A Unified Fitting of HI and HeII Ly\alpha Transmitted Flux of QSO HE2347 with LCDM Hydrodynamic Simulations

Using cosmological hydrodynamic simulations of the LCDM model, we present a comparison between the simulation sample and real data sample of HI and HeII Ly\alpha transmitted flux in the absorption spectra of the QSO HE2347-4342. The LCDM model is successful in simultaneously explaining the statistical features of both HI and HeII Ly\alpha transmitted flux. It includes: 1.) the power spectra of the transmitted flux of HI and HeII can be well fitted on all scales > 0.28h^{-1} Mpc for H, and > 1.1h^{-1} Mpc for He; 2.) the Doppler parameters of absorption features of HeII and HI are found to be turbulent-broadening; 3.) the ratio of HeII to HI optical depths are substantially scattered, due to the significant effect of noise. A large part of the \eta-scatter is due to the noise in the HeII flux. However, the real data contain more low-\eta events than simulation sample. This discrepancy may indicate that the mechanism leading extra fluctuations upon the simulation data, such as a fluctuating UV radiation background, is needed. Yet, models of these extra fluctuations should satisfy the constraints: 1.) if the fluctuations are Gaussian, they should be limited by the power spectra of observed HI and HeII flux; 2.) if the fluctuations are non-Gaussian, they should be limited by the observed non-Gaussian features of the HI and HeII flux.Comment: 21 pages, 7 figs, ApJ in pres

Power spectrum and intermittency of the transmitted flux of QSOs Ly-alpha absorption spectra

Using a set of 28 high resolution, high signal to noise ratio (S/N) QSO Ly-alpha absorption spectra, we investigate the non-Gaussian features of the transmitted flux fluctuations, and their effect upon the power spectrum of this field. We find that the spatial distribution of the local power of the transmitted flux on scales k >= 0.05 s/km is highly spiky or intermittent. The probability distribution functions (PDFs) of the local power are long-tailed. The power on small scales is dominated by small probability events, and consequently, the uncertainty in the power spectrum of the transmitted flux field is generally large. This uncertainty arises due to the slow convergence of an intermittent field to a Gaussian limit required by the central limit theorem (CLT). To reduce this uncertainty, it is common to estimate the error of the power spectrum by selecting subsamples with an "optimal" size. We show that this conventional method actually does not calculate the variance of the original intermittent field but of a Gaussian field. Based on the analysis of intermittency, we propose an algorithm to calculate the error. It is based on a bootstrap re-sampling among all independent local power modes. This estimation doesn't require any extra parameter like the size of the subsamples, and is sensitive to the intermittency of the fields. This method effectively reduces the uncertainty in the power spectrum when the number of independent modes matches the condition of the CLT convergence.Comment: 26 pages (incl. figures). Accepted for publication in MNRA

Impact of Lycium barbarum polysaccharide on apoptosis in Mycoplasma-infected splenic lymphocytes

Purpose: To evaluate the effect of Lycium barbarum polysaccharide (LBP) on apoptosis in Mycoplasma-infected splenic lymphocytes (SLs), and the underlying mechanisms.Methods: SLs isolated from C57BL/6J mice were infected with Mycoplasma. The infected SLs were administered at different concentrations of LBP for 4 h, and the proportions of apoptotic cells and levels of relative reactive oxygen species (ROS) were determined by flow cytometry. The expressions of proapoptotic genes and endogenous antioxidant enzymes were investigated by real-time polymerase chain reaction (RT-PCR) and Western blotting.Results: LBP treatment produced dose-dependent reductions in apoptotic ratio and intracellular ROS levels of SLs (p < 0.05). In addition, the expressions of pro-apoptotic genes were decreased by LBP treatment with respect to mRNA and protein levels (p < 0.05). In contrast, mRNA and protein levels of anti-apoptotic factor Bcl-2 were significantly increased in a dose-dependent manner (p < 0.05). Furthermore, RT-PCR and Western blot results demonstrated that the expression levels of mRNA and proteins in Nrf2, HO-1 and NQO1 were up-regulated by Mycoplasma infection (p < 0.01), and further increased by LBP treatment (p < 0.05).Conclusion: LBP exerts a hyperactive antioxidant response encoded by Nrf2 to protect SLs from apoptosis induced by ROS-related oxidative damage after Mycoplasma infection. These results suggest that LBP may serve as a beneficial and dietary anti-Mycoplasma and anti-apoptotic agent.Keywords: Lycium barbarum polysaccharide, Splenic lymphocytes, ROS, Caspase-3, Bax, Nrf