Sunlight materials

Antireflection coatings are used over the silicon surface which, without the coating, reflects ca 35% of incident sunlight. Materials such as titanium dioxide, Ti02- tantalum pentoxide, TajOj, or silicon nitride, S13N4, ca 0.08-pm thick are common. 

Air pollution can be considered to have three components sources, transport and transformations in the atmosphere, and receptors. The source emits airborne substances that, when released, are transported through the atmosphere. Some of the substances interact with sunlight or chemical species in the atmosphere and are transformed. Pollutants that are emitted directiy to the atmosphere are called primary pollutants pollutants that are formed in the atmosphere as a result of transformations are called secondary pollutants. The reactants that undergo transformation are referred to as precursors. An example of a secondary pollutant is O, and its precursors are NMHC and nitrogen oxides, NO, a combination of nitric oxide [10102-43-9] NO, and NO2. The receptor is the person, animal, plant, material, or ecosystem affected by the emissions. 

Ultraviolet Aging. Nylon parts exposed to sunlight and uv rays undergo a similar free-radical aging process. Again, this can be reduced with appropriately stabilized materials. 

Durability. Grass-like surfaces intended for heavy-duty athletic use should have a service life of at least eight years, a common warranty period provided by suppHers. Lifetime is more or less proportional to the ultraviolet (uv) exposure (sunlight) and to the amount of face ribbon available for wear, but pile density and height also have an effect. Color is a factor generally uv absorption is highest with red fabrics and least with blue. In addition, different materials respond differendy to abrasive wear. These effects caimot be measured except in simulated field use and controlled laboratory experiments, which do not necessarily redect field conditions. 

Vitamin D [1406-12-2] is a material that is formed ia the skin of animals upon kradiation by sunlight and serves as a precursor for metaboUtes that control the animal s calcium homeostasis and act ki other hormonal functions. A deficiency of vitamin D can cause rickets, as weU as other disease states. This tendency can be a problem wherever animals, including humans, especially kifants and children, receive an kiadequate amount of sunshine. The latter phenomenon became prevalent with the advent of the kidustrial revolution, and efforts to cute rickets resulted ki the development of commercial sources of vitamin D for supplementation of the diet of Hvestock, pets, and humans. 

Decontamination. If contaminated equipment or material does not have to be used immediately, natural aeration is an effective decontaminant procedure, as most chemical agents, including the bHster and V-agents, are volatile to a certain degree. Wind accelerates their evaporation and hastens their dissipation. Rain and dew may also cause sufficient hydrolysis of some agents. Sunlight increases the surface temperatures of military equipment and thus accelerates agent evaporation. 

The marine environment is highly aggressive. Materials in marine service are constantly exposed to water, corrosive salts, strong sunlight, extremes in temperature, mechanical abuse, and chemical pollution in ports. This climate is very severe on ships, buoys, and navigational aids, offshore stmctures such as drilling platforms, and faciUties near the shore such as piers, locks, and bridges. 

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