Fast Numerical Simulation of Two-Phase Transport Model in the Cathode of a Polymer Electrolyte Fuel Cell

In this paper, we apply streamline-diffusion and Galerkin-least-squares finite element methods for 2D steady-state two-phase model in the cathode of polymer electrolyte fuel cell (PEFC) that contains a gas channel and a gas diffusion layer (GDL). This two-phase PEFC model is typically modeled by a modified Navier-Stokes equation for the mass and momentum, with Darcy's drag as an additional source term in momentum for flows through GDL, and a discontinuous and degenerate convection-diffusion equation for water concentration. Based on the mixed finite element method for the modified Navier-Stokes equation and standard finite element method for water equation, we design streamline-diffusion and Galerkin-least-squares to overcome the dominant convection arising from the gas channel. Meanwhile, we employ Kirchhoff transformation to deal with the discontinuous and degenerate diffusivity in water concentration. Numerical experiments demonstrate that our finite element methods, together with these numerical techniques, are able to get accurate physical solutions with fast convergence.     

A Direct Numerical Simulation (DNS) Study on the Effect of Particle Configuration on Drag

Drag correlations are very important in particle-laden two-phase flow simulations. Some statistical studies have investigated extracting particle configurationfactors from simulation data to improve drag correlations. However, little attentionhas been paid to studying particle configuration effects on drag from the perspectiveof the flow mechanism. In this paper, a direct numerical simulation (DNS) methodbased on the second-order accurate immersion interface method is developed to provide highly reliable data. Then, the 'shielding' effect of the two-particle configurationon drag is comprehensively analysed under different angles, distances, and Reynoldsnumber $(Re)$ values, revealing that the complex configuration dependence of the draginfluence is attributed to the dominant flow mechanism, such as the 'pressure regionunit', 'nozzle', and 'wake' effects. Moreover, we study the 'superposition' effect of thethree-particle configuration on drag in a finite $Re$ range. The results show that whenthe surrounding particles do not directly shield each other, the drag influence calculated by pairwise linear superposition is close to the drag influence revealed by DNS.Otherwise, when the shielding phenomenon of the surrounding particles is obviousand the $Re$ is high, the drag influence of the nearest particle can represent the DNSresult.     

Numerical Stability Analysis for a Stationary and Translating Droplet at Extremely Low Viscosity Values Using the Lattice Boltzmann Method Color-Gradient Multi-Component Model with Central Moments Formulation

Multicomponent models based on the Lattice Boltzmann Method (LBM) have clear advantages with respect to other approaches, such as good parallel performances and scalability and the automatic resolution of breakup and coalescence events. Multicomponent flow simulations are useful for a wide range of applications, yet many multicomponent models for LBM are limited in their numerical stability and therefore do not allow exploration of physically relevant low viscosity regimes. Here we perform a quantitative study and validations, varying parameters such as viscosity, droplet radius, domain size and acceleration for stationary and translating droplet simulations for the color-gradient method with central moments (CG-CM) formulation, as this method promises increased numerical stability with respect to the non-CM formulation. We focus on numerical stability and on the effect of decreasing grid-spacing, i.e. increasing resolution, in the extremely low viscosity regime for stationary droplet simulations. The effects of small- and large-scale anisotropy, due to grid-spacing and domain-size, respectively, are investigated for a stationary droplet. The effects on numerical stability of applying a uniform acceleration in one direction on the domain, i.e. on both the droplet and the ambient, is explored into the low viscosity regime, to probe the numerical stability of the method under dynamical conditions.     

