Acute peripheral nerve recording Characteristics of polymer-based longitudinal intrafascicular electrodes

We examined the recording characteristics of two different types of polymer-based longitudinal intrafascicular electrodes (LIFEs) in peripheral nerve: single-stranded (s-polyLIFEs) and multistranded (m-polyLIFEs). Recordings were also made from Pt-Ir wire-based electrodes (PtIrLIFEs) as a control. The electrodes were implanted in either tibial or medial gastrocnemius branches of the rabbit sciatic nerve, and in the sciatic nerve of rats. Recorded neural activity induced by manually elicited afferent neural activity showed that both polyLIFE versions performed comparably to PtIrLIFEs.     

Human nerve stimulation thresholds and selectivity using a multi-contact nerve cuff electrode.

Testing of the recruitment properties and selective activation capabilities of a multi-contact spiral nerve cuff electrode was performed intraoperatively in 21 human subjects. The study was conducted in two phases. An exploratory phase with ten subjects gave a preliminary overview of the data and data collection process and a systematic phase with eleven subjects provided detailed recruitment properties. The mean stimulation threshold of 25 +/- 17 nC was not significantly different than previous studies in animal models but much lower than muscle electrodes. The selectivity, defined as the percent of total activation of the first muscle recruited before another muscle reached threshold, ranged from 27% to 97% with a mean of 55%. In each case, the muscle that was selectively activated was the first muscle to branch distal to the cuff location. This study serves as a preliminary evaluation of nerve cuff electrodes in humans prior to chronic implant in subjects with high tetraplegia.     

Normal molecular repair mechanisms in regenerative peripheral nerve interfaces allow recording of early spike activity despite immature myelination

Clinical use of neurally controlled prosthetics has advanced in recent years, but limitations still remain, including lacking fine motor control and sensory feedback. Indwelling multi-electrode arrays, cuff electrodes, and regenerative sieve electrodes have been reported to serve as peripheral neural interfaces, though long-term stability of the nerve-electrode interface has remained a formidable challenge. We recently developed a regenerative multi-electrode interface (REMI) that is able to record neural activity as early as seven days post-implantation. While this activity might represent normal neural depolarization during axonal regrowth, it can also be the result of altered nerve regeneration around the REMI. This study evaluated high-throughput expression levels of 84 genes involved in nerve injury and repair, and the histological changes that occur in parallel to this early neural activity. Animals exhibiting spike activity increased from 29% to 57% from 7 to 14 days following REMI implantation with a corresponding increase in firing rate of 113%. Two weeks after implantation, numbers of neurofilament-positive axons in the control and REMI implanted nerves were comparable, and in both cases the number of myelinated axons was low. During this time, expression levels of genes related to nerve injury and repair were similar in regenerated nerves, both in the presence or absence of the electrode array. Together, these results indicate that the early neural activity is intrinsic to the regenerating axons, and not induced by the REMI neurointerface.     

Functionally selective peripheral nerve stimulation with a flat interface nerve electrode

One of the important goals of peripheral nerve electrode development is to design an electrode for selective recruitment of the different functions of a common nerve trunk. A challenging task is gaining selective access to central axon populations. In this paper, a simple electrode that takes advantage of the neural plasticity to reshape the nerve is presented. The flat interface nerve electrode (FINE) reshapes the nerve into a flat geometry to increase the surface area and move central axon populations close to the surface. The electrode was implanted acutely on the sciatic nerve of eight cats. The FINE can significantly reshape the nerve and fascicles (p<0.0001) while maintaining the same total nerve cross-sectional area. The stimulation thresholds were 2.89 nC for pulse amplitude modulation and 10.2 nC for pulsewidth modulation. Monopolar, square-pulse stimulation with single contacts on the FINE selectively recruited each of the four main branches of the sciatic nerve. Simultaneous stimulation with two contacts produced moments about the ankle joint that were a combination of the moments produced by the individual contacts when stimulated separately.     

Direct current electrical conduction block of peripheral nerve

Electrical currents can be used to produce a block of action potential conduction in whole nerves. This block has a rapid onset and reversal. The mechanism of electrical nerve conduction block has not been conclusively determined, and inconsistencies appear in the literature regarding whether the block is produced by membrane hyperpolarization, depolarization, or through some other means. We have used simulations in a nerve membrane model, coupled with in vivo experiments, to identify the mechanism and principles of electrical conduction block. A nerve simulation package (Neuron) was used to model direct current (dc) block in squid, frog, and mammalian neuron models. A frog sciatic nerve/gastrocnemius preparation was used to examine nerve conduction block in vivo. Both simulations and experiments confirm that depolarization block requires less current than hyperpolarization block. Dynamic simulations suggest that block can occur under both the real physical electrode as well as adjacent virtual electrode sites. A hypothesis is presented which formulates the likely types of dc block and the possible block current requirements. The results indicate that electrical currents generally produce a conduction block due to depolarization of the nerve membrane, resulting in an inactivation of the sodium channels.     

Wavelength and intensity dependence of retinal evoked responses using in vivo optic nerve recording

We use a whole-animal model and wavelength-selective optical stimulation to investigate relationships between optical stimulus characteristics and neural signaling. Light-emitting diodes are used to selectively stimulate rod and cone pathways in Rana pipiens. A suction electrode is used to make in vivo measurements of the compound action potential from the optic nerve as the wavelength and intensity of the stimulus is varied. Our results demonstrate that the cone and rod pathways can be separately stimulated and analyzed with our method and, thus, provide a means to model the response of such pathways to more complex stimuli.     

