Li-ming Song

Studies of crude chloroform extract of roots ofPodophyllum emoddii var. chinesis Sprague by micellar electrokinetic chromatography

SummaryA crude chloroform extract of the roots ofPodophyllum emoddii var. chinesis Sprague was studied by micellar electrokinetic chromatography. Four peaks belonging to podophyllotoxin, 4′-desmethyl-podophyllotoxin, kaempferol and quercetin were identified by known standards. The four substances are valuable pharmaceutical ingredients of the plant.

A statistical analysis of gamma-ray bursts based on the beaming model

We assume that gamma-ray bursts come from relativistic beaming in random directions, with the bursts being standard candles in their own rest frames and following a power-law distribution, and that the rate of occurrence is a constant in the comoving frame of the Ω = 1, Λ = 0 Friedmann universe. This model is very sensitive to the beaming velocity. For a Lorentz factor Γ < 10 and a power-law index n < 1.0 our calculated statistics agree with the BATSE data of weak bursts and the PVO data of strong bursts.

The fine spectral structure of Cygnus X-1

The power spectral density (PSD) of Cyg X-l is divided into two parts by using the linear state space model (LSSM). One part is the PSD of LSSM, the other is the residual power spectral density (RPSD) defined by the whole PSD minus the model PSD. We focus our attention on analyzing the RPSD. The results show that RPSD has different characteristics in 3 different states-the low/hard, transition and high/soft states. There is a broad peak structure both in the high/soft and low/hard states, with average central frequencies similar to 8Hz and similar to 5 HZ respectively The RPSD in the low/hard state may peak at similar to 0.07 HE. While during the Transition State, the RPSD has a double-peak structure, with the central frequencies in the regions of 0.5-4Hz and 5-11Hz respectively and these are quite close to the QPO central frequencies we have previously obtained. This fact implies that the QPO and the auto-regression that is needed in LSSM belong to different physical processes. Comparing to PSD, the RPSD is more sensitive to variations, such as the QPO, the broken frequencies and so on, The reason for the variable peak in the RPSD is discussed.

The Luminosity of γ -ray Pulsars

Abstract We point out that in the polar cap model, the visible part is only part of the cap and this fact should be taken into account when calculating the pulsar luminosity. When this is done, the calculated luminosities are in basic agreement with the observed values. Based on our calculations we give a list of 12 possible γ-ray candidates.

The generation parameter and γ-ray pulsars☆

Abstract We have calculated the generation parameters for known γ-ray pulsars after allowing for observational effects. The calculated generation parameters show a good linear relation with the observed spectral indices. They are all numerically greater than 2.0, and we suggest that this fact can be used as a criterion for γ-ray pulsar.

Timing analysis of Geminga with a phase cross-correlation method

Abstract Taking advantage of the stability of the spin and frequency variations of Geminga, we have made a phase-correlation analysis of EGRET data from four widely sepataed observing periods. The results are similar to those obtained from period folding over a much longer data set, thus demonstrating the effectiveness of the phase-correlation method in the derivation of the timing parameters of stable γ-ray pulsars.

The intensity and temporal characteristics of BATSE gamma-ray bursts and solar hard X-ray bursts☆

Abstract We have investigated the intensity and temporal characteristics of some 100 γ-bursts and some 4000 hard X-ray bursts found by CGRO/BATSE. We found their intensity distributions to be similar, suggesting a similar mechanism, and casting doubt on the cosmological interpretation of the γ-bursts. We found the duration and intensity of the solar bursts are positively correlated, while for the γ-bursts, the correlation is negative. The intensity and duration of the solar bursts showed long-term variations in the course of BATSE monitoring, such variations have also been found in recent studies of γ-bursts.