e-book Ultraviolet Light Induced Reactions in Polymers: Symposium Proceedings

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Book Description American Chemical Society, Condition: Good. Former Library book. Shows some signs of wear, and may have some markings on the inside. Seller Inventory GRP Seller Inventory ZB Condition: Used: Good. Condition: Very Good. Dust Jacket Condition: Very Good. Seller Inventory Condition: Very Good -. No Jacket. Hard Cover. Condition: Near Fine. Black cloth with gold stamping, previous owner's name stamp on the front flyleaf, otherwise a near fine unmark copy in a like mylar protected DJ. White spine. Phila, Contributions by Norman S. Gaylord, S.

Peter Pappas, Ashok K. Chattapoadhyay, Leland H.


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Carlblom, George B. Butler, William I. Ferree, Jr. Pinazzi, A. Fernandez, Zdzislaw Hippe, Malcolm P. Stevens, R. Later Edition. ISBN X. No dustjacket. Good to Very Good Condition, with some brownspotting and dustsoiling to edges of interior pages, minor rubs to edges and corners of covers. Tight, sound, unmarked copy except for initial written in upper corner of front endpaper. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes.

UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin. Medical organizations recommend that patients protect themselves from UV radiation by using sunscreen. Five sunscreen ingredients have been shown to protect mice against skin tumors. However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells. Several studies suggest that the absence of UVA filters may be the cause of the higher incidence of melanoma found in sunscreen users compared to non-users.

The photochemical properties of melanin make it an excellent photoprotectant.

Ultraviolet Light Induced Reactions in Polymers: Symposium Proceedings (ACS symposium series)

However, sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin and therefore, if sunscreen ingredients penetrate into the lower layers of the skin, the amount of reactive oxygen species may be increased. In an experiment by Hanson et al. In the first 20 minutes, the film of sunscreen had a protective effect and the number of ROS species was smaller.

After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin. Radiation of this wavelength is almost absent from sunlight but is found in welder's arc lights and other artificial sources. Exposure to these can cause "welder's flash" or "arc eye" photokeratitis and can lead to cataracts , pterygium and pinguecula formation. Protective eyewear is beneficial to those exposed to ultraviolet radiation. Since light can reach the eyes from the sides, full-coverage eye protection is usually warranted if there is an increased risk of exposure, as in high-altitude mountaineering.

Mountaineers are exposed to higher-than-ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate , inherently block most UV.

UV degradation is one form of polymer degradation that affects plastics exposed to sunlight. The problem appears as discoloration or fading, cracking, loss of strength or disintegration. The effects of attack increase with exposure time and sunlight intensity. The addition of UV absorbers inhibits the effect. Sensitive polymers include thermoplastics and speciality fibers like aramids. UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure.

Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength. Many pigments and dyes absorb UV and change colour, so paintings and textiles may need extra protection both from sunlight and fluorescent bulbs, two common sources of UV radiation. Window glass absorbs some harmful UV, but valuable artifacts need extra shielding. Many museums place black curtains over watercolour paintings and ancient textiles, for example. Since watercolours can have very low pigment levels, they need extra protection from UV.

Various forms of picture framing glass , including acrylics plexiglass , laminates, and coatings, offer different degrees of UV and visible light protection. Because of its ability to cause chemical reactions and excite fluorescence in materials, ultraviolet radiation has a number of applications. The following table [76] gives some uses of specific wavelength bands in the UV spectrum. Slightly yellow UV-blocking filters are often used for outdoor photography to prevent unwanted bluing and overexposure by UV rays. For photography in the near UV, special filters may be used.

Digital cameras sensors may have internal filters that block UV to improve color rendition accuracy. Sometimes these internal filters can be removed, or they may be absent, and an external visible-light filter prepares the camera for near-UV photography.

A few cameras are designed for use in the UV. Photography by reflected ultraviolet radiation is useful for medical, scientific, and forensic investigations, in applications as widespread as detecting bruising of skin, alterations of documents, or restoration work on paintings. Photography of the fluorescence produced by ultraviolet illumination uses visible wavelengths of light. In ultraviolet astronomy , measurements are used to discern the chemical composition of the interstellar medium, and the temperature and composition of stars. Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space.

