Outpatient visits: A screening visit will be scheduled when a participant expresses interest in the study and is deemed potentially eligible by the study coordinator after a telephone interview. At the screening visit, a study physician will obtain informed consent. Thereafter, a study physician will conduct a history and physical examination, and phlebotomy will be performed. Female subjects will provide urine for pregnancy testing. The purpose of the screening visit is to evaluate potential volunteers based upon the inclusion and exclusion criteria listed above, and to explain the purpose and procedures of the study to the volunteers. If someone is eligible and willing, a baseline inpatient visit will be scheduled.