Cloning and characterization of an endo--1,4-xylanase gene from Colletotrichum lindemuthianum and phylogenetic analysis of similar genes from phytopathogenic fungus

Abstract

Accurate recovery of an absorption lineshape is important in many industrial applications for simultaneous measurement of gas concentration and pressure or temperature. Here, we demonstrate a method, based on a modification to the Hobbs balanced receiver circuit, for background signal nulling when external amplitude modulation of the laser output is used. Compared with direct or non-nulled detection techniques, we demonstrate that the method significantly improves the signal-to-noise ratio to a level comparable with that of the conventional second harmonic wavelength modulation spectroscopy. Most importantly, normalisation and recovery of the lineshape is straightforward and immune to the difficulties that afflict lineshape recovery with the conventional wavelength modulation spectroscopy.