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In crystals, the lattice is a very neat, uniform assembly. However, nearly all crystals have defects in the stacking sequence of these molecules and atoms. A vacancy defect, where an atom is simply missing from its place, leaving an empty "hole", is one type of defect.
UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic. [68] In the past, UVA was considered not harmful or less harmful than UVB, but today it is known to contribute to skin cancer via indirect DNA damage (free radicals such as reactive oxygen species ...
Photochemical immersion well reactor (50 mL) with a mercury-vapor lamp.. Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible (400–750 nm), or infrared radiation (750–2500 nm).
In chemistry, a photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives).
DNA UV mutation. Melanocytes and basal cells are embedded in the epidermal layer. Upon exposure to UVB rays, melanocytes will produce more melanin, a pigment that gives skin its color. UVB can cause the formation of freckles and dark spots, both of which are symptoms of photoaging; these are most common in people with fair or light skin. [7]
A gamma-ray burst in the Milky Way, if close enough to Earth and beamed toward it, could have significant effects on the biosphere. The absorption of radiation in the atmosphere would cause photodissociation of nitrogen, generating nitric oxide that would act as a catalyst to destroy ozone. [22] The atmospheric photodissociation
Because oxybenzone is the least lipophilic of the three most common UV filters, it is the least likely to end up trapped in the stratum corneum and the most likely to be absorbed and metabolized. [26] When applied topically, UV filters, such as oxybenzone, are absorbed through the skin, metabolized, and excreted primarily through the urine. [27]
In chemical terms, actinism is the property of radiation that lets it be absorbed by a molecule and cause a photochemical reaction as a result. Albert Einstein was the first to correctly theorize that each photon would be able to cause only one molecular reaction. This distinction separates photochemical reactions from exothermic reduction ...