A novel hybrid model combining the lattice Boltzmann (LB) and finite difference (FD) methods is proposed to simulate transport in through a junction of actively contracting lymphatic vessels, while also handling flow of interstitial liquid in the surrounding porous tissue. Details of the dynamically flexing walls and valves in the lymphatic vessel and its near vicinity are modeled using a high-resolution LB method, whereas overall efficiency was significantly improved by using low-resolution FD in the larger tissue domain distant from the vessel. Pressure and velocity conditions at the interface between subdomains of the two numerical methods are matched by imposing a partial bounce-back ratio in LB corresponding to the permeability coefficient κ in Darcy's law for flow through porous media. Parameters governing the match between the algorithms at their interface can be estimated from the Kozeny-Carman relationship for porous media and further refined with a simpler, parallel flow geometry that also serves to validate the method. Test calculations show that the hybrid method is roughly four times faster than the LB method and permits computation over significantly larger domains. This method should be applicable to a large range of problems involving fluid flow in porous media with embedded conduits that have non-stationary boundaries.

The lymphatic system plays a vital role in maintaining fluid balance in living tissue and serves as a pathway for the transport of antigen, immune cells, and metastatic cancer cells. In this study, we investigate how the movement of cells through a contracting lymphatic vessel differs from steady flow, using a lattice Boltzmann-based computational model. Our model consists of cells carried by flow in a 2D vessel with regularly spaced, bi-leaflet valves that ensure net downstream flow as the vessel walls contract autonomously in response to calcium and nitric oxide levels regulated by stretch and shear stress levels. The orientation of the vessel with respect to gravity, which may oppose or assist fluid flow, significantly modulates cellular motion due to its effect on the contraction dynamics of the vessel, even when the cells themselves are neutrally buoyant. Additionally, our model shows that cells are carried along with the flow, but when the vessel is actively contracting, they move faster than the average fluid velocity. We also find that the fluid forces cause significant deformation of the compliant cells, especially in the vicinity of the valves. Our study highlights the importance of considering the complex, transient flows near the valves in understanding cellular motion in lymphatic vessels.

为提高流体的计算效率并保证结果的准确性,利用CUDA编程平台和GPU强大的浮点计算能力,实现了基于晶格玻尔兹曼方法的泊松流模拟计算加速.设计了线性寻址和下标寻址2种不同寻址方式,将这2种寻址方式分别应用到晶格玻尔兹曼程序的格点碰撞、迁徙流动、宏观量计算等步骤中,并探讨2种寻址方式对程序计算效率带来的影响.同时在程序中使用统一内存管理,通过这样的方式开辟内存的变量可在主机端和设备端同时使用,简化了代码复杂度,同时降低了频繁为变量开辟内存带来的消耗.使用Intel?Xeon?E-52620 v4 CPU,Nvidia Quadro GP100 GPU进行计算,在线性寻址方法和下标寻址方法中分别获得了71倍和25倍CPU串行代码的加速比.

Physical forces, including mechanical stretch, fluid pressure, and shear forces alter lymphatic vessel contractions and lymph flow. Gravitational forces can affect these forces, resulting in altered lymphatic transport, but the mechanisms involved have not been studied in detail. Here, we combine a lattice Boltzmann-based fluid dynamics computational model with known lymphatic mechanobiological mechanisms to investigate the movement of fluid through a lymphatic vessel under the effects of gravity that may either oppose or assist flow. Regularly spaced, mechanical bi-leaflet valves in the vessel enforce net positive flow as the vessel walls contract autonomously in response to calcium and nitric oxide (NO) levels regulated by vessel stretch and shear stress levels. We find that large gravitational forces opposing flow can stall the contractions, leading to no net flow, but transient mechanical perturbations can re-establish pumping. In the case of gravity strongly assisting flow, the contractions also cease due to high shear stress and NO production, which dilates the vessel to allow gravity-driven flow. In the intermediate range of oppositional gravity forces, the vessel actively contracts to offset nominal gravity levels or to modestly assist the favorable hydrostatic pressure gradients.

