prepare for elsevier 2: change documentclass
prepare for elsevier 2: use yjsco
prepare for elsevier 2: remove defn
prepare for elsevier 2: use frontmatter instead of maketitle
prepare for elsevier 2: use \ead instead of \email
prepare for elsevier 2: change keywords command
prepare for elsevier 2: change title
prepare for elsevier 2: use environment 'ack'
prepare for elsevier 2: do not use \boldsymbol