The Byzantine Empire ruled the northern shores of the Sahara from the 5th to the 7th centuries. After the Muslim conquest of Arabia (Arabian peninsula) the Muslim conquest of North Africa began in the mid-7th to early 8th centuries, Islamic influence expanded rapidly on the Sahara. By the end of 641 all of Egypt was in Muslim hands. The trade across the desert intensified. A significant slave trade crossed the desert. It has been estimated that from the 10th to 19th centuries some 6,000 to 7,000 slaves were transported north each year.
What time period did the Muslim conquest of North Africa take place?
mid-7th to early 8th centuries

The securitization markets supported by the shadow banking system started to close down in the spring of 2007 and nearly shut-down in the fall of 2008. More than a third of the private credit markets thus became unavailable as a source of funds. According to the Brookings Institution, the traditional banking system does not have the capital to close this gap as of June 2009: "It would take a number of years of strong profits to generate sufficient capital to support that additional lending volume." The authors also indicate that some forms of securitization are "likely to vanish forever, having been an artifact of excessively loose credit conditions."
How many years would of strong profit would it take to generate enough capital to support additional lending?
a number of years

Beginning in the late 1910s and early 1920s, Whitehead gradually turned his attention from mathematics to philosophy of science, and finally to metaphysics. He developed a comprehensive metaphysical system which radically departed from most of western philosophy. Whitehead argued that reality consists of processes rather than material objects, and that processes are best defined by their relations with other processes, thus rejecting the theory that reality is fundamentally constructed by bits of matter that exist independently of one another. Today Whitehead's philosophical works particularly Process and Reality are regarded as the foundational texts of process philosophy.
What did Whitehead first study?
mathematics