A method and an apparatus for preparing and culturing cells, particularly bone marrow stromal cells. The method includes providing measurements of vehicle yaw-rate, lateral acceleration, longitudinal speed, and steering angle. The microfluidic devices are useful in methods for analyzing a wide variety of chemical and biological assays such as, for example, molecule-molecule interactions, enzyme-substrate interactions, molecule identification, minimum inhibitory concentrations, therapeutically effective amounts, and toxic amounts. The system also utilizes a single reference oscillator to drive the various frequency synthesizers and the like. Specifically, the present invention provides compounds represented by the following formula, and pharmaceutically acceptable salts thereof:wherein X, R1, R2, R3, R4, R5, R6, R7, L1, L2, and L3 are as defined in the specification. The primary index and any derivative indices may be ranked according to one or more selection criteria, either before or after derivative indices are constructed.