect of sunlight on organic contaminants at the atmosphere-soil interface. In Reactions and movement of organic chemicals in soils. SSSA Special Publication no. 22, 99-110. 

Roburn, J. Effect of sunlight and ultraviolet radiation on chlorinated pesticide residues, Chem. Ind., pp. 1555-1556, 1963. Rochester, H. and Symonds, J.R. Thermodynamic studies of fluoroalcohols, J. Chem. Soc. Faraday Trans. 1, 69 1577-1585, 1973. 

Unstable chemicals are subject to spontaneous reactions. Situations where unstable chemicals may be present include the catalytic effect of containers, materials stored in the same area with the chemical that could initiate a dangerous reaction, presence of inhibitors, and effects of sunlight or temperature change. Examples include acetaldehyde, ethylene oxide, hydrogen cyanide, nitromethane, organic peroxides, styrene, and vinyl chloride. 

Thus we would expect water to climb up the walls of a clean (i.e. water-wetting) glass vessel for a few millimetres but not more, and we would expect a sessile water droplet to reach a height of several mm on a hydrophobic surface, before the droplet surface is flattened by gravitational forces. The curved liquid border at the perimeter of a liquid surface or film is called the Plateau border after the French scientist who studied liquid shapes after the onset of blindness, following his personal experiments on the effects of sunlight on the human eye. 

Smolenski and Plucinski [13] examined the effect of sunlight and found that signs of decomposition are perceptible after only 40 hr of irradiation. A sample so irradiated shows a somewhat lower ignition temperature. 

Figure 26.1 The effect of sunlight (photooxidation) and precipitation (hydrolysis) on the degradation of parathion.

Jorgensen, N. O. G., L. Tranvik, H. Edling, W. Graneli, and M. Lindell. 1998. Effects of sunlight on occurrence and bacterial turnover of specific carbon and nitrogen compounds in lake water. FEMS Microbiology Ecology 25 217-227. 

Lindell, M. J., W. Graneli, and L. J. Tranvik. 1996. Effects of sunlight on bacterial growth in lakes of different humic content. Aquatic Microbial Ecology 11 135-141. 

Shiroishi and Hayakawa (18) have described the effect of sunlight irradiation on pyridoxine and related compounds in aqueous solution at various pH s. Pyridoxine and pyTidoxamine are relatively stable in acidic medium, while pyridoxal decomposes independently of pH. The authors suggested that the aldehydic 0 participates in the photolysis of pyridoxal. The presence of Cu++ had no effect on the stability of these substances. A borate complex of pyridoxine is stable to sunlight irradiation, heating, or autoclaving. Acetic acid and a reddish brown substance were separated as the decomposition products from an irradiated solution of pyridoxine (18). 

The study was designed to examine the effect of sunlight intensity, the importance of volatilization and the extent of partitioning of fenitrothion and degradation products into sediment, plants and fish under field conditions. 

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