47 CFR 90.723 - Selection and assignment of frequencies.

Science.gov (United States)

2010-10-01

... 220-222 MHz Band § 90.723 Selection and assignment of frequencies. (a) Phase II applications for frequencies in the 220-222 MHz band shall specify whether their intended use is for 10-channel nationwide... medical use. Phase II applicants for frequencies for public safety/mutual aid use or emergency medical use...

Multiple spatial frequency channels in human visual perceptual memory.

Science.gov (United States)

Nemes, V A; Whitaker, D; Heron, J; McKeefry, D J

2011-12-08

Current models of short-term visual perceptual memory invoke mechanisms that are closely allied to low-level perceptual discrimination mechanisms. The purpose of this study was to investigate the extent to which human visual perceptual memory for spatial frequency is based upon multiple, spatially tuned channels similar to those found in the earliest stages of visual processing. To this end we measured how performance on a delayed spatial frequency discrimination paradigm was affected by the introduction of interfering or 'memory masking' stimuli of variable spatial frequency during the delay period. Masking stimuli were shown to induce shifts in the points of subjective equality (PSE) when their spatial frequencies were within a bandwidth of 1.2 octaves of the reference spatial frequency. When mask spatial frequencies differed by more than this value, there was no change in the PSE from baseline levels. This selective pattern of masking was observed for different spatial frequencies and demonstrates the existence of multiple, spatially tuned mechanisms in visual perceptual memory. Memory masking effects were also found to occur for horizontal separations of up to 6 deg between the masking and test stimuli and lacked any orientation selectivity. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of spatial frequency information in perceptual memory. However, the broad range of transfer of memory masking effects across spatial location and other dimensions indicates more long range, long duration interactions between spatial frequency channels that are likely to rely contributions from neural processes located in higher visual areas. Copyright © 2011 Elsevier Ltd. All rights reserved.

Single channel speech enhancement in the modulation domain: New insights in the modulation channel selection framework

DEFF Research Database (Denmark)

Boldt, Jesper B.; Bertelsen, Andreas Thelander; Gran, Fredrik

2015-01-01

Recently, the ideal binary mask has been introduced in the modulation domain by extending the ideal channel selection method to modulation channel selection [1]. This new method shows substantial improvement in speech intelligibility but less than its predecessor despite the higher complexity. Here......, we extend the previous finding from [1] and provide a more direct comparison of binary masking in the modulation domain with binary masking in the time-frequency domain. Subjective and objective evaluations are performed and provide additional insight into modulation domain processing....

Performance Analysis of the IEEE 802.11A WLAN Standard Optimum and Sub-Optimum Receiver in Frequency-Selective, Slowly Fading Nakagami Channels with AWGN and Pulsed Noise Jamming

National Research Council Canada - National Science Library

Kalogrias, Christos

2004-01-01

... 802.11a wireless local area network (WLAN) standard receiver when the signal is transmitted over a frequency selective, slow fading Nakagami channel in a worst case, pulse-noise jamming environment...

Frequency Dependence of Measured Massive MIMO Channel Properties

DEFF Research Database (Denmark)

Oliveras Martínez, Àlex; Carvalho, Elisabeth De; Nielsen, Jesper Ødum

2016-01-01

A multi-user massive MIMO measurement campaign is conducted to study the channel propagation characteristics (e.g. user correlation, sum of eigenvalues and condition number), focusing on the stability over frequencies and the impact of the array aperture. We use 3 arrays with 64 antennas (6m linear...... array, 2m linear array and 25cm by 28cm squared 2D array) serving 8 users holding a handset with 2 antennas. The study of the measurements shows that the propagation characteristics of the channel are stable for all the measured frequencies. We also observe that user proximity and user handgrip...... stabilize the studied properties of the channel across the frequencies, and in such case the larger the aperture of the array the more stable the properties. The number of base station antennas improves the propagation characteristics of the channel and stabilizes the properties in the frequency domain....

Tuning In to Sound: Frequency-Selective Attentional Filter in Human Primary Auditory Cortex

Science.gov (United States)

Da Costa, Sandra; van der Zwaag, Wietske; Miller, Lee M.; Clarke, Stephanie

2013-01-01

Cocktail parties, busy streets, and other noisy environments pose a difficult challenge to the auditory system: how to focus attention on selected sounds while ignoring others? Neurons of primary auditory cortex, many of which are sharply tuned to sound frequency, could help solve this problem by filtering selected sound information based on frequency-content. To investigate whether this occurs, we used high-resolution fMRI at 7 tesla to map the fine-scale frequency-tuning (1.5 mm isotropic resolution) of primary auditory areas A1 and R in six human participants. Then, in a selective attention experiment, participants heard low (250 Hz)- and high (4000 Hz)-frequency streams of tones presented at the same time (dual-stream) and were instructed to focus attention onto one stream versus the other, switching back and forth every 30 s. Attention to low-frequency tones enhanced neural responses within low-frequency-tuned voxels relative to high, and when attention switched the pattern quickly reversed. Thus, like a radio, human primary auditory cortex is able to tune into attended frequency channels and can switch channels on demand. PMID:23365225

Channel selection for automatic seizure detection

DEFF Research Database (Denmark)

Duun-Henriksen, Jonas; Kjaer, Troels Wesenberg; Madsen, Rasmus Elsborg

2012-01-01

Objective: To investigate the performance of epileptic seizure detection using only a few of the recorded EEG channels and the ability of software to select these channels compared with a neurophysiologist. Methods: Fifty-nine seizures and 1419 h of interictal EEG are used for training and testing...... of an automatic channel selection method. The characteristics of the seizures are extracted by the use of a wavelet analysis and classified by a support vector machine. The best channel selection method is based upon maximum variance during the seizure. Results: Using only three channels, a seizure detection...... sensitivity of 96% and a false detection rate of 0.14/h were obtained. This corresponds to the performance obtained when channels are selected through visual inspection by a clinical neurophysiologist, and constitutes a 4% improvement in sensitivity compared to seizure detection using channels recorded...

An Adaptive Channel Estimation Algorithm Using Time-Frequency Polynomial Model for OFDM with Fading Multipath Channels

Directory of Open Access Journals (Sweden)

Liu KJ Ray

2002-01-01

Full Text Available Orthogonal frequency division multiplexing (OFDM is an effective technique for the future 3G communications because of its great immunity to impulse noise and intersymbol interference. The channel estimation is a crucial aspect in the design of OFDM systems. In this work, we propose a channel estimation algorithm based on a time-frequency polynomial model of the fading multipath channels. The algorithm exploits the correlation of the channel responses in both time and frequency domains and hence reduce more noise than the methods using only time or frequency polynomial model. The estimator is also more robust compared to the existing methods based on Fourier transform. The simulation shows that it has more than improvement in terms of mean-squared estimation error under some practical channel conditions. The algorithm needs little prior knowledge about the delay and fading properties of the channel. The algorithm can be implemented recursively and can adjust itself to follow the variation of the channel statistics.

Optimal complex exponentials BEM and channel estimation in doubly selective channel

International Nuclear Information System (INIS)

Song, Lijun; Lei, Xia; Yu, Feng; Jin, Maozhu

2016-01-01

Over doubly selective channel, the optimal complex exponentials BEM (CE-BEM) is required to characterize the transmission in transform domain in order to reducing the huge number of the estimated parameters during directly estimating the impulse response in time domain. This paper proposed an improved CE-BEM to alleviating the high frequency sampling error caused by conventional CE-BEM. On the one hand, exploiting the improved CE-BEM, we achieve the sampling point is in the Doppler spread spectrum and the maximum sampling frequency is equal to the maximum Doppler shift. On the other hand we optimize the function and dimension of basis in CE-BEM respectively ,and obtain the closed solution of the EM based channel estimation differential operator by exploiting the above optimal BEM. Finally, the numerical results and theoretic analysis show that the dimension of basis is mainly depend on the maximum Doppler shift and signal-to-noise ratio (SNR), and if fixing the number of the pilot symbol, the dimension of basis is higher, the modeling error is smaller, while the accuracy of the parameter estimation is reduced, which implies that we need to achieve a tradeoff between the modeling error and the accuracy of the parameter estimation and the basis function influences the accuracy of describing the Doppler spread spectrum after identifying the dimension of the basis.

Modeling of Doppler frequency shift in multipath radio channels

Directory of Open Access Journals (Sweden)

Penzin M.S.

2016-06-01

Full Text Available We discuss the modeling of propagation of a quasi-monochromatic radio signal, represented by a coherent pulse sequence, in a non-stationary multipath radio channel. In such a channel, signal propagation results in the observed frequency shift for each ray (Doppler effect. The modeling is based on the assumption that during propagation of a single pulse a channel can be considered stationary. A phase variation in the channel transfer function is shown to cause the observed frequency shift in the received signal. Thus, instead of measuring the Doppler frequency shift, we can measure the rate of variation in the mean phase of one pulse relative to another. The modeling is carried out within the framework of the method of normal waves. The method enables us to model the dynamics of the electromagnetic field at a given point with the required accuracy. The modeling reveals that a local change in ionospheric conditions more severely affects the rays whose reflection region is in the area where the changes occur.

Tuning the ion selectivity of two-pore channels

Energy Technology Data Exchange (ETDEWEB)

Guo, Jiangtao; Zeng, Weizhong; Jiang, Youxing (UTSMC)

2017-01-17

Organellar two-pore channels (TPCs) contain two copies of a Shaker-like six-transmembrane (6-TM) domain in each subunit and are ubiquitously expressed in plants and animals. Interestingly, plant and animal TPCs share high sequence similarity in the filter region, yet exhibit drastically different ion selectivity. Plant TPC1 functions as a nonselective cation channel on the vacuole membrane, whereas mammalian TPC channels have been shown to be endo/lysosomal Na+-selective or Ca2+-release channels. In this study, we performed systematic characterization of the ion selectivity of TPC1 from Arabidopsis thaliana (AtTPC1) and compared its selectivity with the selectivity of human TPC2 (HsTPC2). We demonstrate that AtTPC1 is selective for Ca2+ over Na+, but nonselective among monovalent cations (Li+, Na+, and K+). Our results also confirm that HsTPC2 is a Na+-selective channel activated by phosphatidylinositol 3,5-bisphosphate. Guided by our recent structure of AtTPC1, we converted AtTPC1 to a Na+-selective channel by mimicking the selectivity filter of HsTPC2 and identified key residues in the TPC filters that differentiate the selectivity between AtTPC1 and HsTPC2. Furthermore, the structure of the Na+-selective AtTPC1 mutant elucidates the structural basis for Na+ selectivity in mammalian TPCs.

Radio frequency channel coding made easy

CERN Document Server

Faruque, Saleh

2016-01-01

This book introduces Radio Frequency Channel Coding to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.

Ionic Selectivity and Permeation Properties of Human PIEZO1 Channels.

Directory of Open Access Journals (Sweden)

Radhakrishnan Gnanasambandam

Full Text Available Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2 form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 (hPIEZO1 for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35-55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.

Iterative MMSE Detection for MIMO/BLAST DS-CDMA Systems in Frequency Selective Fading Channels - Achieving High Performance in Fully Loaded Systems

Science.gov (United States)

Silva, João Carlos; Souto, Nuno; Cercas, Francisco; Dinis, Rui

A MMSE (Minimum Mean Square Error) DS-CDMA (Direct Sequence-Code Division Multiple Access) receiver coupled with a low-complexity iterative interference suppression algorithm was devised for a MIMO/BLAST (Multiple Input, Multiple Output / Bell Laboratories Layered Space Time) system in order to improve system performance, considering frequency selective fading channels. The scheme is compared against the simple MMSE receiver, for both QPSK and 16QAM modulations, under SISO (Single Input, Single Output) and MIMO systems, the latter with 2Tx by 2Rx and 4Tx by 4Rx (MIMO order 2 and 4 respectively) antennas. To assess its performance in an existing system, the uncoded UMTS HSDPA (High Speed Downlink Packet Access) standard was considered.

Space-Time Joint Interference Cancellation Using Fuzzy-Inference-Based Adaptive Filtering Techniques in Frequency-Selective Multipath Channels

Directory of Open Access Journals (Sweden)

Chen Yu-Fan

2006-01-01

Full Text Available An adaptive minimum mean-square error (MMSE array receiver based on the fuzzy-logic recursive least-squares (RLS algorithm is developed for asynchronous DS-CDMA interference suppression in the presence of frequency-selective multipath fading. This receiver employs a fuzzy-logic control mechanism to perform the nonlinear mapping of the squared error and squared error variation, denoted by ( , , into a forgetting factor . For the real-time applicability, a computationally efficient version of the proposed receiver is derived based on the least-mean-square (LMS algorithm using the fuzzy-inference-controlled step-size . This receiver is capable of providing both fast convergence/tracking capability as well as small steady-state misadjustment as compared with conventional LMS- and RLS-based MMSE DS-CDMA receivers. Simulations show that the fuzzy-logic LMS and RLS algorithms outperform, respectively, other variable step-size LMS (VSS-LMS and variable forgetting factor RLS (VFF-RLS algorithms at least 3 dB and 1.5 dB in bit-error-rate (BER for multipath fading channels.

The effect of inundation frequency on ground beetle communities in a channelized mountain stream

Science.gov (United States)

Skalski, T.; Kedzior, R.; Radecki-Pawlik, A.

2012-04-01

Under natural conditions, river channels and floodplains are shaped by flow and sediment regime and are one of the most dynamic ecosystems. At present, European river floodplains are among the most endangered landscapes due to human modifications to river systems, including channel regulation and floodplain urbanization, and land use changes in the catchments. Situated in a transition zone between terrestrial and aquatic environments, exposed riverine sediments (ERS) play a key role in the functioning of riverine ecosystems. This study aimed to verify whether the bare granular substrate is the only factor responsible for sustaining the biota associated with ERS or the inundation frequency also plays a role, modifying the potential of particular species to colonize these habitats. Ground beetles (Col. Carabidae) were selected as the investigated group of organisms and the study was carried out in Porębianka, a Polish Carpathian stream flowing through both unconstrained channel sections and sections with varied channelization schemes (rapid hydraulic structures, concrete revetments or rip-rap of various age). In each of the distinguished channel types, four replicates of 10 pitfall traps were established in three rows varying in distance to the mean water level (at three different benches). Almost 7000 individuals belonging to 102 species were collected on 60 plots. Forward selection of redundancy analysis revealed four factors significantly describing the variation in ground beetle species data: bank modification, potential bankfull discharge, frequency of inundation and plant height. Most of the biggest species were ordered at the positive site of first axis having the highest values of periods between floods. Total biomass of ground beetles and mean biomass of individuals differed significantly between sites of various frequency of inundation, whereas the variation in abundance and species richness of ground beetles was independent of the river dynamics. The body

A Framework for Selection of Intermediary in Marketing Channel

Directory of Open Access Journals (Sweden)

Gholamreza Jandaghi

2016-07-01

Full Text Available Purpose – This study seeks to examine how company can select the best intermediary for its Marketing channels with minimum of criteria and time. Design/methodology/approach – A theoretical framework is proposed based on the mostimportance tasks of intermediary and criteria for measuring them. There are four basic tasks and 30 criteria in three independent levels. Subsequently, an exploratory case study in Iranian Food industry is described that illustrates the value of the framework. Findings – It is possible, for example, to apply the theoretical framework to select the intermediary for any industry or any country. Research limitations/implications – The study has possible location- and industry-specific limitations.Originality/value – Moreover, the framework has proven to be useful in improving the selection of the intermediary in marketing channel. This is a notable and promising side-effect of the exploratory study, at least from a managerial point of view.Keywords: Marketing channel, Distribution channel, Channel design, Selection criteria, channel members, Intermediary selection

A review of channel selection algorithms for EEG signal processing

Science.gov (United States)

Alotaiby, Turky; El-Samie, Fathi E. Abd; Alshebeili, Saleh A.; Ahmad, Ishtiaq

2015-12-01

Digital processing of electroencephalography (EEG) signals has now been popularly used in a wide variety of applications such as seizure detection/prediction, motor imagery classification, mental task classification, emotion classification, sleep state classification, and drug effects diagnosis. With the large number of EEG channels acquired, it has become apparent that efficient channel selection algorithms are needed with varying importance from one application to another. The main purpose of the channel selection process is threefold: (i) to reduce the computational complexity of any processing task performed on EEG signals by selecting the relevant channels and hence extracting the features of major importance, (ii) to reduce the amount of overfitting that may arise due to the utilization of unnecessary channels, for the purpose of improving the performance, and (iii) to reduce the setup time in some applications. Signal processing tools such as time-domain analysis, power spectral estimation, and wavelet transform have been used for feature extraction and hence for channel selection in most of channel selection algorithms. In addition, different evaluation approaches such as filtering, wrapper, embedded, hybrid, and human-based techniques have been widely used for the evaluation of the selected subset of channels. In this paper, we survey the recent developments in the field of EEG channel selection methods along with their applications and classify these methods according to the evaluation approach.

