A preprint is a complete scientific manuscript that is uploaded by the authors to a public server.  The preprint contains complete data and methodologies; it is often the same manuscript being submitted to a journal.  After a brief quality-control inspection to ensure that the work is scientific in nature, the author‚s manuscript is posted within a day or so on the Web without peer review and can be viewed without charge by anyone in the world. Based upon feedback and/or new data, new versions of your preprint can be submitted; however, prior preprint versions are also retained.  Preprint servers allow scientists to directly control the dissemination of their work to the world-wide scientific community. In most cases, the same work posted as preprint also is submitted for peer review at a journal.  Thus, preprints (rapid, but not validated through peer-review) and journal publication (slow, but providing validation using peer-review) work in parallel as a communication system for scientific research.
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