Modeling the coupling of action potential and electrodes

The present monograph is a study of pulse propagation in nerves. The main project of this work is modeling and simulation of the action potential propagation in a neuron and its interaction with the electrodes in the context of neurochip application. In the first part, I work with an adapted model of FitzHugh-Nagumo derived from the Hodgkin-Huxley model. The second part was the result of turning the spotlight-on onto the drawbacks of Hodgkin-Huxley model and to bring forth, an alternative model: soliton model. The purpose is to comprehend the role of membrane state in the pulse propagation

Glosarium Matematika

273 p.; 24 cm

Morphoelastic rods Part 1: A single growing elastic rod

A theory for the dynamics and statics of growing elastic rods is presented. First, a single growing rod is considered and the formalism of three-dimensional multiplicative decomposition of morphoelasticity is used to describe the bulk growth of Kirchhoff elastic rods. Possible constitutive laws for growth are discussed and analysed. Second, a rod constrained or glued to a rigid substrate is considered, with the mismatch between the attachment site and the growing rod inducing stress. This stress can eventually lead to instability, bifurcation, and buckling

Effect of capillarity on the breakup of liquid jets, interfacial wave and motion of droplets in immiscible liquids

Whether the end-state of a liquid jet is a uniform-radius cylinder or a chain of droplets is addressed in the present thesis, based on the physical principle of surface energy minimization.In comparison with the classic Plateau-Rayleigh theory, the present stability criterion is for a more broad picture. The derived stability criterion has potential applications, for example,for the fabrication of nanoparticles and inkjet printing. Additionally, the effects of capillary flow on the motion of droplets and spinodal decomposition are discussed

Bibliography of Lewis Research Center technical publications announced in 1987

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1987. All the publications were announced in the 1987 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Investigation of Bipolar Electrochemically Exfoliated Graphene for Supercapacitor Applications

Developing a reliable, simple, cost-efficient and eco-friendly method for scale-up production of high-quality graphene-based materials is essential for the broad applications of graphene. Up to now, various manufacturing methods have been employed for synthesizing high quality graphene, however aggregation and restacking has been a major issue and the majority of commercially available graphene products are actually graphite microplates. In this study, bipolar electrochemistry techniques have been used to exfoliate and deposit graphene nanosheets in a single-step process to enable high performance device application. In the first part of this study, bipolar electrochemistry concept is utilized to design a single-step and controllable process for simultaneously exfoliating a graphite source and depositing both graphene oxide (GO) and reduced graphene oxide (rGO) layers on conductive substrates. The electrochemical performance of the fabricated graphene-based materials as the electrode for supercapacitors has been investigated. Areal capacitance of 1.932 mF cm-2 for the rGO, and 0.404 mF cm-2 for GO at a scan rate of 2 mV s-1 were achieved. Moreover, a cut-off frequency of 1820 Hz was obtained, which is a promising characteristic for AC filtering applications. Although the physicochemical characteristics of produced graphene have been evaluated in the first part, the exfoliation and deposition mechanisms were still unclear. In the second part of this dissertation, a novel modified BPE system with an electrically connected graphite-platinum couple acting as the bipolar electrode has been designed in order to decouple and investigate the contribution of anodic/cathodic exfoliation and deposition of graphene in the BPE process. Electron microscopy and infrared spectroscopy results indicate that both anodic and cathodic exfoliation of graphene could take place regardless of the type of polarization; however, the morphology and deposition rate highly depend on the polarization. Furthermore, the graphene fabricated by anodic exfoliation was found to show higher levels of oxidation compared to the graphene produced by cathodic exfoliation. In the last part of this study, for the first time, a vertically aligned graphene layer was deposited on a micro-sized interdigitated gold current collector by a modified bipolar electrochemistry method. Both time domain and frequency domain electrochemical performance of on-chip micro-supercapacitors (MSCs) were evaluated. An areal capacity of 640.9 μF cm-2 at a scan rate of 2 mV s-1 and 239.31 μF cm-2 at discharge current density of 25 μA cm-2 was delivered with an excellent cyclability. Most importantly, the MSC exhibited a very fast response (cut-off frequency of 3486 Hz) and very close to ideal performance (phase angle reached -83.2°) at low frequencies. For the first time, this dissertation reported the modified BPE method as a novel approach for three in one exfoliation, deposition and reduction of high-quality graphene with vertically aligned and porous structure. The unique design of the BPE cell enabled the author to study the BPE mechanisms and measure the bipolar current for the first time. The method could successfully be employed to fabricate fast response microsupercapacitors based on vertically aligned graphene nanosheets

Molecular simulation of liquid crystals

This article reviews recent progress in the computer simulation of liquid crystals at the molecular level. It covers the use of simple rigid-body models of the constituent molecules, and more detailed modelling via atomistic force fields. Bulk mesophases, inhomogeneous systems, and interfaces, are discussed. Recent progress in calculating elastic properties and dynamics is summarized. As well as presenting an overview, some specific topics of recent interest are highlighted: the biaxial nematic phase, chiral phases, ionic liquid crystals, and charge-transfer systems