Corona discharge on electrical apparatus can be detected by its ultraviolet emissions. Corona causes degradation of electrical insulation and emission of ozone and nitrogen oxide. These modules have a transparent quartz window on the top of the chip that allows the UV radiation in. Colorless fluorescent dyes that emit blue light under UV are added as optical brighteners to paper and fabrics. The blue light emitted by these agents counteracts yellow tints that may be present and causes the colors and whites to appear whiter or more brightly colored.

UV fluorescent dyes that glow in the primary colors are used in paints, papers, and textiles either to enhance color under daylight illumination or to provide special effects when lit with UV lamps. Blacklight paints that contain dyes that glow under UV are used in a number of art and aesthetic applications. Amusement parks often use UV lighting to fluoresce ride artwork and backdrops. This often has the side effect of causing rider's white clothing to glow light-purple. To help prevent counterfeiting of currency, or forgery of important documents such as driver's licenses and passports , the paper may include a UV watermark or fluorescent multicolor fibers that are visible under ultraviolet light.

Postage stamps are tagged with a phosphor that glows under UV rays to permit automatic detection of the stamp and facing of the letter.

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UV fluorescent dyes are used in many applications for example, biochemistry and forensics. Some brands of pepper spray will leave an invisible chemical UV dye that is not easily washed off on a pepper-sprayed attacker, which would help police identify the attacker later. In some types of nondestructive testing UV stimulates fluorescent dyes to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action liquid penetrant inspection or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials magnetic particle inspection.

UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva. Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with UV sensitive dyes may have distinctive fluorescence under UV exposure or may fluoresce differently under short-wave versus long-wave ultraviolet.

Using multi-spectral imaging it is possible to read illegible papyrus , such as the burned papyri of the Villa of the Papyri or of Oxyrhynchus , or the Archimedes palimpsest. The technique involves taking pictures of the illegible document using different filters in the infrared or ultraviolet range, finely tuned to capture certain wavelengths of light. Thus, the optimum spectral portion can be found for distinguishing ink from paper on the papyrus surface.

Simple NUV sources can be used to highlight faded iron-based ink on vellum. Ultraviolet aids in the detection of organic material deposits that remain on surfaces where periodic cleaning and sanitizing may not have been properly accomplished. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are inspected. Perennial news features for many television news organizations involve an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.

UV radiation is often used to excite a given sample where the fluorescent emission is measured with a spectrofluorometer. In biological research, UV radiation is used for quantification of nucleic acids or proteins. Ultraviolet lamps are also used in analyzing minerals and gems. In pollution control applications, ultraviolet analyzers are used to detect emissions of nitrogen oxides, sulfur compounds, mercury, and ammonia, for example in the flue gas of fossil-fired power plants.

In general, ultraviolet detectors use either a solid-state device, such as one based on silicon carbide or aluminium nitride , or a gas-filled tube as the sensing element. UV detectors that are sensitive to UV in any part of the spectrum respond to irradiation by sunlight and artificial light. A burning hydrogen flame, for instance, radiates strongly in the to nanometer range and only very weakly in the IR region, whereas a coal fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus, a fire detector that operates using both UV and IR detectors is more reliable than one with a UV detector alone.

Virtually all fires emit some radiation in the UVC band, whereas the Sun 's radiation at this band is absorbed by the Earth's atmosphere. The result is that the UV detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors. UV detectors are sensitive to most fires, including hydrocarbons , metals, sulfur , hydrogen , hydrazine , and ammonia.

Arc welding , electrical arcs, lightning , X-rays used in nondestructive metal testing equipment though this is highly unlikely , and radioactive materials can produce levels that will activate a UV detection system. The presence of UV-absorbing gases and vapors will attenuate the UV radiation from a fire, adversely affecting the ability of the detector to detect flames.

TYPES OF POLYMERIZATION

Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect. Ultraviolet radiation is used for very fine resolution photolithography , a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist.

