The present invention relates to the use of compounds of formula wherein all substituents are as defined in the claims as optical brighteners as well as to new mixtures of optical brighteners. The nonvolatile memory device includes a memory cell, a first transistor, a second transistor, and a latch circuit. Fluid may also be infused or injected into the tissue region through at least one needle. In another implementation, the computers are secured within each of the cluster modules in a horizontal orientation. The wire defines a loop portion and two leg portions.