ultraviolet

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ultraviolet

 [ul″trah-vi´o-let]
denoting electromagnetic radiation of wavelength shorter than that of the violet end of the spectrum, having wavelengths of 4–400 nanometers.
ultraviolet A (UVA) ultraviolet radiation with wavelengths between 320 and 400 nm, comprising over 99 per cent of such radiation that reaches the surface of the earth. Ultraviolet A enhances the harmful effects of ultraviolet B radiation and is also responsible for some photosensitivity reactions; it is used therapeutically in the treatment of a variety of skin disorders.
ultraviolet B (UVB) ultraviolet radiation with wavelengths between 290 and 320 nm, comprising less than 1 per cent of the ultraviolet radiation that reaches the earth's surface. Ultraviolet B causes sunburn and a number of damaging photochemical changes within cells, including damage to DNA, leading to premature aging of the skin, premalignant and malignant changes, and a variety of photosensitivity reactions; it is also used therapeutically for treatment of skin disorders.
ultraviolet C (UVC) ultraviolet radiation with wavelengths between 200 and 290 nm; all of this type of radiation is filtered out by the ozone layer so that none reaches the earth's surface. Ultraviolet C is germicidal and is also used in ultraviolet phototherapy.
ultraviolet rays electromagnetic radiation beyond the violet end of the visible spectrum; they are not visible to humans. They are produced by the sun but are absorbed to a large extent by particles of dust and smoke in the earth's atmosphere. They are also produced by the so-called sun lamps. They can produce sunburn and affect skin pigmentation, causing tanning. When they strike the skin surface they transform provitamin D, secreted by the glands of the skin, into vitamin D, which is then absorbed into the body. Because ultraviolet rays are capable of killing bacteria and other microorganisms, they are sometimes used to sterilize objects in specially designed cabinets, or to sterilize the air in operating rooms and other areas where destruction of bacteria is necessary.
ultraviolet therapy the employment of ultraviolet radiation in the treatment of diseases, particularly those affecting the skin. See also PUVA therapy and photochemotherapy. Among the diseases that respond to this form of therapy are acne vulgaris, psoriasis, and external ulcers.

Dosage. The dosage unit of ultraviolet radiation is expressed as minimal erythema dose (MED). Because of varying degrees of skin thickness and pigmentation, human skin varies widely in its sensitivity to ultraviolet radiation. The MED refers to the amount of radiation that will produce, within a few hours, minimal erythema (redness caused by engorgement of capillaries) in the average Caucasian skin. Dosage for individual patients is prescribed according to probable sensitivity as determined by that individual's skin type as compared to average sensitivity.
Degrees of Erythema. Minimal erythema is a first degree erythema and usually is produced after about 15 seconds of exposure to a high-pressure mercury arc in a quartz burner placed at a distance of 75 cm (30 in) from the skin. A second degree erythema results from a dose of about 2.5 MED; its effects become apparent about 4 to 6 hours after application and are followed by slight peeling of the skin. A third degree erythema is produced by about 5 MED; it may become apparent within 2 hours after application and is accompanied by edema followed by marked desquamation. A fourth degree erythema is produced by about 10 MED and is characterized by blistering.
Precautions. Ultraviolet therapy is safe only in the hands of a skilled and knowledgeable therapist. Areas of “thin skin” that may be burned more readily than that receiving treatment must be protected by wet towels or dressings. The eye is highly sensitive to ultraviolet radiation; therefore some form of protection, such as goggles, compresses, or cotton balls, should be provided for both the patient and the therapist to avoid damage to the conjunctiva and cornea.



Certain drugs, such as the sulfonamides, greatly increase sensitivity to ultraviolet radiation. All patients scheduled for this form of therapy should be questioned in regard to the medication they are taking so the dosage can be adjusted accordingly or the treatment deferred.

ul·tra·vi·o·let (UV, uv),

(ŭl'tră-vī'ō-let),
Denoting electromagnetic rays at higher frequency than the violet end of the visible spectrum.

ul·tra·vi·o·let

(ŭl'tră-vī'ŏ-lĕt)
Denoting electromagnetic rays at higher frequency than the violet end of the visible spectrum.

ultraviolet (UV) 

Radiant energy of wavelengths smaller than those of the violet end of the visible spectrum and longer than about 1 nm. The wave band comprising radiations between 315 and 380 nm is referred to as UV-A. Excessive exposure to these radiations can cause cataract. The wave band comprising radiations between 280 and 315 nm is referred to as UV-B. Excessive exposure to all these radiations can cause photokeratitis and corneal opacity, while radiations between 295 and 315 nm can cause cataract. The wave band comprising radiations between 200 and 280 nm is referred to as UV-C. Excessive exposure to these radiations can cause photokeratitis and corneal opacity. See blepharospasm; actinic keratoconjunctivitis; excimer laser; absorptive lens; nanometre; pinguecula; wavelength.
Table U1 Divisions of the ultraviolet spectrum
UV-A (near)380-315 nm
UV-B (middle)315-280 nm
UV-C (far)280-200 nm
References in periodicals archive ?
Near UV and visible electromagnetic radiation have significant influence on filter paper made only from virgin fibres without any additives (calcium carbonate, clay, dye, starch, pigment) decrease reflectance value of those papers, especially in blue part spectra.
having higher extinction coefficients in the near UV, or showing a red shift of their absorption spectrum, or being able to be decomposed through excitation transfer, or exhibiting acid releasing properties (for UV activated acid curing), a better compatibility, a lower extractability.
The 5 instruments on-board cover the visible (320-530 nm), near UV (180-300 nm), far UV (130-180 nm), soft X-ray (0.3-8 keV and 2-10 keV) and hard X-ray (3-80 keV and 10-150 keV) regions of the electromagnetic spectrum.
Wu et al., "Near UV LEDs made with in situ doped p-n homojunction ZnO nanowire arrays," Nano Letters, vol.
Users have an unrestricted choice of fluorescent dyes because the instrument can be used alongside other lasers, from near UV to far red.
- Laser: green, blue, red, UV or near UV range for multicolor analysis, upgradeable to at least 6 spatially separated laser (and it is an indication for upgradeability and maximum number of spatially separated laser Demanded),
The 6540 series photostability chambers have an interior volume of approximately 10 cu ft (283 L), and they perform near UV and visual light testing with fluorescent lamps in accordance with ICH GuidelinesQ1 B, Option 2.
: In particular, this must necessarily following functionalities have installations and have the following services are provided - Laser: green, blue, red, UV or near UV range for multi-color analysis, upgradeable to at least 6 spatially separated laser (and the details of upgradeability and maximum number of spatially separated laser it is required), : - Quality control system, : - Sidescatter, : - Forwardsscatter, : - Single cell deposition, : - Storage in various formats to 384-well and single tubes, : - Easy Nozzletausch, : - Min.
The Model A displays a spectral response from near UV to near-IR, with a peak at 850 nm.
In accordance with ICH guidelines option 1, near UV and visible light testing is performed simultaneously.