Techniques are disclosed for concurrently maintaining serialized objects that were created from more than one version of a class definition. The invention also provides a computer system, a website and an IC chip incorporating the program product. Centrifugal force ensures that debris in the oil or coolant is forced to the bottom of the weir where it is trapped. In a further embodiment, a surrogate of cardiac afterload is determined based on a metric of a terminal portion of an arterial PPG waveform. The new variety is well suited for growing as distinctive ornamentation in smaller gardens and along walkways.