Problem: Glass:

The alkali metal ions are small and mobile; their presence in glass allows a degree of electrical conductivity, especially in molten state or at high temperature. Their mobility decreases the chemical resistance of the glass, allowing leaching by water and facilitating corrosion. Alkaline earth ions, with their two positive charges and requirement for two non-bridging oxygen ions to compensate for their charge, are much less mobile themselves and also hinder diffusion of other ions, especially the alkalis. The most common commercial glasses contain both alkali and alkaline earth ions (usually sodium and calcium), for easier processing and satisfying corrosion resistance. Corrosion resistance of glass can be achieved by dealkalization, removal of the alkali ions from the glass surface by reaction with e.g. sulfur or fluorine compounds. Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance; glasses for electronics (sealing, vacuum tubes, lamps...) have to take this in account.

What can alkaline ions in oxygen harm?
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A: unanswerable


Problem: Mexico City:

There is an environmental program, called Hoy No Circula ("Today Does Not Run", or "One Day without a Car"), whereby vehicles that have not passed emissions testing are restricted from circulating on certain days according to the ending digit of their license plates; this in an attempt to cut down on pollution and traffic congestion. While in 2003, the program still restricted 40% of vehicles in the metropolitan area, with the adoption of stricter emissions standards in 2001 and 2006, in practice, these days most vehicles are exempt from the circulation restrictions as long as they pass regular emissions tests.

When were new emisson standards enacted?
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A: 2006


Problem: Heian period:

While on one hand the Heian period was an unusually long period of peace, it can also be argued that the period weakened Japan economically and led to poverty for all but a tiny few of its inhabitants. The control of rice fields provided a key source of income for families such as the Fujiwara and were a fundamental base for their power. The aristocratic beneficiaries of Heian culture, the Ryōmin (良民 "Good People") numbered about five thousand in a land of perhaps five million. One reason the samurai were able to take power was that the ruling nobility proved incompetent at managing Japan and its provinces. By the year 1000 the government no longer knew how to issue currency and money was gradually disappearing. Instead of a fully realised system of money circulation, rice was the primary unit of exchange. The lack of a solid medium of economic exchange is implicitly illustrated in novels of the time. For instance, messengers were rewarded with useful objects, e.g., an old silk kimono, rather than paid a fee.

What was a short period of peace?
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A: unanswerable


Problem: Greeks:

Notable Greek seafarers include people such as Pytheas of Marseilles, Scylax of Caryanda who sailed to Iberia and beyond, Nearchus, the 6th century merchant and later monk Cosmas Indicopleustes (Cosmas who sailed to India) and the explorer of the Northwestern passage Juan de Fuca. In later times, the Romioi plied the sea-lanes of the Mediterranean and controlled trade until an embargo imposed by the Roman Emperor on trade with the Caliphate opened the door for the later Italian pre-eminence in trade.

Who was the well known sea vessel captain of the Greeks who sailed to Asia  ?
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A:
Cosmas Indicopleustes (Cosmas who sailed to India)