A method for purification of a gaseous stream having at least one impurity in which a porous material having at least one polyoxometalate-based material is contacted with the gaseous stream and the at least one impurity is passed through the porous material, producing a purified gaseous stream. In the described embodiment, the transilluminator includes a transmittance plate adapted to support the specimen being tested, and an array of LEDs adapted to emit light through the plate for illumination of the specimen. The display component produces at least one of an optical characteristic change and a light emission. The brake lever and the release lever are further configured relative to the bracket for smooth easy operation by the rider. Upon extension the segments form an interference fit with each adjacent interior and exterior segment forming a rigid handle. 232; \u201ca\u201d is 0\u2266a\u22661; \u201cb\u201d is 0\u2266b\u22661; \u201c\u03b4\u201d is 0.