In order to improve the efficiency of fluid calculations and ensure the accuracy of the results,the CUDA programming platform and the powerful floating-point computing capabilities of the GPU are used to accelerate the Poisseuile flow simulation calculation based on the lattice Boltzmann method.Two different addressing methods,linear addressing and subscript addressing are designed,these two addressing methods are respectively applied to the lattice point colision,migration flow,and macroscopic calculation of the lattice Boltzmann program,then discuss the influence of two addressing methods on the calculation efficiency of the program. At the same time,unified memory management is used in the program,and the variables opened up in this way can be used on the host side and the device side at the same time,which simplifies the code complexity and reduces the consumption of frequently opening up memory for variables.Using Intel(R) Xeon(R) E-52620 v4 CPU and Nvidia Quadro GP100GPU for calculations,the linear addressing method and the subscript addressing method have obtained 71 times and 25 times the speedup ratio of CPU serial code respectively.

The lymphatic system plays an important part in the body’s immunity and cell’s internal environment homeostasis. Like a blood circulatory system, the lymphatic system is a piping system throughout the body, which is composed mainly of lymphatic fluid and lymphatic vessels. The spontaneous contraction of the lymphatic vessels drives the flow of lymphatic fluid in the vessels. The spontaneous contraction-relaxation mechanism of lymphatic vessels is determined by the oscillating feedback of Ca2+ concentration and NO concentration. The distribution of NO in the vessels plays an important role in the contraction cycle of lymphatic vessels. The shear force acting on the lymphatic valves due to the flow of fluid is the main source of NO. In a real system, the distribution of NO in a certain section of lymphatic vessel will be affected by other lymphanion connected to it, especially the upstream connecting fragments. Through the lattice Boltzmann method, a multi-segment lymphatic vessel model with valve structure is established, which reproduces the feedback mechanism of Ca2+ and NO, valve change and fluid flow. There are three types of lymphatic vessels in the model, namely the initial lymphatic vessel, the collecting lymphatic vessel, and the outlet lymphatic vessel. The number of lymphatic vessels can be unlimited and inputted by the parameters. The number of lymphatic vessels is 3－5, and there are two pairs of valves in each lymphatic vessel. In this paper studied are the distribution of NO and pressure in multi-segment lymphatic vessel, and the change in the flow of each vessel in the three-segment vessel model over time.

由于通信网络稀疏多径信道下节点能量受限及大量冗余节点被覆盖,常用节点动态调度会使部分外围节点被忽视,导致通信网络覆盖率下降,因此提出通信网络稀疏多径信道的冗余节点动态调度方法.建立稀疏多径信道方阵,获取信道的增益向量,构建通信网络稀疏多径信道模型;在该模型基础上,获得网络覆盖率,确定冗余节点和正常节点覆盖范围;引入覆盖冗余鉴别模块,通过休眠动态调度算法,完成冗余节点动态调度.经过仿真发现,上述方法不仅能减少网络能量消耗,还能使通信网络覆盖率得到保证,网络能耗均衡,避免了多节点同步休眠和覆盖漏洞的情况,提高了节点调度效率.

The lymphatic system contains intraluminal leaflet valves that function to bias lymph flow back towards the heart. These valves are present in the collecting lymphatic vessels, which generally have lymphatic muscle cells and can spontaneously pump fluid. Recent studies have shown that the valves are open at rest, can allow some backflow, and are a source of nitric oxide (NO). To investigate how these valves function as a mechanical valve and source of vasoactive species to optimize throughput, we developed a mathematical model that explicitly includes Ca2+ -modulated contractions, NO production and valve structures. The 2D lattice Boltzmann model includes an initial lymphatic vessel and a collecting lymphangion embedded in a porous tissue. The lymphangion segment has mechanically-active vessel walls and is flanked by deformable valves. Vessel wall motion is passively affected by fluid pressure, while active contractions are driven by intracellular Ca2+ fluxes. The model reproduces NO and Ca2+ dynamics, valve motion and fluid drainage from tissue. We find that valve structural properties have dramatic effects on performance, and that valves with a stiffer base and flexible tips produce more stable cycling. In agreement with experimental observations, the valves are a major source of NO. Once initiated, the contractions are spontaneous and self-sustained, and the system exhibits interesting non-linear dynamics. For example, increased fluid pressure in the tissue or decreased lymph pressure at the outlet of the system produces high shear stress and high levels of NO, which inhibits contractions. On the other hand, a high outlet pressure opposes the flow, increasing the luminal pressure and the radius of the vessel, which results in strong contractions in response to mechanical stretch of the wall. We also find that the location of contraction initiation is affected by the extent of backflow through the valves.