After removal of unwanted photoresist, a pattern determined by the mask remains on the sample. Steps may then be taken to "etch" away, deposit on or otherwise modify areas of the sample where no photoresist remains. Photolithography is used in the manufacture of semiconductors , integrated circuit components, [91] and printed circuit boards. Electronic components that require clear transparency for light to exit or enter photovoltaic panels and sensors can be potted using acrylic resins that are cured using UV energy. The advantages are low VOC emissions and rapid curing.

Certain inks, coatings, and adhesives are formulated with photoinitiators and resins. When exposed to UV light, polymerization occurs, and so the adhesives harden or cure, usually within a few seconds. Applications include glass and plastic bonding, optical fiber coatings, the coating of flooring, UV coating and paper finishes in offset printing , dental fillings, and decorative fingernail "gels".


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  5. Fast processes such as flexo or offset printing require high-intensity light focused via reflectors onto a moving substrate and medium so high-pressure Hg mercury or Fe iron, doped -based bulbs are used, energized with electric arcs or microwaves. Lower-power fluorescent lamps and LEDs can be used for static applications. Small high-pressure lamps can have light focused and transmitted to the work area via liquid-filled or fiber-optic light guides.

    The impact of UV on polymers is used for modification of the roughness and hydrophobicity of polymer surfaces. For example, a poly methyl methacrylate surface can be smoothed by vacuum ultraviolet. UV radiation is useful in preparing low-surface-energy polymers for adhesives. Polymers exposed to UV will oxidize, thus raising the surface energy of the polymer.

    Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer is stronger. Using a catalytic chemical reaction from titanium dioxide and UVC exposure, oxidation of organic matter converts pathogens , pollens , and mold spores into harmless inert byproducts. However, the reaction of titanium dioxide and UVC is not a straight path. Several hundreds of reactions occur prior to the inert byproducts stage and can hinder the resulting reaction creating formadehyde, aldehyde, and other VOC's en route to a final stage.

    Controlled polymers: accessing new platforms for material synthesis

    Thus, the use of Titanium Dioxide and UVC requires very specific parameters for a successful outcome. The cleansing mechanism of UV is a photochemical process. Short-wave ultraviolet radiation can destroy DNA in living microorganisms. UV has also been shown to reduce gaseous contaminants such as carbon monoxide and VOCs.

    This arrangement prevents the introduction of ozone into the treated air. Ultraviolet lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. UV at these germicidal wavelengths damage a microorganism's DNA so that it cannot reproduce, making it harmless, even though the organism may not be killed. Since microorganisms can be shielded from ultraviolet rays in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques. This is especially important knowing that pathogens vary in their sensitivity to specific UV wavelengths.

    Disinfection using UV radiation is commonly used in wastewater treatment applications and is finding an increased usage in municipal drinking water treatment. Many bottlers of spring water use UV disinfection equipment to sterilize their water. Solar water disinfection [99] has been researched for cheaply treating contaminated water using natural sunlight. The UV-A irradiation and increased water temperature kill organisms in the water. Ultraviolet radiation is used in several food processes to kill unwanted microorganisms. UV can be used to pasteurize fruit juices by flowing the juice over a high-intensity ultraviolet source.

    Pulsed light PL is a technique of killing microorganisms on surfaces using pulses of an intense broad spectrum, rich in UV-C between and nm. Pulsed light works with xenon flash lamps that can produce flashes several times per second. Disinfection robots use pulsed UV []. Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet wavelengths. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision.

    Scorpions glow or take on a yellow to green color under UV illumination, thus assisting in the control of these arachnids. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and human beings, are much easier to spot with ultraviolet.

    Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings. Butterflies use ultraviolet as a communication system for sex recognition and mating behavior. For example, in the Colias eurytheme butterfly, males rely on visual cues to locate and identify females. Instead of using chemical stimuli to find mates, males are attracted to the ultraviolet-reflecting color of female hind wings. This suggested that it was evolutionarily more difficult to increase the UV-sensitivity of the eyes of the males than to increase the UV-signals emitted by the females.

    Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emitter will normally disrupt the navigation process and will eventually attract the flying insect. The green fluorescent protein GFP is often used in genetics as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of interest in biochemistry and related fields. UV-capable spectrophotometers are common in such laboratories.

