Porcine Choroid plexus epithelial cells in culture: regulation of barrier properties and transport processes

The epithelial cells of the choroid plexus are the structural basis of the blood-cerebrospinal fluid (CSF)-barrier. Here we summarise our recent efforts to culture those cells mainly on permeable supports in vitro. Isolated from porcine brains, we report a simple protocol for the primary culture using cytosine arabinoside as an additive that is cytotoxic for other cells except the plexus epithelial cells. Enhanced barrier properties are obtained by withdrawal of serum from the culture medium after confluency is reached. Cells improve their polarity, permeability for hydrophilic substrates is lowered, electrical resistance is increased tenfold, and a pH-gradient is built up across the cell monolayer. Polarised secretion of proteins and most importantly fluid secretion into the apical filter compartment was attained and proven to be dependent on the Na(+),K(+)-ATPase activity. Active transport processes (penicillin G, riboflavin, myo-inositol, ascorbic acid) were studied and clearly showed the involvement of the organic anion transporter. The permeability of the barrier was found to be regulated by cyclic adenosine monophosphate (cAMP). Moreover, we report that cell proliferation and differentiation is controlled by components of the extracellular matrix. The present culture model could now be used as an in vitro system to quantify drug transport across the blood-CSF-barrier.     

Electron diffraction analysis and techniques for studying polypeptides and other polymers

A review of electron diffraction studies of polypeptide structures is given together with a discussion of the methods for obtaining diffraction patterns without serious specimen damage by electrons. Electron diffraction studies of poly-β-benzyl-L-aspartate show that diffraction intensities can be used quantitatively to determine polypeptide structures and the advantages of these studies in observing high angle meridional reflections are shown up by the observation of a novel structure in the unheated left handed helical form of the polypeptide. A large catalogue of techniques for preparing orientated films of polypeptides suitable for electron diffraction investigations makes the technique a powerful one for studying these structures. Polypeptides are shown to be useful for studying electron beam damage in protein-like materials.     

Function to structure/material mappings for conceptual design synthesis and their supportive strategies

Conceptual design aims at developing design concepts that can satisfy the specified design requirements, where the design concepts are normally in the form of a physical structure. There has been quite a lot of work done in this area of design research, from which it is now generally agreed that functional decomposition and function to structure mapping are two fundamental steps of design task in synthesis for design solution. However, there have not been many strategies to support these design tasks, especially for the function to structure mapping. In addition, design solutions may not just consist of physical structure. Sometimes only materials can provide a feasible design solution; sometimes a materials solution might be more effective and/or more economic than a structural solution. Again, there have not been many strategies that explicitly considered materials solution at the early design stage. To address these problems, this paper proposes three mappings from function to both structure and material. Several embodiment strategies supporting these mappings are also proposed, including four functional matches used for identifying functional design solutions, and a performance match used for ensuring that the identified solution can satisfy the performance requirements or constraints. A design case is also studied to illustrate as well as to test the effectiveness of these strategies.     

Toxicology of choroid plexus: special reference to metal-induced neurotoxicities

The chemical stability in the brain underlies normal human thinking, learning, and behavior. Compelling evidence demonstrates a definite capacity of the choroid plexus in sequestering toxic heavy metal and metalloid ions. As the integrity of blood-brain and blood-CSF barriers, both structurally and functionally, is essential to brain chemical stability, the role of the choroid plexus in metal-induced neurotoxicities has become an important, yet under-investigated research area in neurotoxicology. Metals acting on the choroid plexus can be categorized into three major groups. A general choroid plexus toxicant can directly damage the choroid plexus structure such as mercury and cadmium. A selective choroid plexus toxicant may impair specific plexus regulatory pathways that are critical to brain development and function, rather than induce massive pathological alteration. The typical examples in this category include lead-induced alteration in transthyretin production and secretion as well as manganese interaction with iron in the choroid plexus. Furthermore, a sequestered choroid plexus toxicant, such as iron, silver, or gold, may be sequestered by the choroid plexus as an essential CNS defense mechanism. Our current knowledge on the toxicological aspect of choroid plexus research is still incomplete. Thus, the future research needs have been suggested to focus on the role of choroid plexus in early CNS development as affected by metal sequestration in this tissue, to explore how metal accumulation alters the capacity of the choroid plexus in regulation of certain essential elements involved in the etiology of neurodegenerative diseases, and to better understand the blood-CSF barrier as a defense mechanism in overall CNS function.     

