\documentclass{ppex}
\nonstopmode
\usepackage [all,knot,poly,dvips]{xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [all,knot,poly,dvips]{xy}
\[
\UseTips
\knotholesize{2mm}
\xygraph{!{0;/r1cm/:}
  !P5"p"{~>{.}}
  !P10"d"{~:{(1.7,0):}~>{.}}
  !P20"D"{~={-9}~:{(2.2,0):}~>{.}}
  !{\xunderv~{"d3"}{"d2"}{"p2"}{"p1"}}
  !{\xunderv~{"d5"}{"d4"}{"p3"}{"p2"}}
  !{\xunderv~{"d7"}{"d6"}{"p4"}{"p3"}}
  !{\xunderv~{"d9"}{"d8"}{"p5"}{"p4"}}
  !{\xunderv~{"d1"}{"d10"}{"p1"}{"p5"}}
  !{\vloop~{"D3"}{"D2"}{"d2"}{"d1"}|>|{a}}
  !{\vloop~{"D7"}{"D6"}{"d4"}{"d3"}|>|{b}}
  !{\vloop~{"D11"}{"D10"}{"d6"}{"d5"}|>|{c}>}
  !{\vloop~{"D15"}{"D14"}{"d8"}{"d7"}|>|{d}}
  !{\vloop~{"D19"}{"D18"}{"d10"}{"d9"}|>|{e}}
}\]
\end{document}