The post-edge background was removed by using a derivative method [28,29].
Pre-edge background subtraction and XANES normalization were carried out by fitting a linear polynomial to the pre-edge region and a quadratic polynomial to the postedge region of the absorption spectrum.
A linear pre-edge background function was subtracted from the averaged spectrum, and normalization was performed at an energy value above the absorption edge (11,915 eV), as described by Bhandari et al. [50].
Then, for increasing the difference between edges, background and noise, the fuzzy enhancement operator which takes not only the wavelet module magnitude into account, but also the wavelet gradient direction is designed.
Looking at the XEOL-XANES, we see that there is a 7% decrease in the pre-edge background, between the first and second spectra, with a corresponding decrease in the postedge average.
EELS was used to identify the oxidation state of the Cu-containing particles (Additional file 1: Figure S1), which shows the spectrum of a Cu-containing particle with the pre-edge background subtracted.
Comparison between XANES and XEOL-XANES for the cuprite and copper samples shows that the pre-edge background in the XEOL-XANES comes from emission channels, which are blocked with the onset of K-level ionization.
The geometrical similarity of the edge and postedge regions in both types of spectrum (especially the similar relative positions of the midedge feature) shows that, as for copper, the pre-edge background in the XEOL-XANES comes from emission channels which turn off at the edge.
General Settings allows for changing the directory that contains domain information (e.g., property information file used in the property-based clustering), a VizMapper file (a file used by Cytoscape to describe visual appearances of nodes, edges, background, etc)., and a graph layout algorithm used when loading networks.
Using the same threshold Th generated from the character histogram, the text, edge, and background regions are identified to extract the noise energy and average gradient features.
