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Dale's Principle is necessary for an optimal neuronal network's dynamics 戴尔原理是最优神经网络动力学的必要条件
Pub Date : 2013-07-02 DOI: 10.4236/am.2013.410A2002
E. Catsigeras
We study a mathematical model of biological neuronal networks composed by any finite number $N geq 2$ of non necessarily identical cells. The model is a deterministic dynamical system governed by finite-dimensional impulsive differential equations. The statical structure of the network is described by a directed and weighted graph whose nodes are certain subsets of neurons, and whose edges are the groups of synaptical connections among those subsets. First, we prove that among all the possible networks such that their respective graphs are mutually isomorphic, there exists a dynamical optimum. This optimal network exhibits the richest dynamics: namely, it is capable to show the most diverse set of responses (i.e. orbits in the future) under external stimulus or signals. Second, we prove that all the neurons of a dynamically optimal neuronal network necessarily satisfy Dale's Principle, i.e. each neuron must be either excitatory or inhibitory, but not mixed. So, Dale's Principle is a mathematical necessary consequence of a theoretic optimization process of the dynamics of the network. Finally, we prove that Dale's Principle is not sufficient for the dynamical optimization of the network.
我们研究了由任意有限数目的$N geq 2$不一定相同的细胞组成的生物神经网络的数学模型。该模型是由有限维脉冲微分方程控制的确定性动力系统。网络的静态结构由一个有向加权图来描述,其节点是神经元的某些子集,其边是这些子集之间的突触连接组。首先,我们证明了在所有可能的网络中,它们各自的图是相互同构的,存在一个动态最优。这种最优网络表现出最丰富的动态:即,它能够在外部刺激或信号下显示最多样化的响应集(即未来的轨道)。其次,我们证明了动态最优神经网络的所有神经元都必须满足戴尔原理,即每个神经元必须是兴奋性或抑制性的,但不能混合。因此,戴尔原理是网络动力学理论优化过程的数学必然结果。最后,我们证明了Dale原理对于网络的动态优化是不充分的。
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引用次数: 7
Modeling of blood vessel constriction in 2-D case using molecular dynamics method 用分子动力学方法建立二维病例血管收缩模型
Pub Date : 2013-06-25 DOI: 10.1063/1.4868829
M. Rendi, Suprijadi, S. Viridi
Blood vessel constriction is simulated with particle-based method using a molecular dynamics authoring software known as Molecular Workbench (WM). Blood flow and vessel wall, the only components considered in constructing a blood vessel, are all represented in particle form with interaction potentials: Lennard-Jones potential, push-pull spring potential, and bending spring potential. Influence of medium or blood plasma is accommodated in plasma viscosity through Stokes drag force. It has been observed that pressure p is increased as constriction c is increased. Leakage of blood vessel starts at 80% constriction, which shows existence of maximum pressure that can be overcome by vessel wall.
血管收缩是用分子动力学创作软件分子工作台(WM)以粒子为基础的方法模拟的。血流和血管壁是构成血管的唯一组成部分,它们都以粒子形式表示为相互作用势:Lennard-Jones势、推拉弹簧势和弯曲弹簧势。介质或血浆的影响通过斯托克斯阻力调节在血浆粘度中。已经观察到,压力p随着收缩度c的增大而增大。血管在收缩80%时开始渗漏,表明存在血管壁可以克服的最大压力。
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引用次数: 2
Non-Thermal Mechanism of Weak Microwave Fields Influence on Nerve Fiber 弱微波场对神经纤维影响的非热机制
Pub Date : 2013-05-09 DOI: 10.1063/1.4821027
M. Shneider, M. Pekker
We propose a non-thermal mechanism of weak microwave field impact on a nerve fiber. It is shown that in the range of about 30 - 300 GHz there are strongly pronounced resonances associated with the excitation of ultrasonic vibrations in the membrane as a result of interaction with electromagnetic radiation. These vibrations create acoustic pressure which may lead to the redistribution of the protein transmembrane channels, and, thus, changing the threshold of the action potential excitation in the axons of the neural network. The influence of the electromagnetic microwave radiation on various specific areas of myelin nerve fibers was analyzed: the nodes of Ranvier, and the so-called initial segment - the area between the neuron hillock and the first part of the axon covered with the myelin layer. It is shown that the initial segment is the most sensitive area of the myelined nerve fibers from which the action potential normally starts.
