We aimed to find the correlation between serum sPD-L1 (soluble programmed cell death L-1 ligand) and sepsis. Totally 91 consecutive patients with sepsis were performed in a 15-bed medical intensive care unit (ICU) of the second affiliated hospital, Xi'an Jiaotong University in Xi'an, China, between February 2015 and May 2016. Healthy controls (HC) consisted of 29 healthy volunteer. Baseline demographic data were recorded. Blood samples were collected through an indwelling central venous or by peripheral venipuncture. Serum sPD-L1 and sPD-1 levels were determined with enzyme-linked immunosorbent assay kits (Elabscience Biotechnology Co. Ltd, Wuhan, China). SPSS19.0 software (SPSS Inc., Chicago, Illinois, USA) was used for statistical analysis. Kaplan-Meier survival analysis and Cox regression analysis were also performed. Serum sPD-L1 levels and sPD-1 levels were significantly increased in septic patients compared with HC (P = 0.000). Serum sPD-L1 levels were significantly increased in non-survivors compared with survivors (P < 0.05), but there was no statistically difference on serum sPD-1 levels between non-survivors and survivors (P > 0.05). Serum sPD-L1 levels were correlated with absolute lymphocyte (ALC), platelets and SOFA scores. Serum sPD-L1/sPD-1 levels were negatively correlated with ALC and platelets, and SOFA scores. The prognostic accuracy of the sPD-L1 level to predict 28-day mortality was similar to that of the APACHE-II scores and SOFA scores. Cox regression analysis showed that sPD-L1 was an independent prognostic factor. Serum sPD-L1 is upregulated in sepsis and may reflect disease severity and clinical outcomes in patients. Serum sPD-L1 may be an independent prognostic factor for sepsis.
Cyclic blasting excavation of a deep tunnel frequently disturbs the surrounding rock, and cumulative damage effect will occur in cases multiple blasts are applied. To study the damage evolution trend of tunnel surrounding rock under multiple cyclic blasting load, a self-made physical model test system was used to test cyclic blasting excavation of a tunnel under high in-situ stress. Meanwhile, according to the characteristic that the damage of rock under frequent disturbance will appear cumulative superposition, an improved Bingham creep damage constitutive model was established. The constitutive model was applied to the numerical simulation of tunnel cyclic blasting excavation, and the numerical simulation reproduced the physical model test to study the rock damage evolution laws. The results from the physical model test and the numerical simulation revealed that the process of damage evolution of rock in in-situ stress state under the impact of multiple blasting disturbances had a non-linear cumulative characteristic. In addition, the results also shed light on the relationship between the damage zone expansion and the number of cyclic blast. This paper can provide a reference for studies of the damage evolution in deep rock under blasting impact.
Studying the propagation characteristics of blasting seismic waves in surrounding rock under different in situ stresses forms the basic framework for discussing the damage and failure laws of tunnel surrounding rock caused by deep engineering blasting vibration. To study the propagation law of blasting seismic waves under different in situ stresses, an underground engineering model test system is used to simulate tunnel blasting excavation with a nonexplosive electric spark initiation device. The vibration acceleration and strain of the surrounding rock during excavation are collected in real time. Based on the test data system, the blasting vibration response characteristics of tunnel surrounding rock under different in situ stresses are discussed. According to the results of experimental studies, the peak values of radial and axial acceleration show nonlinear attenuation with an increase in distance under different in situ stresses. With an increase in in situ stress, the attenuation rate of the peak value of radial acceleration decreases, while that of axial acceleration increases. Moreover, the peak values of acceleration and strain measured at the same point near the seismic source under different in situ stresses remain unchanged, whereas those measured at the same point far away from the seismic source gradually decrease. Moreover, the attenuation rate at the stage of low in situ stress is greater than that at the stage of high in situ stress. The farther away from the seismic source, the greater the influence of in situ stress on peak acceleration and peak strain. The research results play an important guiding role in the development of deep tunnel blasting theory and safe construction.
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