APPLICATIONS Horn antennas are widely used as satellite dishes and radio telescopes. Antennas 6 2. PARABOLIC ANTENNAS A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves.
Flu (influenza). Flu is usually infectious a day before symptoms start and remains infectious for about five to six days. Children and people with lowered immune systems may be infectious for a few days longer.
An otherwise healthy person who gets the flu will usually improve over two to five days. In some people that tired feeling may last for one week or more and very rarely the symptoms can last for several weeks (post influenza asthenia). A major concern when you get the flu is that complications can arise. This is not strictly a relapse, but the development of another illness. The risk is highest for those with diabetes; heart, lung, or kidney disease; and other chronic diseases that lower the body's resistance to infection. Persons over age 65 are also at greater risk of developing complications from the flu. A very serious complication associated with the flu is pneumonia. Shortness of breath, sharp chest pain on deep breathing, or fever lasting beyond five days are symptoms that may indicate pneumonia.