一种运动目标检测与跟踪的方法研究

针对视频序列中运动目标的检测与跟踪进行了研究,提出了一种基于视频序列的YCbCr模式归一化定义,利用三帧图像差分,区域生长生成运动矩形框的方法对目标进行运动分割;并利用基于速度差的粒子滤波器对运动框的移动进行预测,从而达到快速跟踪运动目标的目的。实验结果表明通过调节内部参数,在固定摄像机不复杂背景下对人、车运动目标检测与跟踪是快速且有效的。     

Controller synthesis for automatic control systems: State and prospects

This paper considers the state and prospects for studies of the central problem of the theory and practice of automatic control—the problem of controller synthesis for systems with nonlinear plants. A crucial factor in the performance of controllers for nonlinear plants is the use of deep feedback for derivatives of the output variable, which provides localization of disturbances in fast subprocesses (against the background of the main processes) and allows the generation of the required dynamic properties     

变维卡尔曼滤波实现运动目标的跟踪

在球坐标激光跟踪测量系统中，由于受到各种干扰的影响，激光跟踪系统测量所得到的目标状态参量的测量值与目标的真实状态往往不尽相同，如何抑制随机误差，成为提高激光跟踪测量系统精度的一个重要问题。本文提出变维卡尔曼滤波算法来抑制随机误差的影响，仿真结果验证了该方法的有效性。     

基于目标成本法的模块化产品变型设计研究

将成本设计理念应用于模块化产品变型设计进行了研究,建立了产品模块化变型设计的目标成本控制模型和流程,实现了产品模块化变型设计过程中功能满足,冗余成本降低的要求,提高了模块化产品的设计效率以及加快了产品的上市时间.     

Structure and expression of the transthyretin gene in the choroid plexus: a model for the study of the mechanism of evolution

Thyroid hormones are key regulators of brain differentiation and function. They permeate strongly into lipid membranes. However, a substantial portion of thyroid hormone is retained in the intravascular/extracellular compartments by binding to plasma proteins. In the brain, transthyretin is the most important of these proteins. This transthyretin is synthesized in the epithelial cells of the choroid plexus and exclusively secreted towards the brain. A net movement of thyroid hormones from the blood to the brain ensues. During evolution, transthyretin synthesis in the choroid plexus and the beginnings of a neocortex first appeared at the stage of the stem reptiles. The affinity of transthyretin for thyroxine increased and that for triiodothyronine decreased during evolution. This could augment the importance of deiodination for regulation of metabolism and gene expression by thyroid hormones in the brain. Successive shifts of the splice site at the 5' end of exon 2 of transthyretin precursor mRNA in the 3' direction led to a shortening of the N-terminal sections and to an increase in hydrophilicity of the N-terminal regions of transthyretin. This shift can be explained by a sequence of single base mutations. It could be an example for a molecular mechanism of positive Darwinian evolution. The selection pressure, which led to the expression of the transthyretin gene in the choroid plexus during evolution, might have been the maintenance of thyroid hormone homeostasis in the extracellular compartment of the brain in the presence of the greatly increasing volume of the lipid phase.     

水下目标自主连续跟踪与定位算法研究

针对水下无人航行器进行纯方位目标运动分析时难以获取精确稳定的目标方位的情况,研究了实时有效的方位预处理方法。针对水下环境噪声起伏变化的特点,采用自动阈值检测和抛物线波束内插方法获取精确的目标方位;提出了一种预置跟踪算法实现对目标方位的连续检测跟踪,克服了方位历程中可能出现的野值和漏检现象,确保基于修正极坐标的扩展卡尔曼滤波算法(modified polar extended Kalman filter,MPEKF)正常工作。试验结果表明,该方法能够对移动目标进行运动分析,正确获取目标距离、速度信息,误差较小,具有很高的工程价值和军事应用前景。     

Vascular wall: potential target for the physicochemical effects of cis-unsaturated free fatty acids

Diets rich in monounsaturated cis-FFA (cis FFA) are associated with a significant reduction of cardiovascular risk. Although several different mechanisms have been proposed to explain this protective effect, the biochemical processes involved have not been fully elucidated. It has been shown that upon their incorporation into the plasma membrane, cis FFA induce a marked perturbation of the lipid domains, altering membrane fluidity as well as lipid-lipid and lipid-protein interactions in the bilayer plane. During the last few years, several lines of evidence have shown that these perturbations disrupt the activity of several membrane proteins and enzymatic systems. As a result, several critical transmembrane signaling systems, including the Ins(1,4,5)P(3)/DAG/[Ca(2+)](i), the cAMP/PKA, and the voltage-operated Ca(2+) influx are strongly inhibited by cis FFA in different experimental models. Furthermore, this inhibition is associated with alterations in the timing of the cell cycle as well as in the final steps of the secretory pathway. We propose that this complex set of biological actions exerted by cis FFA at the plasma membrane may contribute to explain the protective roles that these molecules appear to exert on the vascular wall.     

