酸性环境抑制高磷诱导大鼠VSMCs钙化的机制研究

目的探讨酸性环境对高磷诱导的大鼠血管平滑肌细胞(VSMCs)钙化的影响及其机制。方法体外分离培养大鼠VSMCs,采用免疫细胞化学法鉴定。将VSMCs按随机数字表法分为正常对照组、高磷+p H 7.4组、高磷+p H 7.1组。刺激4 d后,采用逆转录聚合酶链反应和Western blot检测活化T细胞核因子c1(NFATc1)、Runt相关转录因子2(Runx2)基因和蛋白的表达。刺激14 d后,对各组细胞进行钙化染色、钙含量和碱性磷酸酶(ALP)活性测定。结果与正常对照组比较,高磷+p H 7.4组的钙含量、ALP活性、Runx2和NFATc1表达升高(P<0.05);与高磷+p H 7.4组比较,高磷+p H 7.1组的钙含量、ALP活性、Runx2和NFATc1表达降低(P<0.05)。相关性分析发现,NFATc1蛋白表达水平与ALP活性、Runx2蛋白表达水平呈正相关(P<0.05)。结论酸性环境可以抑制高磷诱导的大鼠VSMCs钙化,其机制可能是通过降低NFATc1表达,抑制VSMCs表型转化来实现的。

Research on the influences of confining pressure and strain rate on NEPE propellant:Experimental assessment and constitutive model

In order to study the influences of confining pressure and strain rate on the mechanical properties of the Nitrate Ester Plasticized Polyether(NEPE)propellant,uniaxial tensile tests were conducted using the selfmade confining pressure system and material testing machine.The stress-strain responses of the NEPE propellant under different confining pressure conditions and strain rates were obtained and analyzed.The results show that confining pressure and strain rate have a remarkably influence on the mechanical responses of the NEPE propellant.As confining pressure increases(from 0 to 5.4 MPa),the maximum tensile stress and ultimate strain increase gradually.With the coupled effects of confining pressure and strain rate,the value of the maximum tensile stress and ultimate strain at 5.4 MPa and 0.0667 s^(-1)is 2.03 times and 2.19 times of their values under 0 MPa and 0.00333 s^(-1),respectively.Afterwards,the influence mechanism of confining pressure on the NEPE propellant was analyzed.Finally,based on the viscoelastic theory and continuous damage theory,a nonlinear constitutive model considering confining pressure and strain rate was developed.The damage was considered to be rate-dependent and pressuredependent.The constitutive model was validated by comparing experimental data with predictions of the constitutive model.The whole maximum stress errors of the model predictions are lower than 4%and the corresponding strain errors are lower than 7%.The results show that confining pressure can suppress the damage initiation and evolution of the NEPE propellant and the nonlinear constitutive model can describe the mechanical responses of the NEPE propellant under various confining pressure conditions and strain rates.This research can lay a theoretical foundation for analyzing the structural integrity of propellant grain accurately under working pressure loading.

Analysis on damage characteristics and detonation performance of solid rocket engine charge subjected to jet

To further explore the damage characteristics and impact response of the shaped charge to the solid rocket engine(SRE) in storage or transportation, protective armor was designed and the shelled charges model(SCM)/SRE with protective armor impacting by shaped charge tests were conducted. Air overpressures at 5 locations and axial acceleration caused by the explosion were measured, and the experimental results were compared with two air overpressure curves of propellant detonation obtained by related scholars. Afterwards, the finite element software AUTODYN was used to simulate the SCM impacted process and SRE detonation results. The penetration process and the formation cause of damage were analyzed. The detonation performance of TNT, reference propellant, and the propellant used in this experiment was compared. The axial acceleration caused by the explosion was also analyzed.By comprehensive comparison, the energy released by the detonation of this propellant is larger, and the HMX or Al particles contained in this propellant are more than the reference propellant, with a TNT equivalent of 1.168-1.196. Finally, advanced protection armor suggestions were proposed based on the theory of woven fabric rubber composite armor(WFRCA).

Prevalence of Chronic Kidney Disease-Mineral Bone Disorder in Hemodialysis Patients in Hebei,China

To the Editor:Chronic kidney disease-mineral bone disorder (CKD-MBD)has been found universally in hemodialysis (HD) patients.It increases the risk of cardiovascular morbidity and mortality,particularly vascular calcification.[1]Consequently, it is crucial to effectively control the biochemical indicators' abnormalities of CKD-MBD.Internation,al guidelines have provided measures for CKD-MBD,but relevant research from developing countries is limited,especially in China.[2]