Pulmonary arterial hypertension is a rare but severe disease with an estimated five-year survival rate of only 57% after diagnosis, according to the Registry to Evaluate Early And Long-term PAH disease management (REVEAL), which registers data from patients in the United States.
Concentration of elements in the ocean relative to the total concentration in the bulk silicate Earth (BSE). Of all the elements, only Cl and Br have a significant fraction in the ocean (see inset), indicating the extreme hydrophilic character for the heavier halogens.
The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt was used as early as 3000 BC and brine as early as 6000 BC. Around 1630, chlorine was recognized as a gas by the Flemish chemist and physician Jan Baptist van Helmont.