Soft and high magnetic moment Co37Fe63 films were electro-deposited with variable additives on Cu/Ti/Si substrates. The correlation between structure and magnetic properties has been investigated. TEM showed the cryst...
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ISBN:
(纸本)9781118029473
Soft and high magnetic moment Co37Fe63 films were electro-deposited with variable additives on Cu/Ti/Si substrates. The correlation between structure and magnetic properties has been investigated. TEM showed the crystal structure of the films to be BCC with a 〈111〉 texture, and a grain size in the range of 10-20 nm. Oxygen in the deposited films has been identified by EDS and EELS using HAADF STEM. SIMS analysis revealed the presence of hydrogen and oxygen in the deposited CoFe films. Electron microscopy results showed that the oxygen was mainly distributed along the grain boundaries in the CoFe film. In regions where oxygen was present in the films, the Fe content was enhanced relative to Co. The magnetic properties of the deposits have been measured by Vibrating Sample Magnetometer (VSM), quantifying the impact of incorporated oxygen in the film on the saturation magnetization and the coercivity.
Information encoded in neuron ensembles has previously been hypothesized to be highly redundant, despite the apparent inefficiency of a redundant encoding system. The recent availability of intracortical, multi-electr...
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Information encoded in neuron ensembles has previously been hypothesized to be highly redundant, despite the apparent inefficiency of a redundant encoding system. The recent availability of intracortical, multi-electrode recordings has enabled the possibility of exploring how neuronal ensembles encode information as a whole. Applying concepts from information theory, we examined the redundancy of the target information encoded in both contralateral and ipsilateral hemispheres of the primary motor cortex (M1) in macaque monkeys performing a center-out reaching task. During movement, we reliably found neurons in contralateral M1 to contain higher target information and to be more redundant than ipsilateral M1 neurons, which is consistent with the conventional understanding that motor control is mainly governed by contralateral M1. Secondly, neuron ensembles in both hemispheres showed largely redundant information encoding. These results suggest that redundancy in information encoding is highly prevalent in the motor cortex and may contribute to proficient motor control.
Neural control of movement is typically studied in constrained environments where there is a reduced set of possible behaviors. This constraint may unintentionally limit the applicability of findings to the generalize...
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Neural control of movement is typically studied in constrained environments where there is a reduced set of possible behaviors. This constraint may unintentionally limit the applicability of findings to the generalized case of unconstrained behavior. We hypothesize that examining the unconstrained state across multiple behavioral contexts will lead to new insights into the neural control of movement and help advance the design of neural prosthetic decode algorithms. However, to pursue electrophysiological studies in such a manner requires a more flexible framework for experimentation. We propose that head-mounted neural recording systems with wireless data transmission, combined with markerless computer-vision based motion tracking, will enable new, less constrained experiments. As a proof-of-concept, we recorded and wirelessly transmitted broadband neural data from 32 electrodes in premotor cortex while acquiring single-camera video of a rhesus macaque walking on a treadmill. We demonstrate the ability to extract behavioral kinematics using an automated computer vision algorithm without use of markers and to predict kinematics from the neural data. Together these advances suggest that a new class of “freely moving monkey” experiments should be possible and should help broaden our understanding of the neural control of movement.
This paper presents a fully complex-valued functional link network (CFLN). The CFLN is a single-layered neural network, which introduces nonlinearity in the input layer using nonlinear functions of the original input ...
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This paper presents a fully complex-valued functional link network (CFLN). The CFLN is a single-layered neural network, which introduces nonlinearity in the input layer using nonlinear functions of the original input variables. In this study, we consider multivariate polynomials as the nonlinear functions. Unlike multilayer neural networks, the CFLN is free from local minima problem, and it offers very fast learning in parameters because of its linear structure. In the complex domain, polynomial based CFLN has an additional advantage of not requiring activation functions, which is a major concern in the complex-valued neural networks. However, it is important to select a smaller subset of polynomial terms (monomials) for faster and better performance, since the number of all possible monomials may be quite large. In this paper, we use the orthogonal least squares method in a constructive fashion (starting from lower degree to higher) for the selection of a parsimonious subset of monomials. Simulation results demonstrate that computing CFLN in purely complex domain is advantageous than in double-dimensional real domain, in terms of number of connection parameters, faster design, and possibly generalization performance. Moreover, our proposed CFLN compares favorably with several other multilayer networks in the complex domain.
