Are there databases specializing in scientific data I am currently comparing file formats (HDF5 , etc.) to DBMS systems for a scientific data repository.

I know of proprietary solutions such as Oracle extensions, but are there open source/free systems for scientific data? I would define that as a system that would have the MKSA unit system integrated, and an extensive library of scientific conversions/operations.
SciDB is an open-source DBMS for scientific data.