Space-Time Joint Interference Cancellation Using Fuzzy-Inference-Based Adaptive Filtering Techniques in Frequency-Selective Multipath Channels

Science.gov (United States)

Hu, Chia-Chang; Lin, Hsuan-Yu; Chen, Yu-Fan; Wen, Jyh-Horng

2006-12-01

An adaptive minimum mean-square error (MMSE) array receiver based on the fuzzy-logic recursive least-squares (RLS) algorithm is developed for asynchronous DS-CDMA interference suppression in the presence of frequency-selective multipath fading. This receiver employs a fuzzy-logic control mechanism to perform the nonlinear mapping of the squared error and squared error variation, denoted by ([InlineEquation not available: see fulltext.],[InlineEquation not available: see fulltext.]), into a forgetting factor[InlineEquation not available: see fulltext.]. For the real-time applicability, a computationally efficient version of the proposed receiver is derived based on the least-mean-square (LMS) algorithm using the fuzzy-inference-controlled step-size[InlineEquation not available: see fulltext.]. This receiver is capable of providing both fast convergence/tracking capability as well as small steady-state misadjustment as compared with conventional LMS- and RLS-based MMSE DS-CDMA receivers. Simulations show that the fuzzy-logic LMS and RLS algorithms outperform, respectively, other variable step-size LMS (VSS-LMS) and variable forgetting factor RLS (VFF-RLS) algorithms at least 3 dB and 1.5 dB in bit-error-rate (BER) for multipath fading channels.

Temporal mode selectivity by frequency conversion in second-order nonlinear optical waveguides

DEFF Research Database (Denmark)

Reddy, D. V.; Raymer, M. G.; McKinstrie, C. J.

2013-01-01

in a transparent optical network using temporally orthogonal waveforms to encode different channels. We model the process using coupled-mode equations appropriate for wave mixing in a uniform second-order nonlinear optical medium pumped by a strong laser pulse. We find Green functions describing the process...... in this optimal regime. We also find an operating regime in which high-efficiency frequency conversion without temporal-shape selectivity can be achieved while preserving the shapes of a wide class of input pulses. The results are applicable to both classical and quantum frequency conversion....

A study of the impact of frequency selectivity on link adaptive wireless LAN systems

OpenAIRE

Armour, SMD; Doufexi, A; Nix, AR; Bull, DR

2002-01-01

Wireless local area networks (WLANs) supporting broadband multimedia communication are being developed and standardized around the world. The HIPERLAN/2, 802.11a and HiSWANa standards provide channel adaptive data rates between 6 and 54 Mbps in the 5GHz radio band. The link adaptation mechanism is not specified in the standards. In this paper the performance of the HIPERLAN/2 system is evaluated in terms of throughput in a range of test channels with different degrees of frequency selectivity...

Opportunistic relaying in multipath and slow fading channel: Relay selection and optimal relay selection period

KAUST Repository

Sungjoon Park,

2011-11-01

In this paper we present opportunistic relay communication strategies of decode and forward relaying. The channel that we are considering includes pathloss, shadowing, and fast fading effects. We find a simple outage probability formula for opportunistic relaying in the channel, and validate the results by comparing it with the exact outage probability. Also, we suggest a new relay selection algorithm that incorporates shadowing. We consider a protocol of broadcasting the channel gain of the previously selected relay. This saves resources in slow fading channel by reducing collisions in relay selection. We further investigate the optimal relay selection period to maximize the throughput while avoiding selection overhead. © 2011 IEEE.

A new method of hybrid frequency hopping signals selection and blind parameter estimation

Science.gov (United States)

Zeng, Xiaoyu; Jiao, Wencheng; Sun, Huixian

2018-04-01

Frequency hopping communication is widely used in military communications at home and abroad. In the case of single-channel reception, it is scarce to process multiple frequency hopping signals both effectively and simultaneously. A method of hybrid FH signals selection and blind parameter estimation is proposed. The method makes use of spectral transformation, spectral entropy calculation and PRI transformation basic theory to realize the sorting and parameter estimation of the components in the hybrid frequency hopping signal. The simulation results show that this method can correctly classify the frequency hopping component signal, and the estimated error of the frequency hopping period is about 5% and the estimated error of the frequency hopping frequency is less than 1% when the SNR is 10dB. However, the performance of this method deteriorates seriously at low SNR.

A Method for Dynamically Selecting the Best Frequency Hopping Technique in Industrial Wireless Sensor Network Applications.

Science.gov (United States)

Fernández de Gorostiza, Erlantz; Berzosa, Jorge; Mabe, Jon; Cortiñas, Roberto

2018-02-23

Industrial wireless applications often share the communication channel with other wireless technologies and communication protocols. This coexistence produces interferences and transmission errors which require appropriate mechanisms to manage retransmissions. Nevertheless, these mechanisms increase the network latency and overhead due to the retransmissions. Thus, the loss of data packets and the measures to handle them produce an undesirable drop in the QoS and hinder the overall robustness and energy efficiency of the network. Interference avoidance mechanisms, such as frequency hopping techniques, reduce the need for retransmissions due to interferences but they are often tailored to specific scenarios and are not easily adapted to other use cases. On the other hand, the total absence of interference avoidance mechanisms introduces a security risk because the communication channel may be intentionally attacked and interfered with to hinder or totally block it. In this paper we propose a method for supporting the design of communication solutions under dynamic channel interference conditions and we implement dynamic management policies for frequency hopping technique and channel selection at runtime. The method considers several standard frequency hopping techniques and quality metrics, and the quality and status of the available frequency channels to propose the best combined solution to minimize the side effects of interferences. A simulation tool has been developed and used in this work to validate the method.

Quantum Interference and Selectivity through Biological Ion Channels.

Science.gov (United States)

Salari, Vahid; Naeij, Hamidreza; Shafiee, Afshin

2017-01-30

The mechanism of selectivity in ion channels is still an open question in biology for more than half a century. Here, we suggest that quantum interference can be a solution to explain the selectivity mechanism in ion channels since interference happens between similar ions through the same size of ion channels. In this paper, we simulate two neighboring ion channels on a cell membrane with the famous double-slit experiment in physics to investigate whether there is any possibility of matter-wave interference of ions via movement through ion channels. Our obtained decoherence timescales indicate that the quantum states of ions can only survive for short times, i.e. ≈100 picoseconds in each channel and ≈17-53 picoseconds outside the channels, giving the result that the quantum interference of ions seems unlikely due to environmental decoherence. However, we discuss our results and raise few points, which increase the possibility of interference.

Like/dislike analysis using EEG: determination of most discriminative channels and frequencies.

Science.gov (United States)

Yılmaz, Bülent; Korkmaz, Sümeyye; Arslan, Dilek Betül; Güngör, Evrim; Asyalı, Musa H

2014-02-01

In this study, we have analyzed electroencephalography (EEG) signals to investigate the following issues, (i) which frequencies and EEG channels could be relatively better indicators of preference (like or dislike decisions) of consumer products, (ii) timing characteristic of "like" decisions during such mental processes. For this purpose, we have obtained multichannel EEG recordings from 15 subjects, during total of 16 epochs of 10 s long, while they were presented with some shoe photographs. When they liked a specific shoe, they pressed on a button and marked the time of this activity and the particular epoch was labeled as a LIKE case. No button press meant that the subject did not like the particular shoe that was displayed and corresponding epoch designated as a DISLIKE case. After preprocessing, power spectral density (PSD) of EEG data was estimated at different frequencies (4, 5, …, 40 Hz) using the Burg method, for each epoch corresponding to one shoe presentation. Each subject's data consisted of normalized PSD values (NPVs) from all LIKE and DISLIKE cases/epochs coming from all 19 EEG channels. In order to determine the most discriminative frequencies and channels, we have utilized logistic regression, where LIKE/DISLIKE status was used as a categorical (binary) response variable and corresponding NPVs were the continuously valued input variables or predictors. We observed that when all the NPVs (total of 37) are used as predictors, the regression problem was becoming ill-posed due to large number of predictors (compared to the number of samples) and high correlation among predictors. To circumvent this issue, we have divided the frequency band into low frequency (LF) 4-19 Hz and high frequency (HF) 20-40 Hz bands and analyzed the influence of the NPV in these bands separately. Then, using the p-values that indicate how significantly estimated predictor weights are different than zero, we have determined the NPVs and channels that are more influential

A Novel Comb-Pilot Transform Domain Frequency Diversity Channel Estimation for OFDM System

Directory of Open Access Journals (Sweden)

L. Liu

2009-12-01

Full Text Available Due to implementation complexity, the transform domain channel estimation based on training symbols or comb-type pilots has been paid more attention because of its efficient algorithm FFT/IFFT. However, in a comb-type OFDM system, the length of the channel impulse response is much smaller than the pilot number. In this case, the comb-pilot transform domain channel estimation only works as interpolation like the Least Squares (LS algorithm, but loses the noise suppression function. In this paper, we propose a novel frequency diversity channel estimation method via grouped pilots combining. With this estimator, not only the channel frequency response on non-pilot subcarriers can be interpolated, but also the noise can be better suppressed. Moreover, it does not need prior statistical characteristics of the wireless channel.

Standard compliant channel selection scheme for TV white space networks

CSIR Research Space (South Africa)

Masonta, MT

2014-08-01

Full Text Available CHANNEL DECISION SCHEME The proposed channel selection model is performed based on the flowchart shown in Fig. 1. We assume that the TVWS- BS is authorised and registered with the national GSDB. The model starts when the TVWS-BS queries the GSDB after...-BS will query the GSDB after a predefined period of time until at least more than one channel is available to allow the channel allocation process to start. Fig. 1: Proposed channel selection scheme flowchart A. White Space Channel Attributes Collection Based...

Frequency-Selective Signal Sensing with Sub-Nyquist Uniform Sampling Scheme

DEFF Research Database (Denmark)

Pierzchlewski, Jacek; Arildsen, Thomas

2015-01-01

In this paper the authors discuss a problem of acquisition and reconstruction of a signal polluted by adjacent- channel interference. The authors propose a method to find a sub-Nyquist uniform sampling pattern which allows for correct reconstruction of selected frequencies. The method is inspired...... by the Restricted Isometry Property, which is known from the field of compressed sensing. Then, compressed sensing is used to successfully reconstruct a wanted signal even if some of the uniform samples were randomly lost, e. g. due to ADC saturation. An experiment which tests the proposed method in practice...

Frequency selectivity at very low centre frequencies

DEFF Research Database (Denmark)

Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Marquardt, Torsten

2010-01-01

measurements based on OAE suppression techniques and notched-noise masking data psychophysically measured for centre frequencies in the range 50-125 Hz, this study examines how individual differences in frequency selectivity, as well as in masking, may occur at very low CFs due to individual differences...

Theory of Alike Selectivity in Biological Channels

Science.gov (United States)

Luchinsky, Dmitry G.; Gibby, Will A. T.; Kaufman, Igor Kh.; Eisenberg, Robert S.; McClintock, Peter V. E.

2016-01-01

We introduce a statistical mechanical model of the selectivity filter that accounts for the interaction between ions within the channel and derive Eisenman equation of the filter selectivity directly from the condition of barrier-less conduction.

A Triply Selective MIMO Channel Simulator Using GPUs

Directory of Open Access Journals (Sweden)

R. Carrasco-Alvarez

2018-01-01

Full Text Available A methodology for implementing a triply selective multiple-input multiple-output (MIMO simulator based on graphics processing units (GPUs is presented. The resulting simulator is based on the implementation of multiple double-selective single-input single-output (SISO channel generators, where the multiple inputs and the multiple received signals have been transformed in order to supply the corresponding space correlation of the channel under consideration. A direct consequence of this approach is the flexibility provided, which allows different propagation statistics to each SISO channel to be specified and thus more complex environments to be replicated. It is shown that under some specific constraints, the statistics of the triply selective MIMO simulator are the same as those reported in the state of art. Simulation results show the computational time improvement achieved, up to 650-fold for an 8 × 8 MIMO channel simulator when compared with sequential implementations. In addition to the computational improvement, the proposed simulator offers flexibility for testing a variety of scenarios in vehicle-to-vehicle (V2V and vehicle-to-infrastructure (V2I systems.

Physical origin of selectivity in ionic channels of biological membranes.

Science.gov (United States)

Laio, A; Torre, V

1999-01-01

This paper shows that the selectivity properties of monovalent cation channels found in biological membranes can originate simply from geometrical properties of the inner core of the channel without any critical contribution from electrostatic interactions between the permeating ions and charged or polar groups. By using well-known techniques of statistical mechanics, such as the Langevin equations and Kramer theory of reaction rates, a theoretical equation is provided relating the permeability ratio PB/PA between ions A and B to simple physical properties, such as channel geometry, thermodynamics of ion hydration, and electrostatic interactions between the ion and charged (or polar) groups. Diffusive corrections and recrossing rates are also considered and evaluated. It is shown that the selectivity found in usual K+, gramicidin, Na+, cyclic nucleotide gated, and end plate channels can be explained also in the absence of any charged or polar group. If these groups are present, they significantly change the permeability ratio only if the ion at the selectivity filter is in van der Waals contact with them, otherwise these groups simply affect the channel conductance, lowering the free energy barrier of the same amount for the two ions, thus explaining why single channel conductance, as it is experimentally observed, can be very different in channels sharing the same selectivity sequence. The proposed theory also provides an estimate of channel minimum radius for K+, gramicidin, Na+, and cyclic nucleotide gated channels.

HCN Channels Modulators: The Need for Selectivity

Science.gov (United States)

Romanelli, Maria Novella; Sartiani, Laura; Masi, Alessio; Mannaioni, Guido; Manetti, Dina; Mugelli, Alessandro; Cerbai, Elisabetta

2016-01-01

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, the molecular correlate of the hyperpolarization-activated current (If/Ih), are membrane proteins which play an important role in several physiological processes and various pathological conditions. In the Sino Atrial Node (SAN) HCN4 is the target of ivabradine, a bradycardic agent that is, at the moment, the only drug which specifically blocks If. Nevertheless, several other pharmacological agents have been shown to modulate HCN channels, a property that may contribute to their therapeutic activity and/or to their side effects. HCN channels are considered potential targets for developing drugs to treat several important pathologies, but a major issue in this field is the discovery of isoform-selective compounds, owing to the wide distribution of these proteins into the central and peripheral nervous systems, heart and other peripheral tissues. This survey is focused on the compounds that have been shown, or have been designed, to interact with HCN channels and on their binding sites, with the aim to summarize current knowledge and possibly to unveil useful information to design new potent and selective modulators. PMID:26975509

An evolutionarily conserved gene family encodes proton-selective ion channels.