As one of the major causes of cardiovascular diseases, the formation mechanism and the external factors of blood embolism are always the concerned problems of medical field, biological and physical field. Owing to thrombotic formation and structure being complicated, the difficulty in curing thrombosis greatly increases. Pulsation flows have a positive effect on dredging blood embolism. Owing to the blood viscosity and the inertia of red blood cells, waveform, amplitude and frequency of pulsating flow will influence the effect of dredging blood embolism. The research in this paper is mainly based on the lattice Boltzmann method. In conical pipe with embolism, in order to explore the influences of triangle wave pulsating flow waveform, the effects of differential pressure and frequency on vascular thrombus are studied by calculating the effect of dredging blood embolism. Calculation shows that the effect of dredging blood embolism is not obvious under the condition of low frequency and low differential pressure. On the contrary, the effect is good under the condition of high frequency. Appropriately increasing the differential pressure can also improve the frequency of the triangular wave of the bolt.

随着科学技术的迅速发展，知识成为社会和经济健康发展的重要支点。为了使工科大学物理满足科技和社会发展的需求，本文以翻转课堂模式为主体，互联网教学、演示实验教学、课堂教学为辅，对工科大学物理教学模式进行探索与实践，并分析其优势与缺点，指出改革创新之处。

To research the effect of pulsation flow on anti-thrombosis, the plasma is treated as water, and the red blood cells are regarded as suspended rigid particles having the same density as water. First, an appropriate embolism is formed in a tapered pipe under a certain hematocrit and differential pressure, and then a pulsating flow is exerted on the inlet of the tapered pipe to study the positive effect on anti-thrombosis of the pulsating flow.

The lattice Boltzmann method is applied to study the flow in elastic blood vessels. Steady flow in elastic aneurysm models has been examined for several aneurysm sizes. The overall features of the flow and the stresses on the aneurysm walls in steady flow are discussed. The wall shear stress magnitude in the recirculation zone is about ten times less than in the entrance tube. Both wall shear stress and wall normal stress profiles exhibit large magnitude peaks near the reattachment point at the distal end of the aneurysm.

A 2D model of a blood vessel under rolling manipulation ( RM ) is presented. The numerical simulations of blood flow are based on lattice Boltzmann method. It is found that RM can increase the blood flow. Different RM frequency () has different influence on flow. When the frequency is equal to the pulsing flow frequency,the average flow over one period is the largest. Streamlines diagrams in different time when are given. Vortexes can be seen in the region under the stenosis. The distributions of streamlines change periodically.

The mechanism of blood embolism formation always attracts the attention of researchers. Through calculating rigid particle movement in a bifurcated pipe, the blood flow as well as blood embolism in a bifurcated pipe are simulated preliminarily, and the flow speed and the probability to form thrombus are investigated. We can draw a conclusion that the higher the hematocrit is, the easier the blood is to form embolism, meanwhile, the bigger the pressure difference, the harder the blood is to form embolism. We also find that the embolism tends to occur at the entrance of a bifurcated pipe and bifurcation forming place. Beyond the bifurcation place, the hematocrit of the blood in a big tube is larger than that in a small tube.

Aiming at blood embolism problem in the circulation of the blood,the two-dimensional tapered tube model is es-tablished based on lattice Boltzmann method,and blood embolism is simulated in tapered tube regarding rigid particles as red blood cells.The average speed of particles in flow field,snapshots of particles in the pipeline,positions of particles in the pipeline,and the volume rate of particles in the different horizontal pipeline are showed respectively.Meanwhile,particles distribution is recorded when they are embolism in the whole pipe.The results show that the greater hematocrit,the easier em-bolism,and the greater differential pressure,the more difficult embolism,and the tapered tube outletis easily is embolized.

