The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

The Urnero (Leptodactylus latinasus) is a species of frog in the Leptodactylidae family. It is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay. Its natural habitats are subtropical or tropical moist shrub land, subtropical or tropical dry lowland grassland, subtropical or tropical seasonally wet or flooded lowland grassland, freshwater marshes, intermittent freshwater marshes, pastureland, rural gardens, and ponds.

Since 1944, the County of Los Angeles Department of Parks and Recreation has been meeting the diverse needs of not only residents, but also visitors from around the world. With over 63,000 acres of parks, gardens, lakes, trails, natural areas, and the world's largest public golf course system, the Department of Parks and Recreation is committed to providing the public with social, cultural, and recreational activities to enjoy the whole year.

Volunteer hosts went to the airport, picked up assigned students, fed them dinner, took them to the opening lecture at the Clay Center, put them in spare bedrooms for the night, then fed them breakfast this morning and will deliver the outstanding teens to buses that convey them to the mountain retreat where they undergo a month of intensive science training and outdoor fun.

Luckily, this year, enough local families volunteered to host all the brilliant youths. In the past, the number of guest homes sometimes fell short, and some of the visitors slept on cots and sleeping bags at local churches. They're adventurous teens and don't mind this makeshift camp-in but it's better if friendly hosts give them a more personal welcome for their stay.

Water polo, or water ball, is a team water sport. The playing team consists of six field players and one goalkeeper. The winner of the game is the team that scores the most goals. Game play involves swimming, treading water (using a sort of kicking motion known as "eggbeater kick"), players passing the ball while being defended by opponents, and scoring by throwing the ball into a net defended by a goalie. "Man-up" (or "power play") situations occur frequently. Water polo, therefore, has strong similarities to the land-based game of team handball.