Lasers can cause damage in biological tissues, both to the eye and to the skin, due to several mechanisms. Thermal damage, or burn, occurs when tissues are heated to the point where denaturation of proteins occurs. Another mechanism is photochemical damage, where light triggers chemical reactions in tissue.
March 9: Teams are allowed to begin negotiating with other teamsâ players who are set to become unrestricted free agents at the end of the league year. This is the first time the NFL is providing a window to negotiate with other teamsâ free agents prior to the start of free agency.
Getty Images. Photo: A look at the most important dates on the calendar for NFL teams in the spring of 2015: Saturday, March 7: Free agency begins as teams are allowed to contact and enter into contract negotiations with agents of players who will officially become unrestricted free agents at 4 p.m. on March 10. Tuesday, March 10: Player contracts can be executed with new clubs at 4 p.m.