By the mid-30s sperm quality is declining in men and no differences are seen in the proportion of the four kinds of sperm defects between fertile and infertile men. Possible anatomic causes include epididymal obstruction, obstruction of the ejaculatory duct, ejaculatory dysfunction, and abnormal sperm production.
A study of sperm'swim fast genes' or Na+/K+-ATPase components has shown unusual divergent patterns of segregation amongst sibling trios. A higher proportion of infertile men have defective semen quality and these defects do not show a random pattern along the genome. Male infertility accounts for 15 to 20% of infertility. The aetiology of male sterility is unknown in up to 80% of cases, with aetiological causes including teratozoospermia, and chromosomal aberrations.
Graphene forms a hexagonal (6- or graphitic) structure when it is folded by sp2 hybridization forces. In other states, it takes the form of sp3 hybridization or turbostratic. It is known technically as "stacking-faulted bilayer graphene."  The stacking faults are carbon atoms arranged into an orderly hexagonal structure at a point where there are vacancies in an adjacent hexagonal carbon layer. d2c66b5586