    Ultraviolet traps called bug zappers are used to eliminate various small flying insects. They are attracted to the UV and are killed using an electric shock, or trapped once they come into contact with the device.

    Different designs of ultraviolet radiation traps are also used by entomologists for collecting nocturnal insects during faunistic survey studies. Ultraviolet radiation is helpful in the treatment of skin conditions such as psoriasis and vitiligo.

    Supplementary files

    Exposure to UVA, while the skin is hyper-photosensitive, by taking psoralens is an effective treatment for psoriasis. Due to the potential of psoralens to cause damage to the liver , PUVA therapy may be used only a limited number of times over a patient's lifetime. UVB phototherapy does not require additional medications or topical preparations for the therapeutic benefit; only the exposure is needed. However, phototherapy can be effective when used in conjunction with certain topical treatments such as anthralin, coal tar, and vitamin A and D derivatives, or systemic treatments such as methotrexate and Soriatane.

    Reptiles need UVB for biosynthesis of vitamin D, and other metabolic processes. The UVA wavelength is also visible to many reptiles and might play a significant role in their ability survive in the wild as well as visual communication between individuals. Simple supplementation with cholecalciferol Vitamin D3 will not be enough as there's a complete biosynthetic pathway that is "leapfrogged" risks of possible overdoses , the intermediate molecules and metabolites also place important functions in the animals health.

    Natural sunlight in the right levels is always going to be superior to artificial sources, but this might be possible for keepers in different parts of the world. For many keepers there must also be a provision for an adequate heat source this has resulted in the marketing of heat and light "combination" products. A better strategy is to use individual sources of these elements and so they can be placed and controlled by the keepers for the max benefit of the animals.

    The evolution of early reproductive proteins and enzymes is attributed in modern models of evolutionary theory to ultraviolet radiation. UVB causes thymine base pairs next to each other in genetic sequences to bond together into thymine dimers , a disruption in the strand that reproductive enzymes cannot copy. This leads to frameshifting during genetic replication and protein synthesis , usually killing the cell.

    Before formation of the UV-blocking ozone layer, when early prokaryotes approached the surface of the ocean, they almost invariably died out. The few that survived had developed enzymes that monitored the genetic material and removed thymine dimers by nucleotide excision repair enzymes. Many enzymes and proteins involved in modern mitosis and meiosis are similar to repair enzymes, and are believed to be evolved modifications of the enzymes originally used to overcome DNA damages caused by UV.

    From Wikipedia, the free encyclopedia. For other uses, see Ultraviolet disambiguation. For other uses, see UV disambiguation. Electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays. UV radiation is also produced by electric arcs. Arc welders must wear eye protection and cover their skin to prevent photokeratitis and serious sunburn. Two black light fluorescent tubes, showing use. Main article: Blacklight. Main article: Gas-discharge lamp.

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    Ultraviolet - Wikipedia

    Main article: Excimer laser. Further information: Health effects of sunlight exposure. Main article: Sunscreen. Main article: UV degradation. Main article: Ultraviolet photography. See also: Flame detector. Main article: Ultraviolet germicidal irradiation. Main article: Ultraviolet light therapy. Archived from the original on 27 January Retrieved 12 November Living Reviews in Solar Physics. Bibcode : LRSP Archived from the original on 4 March Retrieved 12 July British Journal of Ophthalmology. The Guardian.

    Archived from the original on 23 November Retrieved 2 January Color and Light in Nature 2nd ed. Archived from the original on 31 December Retrieved 12 October Fundamentals Of Ecology 3E. Tata McGraw-Hill Education. Retrieved 18 October Normally the human eye responds to light rays from to nm. This can be extended to a range of to 1, nm under artificial conditions. You're going to need smaller eyes". Archived from the original on 7 May Patterns of light: chasing the spectrum from Aristotle to LEDs.

    New York: Springer. Lyman, T. Astrophysical Journal. Bibcode : ApJ Archived PDF from the original on 29 October Archived from the original PDF on 9 January Retrieved 8 November Archived PDF from the original on 1 November Archived from the original on 29 October Archived from the original on 28 September Archived from the original on 28 December Archived from the original on 27 March Retrieved 20 January Archived from the original on 9 July Retrieved 13 January