Definitions beginning with U

uveal tract - permalink - collapse

(YOO-vee-ul trakt) The middle layer of the wall of the eye. The uveal tract has 3 main parts: (1) the choroid (the tissue layer filled with blood vessels); (2) the ciliary body (the ring of muscle tissue that changes the size of the pupil and the shape of the lens); and (3) the iris (the colored part of the eye). Also called uvea.
National Cancer Institute - Cite This Source - This Definition
Browse Related Terms: angioplasty, balloon angioplasty, plaque (plak), uvea

UV Electro- Optics - permalink - collapse

Technologies/techniques employed by optical sensors in the wavelength spectrum shorter than visible (e.g., less than 4,000 A).
DoD Missile Defense Agency - Cite This Source - This Definition
Browse Related Terms: Electro-Optics Infrared (EO/IR), EO, EO/IR, EOCM, GEODSS, Infrared (IR) Electro-Optics, IR Electro-Optics, UV Electro- Optics, Visible Electro- Optics

UV Index - permalink - collapse

Ultraviolet Index- This index provides important information to help you plan your outdoor activities in ways that prevent overexposure to the sun's rays. It was designed by the National Weather Service (NWS) and the Environmental Protection Agency (EPA). Unlike some countries' indices, the United States UV Index is not based upon surface observations. Rather, it is computed using forecasted ozone levels, a computer model that relates ozone levels to UV incidence on the ground, forecasted cloud amounts, and the elevation of the forecast cities. The calculation starts with measurements of current total ozone amounts for the entire globe, obtained via two satellites operated by the National Oceanic and Atmospheric Administration (NOAA). These data are then used to produce a forecast of ozone levels for the next day at various points around the country.

Category	UV Index	Time to Burn	Actions to Take
Minimal	0 - 2	60 min. +	Apply SPF sunscreen.
Low	3 - 4	45 min.	Apply SPF sunscreen, wear a hat.
Moderate	5 - 6	30 min.	Apply SPF 15, wear a hat.
High	7 - 9	15 - 24 min.	Apply SPF 15 to 30, wear a hat and sunglasses. Limit midday exposure.
Very High	10+	10 min.	Apply SPF 30; wear a hat, sunglasses, and protective clothing; limit midday exposure.

NOAA National Weather Service - Cite This Source - This Definition

Browse Related Terms: DTRT, EPA, Prevention of Significant Deterioration, Ultraviolet Index, Visibility Protection Program

Invisible rays that are part of the energy that comes from the sun. UV radiation also comes from sun lamps and tanning beds. It can damage the skin and cause melanoma and other types of skin cancer. UV radiation that reaches the Earth's surface is made up of two types of rays, called UVA and UVB rays. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass deeper into the skin. Scientists have long thought that UVB radiation can cause melanoma and other types of skin cancer. They now think that UVA radiation also may add to skin damage that can lead to skin cancer and cause premature aging. For this reason, skin specialists recommend that people use sunscreens that reflect, absorb, or scatter both kinds of UV radiation. Also called ultraviolet radiation.
National Cancer Institute - Cite This Source - This Definition
Browse Related Terms: phototesting, sunscreen, ultraviolet radiation, UVA radiation, UVB radiation

uvula - permalink - collapse

All > Medicine > Cancer

The soft flap of tissue that hangs down at the back of the mouth (at the edge of the soft palate). Also called palatine uvula.
National Cancer Institute - Cite This Source - This Definition
Browse Related Terms: hard palate, palate, palatine uvula, soft palate

UVV - permalink - collapse

All > Science > Weather

Upward Vertical Velocity (rising air)
NOAA National Weather Service - Cite This Source - This Definition
Browse Related Terms: Buoyancy, Flow Separation, RSG, Separation Eddy, Thermal, Unstable air, Venturi Effect

UW - permalink - collapse

All > Technology > Defense

Unconventional Warfare. 316
DoD Missile Defense Agency - Cite This Source - This Definition
Browse Related Terms: First Strike, LIWA, MIW, OIW, STW, Unconventional Warfare

UWB - permalink - collapse

All > Technology > Telecommunications

Abbreviation for ultrawideband. 1. Referring to any radio or wireless device where the occupied bandwidth is greater than 25% of the center frequency or greater than 1.5 GHz. 2. A radio or wireless system that uses narrow pulses (on the order of 1 to 10 nanoseconds), also called carrierless or impulse systems, for communications and sensing (short-range radar). 3. A radio or wireless system that uses time-domain modulation methods (e.g., pulse-position modulation) for communications applications, or time-domain processing for sensing applications.
ATIS - Cite This Source - This Definition
Browse Related Terms: pulse-repetition frequency (PRF), Rayleigh distribution, variation monitor