Flow Visualization Study on Centrifugal Blood Pump Using a High Speed Video Camera

Abstract: Flow visualization is widely applied to evaluate rotary blood pumps; however, it is very difficult to visualize flow near the vanes of centrifugal blood pumps because the rotational speed of the impeller is usually several thousand rpm. In this study, a tracer method with a high speed video camera that can take more than 2,000 frames/s was utilized for flow visualization together with computer-assisted image measurement. This method visualized the complex secondary flow pattern near the vanes of the impeller, such as the vortex and recircula-tion. It also visualized the enhanced washout effect by the secondary washout vanes on the backside of the impeller. The proposed method was effective to analyze the flow pattern in the centrifugal blood pump by providing useful information for better design of the pump hemolysis and thrombus formation.     

The Riemann Problem for a Blood Flow Model in Arteries

In this paper, the Riemann solutions of a reduced 6×6 blood flow model in medium-sized to large vessels are constructed. The model is non-strictly hyperbolic and non-conservative in nature, which brings two difficulties of the Riemann problem. One is the appearance of resonance while the other one is loss of uniqueness. The elementary waves include shock wave, rarefaction wave, contact discontinuity and stationary wave. The stationary wave is obtained by solving a steady equation. We construct the Riemann solutions especially when the steady equation has no solution for supersonic initial data. We also verify that the global entropy condition proposed by C.Dafermos can be used here to select the physical relevant solution. The Riemann solutions may contribute to the design of numerical schemes, which can apply to the complex blood flows.     

Numerical Comparative Study on the Hemodynamic Performance of a New Helical Graft With Noncircular Cross Section and SwirlGraft

The helically distributed ribbons of thrombus, formed in the commercially available SwirlGraft (Veryan Medical, London, UK), are the result of its wall shear stress distribution, which has zonary areas of low wall shear stress. In order to overcome the inherent deficiency of the SwirlGraft, a new helical graft with a noncircular cross section was proposed and compared numerically with the SwirlGraft in terms of wall shear stress distribution, helicity of the swirling flow created, and pressure drop over the grafts. The numerical results showed that due to the modification to the geometrical configuration of the SwirlGraft, wall shear stress in the new helical graft model was enhanced, and the zones of low wall shear stress existing in the SwirlGraft were completely eliminated. The present numerical study also predicted a slightly steeper pressure drop and reduction in helicity in the new helical graft model in comparison with the SwirlGraft model. Based on the study, we believe that the new helical graft with a noncircular cross section may reduce the possibility of acute thrombus formation in the graft because the enhanced wall shear stress can impede the stay and adherence of platelets and leukocytes to the surface of the graft.     

肾癌中CD133＋细胞和CD133-细胞生物学特性差异的研究

目的：研究人肾癌细胞系786-O和OS-RC-2中CD133＋细胞和CD133-细胞的生物学特性差异。方法：应用流式细胞仪检测肾癌细胞系786-O和OS-RC-2中CD133的膜表达状况;以免疫磁珠法将CD133＋细胞和CD133-细胞分离纯化,比较两者在光镜下的形态、生长特点、体外增殖能力、长期分化能力及体外克隆形成率的差异;流式细胞术分析两者细胞周期分布的变化,采用MTT法分析两者对化疗药物顺铂（DDP）（10、20、50、80／Lg／ml）敏感性的差别。结果：786-O和0S-RC-2均有CD133的少量表达,表达率为（8．12±0．86）％、（6．83±0．20）％,CD133＋细胞和CD133-细胞相比具有较强的体外增殖、克隆形成及长期分化能力;细胞耐药性实验表明CD133＋细胞、CD133-细胞对50bcg／m1DDP敏感性差异有统计学意义（P〈0．05）。结论：肾癌细胞系中CD133＋细胞具有肾癌干细胞的部分特征,能否作为肾癌干细胞的表面标志还需要进一步的实验加以明确。     

The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system

The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 2 l.min⁻¹) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (5 l.min⁻¹) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 5 l.min⁻¹ fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. Thirty minutes after the start of anaesthesia a control measurement was performed, after which a heat and moisture exchanger was inserted into the breathing system of the three groups randomly allocated to have one. Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l⁻¹) but at a fresh gas flow of 5 l.min⁻¹ there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.     

