Search

In this paper, we present a model-independent approach to calibrate the largest quasar sample. Calibrating quasar samples is essentially constraining the parameters of the linear relation between the log  of the ultraviolet (UV) and X-ray luminosities. This calibration allows quasars to be used as standardized candles. There is a strong correlation between the parameters characterizing the quasar luminosity relation and the cosmological distances inferred from using quasars as standardized candles. We break this degeneracy by using Gaussian process regression to model-independently reconstruct the expansion history of the Universe from the latest type Ia supernova observations. Using the calibrated quasar data set, we further reconstruct the expansion history up to redshift of z ∼ 7.5. Finally, we test the consistency between the calibrated quasar sample and the standard Lambda cold dark matter (⁠|$\rm {\Lambda }CDM$|⁠) model based on the posterior probability distribution of the GP hyperparameters. Our results show that the quasar sample is in good agreement with the standard |$\rm {\Lambda }CDM$| model in the redshift range of the supernova, despite the 2−3σ significant deviations taking place at higher redshifts. Fitting the standard |$\rm {\Lambda }CDM$| model to the calibrated quasar sample, we obtain a high value of the matter density parameter |$\Omega _m = 0.382^{+0.045}_{-0.042}$|⁠ , which is marginally consistent with the constraints from other cosmological observations. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Based on the findings that erythropoietin (EPO) has been proved to be a multiple functional cytokine to attenuate ischemia–reperfusion (I/R) injury in various organs such as brain, heart, and kidney in animals, this experiment was designed to evaluate the effect of pretreatment with recombined human erythropoietin (rhEPO) on I/R-induced lung injury. Methods: Left lungs of rats underwent 90min of ischemia and then were reperfused for up to 2h. Animals were randomly divided into three experimental groups as sham group, I/R group, and rhEPO+I/R group (a single dose of rhEPO was injected intraperitoneally 3000U/kg 24h prior to operation). Lung injury was evaluated according to semi-quantitive analysis of microscopic changes, tissue polymorphonuclear neutrophils (PMNs) accumulation (myeloperoxidase (MPO) activity), and pulmonary microvascular permeability (Evan''s blue dying method). Peripheral arterial and venous blood samples were obtained for blood–gas analysis after 5min occlusion of right lung hilus at the end of reperfusion. The serum concentration of tumor necrosis factor (TNF)-α was also measured by the method of enzyme-linked immunosorbent assay. Results: Histological injury scoring revealed significantly lessened lung alveolus edema and neutrophils infiltration in the rhEPO pretreated group compared with I/R group (p <0.05). The rhEPO pretreated animals exhibited markedly decreased lung microvascular permeability (p <0.05) and myeloperoxidase activity (p <0.05). Blood–gas analysis demonstrated that the pretreated animals had significantly ameliorated pulmonary oxygenation function (p <0.05). The serum concentration of tumor necrosis factor-α in rhEPO pretreated group was markedly decreased compared with that of I/R group (p <0.05). Conclusions: Pretreatment with rhEPO appears to attenuate I/R-induced lung injury. This function is partly related with the capacity that rhEPO inhibits the accumulation of polymorphonuclear neutrophils in lung tissue and decreases the systematic expression of tumor necrosis factor-α. [Copyright &y& Elsevier]