A distance between a cursor and an object displayed on a Web page or other image automatically controls a volume with which an audio file associated with the object is played. Preferably, the virus does not produce a functionally active wild-type gC polypeptide coded for the UL44 gene. The music preference data may be generated by storing user interactions with specific songs. Crosslinked polymer particles and crosslinked polymer particles comprising a polymer and a bioactive material are also provided. Additionally an external pulse oximeter for small rodents, such as mice, provides measurements on a hand or foot of the rodent with a sensor configured to avoid shunting around the rodent appendage, and configured for high heart rates of the subjects.