Dr. Monica Bharel, the chief medical officer for the Boston Health Care for the Homeless Program, will take over for Cheryl Bartlett as commissioner of the Department of Public Health, overseeing a broad array of programs, including the implementation of medical marijuana. Bharel earned her medical degree from Boston University and a graduate degree in public health from Harvard University. “Doctor Bharel has an impressive background as a physician serving the homeless, some of the most vulnerable citizens of the commonwealth,” said Marylou Sudders, the incoming health and human services secretary.