Science.gov (United States)

Tu, Yu-Hsiang; Cooper, Alexander J; Teng, Bochuan; Chang, Rui B; Artiga, Daniel J; Turner, Heather N; Mulhall, Eric M; Ye, Wenlei; Smith, Andrew D; Liman, Emily R

2018-03-02

Ion channels form the basis for cellular electrical signaling. Despite the scores of genetically identified ion channels selective for other monatomic ions, only one type of proton-selective ion channel has been found in eukaryotic cells. By comparative transcriptome analysis of mouse taste receptor cells, we identified Otopetrin1 (OTOP1), a protein required for development of gravity-sensing otoconia in the vestibular system, as forming a proton-selective ion channel. We found that murine OTOP1 is enriched in acid-detecting taste receptor cells and is required for their zinc-sensitive proton conductance. Two related murine genes, Otop2 and Otop3 , and a Drosophila ortholog also encode proton channels. Evolutionary conservation of the gene family and its widespread tissue distribution suggest a broad role for proton channels in physiology and pathophysiology. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

New Concept of PLC Modems: Multi-Carrier System for Frequency Selective Slow-Fading Channels Based on Layered SCCC Turbocodes

Directory of Open Access Journals (Sweden)

J. Zavrtalek

2015-09-01

Full Text Available The article introduces a novel concept of a PLC modem as a complement to the existing G3 and PRIME standards for communications using medium- or high-voltage overhead or cable lines. The proposed concept is based on the fact that the levels of impulse noise and frequency selectivity are lower on high-voltage lines than on low-voltage ones. Also, the demands for “cost-effective” circuitry design are not so crucial as in the case of modems for low-voltage level. In contract to these positive conditions, however, there is the need to overcome much longer distances and to take into account low SNR on the receiving side. With respect to the listed reasons, our concept makes use of MCM, instead of OFDM. The assumption of low SNR is compensated through the use of an efficient channel coding based on a serially concatenated turbo code. In addition, MCM offers lower latency and PAPR compared to OFDM. Therefore, when using MCM, it is possible to excite the line with higher power. The proposed concept has been verified during experimental transmission of testing data over a real, 5 km long, 22kV overhead line.

Performance of Reverse-Link Synchronous DS-CDMA System on a Frequency-Selective Multipath Fading Channel with Imperfect Power Control

Directory of Open Access Journals (Sweden)

Duk Kyung Kim

2002-08-01

Full Text Available We analyze the performance for reverse-link synchronous DS-CDMA system in a frequency-selective Rayleigh fading channel with an imperfect power control scheme. The performance degradation due to power control error (PCE, which is approximated by a log-normally distributed random variable, is estimated as a function of the standard deviation of the PCE. In addition, we investigate the impacts of the multipath intensity profile (MIP shape and the number of resolvable paths on the performance. Finally, the coded bit error performance is evaluated in order to estimate the system capacity. Comparing with the conventional CDMA system, we show an achievable gain of from 59% to 23% for reverse-link synchronous transmission technique (RLSTT in the presence of imperfect power control over asynchronous transmission for BER=10−6. As well, the effect of tradeoff between orthogonality and diversity can be seen according to the number of multipaths, and the tendency is kept even in the presence of PCE. We conclude that the capacity can be further improved via the RLSTT, because the DS-CDMA system is very sensitive to power control imperfections.

Channel Estimation in DCT-Based OFDM

Science.gov (United States)

Wang, Yulin; Zhang, Gengxin; Xie, Zhidong; Hu, Jing

2014-01-01

This paper derives the channel estimation of a discrete cosine transform- (DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic. PMID:24757439

Ultrasonic flow-through filtration of microparticles in a microfluidic channel using frequency sweep technique

International Nuclear Information System (INIS)

Seo, Dae Cheol; Ahn, Bong Young; Cho, Seung Hyun; Siddique, A. K. M. Ariful Haque; Kim, Cheol Gi

2013-01-01

Many studies have been conducted on the filtration of microparticles using the acoustic radiation force of ultrasonic standing wave. The present work concerns a flow-through particle filtration method by utilizing frequency varying ultrasound. The periodical frequency sweep of the ultrasonic standing wave translocates particles across a microchannel, where particles in fluid flow are filtrated without barriers. The present filtration technique in a microfluidic channel was proposed conceptually in the 1990s. However, its experimental realization on actual particles in a microfluidic channel has not been carried out in a notable way. Several sizes of polystyrene microspheres (10 µm to 90 µm) and silicon carbide (SiC) particles (37 µm) suspended in water were applied as a test sample. For filtration of those particles, a Y-branched microfluidic channel with one inlet and two outlets was made out of steel and acrylic as a form of modulized device. Ultrasound of a few MHz in band frequency (1.75 MHz to 3.05 MHz) was transmitted into one side of the channel wall to generate a standing wave field in fluid flow. The periodical frequency sweep operation showed successful filtration performance, whereby particles in water flowed into one outlet and purified water flowed into the other outlet of the Y branch of the channel.

Binaural frequency selectivity in humans.

Science.gov (United States)

Verhey, Jesko L; van de Par, Steven

2018-01-23

Several behavioural studies in humans have shown that listening to sounds with two ears that is binaural hearing, provides the human auditory system with extra information on the sound source that is not available when sounds are only perceived through one ear that is monaurally. Binaural processing involves the analysis of phase and level differences between the two ear signals. As monaural cochlea processing (in each ear) precedes the neural stages responsible for binaural processing properties it is reasonable to assume that properties of the cochlea may also be observed in binaural processing. A main characteristic of cochlea processing is its frequency selectivity. In psychoacoustics, there is an ongoing discussion on the frequency selectivity of the binaural auditory system. While some psychoacoustic experiments seem to indicate poorer frequency selectivity of the binaural system than that of the monaural processing others seem to indicate the same frequency selectivity for monaural and binaural processing. This study provides an overview of these seemingly controversial results and the different explanations that were provided to account for the different results. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Modulation of low-frequency oscillations in GaAs MESFETs' channel current by sidegating bias

Institute of Scientific and Technical Information of China (English)

DING Yong; LU Shengli; ZHAO Fuchuan

2005-01-01

Low-frequency oscillations in channel current are usually observed when measuring the GaAs MESFET's output characteristics. This paper studies the oscillations by testing the MESFET's output characteristics under different sidegate bias conditions. It is shown that the low-frequency oscillations of channel current are directly related to the sidegate bias. In other words, the sidegate bias can modulate the oscillations. Whether the sidegate bias varies positively or negatively, there will inevitably be a threshold voltage after which the low-frequency oscillations disappear. The observation is strongly dependent upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL2 under high field. This conclusion is of particular pertinence to the design of low-noise GaAs IC's.

Frequency of V1016I and F1534C mutations in the voltage-gated sodium channel gene in Aedes aegypti in Venezuela.

Science.gov (United States)

Alvarez, Leslie C; Ponce, Gustavo; Saavedra-Rodriguez, Karla; Lopez, Beatriz; Flores, Adriana E

2015-06-01

The V1016I and F1534C mutations in the voltage-gated sodium channel gene have been associated with resistance to pyrethroids and DDT in Aedes aegypti mosquitoes. A study was carried out to determine the frequency of I1016 and C1534 by real-time PCR in five natural populations of Ae. aegypti in Venezuela during 2008, 2010 and 2012, as well as in a strain selected with 0.14 µg of deltamethrin for 15 generations. In natural populations, frequencies of I1016 varied between 0.01 and 0.37, and frequencies of C1534 between 0.35 and 1.0. In the Pampanito strain, the frequency of I1016 increased from 0.02 in F1 up to 0.5 in F15 and from 0.35 up to fixation for C1534 after selection with deltamethrin. The results showed that C1534 frequencies are higher than I1016 frequencies in natural populations of Ae. aegypti in Venezuela, and that deltamethrin selected the C1534 more rapidly than I1016. © 2014 Society of Chemical Industry.

Relay selection in cooperative communication systems over continuous time-varying fading channel

Directory of Open Access Journals (Sweden)

Ke Geng

2017-02-01

Full Text Available In this paper, we study relay selection under outdated channel state information (CSI in a decode-and-forward (DF cooperative system. Unlike previous researches on cooperative communication under outdated CSI, we consider that the channel varies continuously over time, i.e., the channel not only changes between relay selection and data transmission but also changes during data transmission. Thus the level of accuracy of the CSI used in relay selection degrades with data transmission. We first evaluate the packet error rate (PER of the cooperative system under continuous time-varying fading channel, and find that the PER performance deteriorates more seriously under continuous time-varying fading channel than when the channel is assumed to be constant during data transmission. Then, we propose a repeated relay selection (RRS strategy to improve the PER performance, in which the forwarded data is divided into multiple segments and relay is reselected before the transmission of each segment based on the updated CSI. Finally, we propose a combined relay selection (CRS strategy which takes advantage of three different relay selection strategies to further mitigate the impact of outdated CSI.

Multiple flow profiles for two-phase flow in single microfluidic channels through site-selective channel coating.

Science.gov (United States)

Logtenberg, Hella; Lopez-Martinez, Maria J; Feringa, Ben L; Browne, Wesley R; Verpoorte, Elisabeth

2011-06-21

An approach to control two-phase flow systems in a poly(dimethylsiloxane) (PDMS) microfluidic device using spatially selective surface modification is demonstrated. Side-by-side flows of ethanol : water solutions containing different polymers are used to selectively modify both sides of a channel by laminar flow patterning. Introduction of air pockets during modification allows for control over the length of the channel section that is modified. This approach makes it possible to achieve slug flow and side-by-side flow of water : 1-octanol simultaneously within the same PDMS channel, without the need of additional structural elements. A key finding is that conditioning of the PDMS channels with 1-octanol before polymer deposition is crucial to achieving stable side-by-side flows.

Frequency, delay and velocity analysis for intrinsic channel region of carbon nanotube field effect transistors

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P. Geetha

2014-03-01

Full Text Available Gate wrap around field effect transistor is preferred for its good channel control. To study the high frequency behaviour of the device, parameters like cut-off frequency, transit or delay time, velocity are calculated and plotted. Double-walled and array of channels are considered in this work for enhanced output and impedance matching of the device with the measuring equipment terminal respectively. The perfomance of double-walledcarbon nanotube is compared with single-walled carbon nanotube and found that the device with double-wall shows appreciable improvement in its characteristics. Analysis of these parameters are done with various values of source/drain length, gate length, tube diameters and channel densities. The maximum cut-off frequency is found to be 72.3 THz with corresponding velocity as 5x106 m/s for channel density as 3 and gate length as 11nm. The number of channel is varied from 3 to 21 and found that the perfromance of the device containing double-walled carbon nano tube is better for channel number lesser than or equal to 12. The proposed modelling can be used for designing devices to handle high speed applications of future generation.

Sniffer Channel Selection for Monitoring Wireless LANs

Science.gov (United States)

Song, Yuan; Chen, Xian; Kim, Yoo-Ah; Wang, Bing; Chen, Guanling

Wireless sniffers are often used to monitor APs in wireless LANs (WLANs) for network management, fault detection, traffic characterization, and optimizing deployment. It is cost effective to deploy single-radio sniffers that can monitor multiple nearby APs. However, since nearby APs often operate on orthogonal channels, a sniffer needs to switch among multiple channels to monitor its nearby APs. In this paper, we formulate and solve two optimization problems on sniffer channel selection. Both problems require that each AP be monitored by at least one sniffer. In addition, one optimization problem requires minimizing the maximum number of channels that a sniffer listens to, and the other requires minimizing the total number of channels that the sniffers listen to. We propose a novel LP-relaxation based algorithm, and two simple greedy heuristics for the above two optimization problems. Through simulation, we demonstrate that all the algorithms are effective in achieving their optimization goals, and the LP-based algorithm outperforms the greedy heuristics.

Channel Model on Various Frequency Bands for Wearable Body Area Network

Science.gov (United States)

Katayama, Norihiko; Takizawa, Kenichi; Aoyagi, Takahiro; Takada, Jun-Ichi; Li, Huan-Bang; Kohno, Ryuji

Body Area Network (BAN) is considered as a promising technology in supporting medical and healthcare services by combining with various biological sensors. In this paper, we look at wearable BAN, which provides communication links among sensors on body surface. In order to design a BAN that manages biological information with high efficiency and high reliability, the propagation characteristics of BAN must be thoroughly investigated. As a preliminary effort, we measured the propagation characteristics of BAN at frequency bands of 400MHz, 600MHz, 900MHz and 2400MHz respectively. Channel models for wearable BAN based on the measurement were derived. Our results show that the channel model can be described by using a path loss model for all frequency bands investigated.

Frequency Characteristics of Path Loss and Delay-Angular Profile of Propagation Channels in An Indoor Room Environment in SHF Bands

DEFF Research Database (Denmark)

HANPINITSAK, Panawit; SAITO, Kentaro; Fan, Wei

2017-01-01

Comparison of channel characteristics at many frequency bands is necessary to study the frequency-de-pendency which is important for consistent multi-frequency spatial-temporal channel model. Path loss (PL) and power spectrum characteristics of the channel measured in a typical classroom line...

Channel Selection Based on Trust and Multiarmed Bandit in Multiuser, Multichannel Cognitive Radio Networks

Directory of Open Access Journals (Sweden)

Fanzi Zeng

2014-01-01

Full Text Available This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme.

Protein structure and ionic selectivity in calcium channels: selectivity filter size, not shape, matters.

Science.gov (United States)

Malasics, Attila; Gillespie, Dirk; Nonner, Wolfgang; Henderson, Douglas; Eisenberg, Bob; Boda, Dezso

2009-12-01

Calcium channels have highly charged selectivity filters (4 COO(-) groups) that attract cations in to balance this charge and minimize free energy, forcing the cations (Na(+) and Ca(2+)) to compete for space in the filter. A reduced model was developed to better understand the mechanism of ion selectivity in calcium channels. The charge/space competition (CSC) mechanism implies that Ca(2+) is more efficient in balancing the charge of the filter because it provides twice the charge as Na(+) while occupying the same space. The CSC mechanism further implies that the main determinant of Ca(2+) versus Na(+) selectivity is the density of charged particles in the selectivity filter, i.e., the volume of the filter (after fixing the number of charged groups in the filter). In this paper we test this hypothesis by changing filter length and/or radius (shape) of the cylindrical selectivity filter of our reduced model. We show that varying volume and shape together has substantially stronger effects than varying shape alone with volume fixed. Our simulations show the importance of depletion zones of ions in determining channel conductance calculated with the integrated Nernst-Planck equation. We show that confining the protein side chains with soft or hard walls does not influence selectivity.

An Improved User Selection Algorithm in Multiuser MIMO Broadcast with Channel Prediction

Science.gov (United States)

Min, Zhi; Ohtsuki, Tomoaki

In multiuser MIMO-BC (Multiple-Input Multiple-Output Broadcasting) systems, user selection is important to achieve multiuser diversity. The optimal user selection algorithm is to try all the combinations of users to find the user group that can achieve the multiuser diversity. Unfortunately, the high calculation cost of the optimal algorithm prevents its implementation. Thus, instead of the optimal algorithm, some suboptimal user selection algorithms were proposed based on semiorthogonality of user channel vectors. The purpose of this paper is to achieve multiuser diversity with a small amount of calculation. For this purpose, we propose a user selection algorithm that can improve the orthogonality of a selected user group. We also apply a channel prediction technique to a MIMO-BC system to get more accurate channel information at the transmitter. Simulation results show that the channel prediction can improve the accuracy of channel information for user selections, and the proposed user selection algorithm achieves higher sum rate capacity than the SUS (Semiorthogonal User Selection) algorithm. Also we discuss the setting of the algorithm threshold. As the result of a discussion on the calculation complexity, which uses the number of complex multiplications as the parameter, the proposed algorithm is shown to have a calculation complexity almost equal to that of the SUS algorithm, and they are much lower than that of the optimal user selection algorithm.

Protein structure and ionic selectivity in calcium channels: Selectivity filter size, not shape, matters

OpenAIRE

Malasics, Attila; Gillespie, Dirk; Nonner, Wolfgang; Henderson, Douglas; Eisenberg, Bob; Boda, Dezső

2009-01-01

Calcium channels have highly charged selectivity filters (4 COO− groups) that attract cations in to balance this charge and minimize free energy, forcing the cations (Na+ and Ca2+) to compete for space in the filter. A reduced model was developed to better understand the mechanism of ion selectivity in calcium channels. The charge/space competition (CSC) mechanism implies that Ca2+ is more efficient in balancing the charge of the filter because it provides twice the charge as Na+ while occupy...

