检索结果-内蒙古大学图书馆

Analog Signaling With the "Digital" Molecular Switch CaMKII

FRONTIERS IN COMPUTATIONAL NEUROSCIENCE 2018年 12卷 92页

作者： Clarke, Stephen E. Stanford Univ Dept Neurosurg Dept Bioengn Stanford CA 94305 USA

Molecular switches, such as the protein kinase CaMKII, play a fundamental role in cell signaling by decoding inputs into either high or low states of activity;because the high activation state can be turned on and persist after the input ceases, these switches have earned a reputation as "digital." Although this on/off, binary perspective has been valuable for understanding long timescale synaptic plasticity, accumulating experimental evidence suggests that the CaMKII switch can also control plasticity on short timescales. To investigate this idea further, a non-autonomous, nonlinear ordinary differential equation, representative of a general bistable molecular switch, is analyzed. The results suggest that switch activity in regions surrounding either the high- or low-stable states of activation could act as a reliable analog signal, whose short timescale fluctuations relative to equilibrium track instantaneous input frequency. The model makes intriguing predictions and is validated against previous work demonstrating its suitability as a minimal representation of switch dynamics;in combination with existing experimental evidence, the theory suggests a multiplexed encoding of instantaneous frequency information over short timescales, with integration of total activity over longer timescales.

关键词： molecular switches frequency coding stochastic resonance cellular computation CaMKII synaptic plasticity burst detection hill function

来源：评论

学校读者我要写书评

暂无评论

The sequential processing of visual motion in the human electroretinogram and visual evoked potential

引用

VISUAL NEUROSCIENCE 2000年第4期17卷 631-646页

作者： Korth, M Rix, R Sembritzki, O Univ Erlangen Nurnberg Dept Ophthalmol D-91054 Erlangen Germany Siemens AG Med Engn Grp D-91052 Erlangen Germany

Mechanisms of motion vision in the human have been studied extensively by psychophysical methods but less frequently by electrophysiological techniques. It is the purpose of the present investigation to study electrical potentials of the eye (electroretinogram, ERG) and of the brain (visual evoked potential, VEP) in response to moving regular square-wave stripe patterns spanning a wide range of contrasts, spatial frequencies, and speeds. The results show that ERG amplitudes increase linearly with contrast while VEPs, in agreement with the literature, show an amplitude saturation at low contrast. Furthermore, retinal responses oscillate with the fundamental temporal stimulus frequency of the moving pattern while brain responses do not. In both the retina and the brain, the response amplitudes are tuned to certain speeds which is in agreement with the nonlinear correlation-type motion detector. Along the ascending slopes (which means increasing amplitudes) of the tuning functions, the ERG curves overlap at all spatial frequencies if plotted as a function of temporal stimulation frequency. The ascending slopes of the tuning functions of the VEP overlap if plotted as a function of speed. The descending slopes (which means decreasing amplitudes) of the tuning functions show little (ERG) or no (VEP) overlap and the waveforms at high speeds approach pattern-offset-onset responses. These observations suggest that in the retina motion processing along the ascending slopes of the tuning curves takes place by coding the temporal stimulation frequency which depends on the spatial frequency of the moving pattern. In the brain, however, motion processing is by speed independent of spatial frequency. Simple calculations show that the VEP information is decoded from the ERG signal into a speed signal.

关键词： visual motion processing electroretinogram visual evoked potential speed coding frequency coding

来源：评论

学校读者我要写书评

暂无评论

Joint Transm ission Method in Coordinated Multi-Point Transm ission and Reception Systems

引用

ZTE Communications 2010年第1期8卷 40-43页

作者： Sun Yunfeng diang ding Hu Liujun Products and Marketing System of ZT＇ECorporation Shenzhen 518004 P. R. China

In this paper, we propose a multi-point joint transmission method for Coordinated Multi-Point （CoMP） systems. Thins solution combines space time/frequency coding and precoding with beamforming technology. The multi-path data obtained by space time/ frequency coding and precoding can be mapped by beamforming technology to multiple coordinated nodes for transmission. The signal receiver can also obtain bigger diversity gain and beamforming gain as well through the combination of space time/frequency coding and beamforming. Moreover, precoding and beamforming can help the signals transmitted from separate nodes in CoMP system combine at the receiver, which makes the signals at different layers more independent and obtains beamforming gain.