我们提出了弱微波场对神经纤维影响的非热机制。结果表明,在大约30 - 300 GHz的范围内,由于与电磁辐射的相互作用,膜中存在与超声振动激发有关的强烈明显的共振。这些振动产生的声压可能导致蛋白质跨膜通道的重新分配,从而改变神经网络轴突中动作电位激发的阈值。分析了电磁微波辐射对髓鞘神经纤维的各个特定区域的影响:Ranvier节点和所谓的初始段-神经元丘和覆盖髓鞘层的轴突的第一部分之间的区域。结果表明,初始节段是有髓神经纤维中最敏感的区域,动作电位通常从这里开始。
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引用次数: 19
Coherent Diffraction and Holographic Imaging of Individual Biomolecules Using Low-Energy Electrons 利用低能电子对单个生物分子进行相干衍射和全息成像
Pub Date : 2013-05-07 DOI: 10.1007/978-94-007-6232-9_29
T. Latychevskaia, J. Longchamp, C. Escher, H. Fink
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引用次数: 7
Measuring leaf chlorophyll concentration from its color: A way in monitoring environment change to plantations 从叶片颜色测量叶绿素浓度:监测人工林环境变化的一种方法
Pub Date : 2013-05-06 DOI: 10.1063/1.4820322
Muhammad Abdul Hakim Shibghatallah, S. Khotimah, S. Suhandono, S. Viridi, T. Kesuma
Leaf colors of a plant can be used to identify stress level due to its adaptation to environmental change. For most leaves green-related colors are sourced from chlorophyll a and b. Chlorophyll concentration is normally measured using a spectrophotometer in laboratory. In some remote observation places, it is impossible to collect the leaves, preserve them, and bring them to laboratory to measure their chlorophyll content. Based on this need, measurement of chlorophyll content is observed through its color. Using CIE chromaticity diagram leaf_color information in RGB is transformed into wavelength (in nm). Paddy seed with variety name IR-64 is used in observation during its vegetation stage t (age of 0-10 days). Light exposure time τ is chosen as environmental change, which normally should be about 12 hours/day, is varied (0-12 hours/day). Each day sample from different exposure time is taken, its color is recorded using HP Deskjet 1050 scanner with 1200 dpi, and its chlorophyll content is obtained from a...
由于植物对环境变化的适应,叶子颜色可以用来识别胁迫水平。对于大多数叶子,与绿色相关的颜色来自叶绿素a和b。叶绿素浓度通常在实验室使用分光光度计测量。在一些偏远的观测地点,不可能收集、保存叶片,并将其带到实验室测量叶绿素含量。基于这种需要,通过其颜色来测量叶绿素含量。使用CIE色度图将RGB中的leaf_color信息转换为波长(以nm为单位)。采用品种号IR-64的水稻种子,在其植被期(0-10天)进行观察。当环境变化时,选择光照时间τ,通常应为12小时/天左右,变化范围为0-12小时/天。每天采集不同曝光时间的样品,使用1200 dpi的HP Deskjet 1050扫描仪记录其颜色,其叶绿素含量由…
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引用次数: 73
Penetration Deep into Tissues of Reactive Oxygen Species Generated in Floating-Electrode Dielectric Barrier Discharge (FE-DBD): in Vitro Agarose Gel Model Mimicking an Open Wound 漂浮电极介质阻挡放电(FE-DBD)中产生的活性氧深入组织:模拟开放性伤口的琼脂糖凝胶模型
Pub Date : 2013-03-14 DOI: 10.1615/PLASMAMED.2013006218
D. Dobrynin, G. Fridman, G. Friedman, A. Fridman
In this manuscript we present an in vitro model based on agarose gel that can be used to simulate a dirty, oily, bloody, and morphologically complex surface of, for example, an open wound. We show this models effectiveness in simulating depth of penetration of reactive species generated in plasma deep into tissue of a rat and confirm the penetration depths with agarose gel model. We envision that in the future such a model could be used to study plasma discharges (and other modalities) and minimize the use of live animals: plasma can be optimized on the agarose gel wound model and then finally verified using an actual wound.
