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Objective To investigate the influence of acute blood stasis on nitric oxide (NO), angiotensin II (Ang II), angiopoietin-like protein 4 (ANGPTL4) mRNA, neuregulin 1 (NRG-1) mRNA, and platelet endothelial cell adhesion molecule-1 (PECAM-1) in rats with stasis induced by high-molecular-weight dextran (HMWD). Methods Seventy-five Sprague Dawley rats were divided randomly into five groups (n = 15 in each group): control group, immediate group, 1 h group, 3 h group, and 6 h group. A model of acute blood stasis was established via injection of HMWD into the tail vein. After performing electrocardiogram at the predetermined times according to the grouping, we collected blood and cardiac samples for hematoxylin-eosin (HE) staining and histopathological examination via transmission electron microscopy. Enzyme-linked immunosorbent assay was used to detect plasma levels of NO, Ang II, and fibrinogen. Real-time polymerase chain reaction was used to detect the expression of ANGPTL4 mRNA and NRG-1 mRNA. Immunohistochemical methods were used to detect PECAM-1 protein expression. Results The rat model of blood stasis showed blood retention in the capillary lumens. The ST segment showed gradual elevation, and was still elevated at 3 and 6 h after induction of blood stasis. HE staining showed myocardial cell necrosis and dissolution after modeling, along with basement membrane rupture and mitochondrial structural damage. Transmission electron microscopy showed endothelial cell swelling and an increase in absorption vesicles immediately after modeling. Endothelial cell apoptosis was increased at 3 and 6 h after modeling. Cardiac muscle fibers were disordered and intercalated discs were blurred immediately after modeling. There were massive numbers of dissolved cardiac muscle fibers, ruptured basement membranes, and mitochondrial structural damage at 3 and 6 h after modeling. NO plasma concentration was significantly reduced immediately and 1 h after modeling, while it was increased at 3 and 6 h. Ang II plasma concentration was decreased immediately after modeling, but increased at 1, 3, and 6 h. Fibrinogen plasma concentration was significantly increased at immediate, 1, 3, and 6 h after modeling. PECAM-1 protein expression was obviously increased immediately after modeling, at 1, 6 h was found mild augment. Expression of AngPTL4 mRNA was increased at immediate, 1, 3, and 6 h after modeling, and was found further augment at 3, and 6 h. Expression of NRG-1 mRNA was increased at immediate, 1, 3, and 6 h after modeling, and the strongest expression was at 1 h. Conclusion The pathological manifestation of acute blood stasis is characterized by microvascular blood retention. Prolonged blood stasis leads to worsening endothelial cell and cardiomyocyte damage, along with imbalances in the expression of vasomotor factors and increased vascular tone. The pathological damage caused by blood stasis also promotes the expression of cell protection factors.

In the pipeline system of nuclear industry, shock wave pressure in a pipe will be caused by the fast closing check valve after the pumping stops. This phenomenon is known as water hammer, which brings hidden danger to the security and reliability of the pipeline system. Specially, water hammer may cause serious damage on the pipeline system by the valve misoperation, by the valve malfunction, or by other unexpected events. A vortex diode is used as a highly reliable check-valve in nuclear applications, where it mainly benefits from the intrinsic properties of no moving parts and no leakage. In this paper, we proposed a novel method based on a vortex diode to protect water hammer. In the traditional analysis, a simple one-dimensional (1D) model is often used to simulate the water hammer. However, it is difficult to get the transient flow characteristics in a vortex diode using a 1D model. Thus, a three-dimensional (3D) model using computational fluid dynamics (CFD) is proposed to analyze water hammer in a pipeline system with a vortex diode. The 3D model was firstly verified by comparing the numerical results of CFD with experimental results of a water hammer test. Based on the 3D model, the water hammer was simulated at different inlet conditions in a pipeline system with a vertex diode. In order to investigate the vortex diode used as a leaky check-valve, the inlet pressure was decreased by the corresponding value of pump head to simulate the pump stop after the quasi-steady state was achieved in the vortex diode. It is found that the pressure fluctuation of water hammer is comparable to the pump value, which is not varying with initial velocity in the pipeline system. Thus, we have proved that a vortex diode in the pipeline system acts significantly in suppressing pressure fluctuation of water hammer. This study presents a CFD-based numerical method for water hammer and could be useful in protecting water hammer in nuclear industry.

