Melittin Makes “Ion Channel” on the Membrane of Cells

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轮胎接触面对车－简支梁桥耦合振动的影响

现有分析车一桥耦合振动的研究中,都假设移动车辆与路面的接触关系为点接触．事实上,轮胎与路面是通过面接触的,通过建立新的三维车轮模型,分析了面接触对车一桥耦合振动的影响,将车轮与路面的接触面简化为长方形,通过接触面间的位移协调条件和力相互作用建立车一桥耦合振动方程,同时还研究了接触面对车一桥耦合振动的影响。     

一种改进的补丁比较模型的研究与实现

补丁比较技术可以定位程序补丁前后的差异,在漏洞发掘、病毒变种分析等领域得到了广泛的应用。以结构化比较技术为基础,建立了层次化的补丁比较模型IPCTM(Improved Patch Comparison Technique Model);改进了固定点传播算法,提出了一种针对错误匹配的修正机制;设计了控制流图重构和代码辅助匹配策略,增加了对未配对函数和基本块的补充处理。实验结果表明,IPCTM能够准确识别语义变动,消除部分非语义变动带来误差,有效减少了后续分析的工作量。     

Relationship between action potential, contraction-relaxation pattern, and intracellular Ca2+ transient in cardiomyocytes of dogs with chronic heart failure

Abnormalities of contractile function have been identified in cardiomyocytes isolated from failed human hearts and from hearts of animals with experimentally induced heart failure (HF). The mechanism(s) responsible for these functional abnormalities are not fully understood. In the present study, we examined the relationship between action potential duration, pattern of contraction and relaxation, and associated intracellular Ca²⁺ transients in single cardiomyocytes isolated from the left ventricle (LV) of dogs (n = 7) with HF produced by multiple sequential intracoronary microembolizations. Comparisons were made with LV cardiomyocytes isolated from normal dogs. Action potentials were measured in isolated LV cardiomyocytes by perforated patch clamp, Ca²⁺ transients by fluo 3 probe fluorescence, and cardiomyocyte contraction and relaxation by edge movement detector. HF cardiomyocytes exhibited an abnormal pattern of contraction and relaxation characterized by an attenuated initial twitch (spike) followed by a sustained contracture ('dome') of 1 to 8 s in duration and subsequent delayed relaxation. This pattern was more prominent at low stimulation rates (58% at 0.2 Hz, n = 211, 21% at 0.5 Hz, n = 185). Measurements of Ca²⁺ transients in HF cardiomyocytes at 0.2 Hz manifested a similar spike and dome configuration. The dome phase of both the contraction/relaxation pattern and Ca²⁺ transients seen in HF cardiomyocytes coincided with a sustained plateau of the action potential. Shortening of the action potential duration by administration of saxitoxin (100 nM) or lidocaine (30 μM) reduced the duration of the dome phase of both the contraction/relaxation profile as well as that of the Ca²⁺ transient profile. An increase of stimulation rate up to 1 Hz caused shortening of the action potential and disappearance of the spike-dome profile in the majority of HF cardiomyocytes. In HF cardiomyocytes, the action potential and Ca²⁺ transient duration were not significantly different from those measured in normal cells. However, the contraction-relaxation cycle was significantly longer in HF cells (314 ± 67 ms, n = 21, vs. 221 ± 38 ms, n = 46, mean ± SD), indicating impaired excitation-contraction uncou pling in HF cardiomyocytes. The results show that, in cardiomyocytes isolated from dogs with HF, contractile abnormalities and abnormalities of intracellular Ca²⁺ transients at low stimulation rates are characterized by a spike-dome configuration. This abnormal pattern appears to result from prolongation of the action potential. Received 22 January 1998; received after revision 16 March 1998; accepted 27 March 1998     

一类有效的板弯曲单元

鉴于Ｉｒｏｎｓ的分片检验条件，在修正势能泛函中引入更一般的广义协调概念，可以推出两种简单易行的板弯曲单元。这类单元总能通过分片检验，而且可以以较少的自由度获得较高的计算精度。     

从发明先进医学设备获诺贝尔医学奖中得到的启示

百年来的诺贝尔生理或医学奖中,因发明先进的仪器设备而获诺贝尔医学奖共有四次,它们是:1924年爱因托芬(荷兰)发明了心电图机;1979年科马克(美国)亨斯菲尔德(英国)发明了电脑辅助X线断层摄影(CT);1980年内尔(德国)萨克曼(德国)发明了应用膜片钳技术;2003年比德.曼斯菲尔德(英国)和保罗.劳特布尔在核磁共振成像技术领域的突破性成就。这些先进的仪器设备的发明对人类的科学与文明的贡献是巨大的,我们从多方面可以得到深刻的启示[1]。     

