Professors keep up with developments in their field by reading scholarly articles, talking with colleagues, and participating in professional conferences. To gain tenure (a guarantee that a professor cannot be fired without just cause), they must do research, such as experiments, document analysis, or critical reviews, and publish their findings. Full-time professors, particularly those who have tenure, often are expected to spend more time on their research. They also may be expected to serve on more college and university committees. Part-time professors, often known as adjunct professors, spend most of their time teaching students.