Problem: Light-emitting diode:

With nitrides containing aluminium, most often AlGaN and AlGaInN, even shorter wavelengths are achievable. Ultraviolet LEDs in a range of wavelengths are becoming available on the market. Near-UV emitters at wavelengths around 375395 nm are already cheap and often encountered, for example, as black light lamp replacements for inspection of anti-counterfeiting UV watermarks in some documents and paper currencies. Shorter-wavelength diodes, while substantially more expensive, are commercially available for wavelengths down to 240 nm. As the photosensitivity of microorganisms approximately matches the absorption spectrum of DNA, with a peak at about 260 nm, UV LED emitting at 250270 nm are to be expected in prospective disinfection and sterilization devices. Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices. UV-C wavelengths were obtained in laboratories using aluminium nitride (210 nm), boron nitride (215 nm) and diamond (235 nm).

What substance does nitrides contain?
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A: aluminium

Problem: Hard rock:

The roots of hard rock can be traced back to the 1950s, particularly electric blues, which laid the foundations for key elements such as a rough declamatory vocal style, heavy guitar riffs, string-bending blues-scale guitar solos, strong beat, thick riff-laden texture, and posturing performances. Electric blues guitarists began experimenting with hard rock elements such as driving rhythms, distorted guitar solos and power chords in the 1950s, evident in the work of Memphis blues guitarists such as Joe Hill Louis, Willie Johnson, and particularly Pat Hare, who captured a "grittier, nastier, more ferocious electric guitar sound" on records such as James Cotton's "Cotton Crop Blues" (1954). Other antecedents include Link Wray's instrumental "Rumble" in 1958, and the surf rock instrumentals of Dick Dale, such as "Let's Go Trippin'" (1961) and "Misirlou" (1962).

When was "Rumble" released?
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A: 1958

Problem: Seattle:

After a difficult winter, most of the Denny Party relocated across Elliott Bay and claimed land a second time at the site of present-day Pioneer Square. Charles Terry and John Low remained at the original landing location and reestablished their old land claim and called it "New York", but renamed "New York Alki" in April 1853, from a Chinook word meaning, roughly, "by and by" or "someday". For the next few years, New York Alki and Duwamps competed for dominance, but in time Alki was abandoned and its residents moved across the bay to join the rest of the settlers.

When was New York Alki established?
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A: April 1853

Problem: 51st state:

Other less likely contenders are Guam and the United States Virgin Islands, both of which are unincorporated organized territories of the United States. Also, the Northern Mariana Islands and American Samoa, an unorganized, unincorporated territory, could both attempt to gain statehood. Some proposals call for the Virgin Islands to be admitted with Puerto Rico as one state (often known as the proposed "Commonwealth of Prusvi", for Puerto Rico/U.S. Virgin Islands, or as "Puerto Virgo"), and for the amalgamation of U.S. territories or former territories in the Pacific Ocean, in the manner of the "Greater Hawaii" concept of the 1960s. Guam and the Northern Mariana Islands would be admitted as one state, along with Palau, the Federated States of Micronesia, and the Marshall Islands (although these latter three entities are now separate sovereign nations, which have Compact of Free Association relationships with the United States). Such a state would have a population of 412,381 (slightly lower than Wyoming's population) and a land area of 911.82 square miles (2,361.6 km2) (slightly smaller than Rhode Island). American Samoa could possibly be part of such a state, increasing the population to 467,900 and the area to 988.65 square miles (2,560.6 km2). Radio Australia, in late May 2008, issued signs of Guam and the Northern Mariana Islands becoming one again and becoming the 51st state.

What is another likely country for free association?
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A:
unanswerable