Relationship between plant species diversity and patch characteristics in a marsh in the Sangjiang Plain, China —Using Yaluhe farm as an example

Based on Quick Bird satellite image data, the present study examined small-scale herbaceous community patches in the marsh of the Sanjiang Plain and measured patch characteristics such as the area, perimeter and shape by GPS. The coenological characteristics of the patches were investigated using quadrat method, and the vascular plant species were recorded using transect method. A total of 219 plant species were recorded, which represents 12.2% of the vascular flora in Heilongjiang Province. Our results showed that species number S correlated with patch area and perimeter; richness index (R) correlated with patch perimeter; Simpson index (D) correlated with patch area and perimeter/area; Shannon-Wiener index (H′) correlated with patch area, perimeter and perimeter/area; Evenness index (Jsw) correlated with perimeter/area. Both S and R have significant difference between different size of patches. Plant diversity in the small-scale herbaceous communities tended to increase with the patch area and perimeter. We concluded that edge effects and the habitat heterogeneity of the patches are important in determining the number of species. The relative smoothness of the patch edges also affects the plant diversity of the patches. The richness of plant species in the marsh in the Sanjiang Plain is highly sensitive to the small-scale patches, which continues to play an important role in preserving plant diversity in the local area.     

Relationship between plant species diversity and patch characteristics in a marsh in the Sangjiang Plain,China—Using Yaluhe farm as an example

Based on Quick Bird satellite image data, the present study examined small-scale herbaceous community patches in the marsh of the Sanjiang Plain and measured patch characteristics such as the area, perimeter and shape by GPS. The coenological characteristics of the patches were investigated using quadrat method, and the vascular plant species were recorded using transect method. A total of 219 plant species were recorded, which represents 12.2% of the vascular flora in Heilongjiang Province. Our results showed that species number S correlated with patch area and perimeter; richness index (R) correlated with patch perimeter; Simpson index (D) correlated with patch area and perimeter/area; Shannon-Wiener index (H′) correlated with patch area, perimeter and perimeter/area; Evenness index (Jsw) correlated with perimeter/area. Both S and R have significant difference between different size of patches. Plant diversity in the small-scale herbaceous communities tended to increase with the patch area and perimeter. We concluded that edge effects and the habitat heterogeneity of the patches are important in determining the number of species. The relative smoothness of the patch edges also affects the plant diversity of the patches. The richness of plant species in the marsh in the Sanjiang Plain is highly sensitive to the small-scale patches, which continues to play an important role in preserving plant diversity in the local area.     

沙坡头地区人工-自然景观空间格局研究

研究人类活动对景观的影响是景观生态学研究的一个很重要的方面。人工－自然荒漠景观的空间结构受其沙漠背景的强烈影响，同时受强化了的人工干扰的影响，其格局带有明显的人为作用，对沙坡头地区荒漠景观生态空间格局基本特点、景观嵌块体类型及人类活动和自然的关系进行了分析，随着人类活动的加剧，景观多样性加大，均匀性、破碎度值和分离度值较大，为人活动已改变了荒漠局地的特性，生态恶化受到一定的遏止，但沙化影响正在威胁着人类对荒漠管理的成果，提出荒漠人工－自然景观研究中应注重景观生态风险及动态监测系统的研究。     

“弄假成真”：基于对抗学习的数据增广方法

 近年来,深度学习在计算机视觉领域取得了巨大的突破,其背后是利用大量标签数据对深度网络进行监督训练,而标注大规模数据集非常昂贵且十分耗时。针对大规模数据集标注问题,苹果公司的Shrivastava团队希望借助现有的计算机仿真技术以及对抗训练的方法,实现仿真图像的无监督学习,从而避免昂贵的图像标注过程。该团队在对抗网络的基础上提出3个创新点：（1）自正则项;（2）局部对抗损失;（3）使用历史生成图片更新判别器,使得生成真实化图片的同时保留输入图像特征。实验结果展示该方法可以生成高度真实化的图片。研究者通过训练凝视估计模型、手部姿态估计模型定量分析生成图片的效果,分析结果表明,使用生成图片训练的模型,在MPⅡGaze数据集上测试效果有很大的提升,达到了当时最好的效果。不过,研究者并未在包含多个物体的复杂场景下进行实验,文中提出的方法在复杂场景下的应用还存在局限性。