Influence of Electromagnetic Fields on Bone Mass and Growth in Developing Rats: A Morphometric,Densitometric, and Histomorphometric Study

The effect of electromagnetic fields on bone is debated. In an experimental study of this effect, we compared two lots of growing female rates (both lots n = 15, age 3 weeks, average weight 23.2 ± 3.3 g), one of which was exposed to a 3-mT, 100-Hz, Helmholtz-type electromagnetic field for 24 hours a day for 30 days, and the other of which served as the control. Bone development and bone mass were evaluated by morphometry, densitometry, and histomorphometry. The rats were killed at 30 days and weighed. The right femurs were dissected, measured, and weighed; bone densitometry was used to determine femoral bone mineral content (BMC) and density (BMD), and histomorphometry of the nondecalcified bone was used to determine trabecular bone volume (Cn-BV-TV%), number (Tb-N mm) and thickness (Tb-Th μm), intertrabecular space (Tb-Sp μm) and growth cartilage thickness (Gc-Th μm). In the rats exposed to the electromagnetic field, BMC and BMD (P= 0.019 and P= 0.002, respectively) and Cn-BV-TV, Tb-N, Tb-Th (P= 0.005, P= 0.036, and P= 0.027, respectively) all were decreased, whereas Tb-Sp was increased (P= 0.002). There were no significant differences in initial and final body weight, or in final femur weight, femur length, and GC-Th. These findings indicate that electromagnetic fields of the type used here reduced bone formation and increased bone resorption without affecting bone development in rats. Received: 12 February 1996 / Accepted: 2 December 1996     

A New Mock Circulatory Loop and Its Application to the Study of Chemical Additive and Aortic Pressure Effects on Hemolysis in the Penn State Electric Ventricular Assist Device

Abstract: A new mock circulatory loop was developed for hemolysis studies associated with the Penn State electric ventricular assist device (EVAD). This flow loop has several advantages over previously designed loops. It is small enough to accommodate experiments in which only single units of blood are available, it is made out of biocompatible materials, it incorporates good geometry, and it provides normal physiological pressures and flows to both the aortic outlet and the venous inlet of the pumping device. Experiments with reduced aortic pressure but normal cardiac output showed that hemolysis in a loop with normal aortic blood pressure was significantly higher than that in a loop with lowered aortic pressure, thereby illustrating the importance of maintaining loop pressures as close as possible to those found in vivo. This data also imply that blood traveling through the left ventricle in an artificial heart may be subject to higher hemolysis rates than that traversing the right ventricle. Another set of experiments to determine the effects of 4 hemolysis or drag-reducing agents (Pluronic F-68, Dextran-40, Polyox WSR-301, and Praestol 2273TR) on blood trauma due to the EVAD and associated valves was performed. Results indicated that none of the additives significantly reduced hemolysis under the conditions found in the mock loop. Finally, a compilation of data gathered in these experiments showed that the index of hemolysis (IH) is dependent on hematocrit (HCT), which suggests that another parameter, IH/HCT, may be more suited to the quantification of hemolysis.     

Dendritic Cell Deficiency in the Blood of Kidney Transplant Patients on Long-Term Immunosuppression: Results of a Prospective Matched-Cohort Study

Evidence from in vitro studies suggests that immunosuppressive drugs interfere with key functions of dendritic cells (DCs), but the in vivo relevance of these findings is elusive. We prospectively analyzed the major DC precursor subsets in the blood of kidney transplant recipients on long-term immunosuppression (> or =1 year). A total of 87 patients were compared to 87 age- and sex-matched controls. Total DC numbers and the precursor subsets, myeloid type 1 DCs, myeloid type 2 DCs (mDC1, mDC2) and plasmacytoid DCs (pDCs) were identified by four color flow cytometry. Long-term immunosuppression was associated with significant reduction of all major DC subsets in comparison to healthy controls (mDC1 p < 0.001; mDC2 p < 0.0001; two-tailed Mann-Whitney U-test) with the strongest negative impact on pDCs (p < 0.00001). In contrast, total leukocyte numbers were not significantly affected. Analysis of the relative impact of different agents revealed a significant impact of prednisolone on pDCs (p = 0.009) and mDCs2 (p = 0.006). The functional relevance of pDC deficiency was confirmed independently by Interferon-alpha analysis after Toll-like receptor 7 (p < or = 0.001) and 9 (p < 0.05) stimulation. These results indicate for the first time a profound negative impact of long-term immunosuppression on major DC subsets in kidney transplant recipients. DC deficiency may have important implications with respect to viral infections and tumor development.     