在这篇论文中,我们提出了一个基于琼脂糖凝胶的体外模型,该模型可用于模拟脏、油、血和形态复杂的表面,例如开放性伤口。我们证明了该模型在模拟等离子体中产生的活性物质深入大鼠组织的渗透深度方面的有效性,并通过琼脂糖凝胶模型证实了渗透深度。我们设想,在未来,这样的模型可以用于研究等离子体放电(和其他模式),并尽量减少活体动物的使用:等离子体可以在琼脂糖凝胶伤口模型上进行优化,然后最终使用实际伤口进行验证。
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引用次数: 33
Effects of anchored flexible polymers on mechanical properties of model biomembranes 锚定柔性聚合物对生物膜模型力学性能的影响
Pub Date : 2013-02-25 DOI: 10.1063/1.4794653
Hao Wu, H. Noguchi
We have studied biomembranes with grafted polymer chains using a coarse-grained membrane simulation, where a meshless membrane model is combined with polymer chains. We focus on the polymer-induced entropic effects on mechanical properties of membranes. The spontaneous curvature and bending rigidity of the membranes increase with increasing polymer density. Our simulation results agree with the previous theoretical predictions.This original published article PDF was submitted in error and has been replaced with the version immediately following the text of this Corrigendum. The original paper is also attached but marked as WITHDRAWN.
我们使用粗粒度膜模拟研究了带有接枝聚合物链的生物膜,其中无网格膜模型与聚合物链相结合。我们关注聚合物诱导的熵效应对膜力学性能的影响。膜的自发曲率和弯曲刚度随聚合物密度的增加而增加。我们的仿真结果同意前面的理论预测。这篇最初发表的文章PDF是错误提交的,并已被本勘误表文本之后的版本所取代。原文也在附件中,但标注为撤回。
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引用次数: 1
Comparative Molecular Mechanics and Quantum Mechanics Study of Microhydration of Nucleic Acid Bases 核酸碱基微水化的分子力学与量子力学比较研究
Pub Date : 2013-02-11 DOI: 10.4236/JBPC.2016.72005
J. Lino, E. Gonz'alez, A. Deriabina, M. Velasco, V. Poltev
DNA is the most important biological molecule, and its hydration contributes essentially to the structure and functions of the double helix. We analyze the microhydration of the individual bases of nucleic acids and their methyl derivatives using methods of molecular mechanics (MM) with the Poltev-Malenkov (PM), AMBER and OPLS force fields, as well as ab initio Quantum Mechanics (QM) calculations at MP2/6-31G(d,p) level of theory. A comparison is made between the calculated interaction energies and the experimental enthalpies of microhydration of bases, obtained from mass spectrometry at low temperatures. Each local water-base interaction energy minimum obtained with MM corresponds to the minimum obtained with QM. General qualitative agreement was observed in the geometrical characteristics of the local minima obtained via the two groups of methods. MM minima correspond to slightly more coplanar structures than those obtained via QM methods, and the absolute MM energy values overestimate corresponding values obtained with QM. For Adenine and Thymine the QM local minima energy values are closer to those obtained by the PM potential (average of 0.72 kcal/mol) than by the AMBER force field (1.86 kcal/mol). The differences in energy between MM and QM results are more pronounced for Guanine and Cytosine, especially for minima with the water molecule forming H-bonds with two proton-acceptor centers of the base. Such minima are the deepest ones obtained via MM methods while QM calculations result in the global minima corresponding to water molecule H-bonded to one acceptor and one donor site of the base. Calculations for trimethylated bases with a water molecule corroborate the MM results. The energy profiles were obtained with some degrees of freedom of the water molecule being frozen. This data will contribute to the improvement of the molecular mechanics force fields.
