Targeting and ultrasound imaging of microbubble-based contrast agents

Preparation and characterization of targeted microbubbles (ultrasound contrast agents) is described. Specific ligands were attached to the microbubble shell, and ligand-coated microbubbles were selectively attached to various targets, using either an avidin-biotin model system or an antigen-antibody system for targeting to live activated endothelial cells. Firm attachment of microbubbles to the target was achieved. Forces necessary to detach microbubbles from the target were estimated to exceed dozens of pN. Microbubbles were bound to the target even in the rapidly moving stream of the aqueous medium. Down to 20 ng of the ultrasound contrast material on the target surface could be detected by the ultrasound imaging with a commercial medical imaging system. At high bubble density on the target surface, strong ultrasound image attenuation was observed.  

中压配电网接线模式综合比较

针对当前中压配电系统接线模式研究中对比因素不全面、供电模式粗糙等问题,提出典型接线模式综合对比方法。基于当前我国中压配电网普遍采用的各类接线模式,建立了接线模式对比因素体系和研究思路,并构建了理论分析模型。从可靠性、电压质量、经济性和适应性等角度全面分析和对比各类城市中压配电网典型接线模型的优缺点,得到了对各种负荷密度下接线模式选择非常有益的结论,为电网规划运行人员提供了实际指导。  

Specific targeting of folate–dendrimer MRI contrast agents to the high affinity folate receptor expressed in ovarian tumor xenografts

The need to develop target-specific MRI contrast agents to aid in disease characterization remains highly essential. In this study, we present a generation four polyamidoamine (PAMAM) folate-dendrimer that specifically targets the high affinity folate receptor (hFR) overexpressed on more than 80% of ovarian tumors. In vitro, mouse erythroleukemia cells expressing the hFR bind the radiolabeled folate-dendrimer chelate resulting in over 2700% increase in binding compared with untreated cells. The binding was inhibited by free folic acid to levels observed on folate-receptor-negative cells. In vivo, ovarian tumor xenografts resulted in a 33% contrast enhancement, following the folate-dendrimer chelate administration, that was significantly different compared with results obtained with a non-specific, extracellular fluid space agent, Gd-HP-DO3A. In addition, this contrast enhancement was absent in saline-treated animals, folate-receptor-negative tumors, and was inhibited by free folic acid. Results suggest that a macromolecular, dendrimeric MRI agent with high molecular relaxivities (1646 mM⁻¹ s⁻¹) can be used in specifically targeting the hFR on tumor cells and ovarian tumors.  

暗适应时间、背景亮度和眩光对人眼对比度阈值影响的探讨

目的评估3种背景环境下的中间视觉对比度阈值,并探讨暗适应时间、背景亮度和眩光对人眼对比度阈值的影响。方法实验主要由三名视力正常的受试者参与。每位受试者的矫正视力都达到1.0以上。三种背景环境下的中间视觉对比度阈值由Mesoptometer Ⅱ来测得。结论实验测得在没有眩光的情况下当背景亮度从L=0.1cd·m-2。下降到L=0.032cd·m-2时,或者在L=0.1cd·m-2时眩光的参与,都会造成对比度阈值的上升。在L=0.032cd·m-2无眩光以及L=0.1cd·m-2有眩光这两种情况下,对比度都会在20分钟左右达到一个最大值。  

Pharmacokinetics of Gadomer-17, a new dendritic magnetic resonance contrast agent