Denosumab联合手术治疗桡骨骨巨细胞瘤——外科降级及预后

目的 桡骨是骨巨细胞瘤好发部位,囊内刮除术后复发率高,广泛切除术后功能欠佳。本研究旨在评估Denosumab治疗桡骨GCT的疗效和安全性,分析Denosumab对手术方式及预后的影响。 方法 2014年1月-2016年4月,7例复杂难治桡骨GCT患者在围手术期接受Denosumab治疗。比较应用Denosumab后手术方案的差异,监测用药过程中的副反应。随访患者的肿瘤学预后、术后功能。 结果 平均年龄28.43岁（23-33岁,中位年龄29岁）,男性4例,女性3例。所有患者均有明确骨巨细胞瘤病理诊断, 2例为初次手术后复发。以手术结束为随访开始时间,末次随访时间为2017年12月。随访时间20-41个月（平均26.71个月）。用药期间无死亡病例,患者均按计划用药,用药总次数4-10次（平均7.71次）。未见下颌骨坏死。血钙、碱性磷酸酶、肝肾功能、血色素、白细胞、血小板等实验室指标未见异常。85.71 %（6/7）的病人外科手术降级（行囊内刮除术5例,瘤段广泛切除2例）,7例患者随访期内均未见肿瘤复发。患者术后MSTS功能评分平均27.86（92.87%）,DASH评分7.43,VAS评分1分。 结论 Denosumab是治疗桡骨骨巨细胞瘤的有效手段,围手术期用药可降低手术难度,从而实现外科降级并降低复发风险。     

Experimental Study on the Prevention of Posttraumatic Osteoarthritis in the Rabbit Knee Using a Hinged External Fixator in Combination with Exercises

Abstract

Objective: To report the design and effect of our proprietary hinged external fixator, used in combination with treadmill exercise for rabbits with intra-articular inflammation and cartilage degeneration. Methods: Thirty-two white rabbits were randomly allocated into four groups: No treatment (NT), Distraction only (D), Exercise only (Ex), and Distraction plus exercise (D?+?Ex). Each rabbit underwent an anterior cruciate ligament transection on the right knee, with the contralateral knee used as a sham control (C). Results: In the D?+?Ex group, the levels of Interleukin (IL)-1β and Tumor necrosis factor (TNF)-α in synovium and TNF-α in joint effusion were significantly lower, while the expression of IL-10 in joint effusion and blood was significantly higher. The ratio of IL-10/TNF-alpha in blood was also the highest in the D?+?Ex group. The condition of collagen loss was examined: the D?+?Ex group had the lowest level of type II collagen in effusion and C-telopeptides of type II collagen (CTX-II) in blood. On the other hand, the D?+?Ex group had the highest expression of cartilage regeneration genes, including type II collagen, Aggrecan (AGN), and SRY-box 9 (SOX9). Finally, the histology showed an attenuation of cartilage degeneration with a lower OA score in the D?+?Ex group. Conclusion: Our hinged external fixator combined with treadmill exercise up-regulated cartilage regeneration genes, reduced synovial and intra-articular inflammation, and reduced type II collagen and proteoglycan loss, indicating the use of the fixator in combination with treadmill exercise could prevent progression of posttraumatic osteoarthritis of knee joint in rabbits.