The Vikings were seafaring north Germanic people who raided, traded, explored, and settled in wide areas of Europe, Asia, and the North Atlantic islands from the late 8th to the mid-11th centuries. The Vikings employed wooden longships with wide, shallow-draft hulls, allowing navigation in rough seas or in shallow river waters. The ships could be landed on beaches, and their light weight enabled them to be hauled over portages. These versatile ships allowed the Vikings to travel as far east as Constantinople and the Volga River in Russia, as far west as Iceland, Greenland, and Newfoundland, and as far south as Nekor. This period of Viking expansion, known as the Viking Age, constitutes an important element of the medieval history of Scandinavia, Great Britain, Ireland, Russia, and the rest of Europe.

Los Angeles County Immunization Program efforts are targeted primarily toward pediatric and adolescent immunizations , with some adult immunization activities. Although this Program serves the entire County population, many activities are specifically directed toward communities with children at high risk of under-immunization. The Immunization Program partners with other organizations to provide outreach and immunization services in pockets of need areas , which are defined as those areas with large numbers of un-immunized and under-immunized children.

The South Shore Estuary is an estuary located along the south shore of Long Island, between the mainland and the outer barrier islands, in eastern New York state. It stretches for over 70 miles (110 km) from West Bay in Nassau County to the Shinnecock Bay in Suffolk County.

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.

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.