Introduction The aim of this study is to determine the effects and mechanisms of budesonide on angiogenesis in a murine asthma model. Material and methods Murine asthma models were established and mice were divided into three groups: the model group (OVA-sensitized and challenged mice), the BUD group (budesonide-treated mice) and the PBS group (normal control mice). Mice in the BUD group were administered with inhaled budesonide (100 µg/kg) daily. The effects on airway inflammation, angiogenesis, expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were examined. Results Administration of budesonide ameliorated allergic airway inflammation (2.90 ±0.18 vs. 4.80 ±0.20, p < 0.01) and significantly reduced the percentage vascularity (0.78 ±0.14 vs. 2.83 ±0.90, p < 0.01) compared with those in the asthmatic model mice. It also reduced the expression of HIF-1α (immunohistochemistry results: 71.70 ±1.40 vs. 89.60 ±0.79, p < 0.001; western blotting results: 0.88 ±0.41 vs. 0.97 ±0.47, p < 0.05), as well as that of VEGF (immunohistochemistry results: 26.30 ±1.03 vs. 93.30 ±1.54, p < 0.001; western blotting results: 1.12 ±0.22 vs. 2.08 ±0.30, p < 0.01). Percentage vascularity had positive correlation with both HIF-1α (r = 0.785, p < 0.01) and VEGF (r = 0.693, p < 0.01) expression. Furthermore, there is positive relationship between HIF-1α and VEGF expression (r = 0.641, p < 0.05). Conclusions The results demonstrate that budesonide has an important inhibitory effect on angiogenesis in asthma. Inhaled administration of budesonide achieved anti-angiogenic activity through inhibition of HIF-1α and VEGF expression. The results support a potential anti-remodeling role for budesonide in the treatment of human asthma.

Based on the lattice Boltzmann method, the motion of single suspended particle in tapered tube is simulated numerically. The distributions of velocity and pressure in the flow field are obtained. The hydrodynamic force on the particle boundary is evaluated by conventional momentum exchange method (CME), lattice-type-dependent momentum-exchange method (LME) and stress tensor integral method (STI) separately. The variations of velocity and the trajectory of the particle which starts at different places are analyzed, the results evaluated by LME are in excellent agreement with those by STI and the results evaluated by CME are slightly different from those by the former two methods.

Electrowetting of electrolyte droplets and flows on flat and rough surfaces were studied using the lattice Boltzmann model. Hysteresis and saturation of the contact angle in electrowetting were observed, and this behavior was much more amplified for the rough surface. On a rough surface, the existence of wide grooves will result in saturation of the contact angle. Alternatively, if there are narrow grooves that can be bridged by the droplet, the contact angle will change with discrete jumps and will exhibit hysteresis. We show that the flux across the channel can be effectively controlled by the external voltage in a rough-wall channel. (C) Koninklijke Brill NV, Leiden, 2011

Lattice Boltzmann method is used to study fluids in a bifurcated tube composed of tubes with different diameters.The flow velocity,streamline distribution and the trajectory of single particle in the bifurcated tube are analyzed for the fulture study on blood flow in the bifurcated tube.

The conventional momentum-exchange method (CME) is verified to be accurate for the stationary boundary by Mei et al. [Phys. Rev. E 65, 041203 (2002)], but it might be inaccurate when the boundary is moving in the lattice Boltzmann simulations. A lattice-type-dependent momentum-exchange method (LME) is presented to evaluate the hydrodynamic force on moving boundaries, in which the additional momenta induced by the type-changing lattices are well considered. LME preserves the superior features of CME, such as reliability, simplicity, and parallelism. Without any interpolation and integration, the algorithm is independent of boundary geometries, and therefore, efficient in computation and easy to be implemented in both two and three dimensions. A series of cylinder sedimentations are simulated to illustrate the accuracy and robustness of LME, and the results are in excellent agreement with those by the arbitrary Lagrangian-Eulerian technique (ALE). The lateral migrations of a particle are also investigated in the simulations of a neutrally buoyant cylinder in a Poiseuille flow, and consistent with the Segré-Silberberg effect.