The present invention relates to certain 2-pyrimidine compounds and pharmaceutically acceptable salts thereof which may be useful in the treatment or prevention of a disease or medical condition mediated through certain mutated forms of epidermal growth factor receptor. The method involves the use of, for example, indocyanine green. The fluid enters the chamber via a controllable flow path and interacts with the impeller and chamber walls to cool and lubricate the impeller. In such methods, a suitable agent is A\u03b2 peptide or an antibody thereto. The theory and use of at least these concepts are introduced by examining how these concepts aid the construction and use of a non-contact laser scanning system. A thin window that is transparent to electrons but impervious to gases is needed in order to prolong the life of the tube and allow the extraction of the electrons.