Communication is key to any project team. Therefore, it is part of the project manager to facilitate an open environment for expressions of any concerns. One should first schedule a meeting with the PM to discuss the issue and then plan accordingly. I believe from personal experience setting up a meeting or having face to face meeting is best. Expressing concerns through text or email may not allow one to get the whole point across. A group meeting is a good idea and typically the PM should host weekly or biweekly meetings to discuss progress on the timeline. It is at this time that team members should address their concerns with the team.

If the PM is being unrealistic, a meeting should be scheduled to discuss potential ideas to meet deadlines. The PM should understand however not everyone is created equal. Sometimes, the research scientist or anyone may not have a choice and will have to get the work done. If at all possible, maybe communicate and ask for help from another scientist in the department.