Problem: By the late 1990s, blue LEDs became widely available. They have an active region consisting of one or more InGaN quantum wells sandwiched between thicker layers of GaN, called cladding layers. By varying the relative In/Ga fraction in the InGaN quantum wells, the light emission can in theory be varied from violet to amber. Aluminium gallium nitride (AlGaN) of varying Al/Ga fraction can be used to manufacture the cladding and quantum well layers for ultraviolet LEDs, but these devices have not yet reached the level of efficiency and technological maturity of InGaN/GaN blue/green devices. If un-alloyed GaN is used in this case to form the active quantum well layers, the device will emit near-ultraviolet light with a peak wavelength centred around 365 nm. Green LEDs manufactured from the InGaN/GaN system are far more efficient and brighter than green LEDs produced with non-nitride material systems, but practical devices still exhibit efficiency too low for high-brightness applications.[citation needed]
How can light emission be varied from red to amber?
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Answer: unanswerable

Problem: Initially, officials were unable to contact the Wolong National Nature Reserve, home to around 280 giant pandas. However, the Foreign Ministry later said that a group of 31 British tourists visiting the Wolong Panda Reserve in the quake-hit area returned safe and uninjured to Chengdu. Nonetheless, the well-being of an even greater number of pandas in the neighbouring panda reserves remained unknown. Five security guards at the reserve were killed by the earthquake. Six pandas escaped after their enclosures were damaged. By May 20, two pandas at the reserve were found to be injured, while the search continued for another two adult pandas that went missing after the quake. By May 28, 2008, one panda was still missing. The missing panda was later found dead under the rubble of an enclosure. Nine-year-old Mao Mao, a mother of five at the breeding center, was discovered on Monday, her body crushed by a wall in her enclosure. Panda keepers and other workers placed her remains in a small wooden crate and buried her outside the breeding centre.
How many pandas escaped the reserve?
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Answer: Six

Problem: From late 2009 a handful of mainly southern eurozone member states started being unable to repay their national Euro-denominated government debt or to finance the bail-out of troubled financial sectors under their national supervision without the assistance of third parties. This so-called European debt crisis began after Greece's new elected government stopped masking its true indebtedness and budget deficit and openly communicated the imminent danger of a Greek sovereign default. Seeing a sovereign default in the eurozone as a shock, the general public, international and European institutions, and the financial community started to intensively reassess the economic situation and creditworthiness of eurozone states. Those eurozone states being assessed as not financially sustainable enough on their current path, faced waves of credit rating downgrades and rising borrowing costs including increasing interest rate spreads. As a consequence, the ability of these states to borrow new money to further finance their budget deficits or to refinance existing unsustainable debt levels was strongly reduced.
What had Greece's previous government been hiding?
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Answer:
its true indebtedness and budget deficit