Social capital and cyberpower in the African American community

What do the authors mean by the term "racial ravine"?
It refers to the difference in digital-divide among different races.

"The digital divide has turned into a "racial ravine" when one looks at access among households of different races and ethnic origins"(Social capital and cyberpower, p177)

What is "public computing"? What is a "Community Technology Center(CTC)?" Define

"In addition to home and work, people access computers and the Internet in public settings including government institutions (such as libraries and schools), commercial enterprises (such as copy shops and private business schools) and other venues making up the public sphere. We call this public computing." (p. 178)

"The community-technology centre is a generic name given to a computer lab open to the public." (p. 178)

The authors invoke Castells' "dual city"? What is it? Briefly identify.
Castells claimed the dual city is that

" By dual city I understand an urban system socially and spatially polarised between high value-making groups and functions on the one hand and devalued social groups and downgraded spaces on the other hand..The power of new information technologies, however, enhances and deepens features present in the social structure and in power relationships (p. 178)