On the variability of manual spike sorting

The analysis of action potentials, or "spikes," is central to systems neuroscience research. Spikes are typically identified from raw waveforms manually for off-line analysis or automatically by human-configured algorithms for on-line applications. The variability of manual spike "sorting" is studied and its implications for neural prostheses discussed. Waveforms were recorded using a micro-electrode array and were used to construct a statistically similar synthetic dataset. Results showed wide variability in the number of neurons and spikes detected in real data. Additionally, average error rates of 23% false positive and 30% false negative were found for synthetic data.     

Modeling and decoding motor cortical activity using a switching Kalman filter

We present a switching Kalman filter model for the real-time inference of hand kinematics from a population of motor cortical neurons. Firing rates are modeled as a Gaussian mixture where the mean of each Gaussian component is a linear function of hand kinematics. A "hidden state" models the probability of each mixture component and evolves over time in a Markov chain. The model generalizes previous encoding and decoding methods, addresses the non-Gaussian nature of firing rates, and can cope with crudely sorted neural data common in on-line prosthetic applications.     

Learning the Statistics of People in Images and Video

This paper address the problems of modeling the appearance of humans and distinguishing human appearance from the appearance of general scenes. We seek a model of appearance and motion that is generic in that it accounts for the ways in which people's appearance varies and, at the same time, is specific enough to be useful for tracking people in natural scenes. Given a 3D model of the person projected into an image we model the likelihood of observing various image cues conditioned on the predicted locations and orientations of the limbs. These cues are taken to be steered filter responses corresponding to edges, ridges, and motion-compensated temporal differences. Motivated by work on the statistics of natural scenes, the statistics of these filter responses for human limbs are learned from training images containing hand-labeled limb regions. Similarly, the statistics of the filter responses in general scenes are learned to define a background distribution. The likelihood of observing a scene given a predicted pose of a person is computed, for each limb, using the likelihood ratio between the learned foreground (person) and background distributions. Adopting a Bayesian formulation allows cues to be combined in a principled way. Furthermore, the use of learned distributions obviates the need for hand-tuned image noise models and thresholds. The paper provides a detailed analysis of the statistics of how people appear in scenes and provides a connection between work on natural image statistics and the Bayesian tracking of people.     

Perceptual time-frequency subtraction algorithm for noise reduction in hearing aids

Sensorineural hearing disorders are a major and universal community health problem. In many cases, hearing aids offer the only solution for people suffering from such disorders. Unfortunately existing aids do not provide any improvement in intelligibility of the signal when background noise is present. A hearing aid system should ideally simulate auditory processes including those aspects of the speech signal that are perceptually important. This work presents a new integrated approach to the design of a digital hearing aid, based on a wavelet transform, as well as a formulation of the temporal and spectral psychoacoustic model of masking. Within the model, the Perceptual Time-Frequency Subtraction (PTFS) algorithm is developed to simulate the masking phenomena and reduce noise in single-input systems. Results show that the use of the PTFS yields a significant improvement in speech quality especially in unvoiced portions. Additionally, the noise component during periods of silence has been attenuated by up to 20 dB. This new noise reduction method is expected to be applicable in a variety of applications, including digital hearing aids and portable communication systems (e.g., cellular telephones).     

Switchable Polymer Based Thin Film Coils as a Power Module for Wireless Neural Interfaces

Reliable chronic operation of implantable medical devices such as the Utah Electrode Array (UEA) for neural interface requires elimination of transcutaneous wire connections for signal processing, powering and communication of the device. A wireless power source that allows integration with the UEA is therefore necessary. While (rechargeable) micro batteries as well as biological micro fuel cells are yet far from meeting the power density and lifetime requirements of an implantable neural interface device, inductive coupling between two coils is a promising approach to power such a device with highly restricted dimensions. The power receiving coils presented in this paper were designed to maximize the inductance and quality factor of the coils and microfabricated using polymer based thin film technologies. A flexible configuration of stacked thin film coils allows parallel and serial switching, thereby allowing to tune the coil's resonance frequency. The electrical properties of the fabricated coils were characterized and their power transmission performance was investigated in laboratory condition.     

Reinforced Stone Columns in Weak Deposits: Laboratory Model Study

This paper investigates the performance of stone columns in a weak deposit such as peat. It evaluates the effects of reinforcing stone columns by jacketing with a tubular wire mesh and bridging reinforcement with a metal rod and a concrete plug. A series of plate loading tests was conducted on isolated stone columns installed in a soil bed consisting of a peat layer sandwiched between two layers of sand. The load–displacement characteristics of footings supported by stone columns were investigated by applying load to a circular plate supported on: (a) untreated soil; (b) soil treated with stone columns; and (c) soil treated with stone columns reinforced with the above reinforcing techniques. The work has shown that the settlement characteristics of the soil can be improved by installing stone columns and that a significant enhancement in the load–settlement response is achieved when the columns are reinforced by the various methods.     

单一5V电源高速放大器针对高分辨率视频而优化

人们不断要求视频运算放大器用更少的资源做更多的事情,就像要求设计这些放大器的优良设计师一样.为了实现更高的视频分辨率,需要更高的模拟视频信号带宽,因而需要更快的运算放大器.同时,设计师们还在不停地寻找以更低的电压甚至是单电源轨来实现更高分辨率的方法.     

Impact of wind generation on the operation and development of the UK electricity systems

Although penetration of wind generation may displace a significant amount of energy produced by large conventional plant, there are issues associated with the extent to which wind generation will be able to replace the capacity and flexibility of conventional generating plant. This is important since wind power is variable, so it will be necessary to retain a significant proportion of conventional plant to ensure security of supply especially under conditions of high demand and low wind. Hence, the capacity value of wind generation will be limited as it will not be possible to displace conventional generation capacity on a “megawatt for megawatt” basis. Wind power is variable and not easy to predict, hence various forms of additional reserves will be needed to maintain the balance between supply and demand at all times. Additionally, if the majority of wind generation plant is located in Scotland and the North of England, reinforcement of the transmission network will be needed to accommodate the increases in the north-south flow of electricity.     

EFFECT OF A MAJOR FLOOD ON BREEDING AND HABITAT OF THE CRIMSON FINCH (NEOCHMIA PHAETON): A RIPARIAN SPECIALIST

Riparian specialists, such as the Crimson Finch (Estrildidae: Neochmia phaeton), are vulnerable to declines in habitat quality, including alterations of flow regime associated with dam construction. Crimson Finches persisted and bred in substantial numbers following two large floods in the Isaac–Connors catchment in early 2008. Major flooding was not detrimental to nesting and breeding success, although the immediate post‐flood period was identified as a bottleneck in the availability of riparian grass seed. Crimson Finches nested at 16 m or more above the normal river level (compared with an average of 2–3 m elsewhere in Northern Australia); indicating that they have adapted to the extreme flood peaks in the Fitzroy River basin. The tall river‐associated grass Chionachne cyathopoda was a key habitat plant, retaining seed well into the dry season when most other grasses are expended. It also provided abundant seeds following floods, coinciding with peaks in abundance of dependent young finches. The adaptations of both Crimson Finches and Chionachne suggest that increased flooding, predicted by climate change, is unlikely to be a problem. In contrast, a proposed dam on the Connors River may be a threat. River regulation that reduces peaks of major floods may favour introduced riparian grasses over flood adapted native grasses such as Chionachne. Any change in the quantity of this species could be detrimental to persistence of Crimson Finches. Environmental managers should carefully consider the ecology of Chionachne when making decisions about river flows. Copyright © 2013 John Wiley & Sons, Ltd.