According to the characteristics of high-order solitons,compressed picosecond pulses are numerically simulated in the photonic crystal fiber (PCF),by means of split-step Fourier method. The results show that,PCF enabl...According to the characteristics of high-order solitons,compressed picosecond pulses are numerically simulated in the photonic crystal fiber (PCF),by means of split-step Fourier method. The results show that,PCF enables input pulse with lower peak power to form high-order solitons for the purpose of femtosecond pulse-width compression. For example,60- femtosecond pulse width was made for 1-ps initial pulse width only over the distance of 2.2 m.Besides,shorter optimum fiber length for compression and higher compression ratio could be obtained on the premise of pre-chirp technique.展开更多
As a part of our interest in biologically active germacranolides from the genus Carpesium （Compositae）, we have investigated the constituents of Carpesium cernuum. This paper reports the isolation and structural elu...As a part of our interest in biologically active germacranolides from the genus Carpesium （Compositae）, we have investigated the constituents of Carpesium cernuum. This paper reports the isolation and structural elucidation of a new germacranolide, cernolide A （Compound 1）, from the herb. The structure of Compound 1 was determined as 2α,3β-dihydroxy-9-angeloxygermacra-4-en-6,12-olide on the basis of spectral evidence. The skeleton of Compound 1 was elucidation by IR, MS, ^1H and ^13C NMR, COSY, HMQC and HMBC experiments. The stereochemistry of Compound 1 was deduced by ROESY spectral data. Finally, the procedures of extraction and isolation were described in detail.展开更多
文摘According to the characteristics of high-order solitons,compressed picosecond pulses are numerically simulated in the photonic crystal fiber (PCF),by means of split-step Fourier method. The results show that,PCF enables input pulse with lower peak power to form high-order solitons for the purpose of femtosecond pulse-width compression. For example,60- femtosecond pulse width was made for 1-ps initial pulse width only over the distance of 2.2 m.Besides,shorter optimum fiber length for compression and higher compression ratio could be obtained on the premise of pre-chirp technique.
文摘As a part of our interest in biologically active germacranolides from the genus Carpesium （Compositae）, we have investigated the constituents of Carpesium cernuum. This paper reports the isolation and structural elucidation of a new germacranolide, cernolide A （Compound 1）, from the herb. The structure of Compound 1 was determined as 2α,3β-dihydroxy-9-angeloxygermacra-4-en-6,12-olide on the basis of spectral evidence. The skeleton of Compound 1 was elucidation by IR, MS, ^1H and ^13C NMR, COSY, HMQC and HMBC experiments. The stereochemistry of Compound 1 was deduced by ROESY spectral data. Finally, the procedures of extraction and isolation were described in detail.