Frequency-specific attentional modulation in human primary auditory cortex and midbrain

NARCIS (Netherlands)

Riecke, Lars; Peters, Judith C; Valente, Giancarlo; Poser, Benedikt A; Kemper, Valentin G; Formisano, Elia; Sorger, Bettina

2018-01-01

Paying selective attention to an audio frequency selectively enhances activity within primary auditory cortex (PAC) at the tonotopic site (frequency channel) representing that frequency. Animal PAC neurons achieve this 'frequency-specific attentional spotlight' by adapting their frequency tuning,

Channel selection for simultaneous and proportional myoelectric prosthesis control of multiple degrees-of-freedom

Science.gov (United States)

Hwang, Han-Jeong; Hahne, Janne Mathias; Müller, Klaus-Robert

2014-10-01

Objective. Recent studies have shown the possibility of simultaneous and proportional control of electrically powered upper-limb prostheses, but there has been little investigation on optimal channel selection. The objective of this study is to find a robust channel selection method and the channel subsets most suitable for simultaneous and proportional myoelectric prosthesis control of multiple degrees-of-freedom (DoFs). Approach. Ten able-bodied subjects and one person with congenital upper-limb deficiency took part in this study, and performed wrist movements with various combinations of two DoFs (flexion/extension and radial/ulnar deviation). During the experiment, high density electromyographic (EMG) signals and the actual wrist angles were recorded with an 8 × 24 electrode array and a motion tracking system, respectively. The wrist angles were estimated from EMG features with ridge regression using the subsets of channels chosen by three different channel selection methods: (1) least absolute shrinkage and selection operator (LASSO), (2) sequential feature selection (SFS), and (3) uniform selection (UNI). Main results. SFS generally showed higher estimation accuracy than LASSO and UNI, but LASSO always outperformed SFS in terms of robustness, such as noise addition, channel shift and training data reduction. It was also confirmed that about 95% of the original performance obtained using all channels can be retained with only 12 bipolar channels individually selected by LASSO and SFS. Significance. From the analysis results, it can be concluded that LASSO is a promising channel selection method for accurate simultaneous and proportional prosthesis control. We expect that our results will provide a useful guideline to select optimal channel subsets when developing clinical myoelectric prosthesis control systems based on continuous movements with multiple DoFs.

Channel estimation for physical layer network coding systems

CERN Document Server

Gao, Feifei; Wang, Gongpu

2014-01-01

This SpringerBrief presents channel estimation strategies for the physical later network coding (PLNC) systems. Along with a review of PLNC architectures, this brief examines new challenges brought by the special structure of bi-directional two-hop transmissions that are different from the traditional point-to-point systems and unidirectional relay systems. The authors discuss the channel estimation strategies over typical fading scenarios, including frequency flat fading, frequency selective fading and time selective fading, as well as future research directions. Chapters explore the performa

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor.

Science.gov (United States)

Capes, Deborah L; Arcisio-Miranda, Manoel; Jarecki, Brian W; French, Robert J; Chanda, Baron

2012-02-14

Voltage-dependent ion channels are crucial for generation and propagation of electrical activity in biological systems. The primary mechanism for voltage transduction in these proteins involves the movement of a voltage-sensing domain (D), which opens a gate located on the cytoplasmic side. A distinct conformational change in the selectivity filter near the extracellular side has been implicated in slow inactivation gating, which is important for spike frequency adaptation in neural circuits. However, it remains an open question whether gating transitions in the selectivity filter region are also actuated by voltage sensors. Here, we examine conformational coupling between each of the four voltage sensors and the outer pore of a eukaryotic voltage-dependent sodium channel. The voltage sensors of these sodium channels are not structurally symmetric and exhibit functional specialization. To track the conformational rearrangements of individual voltage-sensing domains, we recorded domain-specific gating pore currents. Our data show that, of the four voltage sensors, only the domain IV voltage sensor is coupled to the conformation of the selectivity filter region of the sodium channel. Trapping the outer pore in a particular conformation with a high-affinity toxin or disulphide crossbridge impedes the return of this voltage sensor to its resting conformation. Our findings directly establish that, in addition to the canonical electromechanical coupling between voltage sensor and inner pore gates of a sodium channel, gating transitions in the selectivity filter region are also coupled to the movement of a voltage sensor. Furthermore, our results also imply that the voltage sensor of domain IV is unique in this linkage and in the ability to initiate slow inactivation in sodium channels.

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities

Science.gov (United States)

Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

2016-01-01

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones. PMID:27918424

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities.

Science.gov (United States)

Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

2016-12-02

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones.

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities

Directory of Open Access Journals (Sweden)

Saleem Aslam

2016-12-01

Full Text Available This paper highlights three critical aspects of the internet of things (IoTs, namely (1 energy efficiency, (2 energy balancing and (3 quality of service (QoS and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

Directory of Open Access Journals (Sweden)

Yang Li

Full Text Available Voltage-gated sodium (Nav channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions, a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

Science.gov (United States)

Li, Yang; Liu, Huihui; Xia, Mengdie; Gong, Haipeng

2016-01-01

Voltage-gated sodium (Nav) channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions), a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh) to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

DFT-based channel estimation and noise variance estimation techniques for single-carrier FDMA

OpenAIRE

Huang, G; Nix, AR; Armour, SMD

2010-01-01

Practical frequency domain equalization (FDE) systems generally require knowledge of the channel and the noise variance to equalize the received signal in a frequency-selective fading channel. Accurate channel estimate and noise variance estimate are thus desirable to improve receiver performance. In this paper we investigate the performance of the denoise channel estimator and the approximate linear minimum mean square error (A-LMMSE) channel estimator with channel power delay profile (PDP) ...

Selection of Inhibitor-Resistant Viral Potassium Channels Identifies a Selectivity Filter Site that Affects Barium and Amantadine Block

Science.gov (United States)

Fujiwara, Yuichiro; Arrigoni, Cristina; Domigan, Courtney; Ferrara, Giuseppina; Pantoja, Carlos; Thiel, Gerhard; Moroni, Anna; Minor, Daniel L.

2009-01-01

Background Understanding the interactions between ion channels and blockers remains an important goal that has implications for delineating the basic mechanisms of ion channel function and for the discovery and development of ion channel directed drugs. Methodology/Principal Findings We used genetic selection methods to probe the interaction of two ion channel blockers, barium and amantadine, with the miniature viral potassium channel Kcv. Selection for Kcv mutants that were resistant to either blocker identified a mutant bearing multiple changes that was resistant to both. Implementation of a PCR shuffling and backcrossing procedure uncovered that the blocker resistance could be attributed to a single change, T63S, at a position that is likely to form the binding site for the inner ion in the selectivity filter (site 4). A combination of electrophysiological and biochemical assays revealed a distinct difference in the ability of the mutant channel to interact with the blockers. Studies of the analogous mutation in the mammalian inward rectifier Kir2.1 show that the T→S mutation affects barium block as well as the stability of the conductive state. Comparison of the effects of similar barium resistant mutations in Kcv and Kir2.1 shows that neighboring amino acids in the Kcv selectivity filter affect blocker binding. Conclusions/Significance The data support the idea that permeant ions have an integral role in stabilizing potassium channel structure, suggest that both barium and amantadine act at a similar site, and demonstrate how genetic selections can be used to map blocker binding sites and reveal mechanistic features. PMID:19834614

OPRA capacity bounds for selection diversity over generalized fading channels

KAUST Repository

Hanif, Muhammad Fainan

2014-05-01

Channel side information at the transmitter can increase the average capacity by enabling optimal power and rate adaptation. The resulting optimal power and rate adaptation (OPRA) capacity rarely has a closed-form analytic expression. In this paper, lower and upper bounds on OPRA capacity for selection diversity scheme are presented. These bounds hold for variety of fading channels including log-normal and generalized Gamma distributed models and have very simple analytic expressions for easy evaluation even for kth best path selection. Some selected numerical results show that the newly proposed bounds closely approximate the actual OPRA capacity. © 2014 IEEE.

Frequency-specific attentional modulation in human primary auditory cortex and midbrain.

Science.gov (United States)

Riecke, Lars; Peters, Judith C; Valente, Giancarlo; Poser, Benedikt A; Kemper, Valentin G; Formisano, Elia; Sorger, Bettina

2018-07-01

Paying selective attention to an audio frequency selectively enhances activity within primary auditory cortex (PAC) at the tonotopic site (frequency channel) representing that frequency. Animal PAC neurons achieve this 'frequency-specific attentional spotlight' by adapting their frequency tuning, yet comparable evidence in humans is scarce. Moreover, whether the spotlight operates in human midbrain is unknown. To address these issues, we studied the spectral tuning of frequency channels in human PAC and inferior colliculus (IC), using 7-T functional magnetic resonance imaging (FMRI) and frequency mapping, while participants focused on different frequency-specific sounds. We found that shifts in frequency-specific attention alter the response gain, but not tuning profile, of PAC frequency channels. The gain modulation was strongest in low-frequency channels and varied near-monotonically across the tonotopic axis, giving rise to the attentional spotlight. We observed less prominent, non-tonotopic spatial patterns of attentional modulation in IC. These results indicate that the frequency-specific attentional spotlight in human PAC as measured with FMRI arises primarily from tonotopic gain modulation, rather than adapted frequency tuning. Moreover, frequency-specific attentional modulation of afferent sound processing in human IC seems to be considerably weaker, suggesting that the spotlight diminishes toward this lower-order processing stage. Our study sheds light on how the human auditory pathway adapts to the different demands of selective hearing. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

An integrative time-varying frequency detection and channel sounding method for dynamic plasma sheath

Science.gov (United States)

Shi, Lei; Yao, Bo; Zhao, Lei; Liu, Xiaotong; Yang, Min; Liu, Yanming

2018-01-01

The plasma sheath-surrounded hypersonic vehicle is a dynamic and time-varying medium and it is almost impossible to calculate time-varying physical parameters directly. The in-fight detection of the time-varying degree is important to understand the dynamic nature of the physical parameters and their effect on re-entry communication. In this paper, a constant envelope zero autocorrelation (CAZAC) sequence based on time-varying frequency detection and channel sounding method is proposed to detect the plasma sheath electronic density time-varying property and wireless channel characteristic. The proposed method utilizes the CAZAC sequence, which has excellent autocorrelation and spread gain characteristics, to realize dynamic time-varying detection/channel sounding under low signal-to-noise ratio in the plasma sheath environment. Theoretical simulation under a typical time-varying radio channel shows that the proposed method is capable of detecting time-variation frequency up to 200 kHz and can trace the channel amplitude and phase in the time domain well under -10 dB. Experimental results conducted in the RF modulation discharge plasma device verified the time variation detection ability in practical dynamic plasma sheath. Meanwhile, nonlinear phenomenon of dynamic plasma sheath on communication signal is observed thorough channel sounding result.

Electrostatics of aquaporin and aquaglyceroporin channels correlates with their transport selectivity

Science.gov (United States)

Oliva, Romina; Calamita, Giuseppe; Thornton, Janet M.; Pellegrini-Calace, Marialuisa

2010-01-01

Aquaporins are homotetrameric channel proteins, which allow the diffusion of water and small solutes across biological membranes. According to their transport function, aquaporins can be divided into “orthodox aquaporins”, which allow the flux of water molecules only, and “aquaglyceroporins”, which facilitate the diffusion of glycerol and other small solutes in addition to water. The contribution of individual residues in the pore to the selectivity of orthodox aquaporins and aquaglyceroporins is not yet fully understood. To gain insights into aquaporin selectivity, we focused on the sequence variation and electrostatics of their channels. The continuum Poisson-Boltzmann electrostatic potential along the channel was calculated and compared for ten three-dimensional-structures which are representatives of different aquaporin subfamilies, and a panel of functionally characterized mutants, for which high-accuracy three-dimensional-models could be derived. Interestingly, specific electrostatic profiles associated with the main selectivity to water or glycerol could be identified. In particular: (i) orthodox aquaporins showed a distinctive electrostatic potential maximum at the periplasmic side of the channel around the aromatic/Arg (ar/R) constriction site; (ii) aquaporin-0 (AQP0), a mammalian aquaporin with considerably low water permeability, had an additional deep minimum at the cytoplasmic side; (iii) aquaglyceroporins showed a rather flat potential all along the channel; and (iv) the bifunctional protozoan PfAQP had an unusual all negative profile. Evaluation of electrostatics of the mutants, along with a thorough sequence analysis of the aquaporin pore-lining residues, illuminated the contribution of specific residues to the electrostatics of the channels and possibly to their selectivity. PMID:20147624

Joint channel/frequency offset estimation and correction for coherent optical FBMC/OQAM system

Science.gov (United States)

Wang, Daobin; Yuan, Lihua; Lei, Jingli; wu, Gang; Li, Suoping; Ding, Runqi; Wang, Dongye

2017-12-01

In this paper, we focus on analysis of the preamble-based joint estimation for channel and laser-frequency offset (LFO) in coherent optical filter bank multicarrier systems with offset quadrature amplitude modulation (CO-FBMC/OQAM). In order to reduce the noise impact on the estimation accuracy, we proposed an estimation method based on inter-frame averaging. This method averages the cross-correlation function of real-valued pilots within multiple FBMC frames. The laser-frequency offset is estimated according to the phase of this average. After correcting LFO, the final channel response is also acquired by averaging channel estimation results within multiple frames. The principle of the proposed method is analyzed theoretically, and the preamble structure is thoroughly designed and optimized to suppress the impact of inherent imaginary interference (IMI). The effectiveness of our method is demonstrated numerically using different fiber and LFO values. The obtained results show that the proposed method can improve transmission performance significantly.

Frequency-Selective Attention in Auditory Scenes Recruits Frequency Representations Throughout Human Superior Temporal Cortex.

Science.gov (United States)

Riecke, Lars; Peters, Judith C; Valente, Giancarlo; Kemper, Valentin G; Formisano, Elia; Sorger, Bettina

2017-05-01

A sound of interest may be tracked amid other salient sounds by focusing attention on its characteristic features including its frequency. Functional magnetic resonance imaging findings have indicated that frequency representations in human primary auditory cortex (AC) contribute to this feat. However, attentional modulations were examined at relatively low spatial and spectral resolutions, and frequency-selective contributions outside the primary AC could not be established. To address these issues, we compared blood oxygenation level-dependent (BOLD) responses in the superior temporal cortex of human listeners while they identified single frequencies versus listened selectively for various frequencies within a multifrequency scene. Using best-frequency mapping, we observed that the detailed spatial layout of attention-induced BOLD response enhancements in primary AC follows the tonotopy of stimulus-driven frequency representations-analogous to the "spotlight" of attention enhancing visuospatial representations in retinotopic visual cortex. Moreover, using an algorithm trained to discriminate stimulus-driven frequency representations, we could successfully decode the focus of frequency-selective attention from listeners' BOLD response patterns in nonprimary AC. Our results indicate that the human brain facilitates selective listening to a frequency of interest in a scene by reinforcing the fine-grained activity pattern throughout the entire superior temporal cortex that would be evoked if that frequency was present alone. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Channel Islands, Kelp Forest Monitoring, Size and Frequency, Natural Habitat, 1985-2007

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has measurements of the size of selected animal species at selected locations in the Channel Islands National Park. Sampling is conducted annually...

Use of color-coded sleeve shutters accelerates oscillograph channel selection

Science.gov (United States)

Bouchlas, T.; Bowden, F. W.

1967-01-01

Sleeve-type shutters mechanically adjust individual galvanometer light beams onto or away from selected channels on oscillograph papers. In complex test setups, the sleeve-type shutters are color coded to separately identify each oscillograph channel. This technique could be used on any equipment using tubular galvanometer light sources.

Strings on a Violin: Location Dependence of Frequency Tuning in Active Dendrites.

Science.gov (United States)

Das, Anindita; Rathour, Rahul K; Narayanan, Rishikesh

2017-01-01

Strings on a violin are tuned to generate distinct sound frequencies in a manner that is firmly dependent on finger location along the fingerboard. Sound frequencies emerging from different violins could be very different based on their architecture, the nature of strings and their tuning. Analogously, active neuronal dendrites, dendrites endowed with active channel conductances, are tuned to distinct input frequencies in a manner that is dependent on the dendritic location of the synaptic inputs. Further, disparate channel expression profiles and differences in morphological characteristics could result in dendrites on different neurons of the same subtype tuned to distinct frequency ranges. Alternately, similar location-dependence along dendritic structures could be achieved through disparate combinations of channel profiles and morphological characteristics, leading to degeneracy in active dendritic spectral tuning. Akin to strings on a violin being tuned to different frequencies than those on a viola or a cello, different neuronal subtypes exhibit distinct channel profiles and disparate morphological characteristics endowing each neuronal subtype with unique location-dependent frequency selectivity. Finally, similar to the tunability of musical instruments to elicit distinct location-dependent sounds, neuronal frequency selectivity and its location-dependence are tunable through activity-dependent plasticity of ion channels and morphology. In this morceau, we explore the origins of neuronal frequency selectivity, and survey the literature on the mechanisms behind the emergence of location-dependence in distinct forms of frequency tuning. As a coda to this composition, we present some future directions for this exciting convergence of biophysical mechanisms that endow a neuron with frequency multiplexing capabilities.

