Ultraviolet light simulating

Degradation of parathion in soil was by hydrolysis to p-nitro-phenol and diethylthiophosphoric acid and reduction to aminopara-thion (25,26). Chemical oxidation of parathion in soils and waters was not prevalent, although oxidation of the phosphorus-sulfur bond has been shown to occur under ultraviolet light and in oxidizing environments (26). At ordinary levels of application to soil, parathion was degraded within weeks if microbial activity was available (27). Accumulations even after repeated applications were unlikely (28). When higher concentrations were applied to soil, persistence increased. Simulated spills of concentrated parathion resulted in a 15% residue after five years (29) and 0.1% after 16 years (30). 

Ultraviolet light. Black and golden coral are inert under UV light, as are plastics, which are the most likely simulant. Calcareous corals fluoresce under UV light in the same way as their most convincing simulants, shell. They both display a pale, chalky colour, and stronger fluorescence is noted in the paler material. Dark coral shows no discernible fluorescence. 

Forbes PD. Workshop on production and measurement of ultraviolet light light sources for solar simulation in photocarcinogenesis studies. Natl Cancer Inst Monogr 1978 50 91-95. Forbes PD. Design limits and qualification issues for room-size solar simulators in a GLP environment. In Tonnesen HH, ed. Photochemical Stability of Drugs and Drug Formulations. London, U.K. Taylor Francis, 1996 288-294. 

Naphthalene, anthracene, and similar hydrocarbons are termed polycyclic aromatic hydrocarbons (PAHs) because they are composed of multiple aromatic rings. PAHs have been found in meteorites and identified in the material surrounding dying stars. Scientists have mixed PAHs with water ice in a vacuum at -260°C to simulate the conditions found in interstellar clouds. To simulate radiation emitted by nearby stars, they shined ultraviolet light on the mixture. About ten percent of the PAHs were converted to alcohols, ketones, and esters— molecules that can be used to form compounds that are important in biological systems. 

M.K. Blakefield, J. Calkins (1992). Inhibition of phototaxis in Volvox aureus by natural and simulated solar ultraviolet light. Photochem. Photobiol, 55, 867-872. 

Matrix isolation methods have been used to prepare the binary aluminum hydride AI2H6 [7]. Prior to this work, the only known hydride of aluminum was the polymeric (A1H3) solid. The dimer was formed following the reaction of laser-ablated A1 atoms with pure H2 during co-deposition at 3.5 K, followed by radiation with ultraviolet light and heating to 6.5 K. AI2H6 was identified by seven new infrared absorptions that were accurately predicted by quantum mechanical simulations. Many other examples can be found in [8]. 

Of considerable interest in recent years is the laboratory simulation and acceleration of atmospheric pollution effects to evaluate degradation of materials. These tests involve injection of a variety of gases, vapors, and particulate matter into a controlled pressure chamber with controlled condensation on metal specimens. Sometimes, ultraviolet light is used to produce photochemical changes in the gases or vapors to replicate smog conditions. 

It darkens with exposure to the ultraviolet rays in sunlight, and the surface becomes opaque due to oxidation. Examples of beads carved in the Stone Age are usually a deep, dull, reddish colour, but when viewed by transmitted light they glow a deep brownish-red. If one of these beads were broken the inside would be much paler and probably clear. The length of time taken for this to happen varies according to where and how the amber has been stored. It can take from several years to several hundred years to occur naturally, but the effect can be simulated through treatment. 

---