Study is the challenge study in which samples were collected, see Kirby et al. PLOS One 2015 for study references.  Subject is the subject study ID.  Sample is the sample ID.  Time is the time the sample was produced in hours, time of challenge is t=0.  Volume is sample volume in mL.  Titer is viral concentration in genomic equivalent copies/mL.  pH is sample pH.  Missing measurements are indicated with ..  ND indicates that virus was not detected in that sample.  
