Question: Most common glass contains other ingredients to change its properties. Lead glass or flint glass is more 'brilliant' because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses.[citation needed] Iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs UV wavelengths.
Is there an answer to this question: What property of thorium oxide has caused it to no longer be used in projectors?

Answer: unanswerable


Question: The art of writing Chinese characters is called Chinese calligraphy. It is usually done with ink brushes. In ancient China, Chinese calligraphy is one of the Four Arts of the Chinese Scholars. There is a minimalist set of rules of Chinese calligraphy. Every character from the Chinese scripts is built into a uniform shape by means of assigning it a geometric area in which the character must occur. Each character has a set number of brushstrokes; none must be added or taken away from the character to enhance it visually, lest the meaning be lost. Finally, strict regularity is not required, meaning the strokes may be accentuated for dramatic effect of individual style. Calligraphy was the means by which scholars could mark their thoughts and teachings for immortality, and as such, represent some of the more precious treasures that can be found from ancient China.
Is there an answer to this question: What is not required?

Answer: strict regularity


Question: On August 17, 2011, Shueisha's V-Jump magazine announced a sequel set one year later, a third arc of Xros Wars subtitled The Young Hunters Who Leapt Through Time, which aired from October 2, 2011 to March 25, 2012, following on from the previous arc. It focuses on a new protagonist, Tagiru Akashi and his partner Gumdramon who embark on a new journey with an older Mikey, Shoutmon, an older Ewan and the revived Damemon, along with other new comrades as they deal with a hidden dimension that lies between the Human World and the Digital World called DigiQuartz. The series finale reintroduces the heroes of the previous five seasons as they all come together and help the current heroes in the final battle due to the fact that the DigiQuartz is essentially a tear in Space and Time, allowing all of the Digimon universes to converge.
Is there an answer to this question: When was the sequel announcement for the third arc?

Answer: August 17, 2011


Question: The post-Imperial nature of Russian subdivision of government changed towards a generally autonomous model which began with the establishment of the USSR (of which Russia was governed as part). It was liberalized in the aftermath of the Soviet Union, with the reforms under Boris Yeltsin preserving much of the Soviet structure while applying increasingly liberal reforms to the governance of the constituent republics and subjects (while also coming into conflict with Chechen secessionist rebels during the Chechen War). Some of the reforms under Yeltsin were scaled back by Vladimir Putin.
Is there an answer to this question: When was Russia's subdivision liberalized?

Answer:
in the aftermath of the Soviet Union