Blood-brain barrier modeling: challenges and perspectives

The blood-brain barrier （BBB） forms a highly selective inter- face between blood and brain. Extensive research efforts have completely changed our view of the BBB in the last years, from a static, impermeable barrier to a dynamic, highly regulated and specific cellular system. The BBB ultrastructurally consists of specialized brain microvascular endothelial cells （BMEC） characterized by low pinocytic activity,

Study on the Continuous Transition From PTC Effect to GBBL Capacitor of Semiconducting BaTiO_3 Ceramics——Grain Boundary Barrier Model

The Daniels’ barium vacancy layer model of semiconducting BaTiO3 ceramics is analyzed.A grain boundary barrier model with both acceptor states of grain boundary and barium vacancy diffusion layers for the transition from PTC effect to grain boundary barrier layer (GBBL) capacitor is proposed.The proposed model solves the problem occurring in Daniels’ model and makes it possible to calculate physical properties of semiconducting BaTiO3 ceramics and relevant devices.

MODELING OF OCCUPANT DYNAMIC RESPONSE TO CAR-BARRIERS CRASH ON HIGHWAY

The dynamic response involved in car-roadside barrier impacts is studied. Therisk of occupant injures in such accidents is investigated. An approach based on accident analysisand mathematical modeling is developed and described in three steps. Firstly a study of car-roadsidebarrier impact accidents is carried out with available data to define a system including car, road,roadside barrier, and occupant. Secondly a mathematical model to simulate car-to-barrier impact isdeveloped by using multi-body program MADYMO. Finally, dynamic responses of the occupant duringimpact are simulated using a car compartment model with a HYBRID III occupant model and an inputload pulse calculated in the second step. The dynamic responses of the car are analyzed by changingimpact conditions such as impact angle and impact velocity. The injury risks of the occupants arediscussed in terms of the occupant kinematics and calculated parameters: accelerations of the head,chest, and pelvis, as well as HIC value. Verification of model with experimental data is performed.Possible counter-measures for highway vehicle traffic safety and improvement of roadside barrierdesign are presented. Research prospects in this field are also proposed.

ON THE EXPECTED DISCOUNTED PENALTY FUNCTION IN A MARKOV-DEPENDENT RISK MODEL WITH CONSTANT DIVIDEND BARRIER

This article considers a Markov-dependent risk model with a constant dividend barrier. A system of integro-differential equations with boundary conditions satisfied by the expected discounted penalty function, with given initial environment state, is derived and solved. Explicit formulas for the discounted penalty function are obtained when the initial surplus is zero or when all the claim amount distributions are from rational family. In two state model, numerical illustrations with exponential claim amounts are given.

Centrifugal model tests and numerical simulations for barrier dam break due to overtopping

The present study focuses on the breaching process and failure of barrier dams due to overtopping. In this work, a series of centrifugal model tests is presented to examine the failure mechanisms of landslide dams. Based on the experimental results, failure process and mechanism of barrier dam due to overtopping are analyzed and further verified by simulating the experimental overtopping failure process. The results indicate that the barrier dam will develop during the entire process of overtopping in the width direction, whereas the breach will cease to develop at an early stage in the depth direction because of the large particles that accumulate on the downstream slope. Moreover, headcut erosion can be clearly observed in the first two stages of overtopping, and coarsening on the downstream slope occurs in the last stage of overtopping. Thus, the bottom part of the barrier dam can survive after dam breaching and full dam failure becomes relatively rare for a barrier dam. Furthermore, the remaining breach would be smaller than that of a homogeneous cohesive dam under the same conditions.

DISLOCATION EMISSION AND EQUATION OF ENERGY BARRIERS AT MODEL I CRACK TIP

The propagation for the model I crack in aluminum single crystal has been directly studied by in-situ TEM observation.The equation of energy barrier of the dislocation building-up and emission at the model I crack tip has been established by means of Peierls-Nabarro dislocation model and starting from angle of energy.By means of calculation,the critical value of spontaneous emission of the dislocations from tip of the model I crack was obtained.

