*49%*:**Student Learning In Upper-Level Thermal Physics: Comparisons And Contrasts With Students In Introductory Courses***45%*:**Student understanding of unit vectors and coordinate systems beyond cartesian coordinates in upper division physics courses***41%*:**Problem-based learning in upper division courses: Student successes, perceptions, and reactions***39%*:**Conceptual Understanding of Quantum Mechanics: An Investigation into Physics Students’ Depictions of the Basic Concepts of Quantum Mechanics***38%*:**An Investigation of Student Understanding of Basic Concepts in Special Relativity***38%*:**Student Perspectives on Using Clickers in Upper-division Physics Courses***38%*:**Upper-division student understanding of Coulomb's law: Difficulties with continuous charge distributions***38%*:**Initial understanding of vector concepts among students in introductory physics courses***38%*:**Student Estimates of Probability and Uncertainty in Advanced Laboratory and Statistical Physics Courses***37%*:**Investigating student ownership of projects in an upper-division physics lab course***36%*:**Introductory thermal concept evaluation: assessing students' understanding***36%*:**Evaluation of Students’ Understanding of Thermal Concepts in Everyday Contexts***36%*:**How do students in an innovative principle-based mechanics course understand energy concepts?***35%*:**Student difficulties with concepts related to entropy, heat engines and the Carnot cycle***34%*:**Improving Students' Understanding of Quantum Mechanics***34%*:**Investigating student understanding of basic quantum mechanics in the context of time-dependent perturbation theory***33%*:**Improving Students’ Understanding of Quantum Measurement***32%*:**Students’ Understanding of Stern Gerlach Experiment***32%*:**Improving students’ understanding of quantum measurement. II. Development of research-based learning tools**