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 other areas of manufacturing, the goal may be simply to limit the use of helium. Lyttle pointed out the use of a CO 2 laser for welding applications as an example. Traditionally, helium is used as a shielding gas in CO 2 laser welding, but it is supplied in a less-than