DNA是最重要的生物分子,它的水合作用对双螺旋的结构和功能起着至关重要的作用。本文采用分子力学(MM)方法,结合Poltev-Malenkov (PM)、AMBER和ops力场,以及MP2/6-31G(d,p)理论水平的从头算量子力学(QM)计算,分析了核酸中单个碱基及其甲基衍生物的微水合作用。将计算得到的相互作用能与质谱法测定的低温下碱的微水化焓进行了比较。用MM得到的每个局部水基相互作用能最小值与用QM得到的最小值相对应。两组方法得到的局部极小值的几何特征在定性上基本一致。与QM方法相比,MM最小值对应的共面结构略多,MM能量绝对值高估了QM方法得到的相应值。腺嘌呤和胸腺嘧啶的QM局域最小能量值更接近PM电位的局域最小能量值(平均0.72 kcal/mol),而AMBER力场的局域最小能量值为1.86 kcal/mol。对于鸟嘌呤和胞嘧啶,MM和QM结果之间的能量差异更为明显,特别是对于水分子与碱基的两个质子受体中心形成氢键的最小值。这样的最小值是通过MM方法得到的最深的最小值,而QM计算得到的是水分子与碱的一个受体和一个给体位点相对应的全局最小值。三甲基化碱基与水分子的计算证实了MM的结果。能量分布是在水分子被冻结的一定自由度下得到的。这些数据将有助于分子力学力场的改进。
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引用次数: 0
Structure-property-function relationships in triple helical collagen hydrogels 三螺旋胶原水凝胶的结构-性能-功能关系
Pub Date : 2012-12-09 DOI: 10.1557/opl.2012.1653
Giuseppe Tronci, A. Doyle, S. Russell, D. Wood
In order to establish defined biomimetic systems, type I collagen was functionalised with 1,3-Phenylenediacetic acid (Ph) as aromatic, bifunctional segment. Following investigation on molecular organization and macroscopic properties, material functionalities, i.e. degradability and bioactivity, were addressed, aiming at elucidating the potential of this collagen system as mineralization template. Functionalised collagen hydrogels demonstrated a preserved triple helix conformation. Decreased swelling ratio and increased thermo-mechanical properties were observed in comparison to state-of-the-art carbodiimide (EDC)-crosslinked collagen controls. Ph-crosslinked samples displayed no optical damage and only a slight mass decrease (~ 4 wt.-%) following 1-week incubation in simulated body fluid (SBF), while nearly 50 wt.-% degradation was observed in EDC-crosslinked collagen. SEM/EDS revealed amorphous mineral deposition, whereby increased calcium phosphate ratio was suggested in hydrogels with increased Ph content. This investigation provides valuable insights for the synthesis of triple helical collagen materials with enhanced macroscopic properties and controlled degradation. In light of these features, this system will be applied for the design of tissue-like scaffolds for mineralized tissue formation.
为了建立明确的仿生体系,I型胶原蛋白被1,3-苯二乙酸(Ph)功能化为芳香双功能段。在对其分子结构和宏观特性进行研究后,研究了材料的功能,即可降解性和生物活性,旨在阐明该胶原蛋白系统作为矿化模板的潜力。功能化的胶原水凝胶显示出保存的三螺旋构象。与最先进的碳二亚胺(EDC)交联胶原对照相比,肿胀率降低,热机械性能增加。ph交联的样品在模拟体液(SBF)中孵育1周后没有光学损伤,只有轻微的质量下降(约4 wt.-%),而edc交联的胶原蛋白降解了近50 wt.-%。SEM/EDS显示非晶矿物沉积,表明随着Ph值的增加,水凝胶中磷酸钙的比例增加。该研究为合成具有增强宏观性能和降解控制的三螺旋胶原材料提供了有价值的见解。鉴于这些特点,该系统将应用于矿化组织形成的类组织支架的设计。
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引用次数: 16
Chemo-mechanical instabilities in polarizable active layers 极化活性层的化学-机械不稳定性
Pub Date : 2012-07-25 DOI: 10.14288/1.0042953
M. Koepf
We formulate and explore a generic continuum model of a polarizable active layer with neo-Hookean elasticity and chemo-mechanical interactions. Homogeneous solutions of the model equations exhibit a stationary long-wave instability when the medium is activated by expansion, and an oscillatory short-wave instability in the case of compressive activation. Both regimes are investigated analytically and numerically. The long-wave instability initiates a coarsening process, which provides a possible mechanism for the establishment of permanent polarization in spherical geometry.
我们制定并探索了具有新胡克弹性和化学-力学相互作用的极化活性层的一般连续统模型。当介质被膨胀激活时,模型方程的齐次解表现出平稳的长波不稳定性,而在压缩激活的情况下,模型方程的齐次解表现出振荡的短波不稳定性。对这两种情况进行了分析和数值研究。长波不稳定性启动了一个粗化过程,这为球面几何中永久极化的建立提供了可能的机制。
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引用次数: 0
期刊
arXiv: Biological Physics
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