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Most types of capacitor include a dielectric spacer, which increases their capacitance. These dielectrics are most often insulators. However, low capacitance devices are available with a vacuum between their plates, which allows extremely high voltage operation and low losses. Variable capacitors with their plates open to the atmosphere were commonly used in radio tuning circuits. Later designs use polymer foil dielectric between the moving and stationary plates, with no significant air space between them.

What did the later designs of capacitors used in radio tuning circuits no longer have?
Answer: no significant air space
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The Republic of the Congo's sparse population is concentrated in the southwestern portion of the country, leaving the vast areas of tropical jungle in the north virtually uninhabited. Thus, Congo is one of the most urbanized countries in Africa, with 70% of its total population living in a few urban areas, namely in Brazzaville, Pointe-Noire or one of the small cities or villages lining the 534-kilometre (332 mi) railway which connects the two cities. In rural areas, industrial and commercial activity has declined rapidly in recent years, leaving rural economies dependent on the government for support and subsistence.

In what part of the country can most of the Congo's citizens be found?
Answer: southwest
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The first boardwalk was built in 1870 along a portion of the beach in an effort to help hotel owners keep sand out of their lobbies. Businesses were restricted and the boardwalk was removed each year at the end of the peak season. Because of its effectiveness and popularity, the boardwalk was expanded in length and width, and modified several times in subsequent years. The historic length of the boardwalk, before the destructive 1944 Great Atlantic Hurricane, was about 7 miles (11 km) and it extended from Atlantic City to Longport, through Ventnor and Margate.

In what year was the first boardwalk built in Atlantic City?
Answer:
1870