OBJECTIVE To examine the microvascular pathological characteristics and changes in related injury factors in a rat model of acute blood stasis. METHODS A total of 75 Sprague-Dawley rats were divided randomly and equally into a control group and four experimental groups assessed at different times after the induction of stasis (0, 1, 3 or 6 h after stasis) (n = 15). The acute blood stasis model was established through rat tail-vein injection of high-molecular-weight dextran. After Electrocardiograph (ECG) detection at predetermined times (0, 1, 3 and 6 h after induction of stasis), the rats were sacrificed and blood and cardiac samples were harvested for analysis. Hematoxylin-eosin (HE) staining and transmission electron microscopy were used for histopathological detection; an enzyme linked immunosorbent assay (ELISA) was used to detect thromboxane B2 (TXB2) and 6-keto-prostaglandin F1α (6-Keto-PGF1α) concentrations; a real-time polymerase chain reaction (PCR) reaction system was used to detect intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule1 (VCAM-1) mRNA expression; western blotting was used to detect vascular endothelial cadherin (VE-cadherin) protein expression. RESULTS The ST segment in the ECG showed gradual elevation after induction of stasis and continued elevation at a high level at 3 and 6 h. The HE staining showed changes in myocardial cell necrosis and tissue dissociation after the induction of stasis, along with inflammatory infiltration. Results of transmission electron microscopy showed immediate changes in blood stasis and lumen occlusion in the microvasculature, along with endothelial cell swelling. After the induction of stasis, TXB2 concentrations gradually increased while 6-Keto-PGF1α concentrations were immediately significantly reduced. The TXB2/6-Keto-PGF1α ratio was maintained at a high level. ICAM-1 mRNA expression showed an unstable elevation while VCAM-1 mRNA expression was significantly reduced after the induction of stasis. Compared with the control group, VE-cadherin protein expression increased at 0 and 3 h after the induction of stasis, while no change occurred at 1 and 6 h. CONCLUSION The pathological manifestations of acute blood stasis are microvascular blood retention, lumen stenosis and even occlusion. The condition is also called “blood coagulation and weep” in Traditional Chinese Medicine. The blood stasis model resulted in the injury and necrosis of endothelial cells and cardiomyocytes, along with the presence of an imbalance of vasomotor factor levels, platelet activation, and increases in the expression of adhesion molecules and endothelial barrier dysfunction, which corresponds to “blood failed to nourish” in Traditional Chinese Medicine.

Jet pumps have the advantages in reliable operation, none of moving components and simple construction etc, which makes it applicable in a wide range of industry situations. The cavitation easily occurs within jet pumps and it turns to be a bottleneck for the jet pump design. In this paper, the cavitation flow inside the jet pump would be investigated by 2-D axisymmetric CFD simulations. Firstly, the single liquid phase flow in the jet pump would be simulated and the grid independence test would be carried out. The simulation results show that both the pressure ratio (h) and the efficiency (n) would reach to convergence values with 143,484 meshes, which would be adopted in the following simulations. By comparing with the experimental data of single phase flow in literatures, it was found that the Reynolds stress model offered better predictions. Then the cavitation flow in the jet pump was simulated. It could be found that the cavitation phenomenon trends to occur in the shear layer and the wall detached regions of the throat. At last, the influence of saturated vapor pressure model, the outlet pressure and the nozzle-to-throat clearance would be evaluated. It was found that different from the single phase flow, the optimal nozzle-to-throat clearance would vary with the operation conditions.

In most of the previous studies, the vapor bubble parameters were averaging processed in order to establish the empirical-based correlations or mechanism-based models. While it should be noted that the thermal hydraulic parameters around a bubble in a subcooled flow boiling channel are unsteady, that means the vapor bubbles behaves some stochastic characteristics. In the present research, a high speed visualization experiment was conducted in a subcooled flow boiling narrow rectangular channel to investigate the vapor bubble behavior. The working fluid in the experiment was deionized water. The obtained bubble images were processed by a digital image processing program in order to acquire the bubble parameters. The stochastic features of the bubbles were analyzed based on the experimental results. Two types of bubble behaviors were observed under different working conditions, which results in two types of bubble stochastic features. The results shown that the distribution function of the bubble maximum diameter in a specific nucleation site can be expressed by the normal distribution, while in the whole range of the observation window the distribution of the bubble maximum diameter was expressed by the lognormal distribution. The distribution of the second type bubble diameter depends on the local bubble nucleation site and the upstream bubble behaviors.