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.
Epidemiologic data collected during spring 2009 found that most people with the 2009 H1N1 influenza virus who were not hospitalized had a fever that lasted 2 to 4 days; this would require an exclusion period of 3 to 5 days in most cases. Those with more severe illness are likely to have a fever for longer periods of time. Although fever is a component of the case definition of influenza-like illness, the epidemiologic data collected during spring 2009 found that a minority of patients infected with the 2009 H1N1 influenza virus with respiratory symptoms did not have a fever.