Ch 3 it 1 edit mcb

Chapter 3 second half iteration 1 edits
Ch3 it 1b edit dcn

Based on comments from David Noone
Ch 3 it 1b edit mcb

Final iteration 1 edits for last sections of chapter 3 and chapter 4
according to comments by Mary Barth
Shorten abstract

Shortened to the 350-word limit