HD Chemistry Abbreviation

Histone Deacetylase

Hirschsprung Disease

A congenital abnormality of the bowel in which there is absence of the ganglia in the wall of the bowel. Nerves are missing starting at the anus and extending a variable distance up the bowel. This results in megacolon above the point where the nerves are missing. Hirschsprung disease is an important condition. It is the commonest cause of lower intestinal blockage in the newborn period and later in infancy and childhood, Hirschsprung disease is a cause of chronic constipation.

Sulfur Mustard

Hydrogen Damage

A general term for the embrittlement, cracking, blistering and hydride formation that can occur when hydrogen is present in some metals.  A type of corrosion occurring beneath a relative dense deposit. This type of damage can only occur if hydrogen was present in the metal. Failure takes place at thick edges in the form of fracture, rather then thinning. Hydrogen produces the corrosion reaction, moving into underlying metal, causing decarburization and intergranular fissuring of the structure.