Rationale and objectives: Gadomer-17 is a new magnetic resonance (MR) contrast medium presently in clinical development. It is a dendritic gadolinium (Gd) chelate carrying 24 Gd ions. This study investigated the pharmacokinetic behavior of this contrast medium. Methods: The pharmacokinetics of Gadomer-17 were investigated in different species (rat, rabbit, dog, monkey) for up to 7 days after intravenous (i.v.) injection of 25–100 μmol/kg body weight. In addition, elimination and biodistribution were evaluated after single i.v. injection of Gadomer-17 in rats. Results: After i.v. injection Gadomer-17 distributes almost exclusively within the intravascular space without significant diffusion into the interstitial space. The volume of distribution (Vc) in the initial or α-phase ranged from 0.04 1/kg (rats, rabbits) to 0.06 1 kg (monkeys) and 0.07 1/kg (dogs), which reflects mainly the plasma volume. The blood/plasma concentration profile was found to be biphasic. The volume of distribution at a steady state is clearly smaller than that of other contrast media, which distribute to the extracellular space. After single i.v. injection in rats, the dendritic contrast medium was rapidly and completely eliminated from the body, mainly via glomerular filtration. No long-term accumulation or retention of the nonmetabolized agent was detectable in organs or tissues. Conclusions: Gadomer-17 is a promising new MR contrast medium that has an intravascular distribution and a rapid renal elimination.  

不同电网故障情况下DFIG运行特性比较

现代风力发电的发展,对风电生产提出了新的需求,即在电网电压跌落处于一定范围内时风力发电机装置必须保持和电网相连,其中双馈式风力发电机(DFIG)的电压跌落渡过能力是目前风电研究的一个热点。为确保DFIG的低压过渡能力,通过仿真1.5 MW的双馈风力发电机,研究了对称电网电压跌落时,DFIG的定转子的电压电流、电磁转矩、转速、直流侧电压、有功、无功等量的动态响应情况;比较了不同电网电压跌落情况下,各动态响应的剧烈程度;分析了响应产生的原因并介绍了几种可行的双馈风力发电机电压跌落渡过策略。仿真结果说明DFIG在电网电压跌落对称故障下的动态响应由电网电压跌落的程度及系统控制结构决定。  

绝缘子憎水性图像检测方法研究

绝缘子表面憎水性检测是判断绝缘子性能的主要手段，也是确保绝缘子安全运行的重要保证。该文把图像处理技术引入到绝缘子憎水性检测中，通过对绝缘子图像的对比度增强、图像的灰度、梯度及度的信息特征的综合考虑、模糊C均值聚类(fuzzy C-means，FCM)和形态学对憎水性图像进行分割，获取大水珠(或水迹)形状信息，最后用最大面积比法判定绝缘子的憎水性等级。实验结果表明，该算法能够有效地提取出水珠(或水迹)的形状信息、克服传统目测法的主观性，检测结果的准确性满足实际检测的需要。  

单端行波故障测距的组合方法研究

单端辐射状电网发生单相接地故障时,单端行波故障测距的关键是正确识别来自故障点的反射波、对端母线的反射波及健全线路的反射波.行波零模波速具有较强的依频特性,而线模波速较稳定.由于零模波速的不稳定性,当取其为固定值时,导致基于线模、零模波速差的单端行波故障测距精确度不够.针对此问题,首先利用神经网络训练学习,估算出零模波速,基于线模、零模波速差得到初步故障距离,以此初步故障距离从线模行波突变波头中找出故障点反射波头及对端母线反射波头,再把线模波速代入相应的测距公式得到精确故障距离.利用PSCAD/EMTDC搭建仿真模型,对不同的故障情况进行仿真,均验证了该方法具有较高的测量精度和可靠性.  

机器视觉中照明技术的研究进展

本文综述了机器视觉应用中光学测量技术的最新理论与实验研究结果。着重对光源类型、照明方式以及光源颜色的选择和光源位置的控制在机器视觉成像系统的作用做了深入细致的描述。在此基础上展望了光学技术在机器视觉中的应用前景,并指出了目前研究中有待解决的问题。  

金属板屏蔽小室暂态磁场屏蔽效能的对比测试

介绍了一套测量屏蔽小室暂态磁场屏蔽效能的方法,源磁场为冲击电流在发射线圈中激励产生的暂态磁场,发射线圈和接收线圈同轴平行布置。比较开、关门时金属板小室所带3种可拆卸成型门对雷电波和两种频率的阻尼振荡波磁场的屏蔽效能及关门时侧壁对不同暂态磁场屏蔽效能的结果表明,金属板对不同强度暂态磁场的屏蔽效能基本恒定,不同材料结构的门对不同波形暂态磁场的屏蔽效能相差较大,关门后屏蔽效能会提高很多。