Performance analysis of OFDM modulation on indoor broadband PLC channels

Science.gov (United States)

Antonio Cortés, José; Díez, Luis; Cañete, Francisco Javier; Sánchez-Martínez, Juan José; Entrambasaguas, José Tomás

2011-12-01

Indoor broadband power-line communications is a suitable technology for home networking applications. In this context, orthogonal frequency-division multiplexing (OFDM) is the most widespread modulation technique. It has recently been adopted by the ITU-T Recommendation G.9960 and is also used by most of the commercial systems, whose number of carriers has gone from about 100 to a few thousands in less than a decade. However, indoor power-line channels are frequency-selective and exhibit periodic time variations. Hence, increasing the number of carriers does not always improves the performance, since it reduces the distortion because of the frequency selectivity, but increases the one caused by the channel time variation. In addition, the long impulse response of power-line channels obliges to use an insufficient cyclic prefix. Increasing its value reduces the distortion, but also the symbol rate. Therefore, there are optimum values for both modulation parameters. This article evaluates the performance of an OFDM system as a function of the number of carriers and the cyclic prefix length, determining their most appropriate values for the indoor power-line scenario. This task must be accomplished by means of time-consuming simulations employing a linear time-varying filtering, since no consensus on a tractable statistical channel model has been reached yet. However, this study presents a simpler procedure in which the distortion because of the frequency selectivity is computed using a time-invariant channel response, and an analytical expression is derived for the one caused by the channel time variation.

A Study of an Iterative Channel Estimation Scheme of FS-FBMC System

Directory of Open Access Journals (Sweden)

YongJu Won

2017-01-01

Full Text Available A filter bank multicarrier on offset-quadrature amplitude modulation (FBMC/OQAM system is an alternative multicarrier modulation scheme that does not need cyclic prefix (CP even in the presence of a multipath fading channel by the properties of prototype filter. The FBMC/OQAM system can be implemented either by using the poly-phase network with fast fourier transform (PPN-FFT or by using the extended FFT on a frequency-spreading (FS domain. In this paper, we propose an iterative channel estimation scheme for each sub channel of a FBMC/OQAM system over a frequency-spreading domain. The proposed scheme first estimates the channel using the received pilot signal in the subchannel domain and interpolates the estimated channel to fine frequency-spreading domain. Then the channel compensated FS domain pilot is despread again to modify the channel state information (CSI estimation. Computer simulation shows that the proposed method outperforms the conventional FBMC/OQAM channel estimator in a frequency selective channel.

A Wearable Channel Selection-Based Brain-Computer Interface for Motor Imagery Detection.

Science.gov (United States)

Lo, Chi-Chun; Chien, Tsung-Yi; Chen, Yu-Chun; Tsai, Shang-Ho; Fang, Wai-Chi; Lin, Bor-Shyh

2016-02-06

Motor imagery-based brain-computer interface (BCI) is a communication interface between an external machine and the brain. Many kinds of spatial filters are used in BCIs to enhance the electroencephalography (EEG) features related to motor imagery. The approach of channel selection, developed to reserve meaningful EEG channels, is also an important technique for the development of BCIs. However, current BCI systems require a conventional EEG machine and EEG electrodes with conductive gel to acquire multi-channel EEG signals and then transmit these EEG signals to the back-end computer to perform the approach of channel selection. This reduces the convenience of use in daily life and increases the limitations of BCI applications. In order to improve the above issues, a novel wearable channel selection-based brain-computer interface is proposed. Here, retractable comb-shaped active dry electrodes are designed to measure the EEG signals on a hairy site, without conductive gel. By the design of analog CAR spatial filters and the firmware of EEG acquisition module, the function of spatial filters could be performed without any calculation, and channel selection could be performed in the front-end device to improve the practicability of detecting motor imagery in the wearable EEG device directly or in commercial mobile phones or tablets, which may have relatively low system specifications. Finally, the performance of the proposed BCI is investigated, and the experimental results show that the proposed system is a good wearable BCI system prototype.

Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family.

Science.gov (United States)

Kaufman, I; Luchinsky, D G; Tindjong, R; McClintock, P V E; Eisenberg, R S

2013-11-01

We use Brownian dynamics (BD) simulations to study the ionic conduction and valence selectivity of a generic electrostatic model of a biological ion channel as functions of the fixed charge Q(f) at its selectivity filter. We are thus able to reconcile the discrete calcium conduction bands recently revealed in our BD simulations, M0 (Q(f)=1e), M1 (3e), M2 (5e), with a set of sodium conduction bands L0 (0.5e), L1 (1.5e), thereby obtaining a completed pattern of conduction and selectivity bands vs Q(f) for the sodium-calcium channels family. An increase of Q(f) leads to an increase of calcium selectivity: L0 (sodium-selective, nonblocking channel) → M0 (nonselective channel) → L1 (sodium-selective channel with divalent block) → M1 (calcium-selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L0 band is putatively identified with the eukaryotic sodium channel The scheme created is able to account for the experimentally observed mutation-induced transformations between nonselective channels, sodium-selective channels, and calcium-selective channels, which we interpret as transitions between different rows of the identification table. By considering the potential energy changes during permeation, we show explicitly that the multi-ion conduction bands of calcium and sodium channels arise as the result of resonant barrierless conduction. The pattern of periodic conduction bands is explained on the basis of sequential neutralization taking account of self-energy, as Q(f)(z,i)=ze(1/2+i), where i is the order of the band and z is the valence of the ion. Our results confirm the crucial influence of electrostatic interactions on conduction and on the Ca(2+)/Na(+) valence selectivity of calcium and sodium ion channels. The model and results could be also applicable to biomimetic nanopores with charged walls.

Asymptotic analysis for Nakagami-m fading channels with relay selection

KAUST Repository

Zhong, Caijun; Wong, Kaikit; Jin, Shi; Alouini, Mohamed-Slim; Ratnarajah, Tharm

2011-01-01

In this paper, we analyze the asymptotic outage probability performance of both decode-and-forward (DF) and amplify-and-forward (AF) relaying systems using partial relay selection and the "best" relay selection schemes for Nakagami-m fading channels

A new Infrared Atmospheric Sounding Interferometer channel selection and assessment of its impact on Met Office NWP forecasts

Science.gov (United States)

Noh, Young-Chan; Sohn, Byung-Ju; Kim, Yoonjae; Joo, Sangwon; Bell, William; Saunders, Roger

2017-11-01

A new set of Infrared Atmospheric Sounding Interferometer (IASI) channels was re-selected from 314 EUMETSAT channels. In selecting channels, we calculated the impact of the individually added channel on the improvement in the analysis outputs from a one-dimensional variational analysis (1D-Var) for the Unified Model (UM) data assimilation system at the Met Office, using the channel score index (CSI) as a figure of merit. Then, 200 channels were selected in order by counting each individual channel's CSI contribution. Compared with the operationally used 183 channels for the UM at the Met Office, the new set shares 149 channels, while the other 51 channels are new. Also examined is the selection from the entropy reduction method with the same 1D-Var approach. Results suggest that channel selection can be made in a more objective fashion using the proposed CSI method. This is because the most important channels can be selected across the whole IASI observation spectrum. In the experimental trial runs using the UM global assimilation system, the new channels had an overall neutral impact in terms of improvement in forecasts, as compared with results from the operational channels. However, upper-tropospheric moist biases shown in the control run with operational channels were significantly reduced in the experimental trial with the newly selected channels. The reduction of moist biases was mainly due to the additional water vapor channels, which are sensitive to the upper-tropospheric water vapor.

Frequency selective bolometers

DEFF Research Database (Denmark)

Kowitt, M.S.; Fixsen, D.J.; Goldin, A.

1996-01-01

We propose a concept for radiometry in the millimeter, the submillimeter, and the far-IR spectral regions, the frequency selective bolometer (FSB). This system uses a bolometer as a coupled element of a tuned quasi-optical interference filter in which the absorption, the transmission......-dimensional transmission-line model. Instruments based on FSB technology should have several advantages over current multiband bolometric radiometers including smaller and more compact cryogenic optics; reduced demands on cryostat size and weight, high coupling efficiency, minimum constraints on the geometry in the focal...

Theoretical analysis of selectivity mechanisms in molecular transport through channels and nanopores

International Nuclear Information System (INIS)

Agah, Shaghayegh; Pasquali, Matteo; Kolomeisky, Anatoly B.

2015-01-01

Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed

Optimal Channel Selection Based on Online Decision and Offline Learning in Multichannel Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Mu Qiao

2017-01-01

Full Text Available We propose a channel selection strategy with hybrid architecture, which combines the centralized method and the distributed method to alleviate the overhead of access point and at the same time provide more flexibility in network deployment. By this architecture, we make use of game theory and reinforcement learning to fulfill the optimal channel selection under different communication scenarios. Particularly, when the network can satisfy the requirements of energy and computational costs, the online decision algorithm based on noncooperative game can help each individual sensor node immediately select the optimal channel. Alternatively, when the network cannot satisfy the requirements of energy and computational costs, the offline learning algorithm based on reinforcement learning can help each individual sensor node to learn from its experience and iteratively adjust its behavior toward the expected target. Extensive simulation results validate the effectiveness of our proposal and also prove that higher system throughput can be achieved by our channel selection strategy over the conventional off-policy channel selection approaches.

Carrier frequency offset estimation for an acoustic-electric channel using 16 QAM modulation

Science.gov (United States)

Cunningham, Michael T.; Anderson, Leonard A.; Wilt, Kyle R.; Chakraborty, Soumya; Saulnier, Gary J.; Scarton, Henry A.

2016-05-01

Acoustic-electric channels can be used to send data through metallic barriers, enabling communications where electromagnetic signals are ineffective. This paper considers an acoustic-electric channel that is formed by mounting piezoelectric transducers on metallic barriers that are separated by a thin water layer. The transducers are coupled to the barriers using epoxy and the barriers are positioned to axially-align the PZTs, maximizing energy transfer efficiency. The electrical signals are converted by the transmitting transducers into acoustic waves, which propagate through the elastic walls and water medium to the receiving transducers. The reverberation of the acoustic signals in these channels can produce multipath distortion with a significant delay spread that introduces inter-symbol interference (ISI) into the received signal. While the multipath effects can be severe, the channel does not change rapidly which makes equalization easier. Here we implement a 16-QAM system on this channel, including a method for obtaining accurate carrier frequency offset (CFO) estimates in the presence of the quasi-static multipath propagation. A raised-power approach is considered but found to suffer from excessive data noise resulting from the ISI. An alternative approach that utilizes a pilot tone burst at the start of a data packet is used for CFO estimation and found to be effective. The autocorrelation method is used to estimate the frequency of the received burst. A real-time prototype of the 16 QAM system that uses a Texas Instruments MSP430 microcontroller-based transmitter and a personal computer-based receiver is presented along with performance results.

Develop A Framework for Selection of Intermediary in Marketing Channel

Directory of Open Access Journals (Sweden)

Hamid Reza Irani

2011-03-01

Full Text Available This study seeks to examine how a company can select the best intermediary for itsMarketing channels with minimum of criteria and time. A theoretical framework is proposed basedon the most important tasks of intermediary and the criteria to measure them. There are four basictasks and thirty criteria in three independent levels. Subsequently, an exploratory case study inIranian Food industry is described to illustrate the value of the framework. It is possible to apply thetheoretical framework to select the intermediary for any industry or country. However, there mightbe possible location-specific or industry-specific limitations. Moreover, the framework has provedto be useful in improving the selection of the intermediary in marketing channel. This is a notableand promising side-effect of the exploratory study, at least from a managerial point of view.

Performance Analysis of OFDM in Frequency Selective, Slowly Fading Nakagami Channels

National Research Council Canada - National Science Library

Count, Patrick

2001-01-01

In an effort to offer faster, more reliable wireless communications services to the public, many wireless standardization committees have, in recent years, adopted Orthogonal Frequency Division Multiplexing (OFDM...

High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing.

Science.gov (United States)

Worthmann, Brian M; Song, H C; Dowling, David R

2015-12-01

Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m.

A perspective on single-channel frequency-domain speech enhancement

CERN Document Server

Benesty, Jacob

2010-01-01

This book focuses on a class of single-channel noise reduction methods that are performed in the frequency domain via the short-time Fourier transform (STFT). The simplicity and relative effectiveness of this class of approaches make them the dominant choice in practical systems. Even though many popular algorithms have been proposed through more than four decades of continuous research, there are a number of critical areas where our understanding and capabilities still remain quite rudimentary, especially with respect to the relationship between noise reduction and speech distortion. All exis

Overlay Cognitive Radios With Channel-Aware Adaptive Link Selection and Buffer-Aided Relaying

KAUST Repository

Shaqfeh, Mohammad

2015-08-01

The aim of this work is to maximize the long-term average achievable rate region of a primary and a secondary source-destination pairs operating in an overlay setup over block-fading channels. To achieve this objective, we propose an opportunistic strategy to grant channel access to the primary and secondary sources based on the channel conditions in order to exploit the available multiple-link diversity gains in the system. The secondary source has causal knowledge of the primary messages and it acts as a relay of the primary source in return for getting access to the channel. To maximize the gains of relaying, the relay and destination are equipped with buffers to enable the use of channel-aware adaptive link selection. We propose and optimize different link selection policies and characterize their expected achievable rates. Also, we provide several numerical results to demonstrate the evident mutual benefits of buffer-aided cooperation and adaptive link selection to the primary and the secondary source-destination pairs. © 1972-2012 IEEE.

Overlay Cognitive Radios With Channel-Aware Adaptive Link Selection and Buffer-Aided Relaying

KAUST Repository

Shaqfeh, Mohammad; Zafar, Ammar; Alnuweiri, Hussein; Alouini, Mohamed-Slim

2015-01-01

The aim of this work is to maximize the long-term average achievable rate region of a primary and a secondary source-destination pairs operating in an overlay setup over block-fading channels. To achieve this objective, we propose an opportunistic strategy to grant channel access to the primary and secondary sources based on the channel conditions in order to exploit the available multiple-link diversity gains in the system. The secondary source has causal knowledge of the primary messages and it acts as a relay of the primary source in return for getting access to the channel. To maximize the gains of relaying, the relay and destination are equipped with buffers to enable the use of channel-aware adaptive link selection. We propose and optimize different link selection policies and characterize their expected achievable rates. Also, we provide several numerical results to demonstrate the evident mutual benefits of buffer-aided cooperation and adaptive link selection to the primary and the secondary source-destination pairs. © 1972-2012 IEEE.

Bandwidth efficient channel estimation method for airborne hyperspectral data transmission in sparse doubly selective communication channels

Science.gov (United States)

Vahidi, Vahid; Saberinia, Ebrahim; Regentova, Emma E.

2017-10-01

A channel estimation (CE) method based on compressed sensing (CS) is proposed to estimate the sparse and doubly selective (DS) channel for hyperspectral image transmission from unmanned aircraft vehicles to ground stations. The proposed method contains three steps: (1) the priori estimate of the channel by orthogonal matching pursuit (OMP), (2) calculation of the linear minimum mean square error (LMMSE) estimate of the received pilots given the estimated channel, and (3) estimate of the complex amplitudes and Doppler shifts of the channel using the enhanced received pilot data applying a second round of a CS algorithm. The proposed method is named DS-LMMSE-OMP, and its performance is evaluated by simulating transmission of AVIRIS hyperspectral data via the communication channel and assessing their fidelity for the automated analysis after demodulation. The performance of the DS-LMMSE-OMP approach is compared with that of two other state-of-the-art CE methods. The simulation results exhibit up to 8-dB figure of merit in the bit error rate and 50% improvement in the hyperspectral image classification accuracy.

