QUES: Addition of lead(II) oxide lowers melting point, lowers viscosity of the melt, and increases refractive index. Lead oxide also facilitates solubility of other metal oxides and is used in colored glasses. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glasses); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb2+ ion renders it highly immobile in the matrix and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs 106.5 Ohmcm, DC at 250 C). For more details, see lead glass.
What makes glass melt at a lower temperature?

ANS: lead(II) oxide

QUES: Uranium-235 was the first isotope that was found to be fissile. Other naturally occurring isotopes are fissionable, but not fissile. On bombardment with slow neutrons, its uranium-235 isotope will most of the time divide into two smaller nuclei, releasing nuclear binding energy and more neutrons. If too many of these neutrons are absorbed by other uranium-235 nuclei, a nuclear chain reaction occurs that results in a burst of heat or (in special circumstances) an explosion. In a nuclear reactor, such a chain reaction is slowed and controlled by a neutron poison, absorbing some of the free neutrons. Such neutron absorbent materials are often part of reactor control rods (see nuclear reactor physics for a description of this process of reactor control).
What isotope of uranium was the first to be found fissile?

ANS: 235

QUES: On February 8, 1847, Doniphan continued his march with 924 men mostly from Missouri; he accompanied a train of 315 wagons of a large commercial caravan heading to the state capital. Meanwhile, the Mexican forces in the state had time to prepare a defense against the Americans. About 20 miles (32 km) north of the capital where two mountain ranges join from east to west is the only pass into the capital; known as Sacramento Pass, this point is now part of present-day Chihuahua City. The Battle of Sacramento was the most important battle fought in the state of Chihuahua because it was the sole defense for the state capital. The battle ended quickly because of some devastating defensive errors from the Mexican forces and the ingenious strategic moves by the American forces. After their loss at the Battle of Sacramento, the remaining Mexican soldiers retreated south, leaving the city to American occupation. Almost 300 Mexicans were killed in the battle, as well as almost 300 wounded. The Americans also confiscated large amounts of Mexican supplies and took 400 Mexican soldiers prisoners of war. American forces maintained an occupation of the state capital for the rest of the MexicanAmerican War.
How many men did he have?

ANS: 924

QUES: Logan Airport, located in East Boston and operated by the Massachusetts Port Authority (Massport), is Boston's principal airport. Nearby general aviation airports are Beverly Municipal Airport to the north, Hanscom Field to the west, and Norwood Memorial Airport to the south. Massport also operates several major facilities within the Port of Boston, including a cruise ship terminal and facilities to handle bulk and container cargo in South Boston, and other facilities in Charlestown and East Boston.
Who operates Logan Airport?

ANS:
Massport