Comparative Toxicity of Nanomaterials to Air-blood Barrier Permeability Using an In Vitro Model

Objective To comparatively study the toxicity of four metal-containing nanoparticles(MNPs) and their chemical counterparts to the air-blood barrier(ABB) permeability using an in vitro model.Methods ABB model, which was developed via the co-culturing of A549 and pulmonary capillary endothelium, was exposed to spherical CuO-NPs(divided into CuO-40, CuO-80, and CuO-100 based on particle size), nano-Al2O3(sheet and short-rod-shaped), nano-ZnO, nano-Pb S, CuSO4, Al2(SO4)3, Zn(CH3COO)2, and Pb(NO3)2 for 60 min.Every 10 min following exposure, the cumulative cleared volume(ΔTCL) of Lucifer yellow by the model was calculated.A clearance curve was established using linear regression analysis of ΔTCL versus time.Permeability coefficient(P) was calculated based on the slope of the curve to represent the degree of change in the ABB permeability.Results The results found the increased P values of CuO-40, CuO-80, sheet, and short-rod-shaped nano-Al2O3, Al2(SO4)3, and Pb(NO3)2.Among them, small CuO-40 and CuO-80 were stronger than CuO-100 and CuSO4;no difference was observed between Al2(SO4)3 and sheet and short-rod-shaped nano-Al2O3;and nano-Pb S was slightly weaker than Pb(NO3)2.So clearly the MNPs possess diverse toxicity.Conclusion ABB permeability abnormality means pulmonary toxicity potential.More studies are warranted to understand MNPs toxicity and ultimately control the health hazards.

Analytical model including the fringing-induced barrier lowering effect for a dual-material surrounding-gate MOSFET with a high-κ gate dielectric

By solving Poisson＇s equation in both semiconductor and gate insulator regions in the cylindrical coordinates, an analytical model for a dual-material surrounding-gate （DMSG） metal-oxide semiconductor field-effect transistor （MOSFET） with a high-k gate dielectric has been developed. Using the derived model, the influences of fringing-induced barrier lowering （FIBL） on surface potential, subthreshold current, DIBL, and subthreshold swing are investigated. It is found that for the same equivalent oxide thickness, the gate insulator with high-k dielectric degrades the short-channel performance of the DMSG MOSFET. The accuracy of the analytical model is verified by the good agreement of its results with that obtained from the ISE three-dimensional numerical device simulator.

Pricing Stochastic Barrier Options under Hull-White Interest Rate Model

A barrier option valuation model with stochastic barrier which was regarded as the main feature of the model was developed under the Hull-White interest rate model.The purpose of this study was to deal with the stochastic barrier by means of partial differential equation methods and then derive the exact analytical solutions of the barrier options.Furthermore,a numerical example was given to show how to apply this model to pricing one structured product in realistic market.Therefore,this model can provide new insight for future research on structured products involving barrier options.

Human induced pluripotent stem cell based in vitro models of the blood-brain barrier： the future standard？

There is an urgent and tremendous need for human dis- ease models in drug development in order to improve pre- clinical predictability. In the case of brain disorders drugs have to cross the blood-brain barrier （BBB） to enter the central nervous system （CNS）. It was estimated that more than 95% of the drugs cannot cross the BBB.

Various patterns in dielectric barrier glow discharges simulated by a dynamic model

In this paper, various patterns of dielectric barrier glow discharge simulated by a phenomenological dynamic model are reported.The model is constructed based on the basic dynamic process of dielectric barrier glow discharge and involves the voltage-transfer characteristic as well as the lateral inhibition effect.In simulations, different driving voltage profiles are applied to achieve one or two pulsed discharges in each half-period and the corresponding pattern evolution is investigated.The final stable patterns driven by a rectangular wave voltage organize simply as stationary striations or hexagonal lattices.The patterns driven by a multi-step wave appear to be much more complicated, with complementary striations,concentric rings and square superlattices observed.The evolutions of these patterns from the initial uniform state are described and it is found that the spreading of the inhibition effect plays a key role in these evolutions.The numerical simulations in the present work are in excellent accordance with previous experiments and fluid modeling.This dynamic model proves to be a convenient and promising approach to reproducing different pattern structures and pattern evolutions in dielectric barrier glow discharge systems.