MATLAB在磁光记录薄膜温度特性研究中的应用

简要介绍了MATLAB软件及其主要特点,讨论了磁性材料的温度特性及其测量方法,重点分析了MATLAB在磁光记录薄膜温度特性研究中的应用：通过插值方法用已知实验数据点估算新的数据点,应用MATLAB数学函数求解磁光记录薄膜各功能层的居里温度。本文的具体实例表明,在磁学研究中使用MATLAB可以提高实验效率。     

Modeling and simulation for hybrid electric vehicles. I. Modeling

A model for the hybrid electric vehicle (HEV) powertrain simulation has been constructed with a specific power control strategy for an electric-assisted HEV in parallel configuration. The HEV was built by the University of Tennessee, Knoxville. Experimental procedures and data analysis for characterizing power output from the battery and the auxiliary power unit (APU) are presented. The model is implemented based on the empirical formulation and power control scheme, a power control strategy by means of throttle position. It also incorporates regeneration and regenerative braking for battery capacity recovery. The model allows for real time evaluation of a wide range of parameters in vehicle operation as a HEV, a pure electric vehicle, or as a conventional vehicle.     

一种车用动力型蓄电池的建模仿真研究

高效的动力蓄电池对于汽车新型动力而言非常关键。建立合理的电池动态模型对于研究动力电池在动态情况的性能十分有意义。PNGV电池模型运用等效电路的思想来模拟电池的动态特性。通过HPPC测试,对模型的参数进行了合理的估计,并在Matlab/simulink中建立了相应的仿真模型。通过与实验数据的对比,验证了模型的合理性。建立的仿真模型可为新型汽车动力系统的仿真提供基础。     

BCI Meeting 2005--workshop on signals and recording methods.

This paper describes the highlights of presentations and discussions during the Third International BCI Meeting in a workshop that evaluated potential brain-computer interface (BCI) signals and currently available recording methods. It defined the main potential user populations and their needs, addressed the relative advantages and disadvantages of noninvasive and implanted (i.e., invasive) methodologies, considered ethical issues, and focused on the challenges involved in translating BCI systems from the laboratory to widespread clinical use. The workshop stressed the critical importance of developing useful applications that establish the practical value of BCI technology.     

Dynamic control of extracellular environment in in vitro neural recording systems.

A technique is presented for rapid fabrication of microfluidic channels on top of multichannel in vitro neural recording electrode arrays. The channels allow dynamic control of both stable and transient flow patterns over localized areas of the array, over biologically relevant timescales. A cellular model consisting of thermally sensitive dorsal root ganglion neurons was integrated into the devices. The device was used to demonstrate precise control of the extracellular microenvironment of individual cells on the array. Since the methods presented here are not specific to a particular cell type or neural recording system, the technique is amenable to a wide range of applications within the neuroscience field.     

Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.     

发电机变压器组录波再认识

自首个关于发电机变压器组（以下简称发变组）录波的行业标准颁布并实施以来．发变组录波引起了前所未有的关注和讨论.根据发变组保护和录波装置的研发与实践,结合行业标准,对发变组录波的现状、功能定义、通道配置、启动方式,以及抗干扰、采样率、数据安全、供电可靠性、保护录波插件、录波评判等问题进行了讨论,并提出自己的见解.     

18650动力电池SOC的建模与估算研究

为了实现对18650动力电池荷电状态(SOC)的准确在线估算,将外界条件划分为12种情况,研究了有效电量、电池衰老及环境温度对电池SOC的影响。建立了一个BP神经网络模型,在12种条件下对其进行样本学习训练,建立了一种能够适用于不同条件下的基于条件查找方法的SOC估算模型。通过与传统方法对比,证明改进的估算方法具有更好的精度和实用性。     

径向驱动式啮合电机建模与仿真研究

针对一种改进的径向驱动式啮合电机结构,采用有限元方法分析了磁场特性,依据有限元计算结果建立电机的非线性分析模型,将模型与控制协同对径向驱动式啮合电机的动态特性进行仿真分析.研制与仿真模型结构参数完全相同的物理样机,采用不同的控制方式和负载转矩对样机进行加载实验.结果显示:实测负载转矩与仿真分析得到的负载转矩较为接近,从而验证了有限元仿真模型的准确性和有效性;在开环控制时,细分磁极换相控制节拍,并且调整绕组电压能够有效增大输出转矩和减小脉动.     

水电机组调节系统建模与仿真研究

在Matlab／Simulink环境下建立与水轮发电机组及其调节系统实际相一致的仿真模型,能够准确的模拟机组的各种工况。其中水轮机模型以水轮机综合特性曲线为基础,采用曲线的方法来表示水轮机流量和力矩与其它参数之间的关系,引水系统采用弹性水击模型,论证了仿真模型的有效性和实用性。     

微型燃料电池内传输数据模型建立及实验研究

微流体燃料电池其阳极侧燃料传质的控制技术直接决定了电池的整体性能.以强化燃料传质的微射流方法作为研究对象,建立空气自流动微流体燃料电池的三维数学模型,对微射流的物理形状与燃料传输和微电池性能的关系进行分析.结果表明,将射流孔设计在中下部位能够强化燃料传输效果;增加射流孔数量能扩大微射流的作用区域,但会降低射流速度,此时...     

Modeling and inference of multisubject fMRI data.

This article reviews four commonly used approaches to group modeling in fMRI. The methods differ in their computational intensity (FSL with its two-level estimation including MCM being the most intense) and assumptions (SPM2 with its assumption of spatially homogeneous covariance V/sub g/ being most restrictive). This study also distinguishes fixed-effects models from mixed-effects models and motivates the importance of a mixed-effects model for group fMRI analysis. The sections following that describe single-subject modeling and show a general method for estimating the group model.