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.
Thatâs why itâs typically used for those weld applications in which higher heat input is needed for improved wetting of the weld bead. The gas also is useful for enabling a higher travel speed. Helium typically is mixed with varying amounts of argon in shielding gas blends to take advantage of both gasesâ good characteristics.