Polystyrene and deuteropolystyrene plastic scintillators for a polarized active target

Results of light output measurements for a polystyrene scintillator deuterated to a degree of 96 at. % are presented. Applications of the deuterated scintillator are considered, in particular, as an active detector. In order to polarize the hydrogen nuclei in the scintillation target, a special additive, 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO), was introduced into it. This resulted in a light output of the sample with a thickness of 3.6 mm 50% that of the initial sample.     

Design of directional stiffness catheter for enhancing target accessibility

Journal of Mechanical Science and Technology - One of the main problems for precise tip positioning with steerable catheters is bending outside the steering axis. This paper presents a catheter...     

恒高拖靶舵机系统的设计

为了实现某型掠海恒高拖靶系统的高度控制功能,设计了舵机执行机构和舵回路控制电路。舵机执行机构由组合式螺杆驱动系统、滑动块、支撑架、摇臂及翼角反馈电位器等组成。舵回路控制电路由电流环和位置环组成的双闭环控制结构。针对具体性能指标要求,采用了螺旋滑动丝杠传动机构,确定了牙形角、公称直径和导程等参数,并计算了螺母和螺纹的长度,验证了机构自锁条件;通过对减速比的计算,选择了合适的减速箱型号;通过对电机功率及速度常数的计算,参照电机样本数据表资料,完成了电机的正确选型,并进行了指标验算;设计了以1292功放模块为直流电机驱动器的舵回路控制电路,并对位置反馈和电流反馈作了简要说明。实际使用结果表明,该设计合理、可靠,各项性能能够满足使用要求。     

Teams and their Motivation for Business Process Reengineering: A Research Note

When business process reengineering (BPR) is undertaken, one of the requirements leading to its development and implementation is that of teams. There have not been many publications about the teams that are formed for undertaking BPR. This article addresses the theoretical issues surrounding such teams and attempts to provide an understanding of the role of motivation in such teams. Furthermore, an overview of the research process that is undertaken within the article is presented.     

折反式坦克目标跟踪识别红外光学系统设计

基于光学相关探测,根据坦克目标跟踪识别系统的需求,设计了一种新型的卡塞格林红外光学系统,其非球面的主镜和次镜都取代为球面镜,不存在卡塞格林系统大口径非球面主镜、次镜的高加工精度和装调困难的问题;为满足大视场、大孔径的像差要求,用三个校正透镜,在保护罩中用一个偶次非球面.其系统结构紧凑,口径大,焦距长,分辨率高,并且各视场均能获得接近衍射极限的成像质量,满足坦克目标跟踪识别系统的总体要求和像质的要求.     

BP神经网络系统用于目标台测向定位的设计与实现

采用BP神经网络对目标进行测向定位设计,应用MATLAB辅助神经网络实现了对该系统最佳估计点的计算,并将计算结果与F系统定位算法所得计算结果进行了比较,结果证明提出的新方法效果良好。     

Note: Development of target changeable palm-top pyroelectric x-ray tube

A target changeable palm-top size x-ray tube was realized using pyroelectric crystal and detachable vacuum flanges. The target metals can be exchanged easily by attaching them on the brass stage with carbon tape. When silver and titanium palates (area: 10 mm(2)) were used as targets, silver Lα and titanium K lines were clearly observed by bombarding electrons on the targets for 90 s. The intensities were the same or higher than those of previously reported pyroelectric x-ray tubes. Chromium, iron, nickel, copper, and zinc K lines in the x-ray tube (stainless steel and brass) disappeared by replacing the brass stage and the stainless steel vacuum flange with a carbon stage and a glass tube, respectively.     

Robust target cascading for improving firing accuracy of combat vehicle

Journal of Mechanical Science and Technology - Complex systems like combat vehicles contain numerous subsystems and components. Therefore, simultaneous consideration of hierarchy of a system,...