Numerical Methods for Discrete Double Barrier Option Pricing Based on Merton Jump Diffusion Model

As a kind of weak-path dependent options, barrier options are an important kind of exotic options. Because the pricing formula for pricing barrier options with discrete observations cannot avoid computing a high dimensional integral, numerical calculation is time-consuming. In the current studies, some scholars just obtained theoretical derivation, or gave some simulation calculations. Others impose underlying assets on some strong assumptions, for example, a lot of calculations are based on the Black-Scholes model. This thesis considers Merton jump diffusion model as the basic model to derive the pricing formula of discrete double barrier option;numerical calculation method is used to approximate the continuous convolution by calculating discrete convolution. Then we compare the results of theoretical calculation with simulation results by Monte Carlo method, to verify their efficiency and accuracy. By comparing the results of degeneration constant parameter model with the results of previous models we verified the calculation method is correct indirectly. Compared with the Monte Carlo simulation method, the numerical results are stable. Even if we assume the simulation results are accurate, the time consumed by the numerical method to achieve the same accuracy is much less than the Monte Carlo simulation method.

Applying the Socio-Ecological Model to barriers to implementation of ACL injury prevention programs: A systematic review

Background: Preventing anterior cruciate ligament(ACL) injuries is important to avoid long-term adverse health consequences. Identifying barriers to implementation of these prevention programs is crucial to reducing the incidence of these injuries. Our purpose was to identify barriers of implementation for ACL injury prevention programs and suggest mechanisms for reducing the barriers through application of a SocioEcological Model(SEM).Methods: Studies investigating ACL prevention program effectiveness were searched in Medline via PubMed and the Cochrane Library, and a subsequent review of the references of the identified articles, yielded 15 articles total. Inclusion criteria encompassed prospective controlled trials, published in English, with ACL injuries as the primary outcome. Studies were independently appraised by 2 reviewers for methodological quality using the PEDro scale. Barriers to implementation were identified when reported in at least 2 separate studies. A SEM was used to suggest ways to reduce the identified barriers.Results: Five barriers were identified: motivation, time requirements, skill requirements for program facilitators, compliance, and cost. The SEM suggested ways to minimize the barriers at all levels of the model from the individual through policy levels.Conclusion: Identification of barriers to program implementation and suggesting how to reduce them through the SEM is a critical first step toward enabling ACL prevention programs to be more effective and ultimately reducing the incidence of these injuries.

不同地形梯度下秦巴山区乡村振兴潜力及发展路径

我国山地丘陵地区在空间上相对孤立,乡村发展受到阻碍。开展不同地形梯度下乡村振兴潜力及发展路径研究,旨在为山区因地制宜推进乡村振兴提供理论与科学依据。基于陕南秦巴山区地形差异开展典型村域调研,构建评价指标体系测度乡村振兴潜力,结合相关性与障碍度模型,辨识不同地形梯度下乡村振兴的障碍因素,提出差异化发展建议。结果表明:①各地形梯度下乡村振兴综合潜力由大到小依次为低地形梯度、中低地形梯度、高地形梯度、中高地形梯度,地形梯度与秦巴山区乡村振兴综合潜力及区位条件、基础设施潜力成显著负相关关系;②随着地形梯度的上升,秦巴山区乡村主体、产业发展、人居环境、区位条件、基础设施潜力整体上呈减小趋势,资源禀赋潜力先减小后增大;③不同地形梯度下秦巴山区乡村振兴各维度潜力大小及其障碍因子皆存在明显差异。为优化山区乡村发展模式、全面推进乡村振兴,建议低地形梯度村庄重点防止人口、耕地等农业生产要素流失,中低地形梯度村庄优化基层组织、提升引领能力,中高梯度村庄加强基础设施建设、改善人居环境,高地形梯度村庄充分保护并合理利用林地资源,发展特色产业。

