Problem: Light-emitting diode:

The most common symptom of LED (and diode laser) failure is the gradual lowering of light output and loss of efficiency. Sudden failures, although rare, can also occur. Early red LEDs were notable for their short service life. With the development of high-power LEDs the devices are subjected to higher junction temperatures and higher current densities than traditional devices. This causes stress on the material and may cause early light-output degradation. To quantitatively classify useful lifetime in a standardized manner it has been suggested to use L70 or L50, which are the runtimes (typically given in thousands of hours) at which a given LED reaches 70% and 50% of initial light output, respectively.

 What was notable in early white LEDs?
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A: unanswerable


Problem: Molotov%E2%80%93Ribbentrop Pact:

In August 1940, the Soviet Union briefly suspended its deliveries under their commercial agreement after their relations were strained following disagreement over policy in Romania, the Soviet war with Finland, Germany falling behind in its deliveries of goods under the pact and with Stalin worried that Hitler's war with the West might end quickly after France signed an armistice. The suspension created significant resource problems for Germany. By the end of August, relations improved again as the countries had redrawn the Hungarian and Romanian borders, settled some Bulgarian claims and Stalin was again convinced that Germany would face a long war in the west with Britain's improvement in its air battle with Germany and the execution of an agreement between the United States and Britain regarding destroyers and bases. However, in late August, Germany arranged its own occupation of Romania, targeting oil fields. The move raised tensions with the Soviets, who responded that Germany was supposed to have consulted with the Soviet Union under Article III of the Molotov–Ribbentrop Pact.

Who ended refining Romanian oil?
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A: unanswerable


Problem: High-definition television:

Analog tape recorders with bandwidth capable of recording analog HD signals, such as W-VHS recorders, are no longer produced for the consumer market and are both expensive and scarce in the secondary market.

W-VHS recorders aren't capable of recording what kinds of signals?
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A: unanswerable


Problem: Miami:

Miami is a major center, and a leader in finance, commerce, culture, media, entertainment, the arts, and international trade. In 2012, Miami was classified as an Alpha−World City in the World Cities Study Group's inventory. In 2010, Miami ranked seventh in the United States in terms of finance, commerce, culture, entertainment, fashion, education, and other sectors. It ranked 33rd among global cities. In 2008, Forbes magazine ranked Miami "America's Cleanest City", for its year-round good air quality, vast green spaces, clean drinking water, clean streets, and city-wide recycling programs. According to a 2009 UBS study of 73 world cities, Miami was ranked as the richest city in the United States, and the world's fifth-richest city in terms of purchasing power. Miami is nicknamed the "Capital of Latin America", is the second largest U.S. city with a Spanish-speaking majority, and the largest city with a Cuban-American plurality.

Where did Miami rank among cities around the world in regard to finance?
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A:
33rd