Q: Why have some Springer Nature journals not published recently accepted articles?

Firstly, what you are stating is partly true. It’s true for MMI and Journal of the Brazilian Society of Mechanical Sciences and Engineering, where the last published article has the date of November 27. However, The International Journal of Advanced Manufacturing Technology has published a few articles since then, both paywalled and open access (OA), as is clear on their homepage here.

Anyway, what you have observed is perhaps due to the fact that all these journals are now transformative (hybrid) journals, as it states on all their homepages. What this means is that these journals were previously only subscription-based but now offer an option for publishing open access (OA), with the aim to eventually becoming fully OA. With these journals, the author is given the option to choose 'OA' or 'subscription' at the time of submission. So, based on the option your friend and other authors chose (that is, if they didn’t choose OA), their articles may show up on the site later after the end of the embargo period, during which an accepted article is not released for a wider audience.

Find out more about Springer Nature’s transformative journals (TJs) here. On the page, you’ll find a link to download their list of TJs. In the downloaded Excel sheet, on searching, you’ll find the above-mentioned journals listed with other details. About the publisher’s decision to go more OA, you may find this earlier news piece informative: Springer Nature commits to joining Plan S to offer open access routes

Also, while many journals refer to ‘transformative’ and ‘hybrid’ journals interchangeably, there are slight differences between the two. Quite simply, a transformative journal seeks to eventually go fully OA, whereas a hybrid journal offers both subscription and OA options for publishing and may not later become fully OA, choosing instead to remain a hybrid. For more information about these differences, you may download the infographic linked on the same page, or simply view it here.

So, if your friend’s article is indeed under embargo (because he chose not to publish OA), you may write to the journal seeking to know when the embargo period would end and thus when the article would be available for all to view. However, do note that as the holiday period has begun, you may not hear back from them until the second or even the third week of January.

Anyway, hope the matter is sorted out eventually. Until then, for further insights into OA publishing, you may wish to go through the following resources.

• A guide to open access publishing
• Choosing a legitimate open access journal
• "Open" for questions: A curated list of OA queries we've answered