MONETARY TRANSMISSION CHANNELS IN FLEXIBLE MONETARY AND EXCHANGE RATE REGIMES: THE CASE OF SELECTED TRANSITION ECONOMIES

Directory of Open Access Journals (Sweden)

Kosta JOSIFIDIS

2010-01-01

Full Text Available The paper explores selected monetary transmission channels in the case of transition economies. Namely, an exchange rate channel, an interest rate channel, direct and indirect influence to an exchange rate, are focused. Specific (former transition economies are differentiated according the combination of implemented monetary and exchange rate regimes: exchange rate as a nominal anchor and rigid exchange rate regimes, exchange rate as a nominal anchor and intermediate exchange rate regimes, and implicit/explicit inflation targeting monetary regime and floating (managed/free exchange rate regime. The monetary transmission is tracked during different phases in a transition process towards the EU and compared between different nominal anchors and exchange rate regimes. In order to track the influence of a monetary policy instruments (impulses to different goals of a monetary policy (responses during the period from 6-24 months, we use VAR and VEC models. Monthly frequency of following time series are used in the models: nominal exchange rates, consumer price indexes, foreign exchange reserves, and reference interest rates. The aim of the paper is to point to the distinction between de jure and de facto exchange rate regimes, and to the adequacy of used combination of monetary and exchange rate regimes having in mind revealed features of investigated monetary transmission channels.

Multi-carrier Communications over Time-varying Acoustic Channels

Science.gov (United States)

Aval, Yashar M.

Acoustic communication is an enabling technology for many autonomous undersea systems, such as those used for ocean monitoring, offshore oil and gas industry, aquaculture, or port security. There are three main challenges in achieving reliable high-rate underwater communication: the bandwidth of acoustic channels is extremely limited, the propagation delays are long, and the Doppler distortions are more pronounced than those found in wireless radio channels. In this dissertation we focus on assessing the fundamental limitations of acoustic communication, and designing efficient signal processing methods that cam overcome these limitations. We address the fundamental question of acoustic channel capacity (achievable rate) for single-input-multi-output (SIMO) acoustic channels using a per-path Rician fading model, and focusing on two scenarios: narrowband channels where the channel statistics can be approximated as frequency- independent, and wideband channels where the nominal path loss is frequency-dependent. In each scenario, we compare several candidate power allocation techniques, and show that assigning uniform power across all frequencies for the first scenario, and assigning uniform power across a selected frequency-band for the second scenario, are the best practical choices in most cases, because the long propagation delay renders the feedback information outdated for power allocation based on the estimated channel response. We quantify our results using the channel information extracted form the 2010 Mobile Acoustic Communications Experiment (MACE'10). Next, we focus on achieving reliable high-rate communication over underwater acoustic channels. Specifically, we investigate orthogonal frequency division multiplexing (OFDM) as the state-of-the-art technique for dealing with frequency-selective multipath channels, and propose a class of methods that compensate for the time-variation of the underwater acoustic channel. These methods are based on multiple

The role of solvation in the binding selectivity of the L-type calcium channel.

Science.gov (United States)

Boda, Dezső; Henderson, Douglas; Gillespie, Dirk

2013-08-07

We present grand canonical Monte Carlo simulation results for a reduced model of the L-type calcium channel. While charged residues of the protein amino acids in the selectivity filter are treated explicitly, most of the degrees of freedom (including the rest of the protein and the solvent) are represented by their dielectric response, i.e., dielectric continua. The new aspect of this paper is that the dielectric coefficient in the channel is different from that in the baths. The ions entering the channel, thus, cross a dielectric boundary at the entrance of the channel. Simulating this case has been made possible by our recent methodological development [D. Boda, D. Henderson, B. Eisenberg, and D. Gillespie, J. Chem. Phys. 135, 064105 (2011)]. Our main focus is on the effect of solvation energy (represented by the Born energy) on monovalent vs. divalent ion selectivity in the channel. We find no significant change in selectivity by changing the dielectric coefficient in the channel because the larger solvation penalty is counterbalanced by the enhanced Coulomb attraction inside the channel as soon as we use the Born radii (fitted to experimental hydration energies) to compute the solvation penalty from the Born equation.

Development of a novel fast frequency modulation scheme for the JET multi-channel reflectometer

International Nuclear Information System (INIS)

Deliyanakis, N.

1999-10-01

A novel frequency modulation scheme has been developed for the multi-channel reflectometer used to measure density profiles and density fluctuations on the JET tokamak. This reflectometer normally uses slow frequency sweeping, combined with fixed-frequency operation, to measure the group delay, as well as plasma fluctuations, at 10 different microwave frequencies. The novel scheme uses continuous frequency modulation on a time-scale much faster than that of plasma fluctuations, the main aim being to make the group delay measurement more robust against plasma fluctuations. This paper discusses the theoretical background of the scheme, gives a detailed description of the system, and presents results from plasma measurements. (author)

Effects of Carrier Frequency Offset, Timing Offset, and Channel Spread Factor on the Performance of Hexagonal Multicarrier Modulation Systems

Directory of Open Access Journals (Sweden)

Kui Xu

2009-01-01

Full Text Available Hexagonal multicarrier modulation (HMM system is the technique of choice to overcome the impact of time-frequency dispersive transmission channel. This paper examines the effects of insufficient synchronization (carrier frequency offset, timing offset on the amplitude and phase of the demodulated symbol by using a projection receiver in hexagonal multicarrier modulation systems. Furthermore, effects of CFO, TO, and channel spread factor on the performance of signal-to-interference-plus-noise ratio (SINR in hexagonal multicarrier modulation systems are further discussed. The exact SINR expression versus insufficient synchronization and channel spread factor is derived. Theoretical analysis shows that similar degradation on symbol amplitude and phase caused by insufficient synchronization is incurred as in traditional cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM transmission. Our theoretical analysis is confirmed by numerical simulations in a doubly dispersive (DD channel with exponential delay power profile and U-shape Doppler power spectrum, showing that HMM systems outperform traditional CP-OFDM systems with respect to SINR against ISI/ICI caused by insufficient synchronization and doubly dispersive channel.

Channel selection in e-commerce age: A strategic analysis of co-op advertising models

Directory of Open Access Journals (Sweden)

Yongmei Liu

2013-03-01

Full Text Available Purpose: The purpose of this paper is to develop and compare two co-op advertising models: advertising model under traditional channel and co-op advertising model under dual channel, to select optimal channel structure to sell products for manufacturer and to derive optimal co-op advertising strategies for the manufacturer and the retailer.Design/methodology/approach: Stackelberg game theoretical is used to develop two co-op advertising models: co-op advertising model under traditional channel and co-op advertising model under dual channel. Then we compare the two models to select optimal channel structure to sell products for manufacturer and to derive optimal co-op advertising strategies for the manufacturer and the retailer. Furthermore, we analyze the impact of product web-fit on these optimal strategies and illustrate by some numeral examples. Based on our results, we provide some significant theories and managerial insights, and derive some probable paths of future research.Findings: We provide a framework for researching optimal co-op advertising strategies in a two-level supply chain considering different marketing channel structures. First, we discuss the traditional channel co-op adverting model and the dual channel co-op advertising model based on Stackelberg game theoretical, and we derive optimal co-op advertising strategies. Next, comparisons of these two channel structures are discussed and we find that the manufacturer always benefits from dual channel. But the retailer not always benefits from dual channel structure, and dual channel structure is better than retail channel with certain conditions. Also, the optimal co-op advertising strategies for the manufacturer and the retailer are obtained.Research limitations/implications: First, we focus on the aforementioned two channel structures; a further comparison with other channel structures can be investigated. Second, we ignore some factors that influence the demand of product

Efficient collaborative sparse channel estimation in massive MIMO

KAUST Repository

Masood, Mudassir

2015-08-12

We propose a method for estimation of sparse frequency selective channels within MIMO-OFDM systems. These channels are independently sparse and share a common support. The method estimates the impulse response for each channel observed by the antennas at the receiver. Estimation is performed in a coordinated manner by sharing minimal information among neighboring antennas to achieve results better than many contemporary methods. Simulations demonstrate the superior performance of the proposed method.

Efficient collaborative sparse channel estimation in massive MIMO

KAUST Repository

Masood, Mudassir; Afify, Laila H.; Al-Naffouri, Tareq Y.

2015-01-01

We propose a method for estimation of sparse frequency selective channels within MIMO-OFDM systems. These channels are independently sparse and share a common support. The method estimates the impulse response for each channel observed by the antennas at the receiver. Estimation is performed in a coordinated manner by sharing minimal information among neighboring antennas to achieve results better than many contemporary methods. Simulations demonstrate the superior performance of the proposed method.

Voltage-Gated Potassium Channels: A Structural Examination of Selectivity and Gating

Science.gov (United States)

Kim, Dorothy M.; Nimigean, Crina M.

2016-01-01

Voltage-gated potassium channels play a fundamental role in the generation and propagation of the action potential. The discovery of these channels began with predictions made by early pioneers, and has culminated in their extensive functional and structural characterization by electrophysiological, spectroscopic, and crystallographic studies. With the aid of a variety of crystal structures of these channels, a highly detailed picture emerges of how the voltage-sensing domain reports changes in the membrane electric field and couples this to conformational changes in the activation gate. In addition, high-resolution structural and functional studies of K+ channel pores, such as KcsA and MthK, offer a comprehensive picture on how selectivity is achieved in K+ channels. Here, we illustrate the remarkable features of voltage-gated potassium channels and explain the mechanisms used by these machines with experimental data. PMID:27141052

Dual-band frequency selective surface with large band separation and stable performance

Science.gov (United States)

Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

2012-05-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

Experimental investigation of channel avulsion frequency on river deltas under rising sea levels

Science.gov (United States)

Silvestre, J.; Chadwick, A. J.; Steele, S.; Lamb, M. P.

2017-12-01

River deltas are low-relief landscapes that are socioeconomically important; they are home to over half a billion people worldwide. Many deltas are built by cycles of lobe growth punctuated by abrupt channel shifts, or avulsions, which often reoccur at a similar location and with a regular frequency. Previous experimental work has investigated the effect of hydrodynamic backwater in controlling channel avulsion location and timing on deltas under constant sea level conditions, but it is unclear how sea-level rise impacts avulsion dynamics. We present results from a flume experiment designed to isolate the role of relative sea-level rise on the evolution of a backwater-influenced delta. The experiment was conducted in the river-ocean facility at Caltech, where a 7m long, 14cm wide alluvial river drains into a 6m by 3m "ocean" basin. The experimental delta grew under subcritical flow, a persistent backwater zone, and a range of sea level rise rates. Without sea level rise, lobe progradation produced in-channel aggradation and periodic avulsions every 3.6 ± 0.9 hours, which corresponded to when channels aggraded to approximately one-half of their flow depth. With a modest rate of sea-level rise (0.25 mm/hr), we observed enhanced aggradation in the backwater zone, causing channels to aggrade more quickly and avulse more frequently (every 2.1 ± 0.6 hours). In future work, we expect further increases in the rate of relative sea-level rise to cause avulsion frequency to decrease as the delta drowns and the backwater zone retreats upstream. Experimental results can serve as tests of numerical models that are needed for hazard mitigation and coastal sustainability efforts on drowning deltas.

Relay Selections for Security and Reliability in Mobile Communication Networks over Nakagami-m Fading Channels

Directory of Open Access Journals (Sweden)

Hongji Huang

2017-01-01

Full Text Available This paper studies the relay selection schemes in mobile communication system over Nakagami-m channel. To make efficient use of licensed spectrum, both single relay selection (SRS scheme and multirelays selection (MRS scheme over the Nakagami-m channel are proposed. Also, the intercept probability (IP and outage probability (OP of the proposed SRS and MRS for the communication links depending on realistic spectrum sensing are derived. Furthermore, this paper assesses the manifestation of conventional direct transmission scheme to compare with the proposed SRS and MRS ones based on the Nakagami-m channel, and the security-reliability trade-off (SRT performance of the proposed schemes and the conventional schemes is well investigated. Additionally, the SRT of the proposed SRS and MRS schemes is demonstrated better than that of direct transmission scheme over the Nakagami-m channel, which can protect the communication transmissions against eavesdropping attacks. Additionally, simulation results show that our proposed relay selection schemes achieve better SRT performance than that of conventional direct transmission over the Nakagami-m channel.

Partial relay selection based on shadowing side information over generalized composite fading channels

KAUST Repository

Yilmaz, Ferkan

2011-11-01

In this paper, in contrast to the relay selection protocols available in the literature, we propose a partial relay selection protocol utilizing only the shadowing side information of the relays instead of their full channel side information in order to select a relay in a dual-hop relaying system through the available limited feedback channels and power budget. We then presented an exact unified performance expression combining the average bit error probability, ergodic capacity, and moments-generating function of the proposed partial relay selection over generalized fading channels. Referring to the unified performance expression introduced in [1], we explicitly offer a generic unified performance expression that can be easily calculated and that is applicable to a wide variety of fading scenarios. Finally, as an illustration of the mathematical formalism, some numerical and simulation results are generated for an extended generalized-K fading environment, and these numerical and simulation results are shown to be in perfect agreement. © 2011 IEEE.

Channel-Selectable Optical Link Based on a Silicon Microring for on-Chip Interconnection

International Nuclear Information System (INIS)

Qiu Chen; Hu Ting; Wang Wan-Jun; Yu Ping; Jiang Xiao-Qing; Yang Jian-Yi

2012-01-01

A channel-selectable optical link based on a silicon microring resonator is proposed and demonstrated. This optical link consists of the wavelength-tunable microring modulators and the filters, defined on a silicon-on-insulator (SOI) platform. With a p—i—n junction embedded in the microring modulator, light at the resonant wavelength of the ring resonator is modulated. The 2 nd -order microring add-drop filter routes the modulated light. The channel selectivity is demonstrated by heating the microrings. With a thermal tuning efficiency of 5.9 mW/nm, the filter drop port response was successfully tuned with 0.8 nm channel spacing. We also show that modulation can be achieved in these channels. This device aims to offer flexibility and increase the bandwidth usage efficiency in optical interconnection

Ion Selectivity Mechanism in a Bacterial Pentameric Ligand-Gated Ion Channel

International Nuclear Information System (INIS)

Wang, Hailong; Cheng, Xiaolin

2011-01-01

The proton-gated ion channel from Gloeobacter violaceus (GLIC) is a prokaryotic homolog of the eukaryotic nicotinic acetylcholine receptor (nAChR) that responds to the binding of neurotransmitter acetylcholine and mediates fast signal transmission. Recent emergence of a high resolution crystal structure of GLIC captured in a potentially open state allowed detailed, atomic-level insight into ion conduction and selectivity mechanisms in these channels. Herein, we have examined the barriers to ion conduction and origins of ion selectivity in the GLIC channel by the construction of potential of mean force (PMF) profiles for sodium and chloride ions inside the transmembrane region. Our calculations reveal that the GLIC channel is open for a sodium ion to transport, but presents a ∼10 kcal/mol free energy barrier for a chloride ion, which arises primarily from the unfavorable interactions with a ring of negatively charged glutamate residues (E-2) at the intracellular end and a ring of hydrophobic residues (I9) in the middle of the transmembrane domain. Our collective findings further suggest that the charge selection mechanism can, to a large extent, be attributed to the narrow intracellular end and a ring of glutamate residues in this position their strong negative electrostatics and ability to bind cations. By contrast, E19 at the extracellular entrance only plays a minor role in ion selectivity of GLIC. In addition to electrostatics, both ion hydration and protein dynamics are found to be crucial for ion conduction as well, which explains why a chloride ion experiences a much greater barrier than a sodium ion in the hydrophobic region of the pore.

Dual-band frequency selective surface with large band separation and stable performance

International Nuclear Information System (INIS)

Zhou Hang; Qu Shao-Bo; Lin Bao-Qin; Wang Jia-Fu; Ma Hua; Zhang Jie-Qiu; Peng Wei-Dong; Bai Peng; Wang Xu-Hua; Xu Zhuo

2012-01-01

A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Frequency and spatial correlation functions in a fading communication channel through the ionosphere

International Nuclear Information System (INIS)

Liu, C.H.; Yeh, K.C.