关键词： frequency coding technology combination different solution multiple CoMP paper help data

来源：评论

学校读者我要写书评

暂无评论

frequency CODED WAVEFORMS FROM CHAOTIC TIME SERIES

FREQUENCY CODED WAVEFORMS FROM CHAOTIC TIME SERIES

引用

IET International Conference on Radar Systems (Radar 2007)

作者： Stephen Welstead Radiance Technologies Inc. Huntsville AL USA

This paper discusses the construction of frequency coded radar waveforms formed by using a chaotic time series for the frequency coding. These codes provide wide bandwidth, and, hence, high range resolution, and also provide orthogonality. The paper uses simulation results to investigate the properties of these waveforms, including spectral properties, sidelobe levels, range resolution and orthogonality. This study was motivated by the need for a system of coded waveforms that provide both cross-correlation orthogonality and high range resolution. An advantage of these frequency coded waveforms over phase coded waveforms is that bandwidth (and hence range resolution) is independent of pulse width.

关键词： frequency coding Chaotic waveforms

来源：评论

学校读者我要写书评

暂无评论

fMRI of the Central Auditory System

fMRI of the Central Auditory System

引用

作者： Deborah Ann Hall Aspasia Eleni Paltoglou

Over the years, blood oxygen level-dependent (BOLD) fMRI has made important contributions to the understanding of central auditory processing in humans. Although there are significant technical challenges to overcome in the case of auditory fMRI, the unique methodological advantage of fMRI as an indicator of population neural activity lies in its spatial precision. It can be used to examine the neural basis of auditory representation at a number of spatial scales, from the micro-anatomical scale of population assemblies to the macro-anatomical scale of cortico-cortical circuits. The spatial resolution of fMRI is maximised in the case of mapping individual brain activity, and here it has been possible to demonstrate known organisational features of the auditory system that have hitherto been possible only using invasive electrophysiological recording methods. frequency coding in the primary auditory cortex is one such example that we shall discuss in this chapter. Of course, non-invasive procedures for neuroscience are the ultimate aim and as the field moves towards this goal by recording in awake, behaving animals so human neuroimaging techniques will be increasingly relied upon to provide an interpretive link between animal neurophysiology at the multi-unit level and the operation of larger neuronal assemblies, as well as the mechanisms of auditory perception itself. For example, the neural effects of intentional behaviour on stimulus-driven coding have been explored both in animals, using electrophysiological techniques, and in humans, using fMRI. While the feature-specific effects of selective attention are well established in the visual cortex, the effect of auditory attention in the auditory cortex has generally been examined at a very coarse spatial scale. Ongoing research in our laboratory has started to address this question and here we present preliminary evidence for frequency-specific effects of attentional enhancement in the human auditory cortex. We end

关键词： fMRI Neuroimaging Selective attention Technical challenges frequency coding Perceptual representation Task specificity

来源：评论

学校读者我要写书评

暂无评论

fMRI of the Central Auditory System

fMRI of the Central Auditory System

引用

作者： Deborah Ann Hall Aspasia Eleni Paltoglou

Over the years, blood oxygen level-dependent (BOLD) fMRI has made important contributions to the understanding of central auditory processing in humans. Although there are significant technical challenges to overcome in the case of auditory fMRI, the unique methodological advantage of fMRI as an indicator of population neural activity lies in its spatial precision. It can be used to examine the neural basis of auditory representation at a number of spatial scales, from the micro-anatomical scale of population assemblies to the macro-anatomical scale of cortico-cortical circuits. The spatial resolution of fMRI is maximized in the case of mapping individual brain activity, and here it has been possible to demonstrate known organizational features of the auditory system that have hitherto been possible only using invasive electrophysiological recording methods. frequency coding in the primary auditory cortex is one such example that we shall discuss in this chapter. Of course, noninvasive procedures for neuroscience are the ultimate aim and as the field moves towards this goal by recording in awake, behaving animals so human neuroimaging techniques will be increasingly relied upon to provide an interpretive link between animal neurophysiology at the multi-unit level and the operation of larger neuronal assemblies, as well as the mechanisms of auditory perception itself. For example, the neural effects of intentional behavior on stimulus-driven coding have been explored both in animals, using electrophysiological techniques, and in humans, using fMRI. While the feature-specific effects of selective attention are well established in the visual cortex, the effect of auditory attention in the auditory cortex has generally been examined at a very coarse spatial scale. Ongoing research in our laboratory has started to address this question and here we present preliminary evidence for frequency-specific effects of attentional enhancement in the human auditory cortex. We end w

关键词： fMRI Neuroimaging Selective attention Technical challenges frequency coding Perceptual representation Task specificity

来源：评论

学校读者我要写书评

暂无评论

A Pulse-to-Pulse Incoherent Flow Measurement with frequency-Coded Signals

A Pulse-to-Pulse Incoherent Flow Measurement with Frequency-...

