Reasons for attrition were mostly unknown since, for ethical reasons, all participants had the right to withdraw at any stage without any explanation.
The cause for most Alzheimer's cases is still mostly unknown except for 1% to 5% of cases where genetic differences have been identified.
Glimmerglass, Lake George, and the Lincoln Center Festival all fielded mostly young, mostly unknown casts for their productions, proving that celebrity singers aren't needed to attract audiences to new opera.
But you chose mostly unknown actors for the film.
As a result of their isolation from other horses, disease in the breed within Iceland is mostly unknown, except for some kinds of internal parasites.
However, the underlying genetic mechanism in Saturniidae silkmoth silk coloration are mostly unknown, except for A. yamamai and R. fugax, which both have an endogenous pigment known as blue bilin alongside the yellow carotenoids involved in cocoon coloration [ 45, 46].
Boolean algebra and Peirce's work remained mostly unknown and unused for (too) many years, until the 1940s, when a young student by the name of Claude Elwood Shannon picked up Boole's and Peirce's works and recognized their relevance to electronics design.
