ABSTRACT
The application of frequency modulation (FM) spectroscopy technology in the trace gas detection is greatly restricted by the residual amplitude modulation (RAM) which induced by the birefringence of the electro-optic modulator (EOM) and the misaligned linear polarization direction of laser to the EOM. Based on the interaction between the laser field and crystal, a line-shape expression of the FM spectroscopy with RAM is obtained. The angle between the polarization direction of input light and the principle axis of EOM, theta, the phase difference between the two principle axes of electro-optic crystal, delta phi, and the modulation index FM, beta, are the major factors to influence the lineshape. The larger theta and larger delta phi are, the stronger distortion of the lineshape is. Meanwhile a DC offset exists in the FM dispersion spectroscopy which is influenced by theta and delta phi. Finally a servo control of theta and delta phi is suggested to reduce the RAM. These phenomenon and the analysis of the lineshape provide a necessary technical support for the fiber components based FM spectroscopy.
ABSTRACT
OBJECTIVE: Despite achieving very low levels of low-density lipoprotein cholesterol (LDL-C), many patients continue to show disease progression. We sought to characterize the clinical factors that correlate with nonculprit lesion plaque progression in patients with LDL-C level less than 1.8 mmol/l. METHODS: Between May 2006 and December 2009, 653 patients met the following criteria: (i) underwent coronary angiograms again with a time interval from 6 months to 2 years after successful stent implantation, (ii) less than 50% stenoses of nonintervened nonculprit coronary lesions (NCLs), (iii) follow-up LDL-C levels less than 1.8 mmol/l. Patients were classified as progressors [NCL-percutaneous coronary intervention (PCI)] or nonprogressors (non-NCL-PCI). RESULTS: Five patients with de novo NCL and 87 patients with preexisting NCL developed progression. Progressors had higher percentage of acute coronary syndrome (ACS), multivessel diseases and triglycerides (TGs) at baseline PCI. At follow-up, a significant difference was observed between progressors and nonprogressors in TG (1.73 vs. 1.32 mmol/l, P<0.001), change in TG (-0.18±1.01 vs. -0.42±1.02 mmol/l, P=0.032), high-density lipoprotein cholesterol (HDL-C) (0.98±0.22 vs. 1.08±0.25 mmol/l, P=0.001) and change in HDL-C (0.11±0.17 vs. 0.19±0.27 mmol/l, P<0.001). Multivariate logistic regression analysis revealed that ACS, multivessel diseases, on-treatment TG and HDL-C and smaller increases in HDL-C were independent predictors for progression. CONCLUSION: Despite attainment of LDL-C level less than 1.8 mmol/l, NCL had still progressed, mainly in preexisting NCL rather than de novo NCL. ACS, multivessel diseases, on-treatment TG, HDL-C and smaller increases in HDL-C were associated with the NCL progression. This finding highlights the need for intensive modification of global risk in patients with coronary artery disease.
