A pulmonary nodule is a discrete opacity in the lung which may be caused by: 1  Neoplasm: benign or malignant. 2  Granuloma: tuberculosis. 3  Infection: roundish pneumonia. 4  Vascular: infarct, varix, granulomatosis with polyangiitis, rheumatoid arthritis.
1 Helium is also commonly used to pressurize and purge systems of unwanted gases. 2  It is also used in controlled atmospheres when the levels of different gases have to be kept constant. 3  It is used as a protective gas when growing silicon and germanium crystals and when producing titanium and zirconium.
In chemistry, compressed helium is used as a carrier gas for an instrument called a Gas Chromatograph. Its role is propel other molecules through a long tube where they gradually separate and then are detected at the end. It is used because it is so inert and won't interfere with the molecules you're trying to detect. Compressed helium is also used to produce an extremely cold environment. Scientists can almost reach absolute zero with compressed helium. davenpoc Â· 7 years ago.