A robust surface EMG decomposition tool, referred to as tremor-optimized Convolution Kernel Compensation (CKC) technique, is described. This technique modifies and extends the previously published CKC method in order ...
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ISBN:
(纸本)9781424441211
A robust surface EMG decomposition tool, referred to as tremor-optimized Convolution Kernel Compensation (CKC) technique, is described. This technique modifies and extends the previously published CKC method in order to circumvent the typical assumption on regularity and asynchrony of motor unit firings in normal condition and adapt to the discharge patterns in pathological tremor. The results on synthetic and experimental surface EMG signals demonstrate high performance of decomposition. In the case of simulated surface EMG with 20 dB SNR, excitation level of 20% maximum voluntary contraction (MVC) and simulated tremor frequency of 8 Hz, the newly proposed method identified 8 ± 2 motor units with sensitivity of motor unit discharge identification ≥ 95% and false alarm and miss rates ≤ 5%. The performance worsened with increasing noise power, with 5 ± 2 motor units identified at 10 dB SNR and 3 ± 1 at 0 dB SNR. In 24 recordings of high-density surface EMG signals from four tremor-affected patients, the modified CKC technique identified 134 motor units (6 ± 4 motor units per contraction).
In spite of decades of intense research, pathological tremors still constitute unknown disorders. This study addresses, based on a multi-scale model, the behavior of an entire pool of motor neurons in tremor, under th...
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ISBN:
(纸本)9781424441211
In spite of decades of intense research, pathological tremors still constitute unknown disorders. This study addresses, based on a multi-scale model, the behavior of an entire pool of motor neurons in tremor, under the hypothesis that tremor is an oscillation of central origin commonly projected to all motor neurons that innervate a muscle. Our results show that under such conditions both paired discharges and enhanced motor neuron synchronization, two of the characteristic landmarks of tremor, emerge. Moreover, coherence and correlation analyses suggest that the central tremor oscillator is transmitted linearly by the motor neuron pool given that a small set (7 or 8) of motor neurons are sampled.
Topological insulators is a newly discovered class of materials with the Dirac cone type dispersion at the surface and conventional band in the volume of the material. We present results of the study of the low-freque...
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ISBN:
(纸本)9781457701894
Topological insulators is a newly discovered class of materials with the Dirac cone type dispersion at the surface and conventional band in the volume of the material. We present results of the study of the low-frequency excess noise in thin films made of Bi 2 Se 3 topological insulator material. The films were prepared through mechanically cleavage from the bulk crystal via the “graphene-like” exfoliation procedure. We verified the quality and crystallinity of Bi 2 Se 3 samples with the micro-Raman spectroscopy. Our fabricated devices have linear current voltage characteristics in the low bias region with the current fluctuation noise spectral density SI proportional to 1/f for frequency f less than 10 kHz. The noise spectral density SI showed the square law dependence on the source-drain current and changed from about ~10 -22 to 10 -18 A 2 /Hz as current changes form ~10 -7 to 10 -5 A. Our results can be used for understanding electron transport and trap dynamics, and for reducing low-frequency noise in topological insulator devices.
MEMS-based resonant mass sensors can be sensitive tools to measure the physical properties of cells such as their mass. We recently developed an array of sensors that have a uniform mass sensitivity for measuring the ...
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To explore the effect of the location of a visual stimulus on neural responses in the primary visual cortex (V1), a micro-electromechanical system-based microelectrode array with nine channels was implanted on the cer...
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To explore the effect of the location of a visual stimulus on neural responses in the primary visual cortex (V1), a micro-electromechanical system-based microelectrode array with nine channels was implanted on the cerebral dura mater of V1 in adult cats. 2 Hz pattern reversal checkerboard stimuli were used to stimulate the four visual quadrants (i.e., upper left, upper right, lower left, and lower right fields). The results showed that there was a N75 component of the visual evoked potential around 50-80 ms after the onset of a checkerboard stimulus, and the onset of these N75 peaks varied with different stimulus locations. The checkerboard stimuli induced shorter latencies in the contralateral V1 than in the ipsilateral V1, while the checkerboard stimulus in the upper half visual field induced shorter latencies for N75. These results suggested that the pattern-reversal stimuli induced neural activities in V1 that can be recorded with multichannel microelectrodes, and more detailed temporal and spatial properties can be measured.
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