Main-group element Main-group element In chemistry and atomic physics, the main group is the group of elements whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arranged in the periodic table of the elements. The main group includes the elements (except hydrogen, which is sometimes not included) in groups 1 and 2 (s-block), and groups 13 to 18 (p-block). The s-block elements are primarily characterised by one main oxidation state, and the p-block elements, when they have multiple oxidation states, often have common oxidation states separated by two units. Main-group elements (with some of the
Finite element machine (NASA TM 84514). Based on the Finite Element Machine's success in demonstrating Parallel Computing viability, (alongside ILLIAC IV and Goodyear MPP), commercial parallel computers soon were sold. NASA Langley subsequently purchased a Flex/32 Multicomputer (and later Intel iPSC and Intel Paragon) to continue parallel finite element algorithm R&D. In 1989, the parallel equation solver code, first prototyped on FEM, and tested on FLEX was ported to NASA's first Cray YMP via Force (Fortran for Concurrent Execution) to reduce the structural analysis computation time for the space shuttle Challenger Solid Rocket Booster resdesign with 54,870 equations from 14 hours to 6