引用

IEEE International Ultrasonics Symposium

作者： Manuel Haide Institute for Applied Research University of Applied Sciences Ulm Germany 89077

ISBN: (纸本)9781467356855

This article describes a pulsed method, whereby receiving and transmitting takes place intermittently with the same transducer. Similar to the pulse-to-pulse coherent method, in which the velocity and range unambiguousness is limited by the Nyquist-criterion and the pulse repetition frequency, the pulse-to-pulse incoherent method is also subject to restrictions. The boundary conditions for both methods are demonstrated in this paper. With greater penetration depth, it becomes more and more difficult to ensure the unambiguousness. Therefore, signal-coding is required, even for relatively narrow-band ultrasonic transducers. To overcome this weakness a frequency coding concept for a pulse-to-pulse incoherent method is presented. The features of those encoded signals are given by a nearly orthogonal relation to each other and optimal autocorrelation properties. Beyond that, a filter bank with an envelope detector is demonstrated to separate the respective signal codes from the received signal and to determine the runtime of the echo. This concept has been verified by measuring the velocity distribution of air bubbles from a pipe stream. The measurement of the velocity distribution shows a high correlation to the actual flow rate of the pipe and corresponds to the Doppler-spectrum of a continuous wave (CW) sensor.

关键词： ultrasound narrow-band transducer frequency-coding pulse-to-pulse incoherent sonar flow measuring velocity distribution Envelope detectors Ultrasonic Waves Pipe Pulse methods Penetration depth Flow rates Flow measurement PULSE REPETITION RATE signals Filter banks received signal Air bubbles frequency coding Runtime

来源：评论

学校读者我要写书评

暂无评论

GNSS Precise Point Positioning with Android Smartphones and Comparison with High Performance Receivers

GNSS Precise Point Positioning with Android Smartphones and ...

引用

Signal, Information and Data Processing (ICSIDP), IEEE International Conference on

作者： Gérard Lachapelle Paul Gratton University of Calgary Calgary Canada

ISBN: (数字)9781728123455

ISBN: (纸本)9781728123462

Precise Point Positioning (PPP) is becoming increasingly used instead of differential GNSS (DGNSS) due to its ease of use. With PPP, precise satellite orbits and clock corrections are calculated using the numerous International GNSS Service (IGS) permanent stations. The IGS network conceptually replaces the reference station(s) used in DGNSS. Models of the ionosphere and the troposphere are used to aid PPP, especially ionospheric models for single frequency users. In addition to 3D position, PPP provides estimates of GNSS time and zenith tropospheric delays. PPP performance is analysed herein as a function of receiver type, observation time and measurement utilized. The high-end receivers used in this study are multi-frequency multi-constellation Leica GS16. The Android phone used in the new Huawei Mate 20X. The measurements that are intercompared are (1) single frequency code, (2) single frequency code and carrier phase, (3) dual frequency code, and (4) dual frequency code and carrier phase. Results in low and high multipath environments are reported. Focus is on the use of GPS and GLONASS constellations because most IGS stations are equipped with such receivers, which is necessary to calculate precise satellite orbits and clock corrections. In order to assess PPP versus DGNSS performance, the results of a test consisting of an array of receivers are reported and analysed.

关键词： DGNSS PPP carrier phase Huawei Mate 20X positioning DGNSS Public-Private Sector Partnerships Point-to-Point Protocol carrier phase frequency coding Receivers Global Navigation Satellite System single-frequency precise point positioning

来源：评论

学校读者我要写书评

暂无评论

FS4 for partial deafness treatment

引用

Cochlear implants international 2014年 15 Suppl 1卷 S78-80页

作者： Artur Lorens Małgorzata Zgoda Marek Polak Henryk Skarzynski

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：