One remedy for a deficiency of vitamin B12 for the elderly is a regular injection of this important nutrient. The vitamin B12 injection dose depends on factors such as gender and age.
Hydrogen bonds happen in alcohols. As a matter of fact, any molecule that contains a hydrogen atom attached to an atom of nitrogen or oxygen is capable of such a bond. Ethanol is one such alcohol that features hydrogen bonds. Ammonia is an example of hydrogen bonding. In the case of ammonia, however, the hydrogen bond happens to be relatively weak.
This terminology is used in reference to bicyclicsystems such as the norbornane molecule shown below. The rigidity of these systems makes hydrogens (a) and(b) stereochemically nonequivalent. The exo hydrogen points outward from the ring, and the endo hydrogen pointsdownward, opposite to the bridge, as shown.