The __ refers to a cloud of ionized (charged) particlesatoms and molecules with electrons in an unstable state. This electrical imbalance is used to create light from the changes in energy levels as they achieve balance. __ panels (PDPs) create just such a cloud from an inert gas, such as neon, by placing electrodes in front of and behind sealed chambers full of the gas and vaporized mercury. This technology of running a current through an inert gas to ionize it is shared with neon signs and fluorescent bulbs. Because of the pressurized nature of the gas in the chambers, __s are not optimal for high-altitude use, leading to CRTs and LCDs being more popular for high-altitude applications, such as aboard aircraft, where __s can be heard to buzz the way fluorescent bulbs sometimes do. Because of the temporary emission of light that this process produces, plasma displays have more in common with CRTs than they do with LCDs. In fact, as with CRTs, phosphors are responsible for the creation of light in the shade of the three primary colors, red, green, and blue. Because the pixels produce their own light, no backlight is required with plasma displays, also a feature shared with CRTs. The phosphor chemicals in CRTs and PDPs can be used up over time, reducing the overall image quality. The heat generated by CRTs and __s can lead to a loss of phosphorescence in the phosphor chemicals, which results in images burning into the screen. Advancements in the chemistry of plasma phosphors have reduced this tendency in recent years. The refresh rate for plasma displays has always been in the 600Hz range so that the decay of the glow of the cells within each pixel (subpixel) is not perceptible until such time as the image calls for that cell to turn off as well as to ensure fluid video motion. Refresh Rate but note that this rate is approximately 10 times that which is necessary to avoid the human eyes perception of the glows decay. The result is a display that produces the state of the art in video motion fluidity. Higher refresh rates in LCDs lead to an unwanted artificial or noncinematic quality to video known as the soap-opera effect. __s do not suffer from this effect. PDPs can also produce deeper black colors than fluorescent-backlit LCD panels because the backlight cannot be completely blocked by the liquid crystal, thus producing hues that are grayer than black. LCDs backlit with LEDs, however, are able to completely dim selective areas or the entire image. Because of the relative cost-effectiveness to produce __s of the same size as a given LCD panel, plasma displays historically enjoyed more popularity in the larger-monitor market. That advantage is all but gone today, resulting in more LCDs being sold today than plasma displays.