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Free-electron lasers (FELs) are fourth-generation light sources that deliver extremely high intensity, ultrashort light pulses over a broad wavelength range from far-infrared to hard x ray. FELs based on the self-amplified spontaneous emission principle have been successfully operated with ultrahigh brightness and a broad wavelengths tuning range with good transverse coherence but poor temporal coherence. In contrast, the laser-seeded FELs have provided full coherence but at selected central wavelengths, usually the harmonics of the laser seeds, with relatively narrower tuning range. We report the experimental demonstration of a high-gain harmonic-generation (HGHG) FEL that is continuously tunable over a wide range using the combination of optical parametrical amplification, variable-gap undulator, and harmonic selection, where the temporal coherence is preserved as confirmed with the Michelson interferometry. In order to achieve higher photon energies, the first try of cascaded HGHG with a fresh-bunch technique is also made at the Shanghai Deep Ultraviolet Free-electron Laser test facility.

We aimed to investigate the expression of SPARC (secreted protein, acidic and rich in cysteine) in gastric cancer and its relationship with tumor angiogenesis and cancer cells proliferation. Protein expression of SPARC, VEGF, CD34 and Ki-67 in 80 cases of gastric cancer and 30 cases of normal gastric tissue was evaluated by immunohistochemistry. CD34 staining was used as an indicator of microvessel density (MVD). Ki-67 labeling Index (LI) indicated cancer cells proliferation. Statistical analysis was used to investigate its relationship with clinical characteristics, tumor angiogenesis and cancer cells proliferation. SPARC expression was mainly in the stromal cells surrounding the gastric cancer cells, and was statistically significant differences between gastric cancer and normal gastric tissue (P < 0.05). Both the expression of SPARC and VEGF were related to differentiation degree, clinical stage, Lauren classification and lymph node metastasis (P < 0.05). Expression of SPARC was significantly negatively correlated with the expression of VEGF and MVD in gastric cancer tissues. Expression of SPARC was also negatively correlated with Ki-67-LI. Our findings suggest that both the expression of SPARC and VEGF are closed to tumor angiogenesis in gastric cancer, SPARC inhibited tumor angiogenesis but VEGF promoted tumor angiogenesis. SPARC also inhibited cells proliferation of gastric cancer.