Jonas is a veteran of the war in iraq. he suffers from ptsd. now, back home in a quiet california neighborhood, he jumps when he hears a firecracker or a car backfire. in the terminology of classical conditioning, these sounds are best thought of as stimuli.

the aksumite empire was an ancient kingdom located in what is now northern ethiopia from the period of 100 ad to 940 ad. its capital was the city of aksum. the kingdom established itself as one of the 4 great powers at its time, along with persia, rome, and china.

the kingdom was rich in goods like gold, iron, and salt. it established strong commercial ties with the regions governed by rome, egypt, and persia (arabia). aksum was a key location in this commercial network. trade was also facilitated with the introduction of the aksumite currency.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.