The triple turreted castle has been in use by the Corps of Engineers since it was adopted in 1840. Prior to that time an insignia of a similar design was worn on the uniforms of the Corps of Cadets of the United States Military Academy since the Academy was under the supervision and direction of the Chief of Engineers.
The most common cause of energy crisis is a drop of cerebral perfusion (global ischemia), usually resulting from cardiac arrest or severe hypotension (shock). Sustained severe hypoglycemia, and seizures lasting 1-2 hours also cause permanent brain damage. Pure hypoxia in clinical settings is unusual.
Ischemia is caused by problems with the circulatory system causing damage or dysfunction of oxygen sensitive tissues. Most tissues cannot survive more than few minutes without a continuous oxygen supply. Lack of oxygen leads to a process known as Ischemic cascade. The damage is caused by the accumulation of metabolic waste products, damage to cell membranes, mitochondrial (powerhouse of the cell) dysfunction.