Sentence:  The increase in oxygen uptake rates from 1.2 to 2.6 mg / <WSD>l</WSD> / hr which followed an increase in rotor speed was believed to be related to resuspension of solids which had settled at the lower rotor speeds . 
Meaning of the word marked with <WSD> tags:  a metric unit of capacity, formerly defined as the volume of one kilogram of pure water under standard conditions; now equal to 1,000 cubic centimeters (or approximately 1.75 pints)