Article: Glass is in widespread use largely due to the production of glass compositions that are transparent to visible light. In contrast, polycrystalline materials do not generally transmit visible light. The individual crystallites may be transparent, but their facets (grain boundaries) reflect or scatter light resulting in diffuse reflection. Glass does not contain the internal subdivisions associated with grain boundaries in polycrystals and hence does not scatter light in the same manner as a polycrystalline material. The surface of a glass is often smooth since during glass formation the molecules of the supercooled liquid are not forced to dispose in rigid crystal geometries and can follow surface tension, which imposes a microscopically smooth surface. These properties, which give glass its clearness, can be retained even if glass is partially light-absorbing—i.e., colored.

Question: What, in contrast to glass, doesn't let light pass through?
Ans: polycrystalline materials


Here is a question about this article: As economic and demographic methods were applied to the study of history, the trend was increasingly to see the late Middle Ages as a period of recession and crisis. Belgian historian Henri Pirenne continued the subdivision of Early, High, and Late Middle Ages in the years around World War I. Yet it was his Dutch colleague, Johan Huizinga, who was primarily responsible for popularising the pessimistic view of the Late Middle Ages, with his book The Autumn of the Middle Ages (1919). To Huizinga, whose research focused on France and the Low Countries rather than Italy, despair and decline were the main themes, not rebirth.
What is the answer to this question: Which author popularized a pessimistic view of the Late Middle Ages in his 1919 book?
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So... Johan Huizinga


The problem: Answer a question about this article:
There were four major HDTV systems tested by SMPTE in the late 1970s, and in 1979 an SMPTE study group released A Study of High Definition Television Systems:
Who tested the four major HDTV systems in the late 1970's?
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The answer: SMPTE


Problem: Please answer a question about the following article about Infection:
Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed from one person to another. Frequent hand washing remains the most important defense against the spread of unwanted organisms. There are other forms of prevention such as avoiding the use of illicit drugs, using a condom, and having a healthy lifestyle with a balanced diet and regular exercise. Cooking foods well and avoiding foods that have been left outside for a long time is also important.
Avoiding drugs and using condoms are other forms of what?
A: prevention


Question: Read this and answer the question

Alsace-Lorraine was occupied by Germany in 1940 during the Second World War. Although Germany never formally annexed Alsace-Lorraine, it was incorporated into the Greater German Reich, which had been restructured into Reichsgaue. Alsace was merged with Baden, and Lorraine with the Saarland, to become part of a planned Westmark. During the war, 130,000 young men from Alsace and Lorraine were inducted into the German army against their will (malgré-nous) and in some cases, the Waffen SS. Some of the latter were involved in war crimes such as the Oradour-sur-Glane massacre. Most of them perished on the eastern front. The few that could escape fled to Switzerland or joined the resistance. In July 1944, 1500 malgré-nous were released from Soviet captivity and sent to Algiers, where they joined the Free French Forces.

Which group of people were released by the Russians to Algiers?
Answer: malgré-nous


Because of the vastness and diversity of the territory occupied by Slavic people, there were several centers of Slavic consolidation. In the 19th century, Pan-Slavism developed as a movement among intellectuals, scholars, and poets, but it rarely influenced practical politics and did not find support in some nations that had Slavic origins. Pan-Slavism became compromised when the Russian Empire started to use it as an ideology justifying its territorial conquests in Central Europe as well as subjugation of other ethnic groups of Slavic origins such as Poles and Ukrainians, and the ideology became associated with Russian imperialism. The common Slavic experience of communism combined with the repeated usage of the ideology by Soviet propaganda after World War II within the Eastern bloc (Warsaw Pact) was a forced high-level political and economic hegemony of the USSR dominated by Russians. A notable political union of the 20th century that covered most South Slavs was Yugoslavia, but it ultimately broke apart in the 1990s along with the Soviet Union.
The Russian Empire used what as justification for its territorial conquests?
Pan-Slavism