1975-01-01

Equations for the two-frequency two-position mutual coherence functions are derived under the usual parabolic and Markov approximations. These equations are then solved numerically. It is shown that the mutual coherence functions occur naturally in the study of pulse distortion through a random communication channel and in the investigation of signal correlations. Contour plots of correlation functions show the possibility of having equal values at two frequency separations for a given spatial separation. This behavior is explainable in terms of overlapping Fresnel zones

D-BLAST OFDM with Channel Estimation

Directory of Open Access Journals (Sweden)

Du Jianxuan

2004-01-01

Full Text Available Multiple-input and multiple-output (MIMO systems formed by multiple transmit and receive antennas can improve performance and increase capacity of wireless communication systems. Diagonal Bell Laboratories Layered Space-Time (D-BLAST structure offers a low-complexity solution for realizing the attractive capacity of MIMO systems. However, for broadband wireless communications, channel is frequency-selective and orthogonal frequency division multiplexing (OFDM has to be used with MIMO techniques to reduce system complexity. In this paper, we investigate D-BLAST for MIMO-OFDM systems. We develop a layerwise channel estimation algorithm which is robust to channel variation by exploiting the characteristic of the D-BLAST structure. Further improvement is made by subspace tracking to considerably reduce the error floor. Simulation results show that the layerwise estimators require 1 dB less signal-to-noise ratio (SNR than the traditional blockwise estimator for a word error rate (WER of when Doppler frequency is 40 Hz. Among the layerwise estimators, the subspace-tracking estimator provides a 0.8 dB gain for WER with 200 Hz Doppler frequency compared with the DFT-based estimator.

The influence of environmental parameters on the optimal frequency in a shallow underwater acoustic channel

Science.gov (United States)

Zarnescu, George

2015-02-01

In a shallow underwater acoustic channel the delayed replicas of a transmitted signal are mainly due to the interactions with the sea surface and the bottom layer. If a specific underwater region on the globe is considered, for which the sedimentary layer structure is constant across the transmission distance, then the variability of the amplitude-delay profile is determined by daily and seasonal changes of the sound speed profile (SSP) and by weather changes, such as variations of the wind speed. Such a parameter will influence the attenuation at the surface, the noise level and the profile of the sea surface. The temporal variation of the impulse response in a shallow underwater acoustic channel determines the variability of the optimal transmission frequency. If the ways in which the optimal frequency changes can be predicted, then an adaptive analog transceiver can be easily designed for an underwater acoustic modem or it can be found when a communication link has high throughput. In this article it will be highlighted the way in which the amplitude-delay profile is affected by the sound speed profile, wind speed and channel depth and also will be emphasized the changes of the optimal transmission frequency in a configuration, where the transmitter and receiver are placed on the seafloor and the bathymetry profile will be considered flat, having a given composition.

Simultaneous Channel and Feature Selection of Fused EEG Features Based on Sparse Group Lasso

Directory of Open Access Journals (Sweden)

Jin-Jia Wang

2015-01-01

Full Text Available Feature extraction and classification of EEG signals are core parts of brain computer interfaces (BCIs. Due to the high dimension of the EEG feature vector, an effective feature selection algorithm has become an integral part of research studies. In this paper, we present a new method based on a wrapped Sparse Group Lasso for channel and feature selection of fused EEG signals. The high-dimensional fused features are firstly obtained, which include the power spectrum, time-domain statistics, AR model, and the wavelet coefficient features extracted from the preprocessed EEG signals. The wrapped channel and feature selection method is then applied, which uses the logistical regression model with Sparse Group Lasso penalized function. The model is fitted on the training data, and parameter estimation is obtained by modified blockwise coordinate descent and coordinate gradient descent method. The best parameters and feature subset are selected by using a 10-fold cross-validation. Finally, the test data is classified using the trained model. Compared with existing channel and feature selection methods, results show that the proposed method is more suitable, more stable, and faster for high-dimensional feature fusion. It can simultaneously achieve channel and feature selection with a lower error rate. The test accuracy on the data used from international BCI Competition IV reached 84.72%.

Mode Switching for the Multi-Antenna Broadcast Channel Based on Delay and Channel Quantization

Directory of Open Access Journals (Sweden)

Jun Zhang

2009-01-01

Full Text Available Imperfect channel state information degrades the performance of multiple-input multiple-output (MIMO communications; its effects on single-user (SU and multiuser (MU MIMO transmissions are quite different. In particular, MU-MIMO suffers from residual interuser interference due to imperfect channel state information while SU-MIMO only suffers from a power loss. This paper compares the throughput loss of both SU and MU-MIMO in the broadcast channel due to delay and channel quantization. Accurate closed-form approximations are derived for achievable rates for both SU and MU-MIMO. It is shown that SU-MIMO is relatively robust to delayed and quantized channel information, while MU-MIMO with zero-forcing precoding loses its spatial multiplexing gain with a fixed delay or fixed codebook size. Based on derived achievable rates, a mode switching algorithm is proposed, which switches between SU and MU-MIMO modes to improve the spectral efficiency based on average signal-to-noise ratio (SNR, normalized Doppler frequency, and the channel quantization codebook size. The operating regions for SU and MU modes with different delays and codebook sizes are determined, and they can be used to select the preferred mode. It is shown that the MU mode is active only when the normalized Doppler frequency is very small, and the codebook size is large.

OPRA capacity bounds for selection diversity over generalized fading channels

KAUST Repository

Hanif, Muhammad Fainan; Yang, Hongchuan; Alouini, Mohamed-Slim

2014-01-01

, lower and upper bounds on OPRA capacity for selection diversity scheme are presented. These bounds hold for variety of fading channels including log-normal and generalized Gamma distributed models and have very simple analytic expressions for easy

Frequency selective surfaces integrated with phased array antennas

NARCIS (Netherlands)

Monni, S.

2005-01-01

Frequency Selective Surfaces (FSS's) are periodic arrays of patches and/or slots etched on a metal plate, having frequency and angular ??ltering properties. The FSS response to an excitation (for example a plane wave) is characterized in terms of its re ection and transmission coe??cient, and

Optimal Training for Time-Selective Wireless Fading Channels Using Cutoff Rate

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Tong Lang

2006-01-01

Full Text Available We consider the optimal allocation of resources—power and bandwidth—between training and data transmissions for single-user time-selective Rayleigh flat-fading channels under the cutoff rate criterion. The transmitter exploits statistical channel state information (CSI in the form of the channel Doppler spectrum to embed pilot symbols into the transmission stream. At the receiver, instantaneous, though imperfect, CSI is acquired through minimum mean-square estimation of the channel based on some set of pilot observations. We compute the ergodic cutoff rate for this scenario. Assuming estimator-based interleaving and -PSK inputs, we study two special cases in-depth. First, we derive the optimal resource allocation for the Gauss-Markov correlation model. Next, we validate and refine these insights by studying resource allocation for the Jakes model.

Frequency Selection for Multi-frequency Acoustic Measurement of Suspended Sediment

Science.gov (United States)

Chen, X.; HO, H.; Fu, X.

2017-12-01

Multi-frequency acoustic measurement of suspended sediment has found successful applications in marine and fluvial environments. Difficult challenges remain in regard to improving its effectiveness and efficiency when applied to high concentrations and wide size distributions in rivers. We performed a multi-frequency acoustic scattering experiment in a cylindrical tank with a suspension of natural sands. The sands range from 50 to 600 μm in diameter with a lognormal size distribution. The bulk concentration of suspended sediment varied from 1.0 to 12.0 g/L. We found that the commonly used linear relationship between the intensity of acoustic backscatter and suspended sediment concentration holds only at sufficiently low concentrations, for instance below 3.0 g/L. It fails at a critical value of concentration that depends on measurement frequency and the distance between the transducer and the target point. Instead, an exponential relationship was found to work satisfactorily throughout the entire range of concentration. The coefficient and exponent of the exponential function changed, however, with the measuring frequency and distance. Considering the increased complexity of inverting the concentration values when an exponential relationship prevails, we further analyzed the relationship between measurement error and measuring frequency. It was also found that the inversion error may be effectively controlled within 5% if the frequency is properly set. Compared with concentration, grain size was found to heavily affect the selection of optimum frequency. A regression relationship for optimum frequency versus grain size was developed based on the experimental results.

Characteristics of spectro-temporal modulation frequency selectivity in humans.

Science.gov (United States)

Oetjen, Arne; Verhey, Jesko L

2017-03-01

There is increasing evidence that the auditory system shows frequency selectivity for spectro-temporal modulations. A recent study of the authors has shown spectro-temporal modulation masking patterns that were in agreement with the hypothesis of spectro-temporal modulation filters in the human auditory system [Oetjen and Verhey (2015). J. Acoust. Soc. Am. 137(2), 714-723]. In the present study, that experimental data and additional data were used to model this spectro-temporal frequency selectivity. The additional data were collected to investigate to what extent the spectro-temporal modulation-frequency selectivity results from a combination of a purely temporal amplitude-modulation filter and a purely spectral amplitude-modulation filter. In contrast to the previous study, thresholds were measured for masker and target modulations with opposite directions, i.e., an upward pointing target modulation and a downward pointing masker modulation. The comparison of this data set with previous corresponding data with the same direction from target and masker modulations indicate that a specific spectro-temporal modulation filter is required to simulate all aspects of spectro-temporal modulation frequency selectivity. A model using a modified Gabor filter with a purely temporal and a purely spectral filter predicts the spectro-temporal modulation masking data.

The research of characteristic difference of selected frequency luminescence for desert sand

International Nuclear Information System (INIS)

Liu Chao; Wei Mingjian; Li Huhou

2011-01-01

The characters of selected frequency luminescence of four groups of samples from Badain Jaran desert are measured by BG2003 luminescence spectrograph. The measurement subjects include selected frequency optical stimulate luminescence spectrum, selected frequency thermoluminescence spectrum and the dose response curve. A double-peak map is obtained by the result from all groups of data and spectrum. The difference is emerged between each group. The optical stimulate luminescence and thermoluminescence is applied in the measurement process. The dispersion of photon count on every response wavelength is analyzed. Based on the analysis, a better result can be gained by selected frequency thermoluminescence. (authors)

Multisource full waveform inversion of marine streamer data with frequency selection

KAUST Repository

Huang, Yunsong; Schuster, Gerard T.

2013-01-01

Multisource migration with frequency selection is now extended to multisource full waveform inversion (FWI) of supergathers for marine streamer data. There are three advantages of this approach compared to conventional FWI for marine streamer data. 1. The multisource FWI method with frequency selection is computationally more efficient than conventional FWI. 2. A supergather requires more than an order of magnitude less storage than the the original data. 3. Frequency selection overcomes the acquisition mismatch between the observed data and the simulated multisource supergathers for marine data. This mismatch problem has prevented the efficient application of FWI to marine geometries in the space-time domain. Preliminary result of applying multisource FWI with frequency selection to a synthetic marine data set suggests it is at least four times more efficient than standard FWI.

Quantum model for a periodically driven selectivity filter in a K+ ion channel

International Nuclear Information System (INIS)

Cifuentes, A A; Semião, F L

2014-01-01

In this work, we present a quantum transport model for the selectivity filter in the KcsA potassium ion channel. This model is fully consistent with the fact that two conduction pathways are involved in the translocation of ions through the filter, and we show that the presence of a second path may actually bring advantages for the filter as a result of quantum interference. To highlight interferences and resonances in the model, we consider the selectivity filter to be driven by a controlled time-dependent external field, which changes the free-energy scenario and consequently the conduction of the ions. In particular, we demonstrate that the two-pathway conduction mechanism is more advantageous for the filter when dephasing in the transient configurations is lower than in the main configurations. As a matter of fact, K + ions in the main configurations are highly coordinated by oxygen atoms of the filter backbone, and this increases noise. Moreover, we also show that for a wide range of dephasing rates and driving frequencies, the two-pathway conduction used by the filter leads to higher ionic currents than the single–path model. (paper)

Evoked potential correlates of selective attention with multi-channel auditory inputs

Science.gov (United States)

Schwent, V. L.; Hillyard, S. A.

1975-01-01

Ten subjects were presented with random, rapid sequences of four auditory tones which were separated in pitch and apparent spatial position. The N1 component of the auditory vertex evoked potential (EP) measured relative to a baseline was observed to increase with attention. It was concluded that the N1 enhancement reflects a finely tuned selective attention to one stimulus channel among several concurrent, competing channels. This EP enhancement probably increases with increased information load on the subject.

Aluminium and hydrogen ions inhibit a mechanosensory calcium-selective cation channel

Science.gov (United States)

Ding, J. P.; Pickard, B. G.

1993-01-01

The tension-dependent activity of mechanosensory calcium-selective cation channels in excised plasmalemmal patches from onion bulb scale epidermis is modulated by pH in the physiologically meaningful range between 4.5 and 7.2. It is rapidly lowered by lowering pH and rapidly raised by raising pH. Channel activity is effectively inhibited by low levels of aluminium ions and activity can be partially restored by washing for a few minutes. We suggest that under normal conditions the sensitivity of the mechanosensory channels to pH of the wall free space plays important roles in regulation of plant activities such as growth. We further suggest that, when levels of acid and aluminium ions in the soil solution are high, they might inhibit similar sensory channels in cells of the root tip, thus contributing critically to the acid soil syndrome.

Selective spider toxins reveal a role for Nav1.1 channel in mechanical pain

OpenAIRE

Osteen, Jeremiah D.; Herzig, Volker; Gilchrist, John; Emrick, Joshua J.; Zhang, Chuchu; Wang, Xidao; Castro, Joel; Garcia-Caraballo, Sonia; Grundy, Luke; Rychkov, Grigori Y.; Weyer, Andy D.; Dekan, Zoltan; Undheim, Eivind A. B.; Alewood, Paul; Stucky, Cheryl L.

2016-01-01

Voltage-gated sodium (Nav) channels initiate action potentials in most neurons, including primary afferent nerve fibers of the pain pathway. Local anesthetics block pain through non-specific actions at all Nav channels, but the discovery of selective modulators would facilitate the analysis of individual subtypes and their contributions to chemical, mechanical, or thermal pain. Here, we identify and characterize spider toxins that selectively activate the Nav1.1 subtype, whose role in nocicep...

Game Theoretical Approaches for Transport-Aware Channel Selection in Cognitive Radio Networks

Directory of Open Access Journals (Sweden)

Chen Shih-Ho

2010-01-01

Full Text Available Effectively sharing channels among secondary users (SUs is one of the greatest challenges in cognitive radio network (CRN. In the past, many studies have proposed channel selection schemes at the physical or the MAC layer that allow SUs swiftly respond to the spectrum states. However, they may not lead to enhance performance due to slow response of the transport layer flow control mechanism. This paper presents a cross-layer design framework called Transport Aware Channel Selection (TACS scheme to optimize the transport throughput based on states, such as RTT and congestion window size, of TCP flow control mechanism. We formulate the TACS problem as two different game theoretic approaches: Selfish Spectrum Sharing Game (SSSG and Cooperative Spectrum Sharing Game (CSSG and present novel distributed heuristic algorithms to optimize TCP throughput. Computer simulations show that SSSG and CSSG could double the SUs throughput of current MAC-based scheme when primary users (PUs use their channel infrequently, and with up to 12% to 100% throughput increase when PUs are more active. The simulation results also illustrated that CSSG performs up to 20% better than SSSG in terms of the throughput.

Application of high Tc superconductors as frequency selective surfaces: Experiment and theory

International Nuclear Information System (INIS)

Dawei Zhang; Yahya Rahmat-Samii; Fetterman, H.R.

