Riesling grapes are naturally very high in acid, and the cool, northern climate of Germany means this ripping acid stays in the grapes even into the fall harvest season. So winemakers let the fermentations stop before the wine is completely dry, retaining a little sweetness in order to strike balance in the wine.
Oxygenation refers to the process of adding oxygen to the body system. There is no way to reliably measure arterial oxygenation via clinical signs alone. Cyanosis, pallor and other physical findings are not reliable.
Hydrogenation is the chemical name for the addition of hydrogen to an existing molecule, usually an organic molecule which has a doubl-bond between two carbon atoms. That bond is broken and a hydrogen atom binds to each of the free bonds on adjacent carbon atoms. H2C=CH2 becomes H3C-CH3.