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This paper presents an algorithm for the efficient numerical analysis and simulation of contact/impact problems in tree topology multi-rigid-body dynamic systems. The algorithm can accommodate the jumps in structure which occur in the equations of motion of general multi-rigid-body tree systems due to a contact/impact event between bodies, or due to the locking of joints. The presented method uses a generalized momentum balance approach to determine the velocity jumps which take place across impacts in such multibody dynamic systems, and where necessary explicitly determines impact impulsive loads (both working and non-working). The presented method does not suffer from the performance (speed) penalty encountered by most other momentum balance methods given its O(n) overall cost, and exact direct embedded consideration of the all constraints. Due to these characteristics, the presented algorithm offers superior computing performance relative to other methods in situations involving both large n and potentially many unilateral constraints.

The ethylene oxide (EO) product test of sterility (ToS) can be conducted to comply with ANSI/AAMI/ISO 11135:2014 for the generation of data to demonstrate the appropriateness of the biological indicator (BI) that is used to develop and qualify the EO sterilization process. Clause D.8.6 of 11135 provides an option to perform a sublethal EO process, followed by conducting a product ToS, performing sterility testing of BIs from the process challenge device, and comparing the test results. Certain limitations for the EO product ToS should be considered when conducting studies that feature the use of this test, in order to support compliance with this requirement. Limitations for any sterility test include sample size, testing frequency, detection sensitivity, and/or the potential for false-positive/false-negative results, each of which must be recognized and well understood in order to support compliance with the standard. In addition, the experimental design of any study featuring the use of a sterility test should be carefully developed to ensure the generation of scientifically sound results and conclusions to support the study objective.

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