Problem: A P-N junction can convert absorbed light energy into a proportional electric current. The same process is reversed here (i.e. the P-N junction emits light when electrical energy is applied to it). This phenomenon is generally called electroluminescence, which can be defined as the emission of light from a semi-conductor under the influence of an electric field. The charge carriers recombine in a forward-biased P-N junction as the electrons cross from the N-region and recombine with the holes existing in the P-region. Free electrons are in the conduction band of energy levels, while holes are in the valence energy band. Thus the energy level of the holes will be lesser than the energy levels of the electrons. Some portion of the energy must be dissipated in order to recombine the electrons and the holes. This energy is emitted in the form of heat and light.
Why is some energy in the electroluminescence process emitted as heat and light?
The answer is the following: to recombine the electrons and the holes

Problem: The clergy was divided into two types: the secular clergy, who lived out in the world, and the regular clergy, who lived under a religious rule and were usually monks. Throughout the period monks remained a very small proportion of the population, usually less than one per cent. Most of the regular clergy were drawn from the nobility, the same social class that served as the recruiting ground for the upper levels of the secular clergy. The local parish priests were often drawn from the peasant class. Townsmen were in a somewhat unusual position, as they did not fit into the traditional three-fold division of society into nobles, clergy, and peasants. During the 12th and 13th centuries, the ranks of the townsmen expanded greatly as existing towns grew and new population centres were founded. But throughout the Middle Ages the population of the towns probably never exceeded 10 per cent of the total population.
From what class were many parish priests?
The answer is the following: the peasant class

Problem: Mexico City is Latin America's leading center for the television, music and film industries. It is also Mexico's most important for the printed media and book publishing industries. Dozens of daily newspapers are published, including El Universal, Excelsior, Reforma and La Jornada. Other major papers include Milenio, Cronica, El Economista and El Financiero. Leading magazines include Expansion, Proceso, Poder, as well as dozens of entertainment publications such as Vanidades, Quien, Chilango, TV Notas, and local editions of Vogue, GQ, and Architectural Digest.
How many entertainment magazines are published in Mexico City?
The answer is the following: dozens

Problem: In 1989, Gaddafi was overjoyed by the foundation of the Arab Maghreb Union, uniting Libya in an economic pact with Mauritania, Morocco, Tunisia and Algeria, viewing it as beginnings of a new Pan-Arab union. Meanwhile, Libya stepped up its support for anti-western militants such as the Provisional IRA, and in 1988, Pan Am Flight 103 was blown up over Lockerbie in Scotland, killing 243 passengers and 16 crew members, plus 11 people on the ground. British police investigations identified two Libyans Abdelbaset al-Megrahi and Lamin Khalifah Fhimah as the chief suspects, and in November 1991 issued a declaration demanding that Libya hand them over. When Gaddafi refused, citing the Montreal Convention, the United Nations (UN) imposed Resolution 748 in March 1992, initiating economic sanctions against Libya which had deep repercussions for the country's economy. The country suffered an estimated $900 million financial loss as a result. Further problems arose with the west when in January 1989, two Libyan warplanes were shot down by the U.S. off the Libyan coast. Many African states opposed the UN sanctions, with Mandela criticising them on a visit to Gaddafi in October 1997, when he praised Libya for its work in fighting apartheid and awarded Gaddafi the Order of Good Hope. They would only be suspended in 1998 when Libya agreed to allow the extradition of the suspects to the Scottish Court in the Netherlands, in a process overseen by Mandela.
Along with Libya, Morocco, Tunisia and Algeria, who was a founding member of the Arab Maghreb Union?
The answer is the following:
Mauritania