Problem: The structure of QD-LEDs used for the electrical-excitation scheme is similar to basic design of OLEDs. A layer of quantum dots is sandwiched between layers of electron-transporting and hole-transporting materials. An applied electric field causes electrons and holes to move into the quantum dot layer and recombine forming an exciton that excites a QD. This scheme is commonly studied for quantum dot display. The tunability of emission wavelengths and narrow bandwidth is also beneficial as excitation sources for fluorescence imaging. Fluorescence near-field scanning optical microscopy (NSOM) utilizing an integrated QD-LED has been demonstrated.
What is one material used in electrical-excitation?
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Answer: hole-transporting materials

Problem: Prior to the emergence of Kievan Rus' in the 9th century AD, the lands between the Baltic Sea and Black Sea were primarily populated by eastern Slavic tribes. In the northern region around Novgorod were the Ilmen Slavs and neighboring Krivichi, who occupied territories surrounding the headwaters of the West Dvina, Dnieper, and Volga Rivers. To their north, in the Ladoga and Karelia regions, were the Finnic Chud tribe. In the south, in the area around Kiev, were the Poliane, a group of Slavicized tribes with Iranian origins, the Drevliane to the west of the Dnieper, and the Severiane to the east. To their north and east were the Vyatichi, and to their south was forested land settled by Slav farmers, giving way to steppelands populated by nomadic herdsmen.
Which tribe resided in the south?
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Answer: Poliane

Problem: On October 11, 1944, the Tuvan People's Republic joined the Russian SFSR as the Tuvan Autonomous Oblast, in 1961 becoming an Autonomous Soviet Socialist Republic.
What was the Tuvan People's Republic renamed when it exited the RSFSR?
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Answer:
unanswerable