Periodontal treatment is the specialist cleaning of your teeth and gums to help control the bacteria that cause gum disease. Gum disease is caused by the germs (bacteria) which live in your mouth. The bacteria stick to your teeth, irritate the gums and make them bleed.
(Redirected from Ground effect in aircraft) In fixed-wing aircraft, ground effect is the increased lift (force) and decreased aerodynamic drag that an aircraft's wings generate when they are close to a fixed surface. When landing, ground effect can give the pilot the feeling that the aircraft is floating.
Doppler effect. The Doppler effect is defined as a noticeable change in the frequency of sound, light or water waves as the source and the observer move. An example of the Doppler effect is that the frequency of the sound increases as the source moves closer to the observer.