Please book your own travel. If you hope to get supported for airfare by the U.S. National Science Foundation, please use a U.S. flag carrier (or code share flights with U.S. flag carrier flight numbers, e.g., United airlines UA 8852 instead of Lufthansa LH 423), and make sure the ticket is from a U.S. flag carrier.
This website describes how to get to Tufts from the airport and South Station (the Amtrak station in Boston). The Silver Line from the airport is free. However, you need a Charlie Ticket or Charlie Card to use the other buses and subways.
At the Airport: Charlie Tickets are valid for travel on the subway and local bus routes. You can buy them at fare vending machines in the terminals at Logan Airport, at the Airport Station, and at South Station and any other subway station.
This website is an overview of Charlie Tickets and the 7-Day Link Pass as well as other info about the T, our mass transit system.