CMC-EBC损伤耦合机理及一体化设计研究进展

陶瓷基复合材料与环境障碍涂层组合(CMC-EBC)是目前航空航天领域最具应用前景的热结构材料体系。本文对CMC-EBC失效机理与分析模型的研究进展进行综述。首先,简要回顾了CMC-EBC材料体系的发展及主要制备工艺。然后,综述了CMC-EBC在服役环境下的主要损伤模式与失效机理,总结发现CMC预制体结构、孔洞缺陷和EBC内裂纹等损伤演化相互影响,这种细观损伤模式的耦合是决定其寿命的关键因素之一,但目前的机理研究主要集中于涂层本身性能及其受环境因素的影响,缺乏对涂层和复合材料编制结构在损伤演化过程中协同效应的考虑。接下来,详细分析了CMC-EBC的失效模拟与预测模型研究的历史与现状,指出其中存在的问题,包括环境因素建模方法和损伤耦合演化模拟技术。目前大部分工作致力于分别开发CMC和EBC的失效模型,而对于CMC-EBC构件的失效预测应考虑其损伤演化与微观结构之间的相互耦合影响。最后,对CMC-EBC材料体系研发与服役性能预测方法进行了展望,认为CMC本体和EBC失效模式相互耦合,开展结构功能一体化设计和分析是CMC-EBC构件研究的趋势。

基于主次屏障的化工装置事故根因分析及“双预”机制应用

双重预防机制(“双预”)是当前国内危化品领域正在广泛推行的一种风险管控系统,但目前缺乏底层和运行层面的理论架构,更缺乏以根因分析(RCA)结果来指导实施“双预”的方法工具,为此,提出“主-次”屏障理论与事件与原因因素分析(ECF)相结合的可视化主-次屏障(VPSB)模型。ECF作为一种典型的RCA技术,由特定主/次屏障失效模式组成灾害事件的致因路径,为VPSB建模提供可视化框图。应用该模型对英国石油BP公司的Texas爆炸中的典型事故场景进行隐患识别和RCA,获得“双预”相关管理措施的具体失效模式,通过与美国化学品安全委员会(CSB)和英国石油(BP)公司对该事件的调查结果对比,发现CSB和BP公司将人的不安全动作作为直接原因开展深层次的原因分析,将关注点放在了人的管理上,并将根本原因宏观地总结为安全主管失职和操作工违规作业,而VPSB模型则关注的是对重大事故隐患本身和工艺过程的管理,用描述具体的次屏障失效模式来突出管理系统存在的根本性问题,其中,在机械完整性管理上的问题最多,且主要是由于管理措施未被合规执行。这为企业优化“双预”的相关工作内容提供了重点整改方向和可操作性建议。

Moments of Discounted Dividend Payments in the Sparre Andersen Model with a Constant Dividend Barrier

We consider the Sparre Andersen risk process in the presence of a constant dividend barrier, and propose a new expected discounted penalty function which is different from that of Gerber and Shiu. We find that iteration mothed can be used to compute the values of expected discounted dividends until ruin and the new penalty function. Applying the new function and the recursion method proposed in Section 5, we obtain the arbitrary moments of discounted dividend payments until ruin.

基于Kriging代理模型的无刷双馈发电机转子优化设计

无刷双馈发电机由于其自身没有电刷、滑环等结构特点,因此被认为是最有希望成为风力发电系统的主流发电机之一。无刷双馈发电机是依靠转子的磁场调制机理实现机电能量转换,其转子的耦合能力是影响电机性能的重要因素。因此本文提出了一种串联笼条辅助磁障转子的新型转子结构,分析了该种转子不同结构参数对电机性能的影响,并提出一种基于Kriging代理模型的多目标差分进化算法的无刷双馈发电机转子优化设计方法。首先建立该种新型转子的参数化模型,通过Kriging代理模型建立优化变量与优化目标之间的响应关系,再利用多目标差分进化算法找到最优的变量组合,最后通过有限元仿真对电机的性能进行分析。

一种高效的持续有向栅栏覆盖算法

如何高效实现持续有向栅栏覆盖是无线充电传感器网络的研究热点,采用射频能量捕获技术可以解决栅栏中节点能量受限的问题。在已知网络区域中构建栅栏的节点分布和候选部署位置的情况下,研究射频能量源(Energy source,ES)的部署方案,从而满足所有节点的充电需求。首先,确定网络区域中的栅栏矩形;然后,提出一种基于有向发射的射频能量源最优部署算法(OdepD算法),根据候选位置与栅栏矩形的位置关系得到各个ES的射频能量发射方向和角度,根据有向能量发送模型和充电需求计算各个ES的发射功率;最后,以最小化网络充电总能耗为目标,通过离散粒子群优化充电部署位置,确定最终部署策略。仿真结果证明:OdepD算法可以明显降低网络充电总能耗,高效地实现持续栅栏覆盖。