Although your dissertation has been published in ProQuest Dissertations & Theses, you are still the copyright holder.
As long as you hold the copyright, you are able to decide how your dissertation may be made available (e.g., reworked into a book, divided into a few journal articles, presented at a poster session, etc.). For additional information, please see Copyright and Your Dissertation or Thesis: Ownership, Fair Use, and Your Rights and Responsibilities.
Note, however, that you will need to ensure that you have permission to reproduce images, test instruments, etc. in other formats. This may require contacting the author or copyright holder of the work.
For additional information, please see the following resources: