Noise and fluorescent background are two major problems for acquiring Raman spectra from samples, which blur Raman spectra and make Raman detection or imaging difficult. In this paper, a novel algorithm based on wavelet transform that contains denoising and baseline correction is presented to automatically extract Raman signals. For the denoising section, the improved conventional-scale correlation denoising method is proposed. The baseline correction section, which is performed after denoising, basically consists of five aspects: (1) detection of the peak position; (2) approximate second derivative calculation based on continuous wavelet transform is performed using the Haar wavelet function to find peaks and background areas; (3) the threshold is estimated from the peak intensive area for identification of peaks; (4) correction of endpoints, spectral peaks, and peak position; and (5) determine the endpoints of the peak after subtracting the background. We tested this algorithm for simulated and experimental Raman spectra, and a satisfactory denoising effect and a good capability to correct background are observed. It is noteworthy that this algorithm requires few human interventions, which enables automatic denoising and background removal.
Our results suggest that age of onset, first diagnosis at stage II or III, and stage II upgrade to stage III were discovered as risk factors for the pneumoconiosis patients’ survival. Furthermore, the overall survival for silicosis and CWP were the lowest, which should pay extra attention in Jiangsu Province.
We proposed a film-coupled nanoframe optical cavity which produces a significant near-field enhancement in the visible and near-infrared region. The resonant characteristics of the cavity with cavity dimensions are analyzed in detail. The maximum electric field enhancement was obtained by matching the cavity size with the excitation wavelength, which is different from the traditional SERS strategy with minimized nanogap. Attractively, resonator modes between nanoframes and Au film exist while the gap varies in a large range, which permits for SERS application on the condition that the sample thickness cannot be accurately controlled. Furthermore, the film-coupled nanoframe is of particular interest because it is easy for light to go through the nanoframe for excitation of cavity modes in a broad spectral range from visible to near-infrared. The strong and homogeneous field enhancement in the cavity makes it possible for Raman detection for biological mixtures.
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