The trajectories of electrons originating from different initial locations in the unperturbed plasma during the interaction of an ultraintense laser with underdense plasma in the bubble regime are followed by particle-in-cell simulation. It is found that plasma electrons initially aligned with the rim of the laser focal spot contribute most to the bow wave in front of the bubble and those aligned with the lateral bubble sheath edge contribute most to the self-injection at the back of the bubble. A scaling law between the transverse electric and magnetic fields for the case where there are many electrons in the bubble is given and discussed in terms of betatron oscillations of the injected electrons.

Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly.

AIM To investigate the protective effects of polydatin (PD) against injury to primarily cultured rat hepatocytes induced by CCl4. METHODS Rat hepatocytes were separated by methods of liver infusion in vivo and cultured medium (7.5×10 5 cells/mL). Two mL or 0.2mL was added into 24-well or 96-well plates respectively. Twenty-four hours after cell preculture, PD at concentrations of 10 -7 mol/L-10 -4 mol/L was added into each plate. At the same time injury to hepatocytes was induced by adding 10mmol/L-CCl 4 . Then, 0.1mL or 1mL-culture solution was removed from the 96-well or 24-well plates at 6h, 12h, 2 4h and 48h after CCl 14 intoxication respectively for the determination of GPT, GSH and MDA. At 48h, the survivability of rat hepatocytes was assayed by the MTT colormetric method. RESULTS After CCl4 challenge, the release of GPT and the form ation of MDA in rat hepatocytes markedly increased and maintained at a high level in 48h, whereas PD with different concentrations could markedly inhibit this elevation with 10 -5 mol/L PD having the strongest effects and inhibiting rate was over 50%. PD could also improve the decreased content of GSH caused by CCl 4 in accordance with the doses used. CCl 4 evidently decreased the he patocyte survivability from 91.0%±7.9% to 35.4%±3.8%. On the other hand, PD at 10 -7 mol/L-10

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An analytical expression based on the paraxial approximation describing the propagation of a subcycle axicon Gaussian laser pulse in vacuum is obtained. The broad spectrum of the ultrashort pulse is given in terms of a Taylor series in the main wave frequency. The spatial and temporal characteristics of the pulse are strongly coupled. The model is used to consider electron acceleration by the light pressure of an intense subcycle laser pulse. The pulse model can also be applied to other short pulse profiles.