Spring is usually the season for Ticemed conferences. The twelfth in the series, Ticemed12, prepared at Panteion University of Athens for April 7-9, 2020 had to be canceled days before its opening due to the Covid-19 pandemic. Months of work by speakers, reviewers and organizers risked being erased altogether. However, it is a tradition in these conferences to publish the texts of the lecturers in pre-proceedings before the conference is held. The upheavals of the past year did not make it possible to publish within those deadlines, but it seemed essential for the organizers and the Ticemed community to carry out the equivalent of preprints and to make them available to the public on the net. This is the subject of this volume. Although the conditions are exceptional, it should be remembered that the texts of the papers collected here have been double-blind evaluated and selected by a scientific committee in accordance with the usual rules of ethics. They were received after a call for papers which sets out the scientific and organizational framework for the conference.