排序方式: 共有15条查询结果,搜索用时 421 毫秒
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The objective of this study was to create a thin film optode for fast pH measurements that meets the requirements for imaging pH-responses from cells as well as for a future hybrid design for detection of multiple analytes simultaneously. The sensor is based on the covalent attachment of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to a film forming cellulose acetate material through a sulfonamide linkage. The synthesis routes of the cellulose material and regio-specific covalent attachment of the dye are described in detail. The sensor was sterilized in two different ways and showed excellent biocompatibility with Chinese hamster ovary cells. Imprints from cells and μm thin cell extensions were visualized when altering pH of the surrounding solution. The sensor was tested together with time-dependent sigmoidal calibrations giving pH determinations with an exceptional precision and accuracy during measurement within pH 6-8. The precision of the optode, calculated as pooled S.D. (n = 8) according to IUPAC recommendations between pH 6.641 and 7.742 was 0.0029. The accuracy was significantly better than the electrode used as reference during the measurements. The response time (0-95%) was 100 s between pH 6.641 and 7.742 and the reverse response (95-0%) was 80 s. The sensor shows great potential for extra-cellular pH determination over time during cell growth and pharmacological exposure. 相似文献
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Coronal sections of unfixed rat brain samples were prepared on a flat substrate in order to reveal hippocampal formation (CA1-4 pyramidal neurons) and adjacent neocortical white matter. We demonstrate the feasibility of using surface sensitive techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and scanning probe microscopy (SPM) to probe lipid distribution, as well as the subcellular features of neurons. In the same anatomical areas, the phase shift image in SPM is especially useful in revealing the cross-section of subcellular structures. We show that the phase shift images reveal distinctive subcellular features and ion images of CN− and PO2− fragments from ToF-SIMS appear to define some of the subcellular features. 相似文献
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Ha Youn Lee 《Physica A》2010,389(15):2975-2980
As borders between different regions, lines are an important element of natural images. Already at the level of the mammalian primary visual cortex (V1), neurons respond best to oriented bars. We reduce a set of images to linear segments and analyze their statistical properties. In particular, appropriately defined Fourier spectra show more power in their transverse component than in the longitudinal one. We then characterize filters that are best suited for extracting information from such images, and find some qualitative consistency with neural connections in V1. We also demonstrate that such filters are efficient in reconstructing missing lines in an image. 相似文献
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Bayram Unal 《Applied Surface Science》2011,258(1):207-211
In this work, the degradation of visible photoluminescence of porous silicon (PSi) under the influential actions of cell culture medium has been mainly studied in order to comprehend the quenching mechanisms necessitating the cell growth on spongy-like-silicon structures, which could form either micro- and/or nano-dimensional morphologies after stain-etching of the poly- or single-crystalline Si surfaces. Quenching effect of the neuron culture medium on visibly luminescent and non-luminescent porous silicon is found to be quite obvious so that this step of the culture process, especially, over nanostructured silicon is extremely essential for a variety of bionanotechnological applications. 相似文献
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In this paper, we numerically study the effect of channel block on the spiking temporal coherence and spatial synchronization on Hodgkin-Huxley (HH) neuron networks. It is found that under sodium CB the spike coherence is badly reduced, and the synchronization can, depending on the network randomness (the fraction of random shortcuts), be either enhanced or reduced, while, under potassium CB, the spike coherence can be enhanced but the synchronization is reduced. Interestingly, for certain networks of relatively large randomness, the neuron firings can achieve the best temporal coherence at an optimal potassium CB. These results show that under certain conditions channel blocking can increase and optimize the spike coherence and the synchronization on the complex HH neuron networks, whereby the neurons would exhibit a better and the best sub-threshold signal encoding. 相似文献
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A novel approach was developed to form engineered, electrically viable, neuronal networks, consisting of ganglion-like clusters of neurons. In the present method, the clusters are formed as the cells migrate on low affinity substrate towards high affinity, lithographically defined carbon nanotube templates on which they adhere and assemble. Subsequently, the gangliated neurons send neurites to form interconnected networks with pre-designed geometry and graph connectivity. This process is distinct from previously reported formation of clusterized neural networks in which a network of linked neurons collapses via neuronal migration along the inter-neuron links. The template preparation method is based on photo-lithography, micro-contact printing and carbon nanotube chemical vapor deposition techniques. The present work provides a new approach to form complex, engineered, interconnected neuronal network with pre-designed geometry via engineering the self-assembly process of neurons. 相似文献
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Ali H. Nayfeh 《Nonlinear dynamics》2008,51(4):483-500
We compare two approaches for determining the normal forms of Hopf bifurcations in retarded nonlinear dynamical systems; namely,
the method of multiple scales and a combination of the method of normal forms and the center-manifold theorem. To describe
and compare the methods without getting involved in the algebra, we consider three examples: a scalar equation, a single-degree-of-freedom
system, and a three-neuron model. The method of multiple scales is directly applied to the retarded differential equations.
In contrast, in the second approach, one needs to represent the retarded equations as operator differential equations, decompose
the solution space of their linearized form into stable and center subspaces, determine the adjoint of the operator equations,
calculate the center manifold, carry out details of the projection using the adjoint of the center subspace, and finally calculate
the normal form on the center manifold. We refer to the second approach as center-manifold reduction. Finally, we consider
a problem in which the retarded term appears as an acceleration and treat it using the method of multiple scales only.
Communicated by G. Rega 相似文献
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阎子勤 《长沙理工大学学报(自然科学版)》1999,(1)
本文论述了一种基于自适应神经元方法实现输电线路的单片机反时特性曲线的新技术。该技术在对故障电流量进行测量、分析和判断的基础上,采用三种典型的反时限特性方程,基于自适应神经元的方法,综合考虑线路故障状态的特征,使用三个自适应神经元,并根据单个神经元的智能控制算法,推导出自适应神经元的反时限保护特性算法,从而解决了单片机不能实现的反对限指数运算,减小或消除了采用查表法的相对误差和时延。该方案具有很强的实用性。 相似文献