1993-01-01

YBa 2 Cu 3 O 7-x and Tl 2 CaBa 2 Cu 2 O 8 high temperature superconducting thin films were utilized to fabricate frequency selective surfaces (FSS) at millimeter-wave frequencies (75--110 GHz). An analytical/numerical model was applied, using a Floquet expansion and the Method of Moments, to analyze bandstop superconducting frequency selective surfaces. Experimental results were compared with the model, and showed a good agreement with resonant frequency prediction with an accuracy of better than 1%. The use of the superconducting frequency selective surfaces as quasi-optical millimeter-wave bandpass filters was also demonstrated

Chip-Level Channel Equalization in WCDMA Downlink

Directory of Open Access Journals (Sweden)

Kari Hooli

2002-08-01

Full Text Available The most important third generation (3G cellular communications standard is based on wideband CDMA (WCDMA. Receivers based on TDMA style channel equalization at the chip level have been proposed for a WCDMA downlink employing long spreading sequences to ensure adequate performance even with a high number of active users. These receivers equalize the channel prior to despreading, thus restoring the orthogonality of users and resulting in multiple-access interference (MAI suppression. In this paper, an overview of chip-level channel equalizers is delivered with special attention to adaptation methods suitable for the WCDMA downlink. Numerical examples on the equalizers′ performance are given in Rayleigh fading frequency-selective channels.

Centrifugal sedimentation for selectively packing channels with silica microbeads in three-dimensional micro/nanofluidic devices.

Science.gov (United States)

Gong, Maojun; Bohn, Paul W; Sweedler, Jonathan V

2009-03-01

Incorporation of nanofluidic elements into microfluidic channels is one approach for adding filtration and partition functionality to planar microfluidic devices, as well as providing enhanced biomolecular separations. Here we introduce a strategy to pack microfluidic channels with silica nanoparticles and microbeads, thereby indirectly producing functional nanostructures; the method allows selected channels to be packed, here demonstrated so that a separation channel is packed while keeping an injection channel unpacked. A nanocapillary array membrane is integrated between two patterned microfluidic channels that cross each other in vertically separated layers. The membrane serves both as a frit for bead packing and as a fluid communication conduit between microfluidic channels. Centrifugal force-assisted sedimentation is then used to selectively pack the microfluidic channels using an aqueous silica bead suspension loaded into the appropriate inlet reservoirs. This packing approach may be used to simultaneously pack multiple channels with silica microbeads having different sizes and surface properties. The chip design and packing method introduced here are suitable for packing silica particles in sizes ranging from nanometers to micrometers and allow rapid (approximately 10 min) packing with high quality. The liquid/analyte transport characteristics of these packed micro/nanofluidic devices have potential utility in a wide range of applications, including electroosmotic pumping, liquid chromatographic separations, and electrochromatography.

Atrial-selective K+ channel blockers: potential antiarrhythmic drugs in atrial fibrillation?

Science.gov (United States)

Ravens, Ursula

2017-11-01

In the wake of demographic change in Western countries, atrial fibrillation has reached an epidemiological scale, yet current strategies for drug treatment of the arrhythmia lack sufficient efficacy and safety. In search of novel medications, atrial-selective drugs that specifically target atrial over other cardiac functions have been developed. Here, I will address drugs acting on potassium (K + ) channels that are either predominantly expressed in atria or possess electrophysiological properties distinct in atria from ventricles. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting I Kur , the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting I K,ACh , the Ca 2+ -activated K + channels of small conductance (SK) conducting I SK , and the two-pore domain K + (K2P) channels (tandem of P domains, weak inward-rectifying K + channels (TWIK-1), TWIK-related acid-sensitive K + channels (TASK-1 and TASK-3)) that are responsible for voltage-independent background currents I TWIK-1 , I TASK-1 , and I TASK-3 . Direct drug effects on these channels are described and their putative value in treatment of atrial fibrillation is discussed. Although many potential drug targets have emerged in the process of unravelling details of the pathophysiological mechanisms responsible for atrial fibrillation, we do not know whether novel antiarrhythmic drugs will be more successful when modulating many targets or a single specific one. The answer to this riddle can only be solved in a clinical context.

Allele frequency changes due to hitch-hiking in genomic selection programs

DEFF Research Database (Denmark)

Liu, Huiming; Sørensen, Anders Christian; Meuwissen, Theo H E

2014-01-01

of inbreeding due to changes in allele frequencies and hitch-hiking. This study aimed at understanding the impact of using long-term genomic selection on changes in allele frequencies, genetic variation and the level of inbreeding. Methods Selection was performed in simulated scenarios with a population of 400......-BLUP, Genomic BLUP and Bayesian Lasso. Changes in allele frequencies at QTL, markers and linked neutral loci were investigated for the different selection criteria and different scenarios, along with the loss of favourable alleles and the rate of inbreeding measured by pedigree and runs of homozygosity. Results...

Preamble and pilot symbol design for channel estimation in OFDM systems with null subcarriers

Directory of Open Access Journals (Sweden)

Ohno Shuichi

2011-01-01

Full Text Available Abstract In this article, design of preamble for channel estimation and pilot symbols for pilot-assisted channel estimation in orthogonal frequency division multiplexing system with null subcarriers is studied. Both the preambles and pilot symbols are designed to minimize the l 2 or the l ∞ norm of the channel estimate mean-squared errors (MSE in frequency-selective environments. We use convex optimization technique to find optimal power distribution to the preamble by casting the MSE minimization problem into a semidefinite programming problem. Then, using the designed optimal preamble as an initial value, we iteratively select the placement and optimally distribute power to the selected pilot symbols. Design examples consistent with IEEE 802.11a as well as IEEE 802.16e are provided to illustrate the superior performance of our proposed method over the equi-spaced equi-powered pilot symbols and the partially equi-spaced pilot symbols.

High spin spectroscopy near the N=Z line: Channel selection and excitation energy systematics

Energy Technology Data Exchange (ETDEWEB)

Svensson, C.E.; Cameron, J.A.; Flibotte, S. [McMaster Univ., Ontario (Canada)] [and others

1996-12-31

The total {gamma}-ray and charged-particle energies emitted in fusion-evaporation reactions leading to N=Z compound systems in the A = 50-70 mass region have been measured with the 8{pi} {gamma}-ray spectrometer and the miniball charged-particle detector array. A new method of channel selection has been developed which combines particle identification with these total energy measurements and greatly improves upon the selectivity possible with particle detection alone. In addition, the event by event measurement of total {gamma}-ray energies using the BGO ball of the 8{pi} spectrometer has allowed a determination of excitation energies following particle evaporation for a large number of channels in several different reactions. The new channel selection procedure and excitation energy systematics are illustrated with data from the reaction of {sup 24}Mg on {sup 40}Ca at E{sub lab} = 80MeV.

Selecting participants for listening tests of multi-channel reproduced sound

DEFF Research Database (Denmark)

Wickelmaier, Florian; Choisel, Sylvain

2005-01-01

A selection procedure was devised in order to select listeners for experiments in which their main task will be to judge multi-channel reproduced sound. 91 participants filled in a web-based questionnaire. 78 of them took part in an assessment of their hearing thresholds, their spatial hearing......, and their verbal production abilities. The listeners displayed large individual differences in their performance. 40 subjects were selected based on the test results. The self-assessed listening habits and experience in the web questionnaire could not predict the results of the selection procedure. Further......, the hearing thresholds did not correlate with the spatial-hearing test. This leads to the conclusion that task-specific performance tests might be the preferable means of selecting a listening panel....

Asymptotic analysis for Nakagami-m fading channels with relay selection

KAUST Repository

Zhong, Caijun

2011-06-01

In this paper, we analyze the asymptotic outage probability performance of both decode-and-forward (DF) and amplify-and-forward (AF) relaying systems using partial relay selection and the "best" relay selection schemes for Nakagami-m fading channels. We derive their respective outage probability expressions in the asymptotic high signal-to-noise ratio (SNR) regime, from which the diversity order and coding gain are analyzed. In addition, we investigate the impact of power allocation between the source and relay terminals and derive the diversity-multiplexing tradeoff (DMT) for these relay selection systems. The theoretical findings suggest that partial relay selection can improve the diversity of the system and can achieve the same DMT as the "best" relay selection scheme under certain conditions. © 2011 IEEE.

On-line adaptive line frequency noise cancellation from a nuclear power measuring channel

Directory of Open Access Journals (Sweden)

Qadir Javed

2011-01-01

Full Text Available On-line software for adaptively canceling 50 Hz line frequency noise has been designed and tested at Pakistan Research Reactor 1. Line frequency noise causes much problem in weak signals acquisition. Sometimes this noise is so dominant that original signal is totally corrupted. Although notch filter can be used for eliminating this noise, but if signal of interest is in close vicinity of 50 Hz, then original signal is also attenuated and hence overall performance is degraded. Adaptive noise removal is a technique which could be employed for removing line frequency without degrading the desired signal. In this paper line frequency noise has been eliminated on-line from a nuclear power measuring channel. The adaptive LMS algorithm has been used to cancel 50 Hz noise. The algorithm has been implemented in labVIEW with NI 6024 data acquisition card. The quality of the acquired signal has been improved much as can be seen in experimental results.

New selection criteria for channel refueling of a Candu-6 reactor: introduction to floppy rules

International Nuclear Information System (INIS)

Brissette, D.

2001-01-01

A revised set of rules is in use at Gentilly-2 NGS for the selection of channels for refuelling. Traditional hard channel rejection rules (of go/no-go type) have been replaced by a more efficient set of soft evaluation rules based on concepts borrowed to the Fuzzy Logic. New evaluation rules, labelled as 'Floppy Rules', enable to assess and rate the channel suitability for refuelling by using a smooth and natural continuum of values qualifying excellent, good, fair and poor choices. Global channel suitability for refuelling is measured by combining separate ratings obtained from individual evaluation rules. Each evaluation rule is based on a specific control parameter related to local or lumped core properties. Two new software codes (NEWRULES and REFUEL) designed around the concept of Floppy Rules enable to perform a very efficient selection of optimized channel refuelling sequences either in manual and automatic mode. (author)

Path loss variation of on-body UWB channel in the frequency bands of IEEE 802.15.6 standard.

Science.gov (United States)

Goswami, Dayananda; Sarma, Kanak C; Mahanta, Anil

2016-06-01

The wireless body area network (WBAN) has gaining tremendous attention among researchers and academicians for its envisioned applications in healthcare service. Ultra wideband (UWB) radio technology is considered as excellent air interface for communication among body area network devices. Characterisation and modelling of channel parameters are utmost prerequisite for the development of reliable communication system. The path loss of on-body UWB channel for each frequency band defined in IEEE 802.15.6 standard is experimentally determined. The parameters of path loss model are statistically determined by analysing measurement data. Both the line-of-sight and non-line-of-sight channel conditions are considered in the measurement. Variations of parameter values with the size of human body are analysed along with the variation of parameter values with the surrounding environments. It is observed that the parameters of the path loss model vary with the frequency band as well as with the body size and surrounding environment. The derived parameter values are specific to the particular frequency bands of IEEE 802.15.6 standard, which will be useful for the development of efficient UWB WBAN system.

Identification and analysis of genome-wide SNPs provide insight into signatures of selection and domestication in channel catfish (Ictalurus punctatus.

Directory of Open Access Journals (Sweden)

Luyang Sun

Full Text Available Domestication and selection for important performance traits can impact the genome, which is most often reflected by reduced heterozygosity in and surrounding genes related to traits affected by selection. In this study, analysis of the genomic impact caused by domestication and artificial selection was conducted by investigating the signatures of selection using single nucleotide polymorphisms (SNPs in channel catfish (Ictalurus punctatus. A total of 8.4 million candidate SNPs were identified by using next generation sequencing. On average, the channel catfish genome harbors one SNP per 116 bp. Approximately 6.6 million, 5.3 million, 4.9 million, 7.1 million and 6.7 million SNPs were detected in the Marion, Thompson, USDA103, Hatchery strain, and wild population, respectively. The allele frequencies of 407,861 SNPs differed significantly between the domestic and wild populations. With these SNPs, 23 genomic regions with putative selective sweeps were identified that included 11 genes. Although the function for the majority of the genes remain unknown in catfish, several genes with known function related to aquaculture performance traits were included in the regions with selective sweeps. These included hypoxia-inducible factor 1β. HIFιβ.. and the transporter gene ATP-binding cassette sub-family B member 5 (ABCB5. HIF1β. is important for response to hypoxia and tolerance to low oxygen levels is a critical aquaculture trait. The large numbers of SNPs identified from this study are valuable for the development of high-density SNP arrays for genetic and genomic studies of performance traits in catfish.

Eigenstructures of MIMO Fading Channel Correlation Matrices and Optimum Linear Precoding Designs for Maximum Ergodic Capacity

Directory of Open Access Journals (Sweden)

Hamid Reza Bahrami

2007-01-01

Full Text Available The ergodic capacity of MIMO frequency-flat and -selective channels depends greatly on the eigenvalue distribution of spatial correlation matrices. Knowing the eigenstructure of correlation matrices at the transmitter is very important to enhance the capacity of the system. This fact becomes of great importance in MIMO wireless systems where because of the fast changing nature of the underlying channel, full channel knowledge is difficult to obtain at the transmitter. In this paper, we first investigate the effect of eigenvalues distribution of spatial correlation matrices on the capacity of frequency-flat and -selective channels. Next, we introduce a practical scheme known as linear precoding that can enhance the ergodic capacity of the channel by changing the eigenstructure of the channel by applying a linear transformation. We derive the structures of precoders using eigenvalue decomposition and linear algebra techniques in both cases and show their similarities from an algebraic point of view. Simulations show the ability of this technique to change the eigenstructure of the channel, and hence enhance the ergodic capacity considerably.

Transmit selection algorithms for imperfect threshold-based receive MRC in the presence of co-channel interference

KAUST Repository

Radaydeh, Redha Mahmoud Mesleh

2010-01-01

The performance of transmit antenna selection for threshold-based maximal ratio combining (MRC) diversity receivers in the presence of multiple co-channel interfering signals is studied. The impact of imperfect channel estimation of desired user signals is considered, and the effect of phase and time misalignments between desired and undesired signals is incorporated in the analysis. Precise formulation for Nakagami-m faded interfering signals is presented. The analysis is applicable for arbitrary transmit antenna selection, which is based on the receiver combined signal-to-noise ratios (SNRs) or combined signal-to-interference-plus-noise ratios (SINRs) for different transmit channels. New expressions for the distribution of combined SINR and outage probability performance are derived considering SNR-based as well as SINR-based selection algorithms. The results can be used to study the performance of different system architectures under various channel conditions when the implementation complexity is of interest. ©2010 IEEE.

Iterative Pilot-Layer Aided Channel Estimation with Emphasis on Interleave-Division Multiple Access Systems

OpenAIRE

Schoeneich Hendrik; Hoeher Peter Adam

2006-01-01

Channel estimation schemes suitable for interleave-division multiple access (IDMA) systems are presented. Training and data are superimposed. Training-based and semiblind linear channel estimators are derived and their performance is discussed and compared. Monte Carlo simulation results are presented showing that the derived channel estimators in conjunction with a superimposed pilot sequence and chip-by-chip processing are able to track fast-fading frequency-selective channels. As opposed ...

Joint duplex mode selection, channel allocation, and power control for full-duplex cognitive femtocell networks

Directory of Open Access Journals (Sweden)

Mingjie Feng

2015-02-01

Full Text Available In this paper, we aim to maximize the sum rate of a full-duplex cognitive femtocell network (FDCFN as well as guaranteeing the quality of service (QoS of users in the form of a required signal to interference plus noise ratios (SINR. We first consider the case of a pair of channels, and develop optimum-achieving power control solutions. Then, for the case of multiple channels, we formulate joint duplex model selection, power control, and channel allocation as a mixed integer nonlinear problem (MINLP, and propose an iterative framework to solve it. The proposed iterative framework consists of a duplex mode selection scheme, a near-optimal distributed power control algorithm, and a greedy channel allocation algorithm. We prove the convergence of the proposed iterative framework as well as a lower bound for the greedy channel allocation algorithm. Numerical results show that the proposed schemes effectively improve the sum rate of FDCFNs.

Divalent Metal Ion Transport across Large Biological Ion Channels and Their Effect on Conductance and Selectivity

Directory of Open Access Journals (Sweden)

Elena García-Giménez

2012-01-01

Full Text Available Electrophysiological characterization of large protein channels, usually displaying multi-ionic transport and weak ion selectivity, is commonly performed at physiological conditions (moderate gradients of KCl solutions at decimolar concentrations buffered at neutral pH. We extend here the characterization of the OmpF porin, a wide channel of the outer membrane of E. coli, by studying the effect of salts of divalent cations on the transport properties of the channel. The regulation of divalent cations concentration is essential in cell metabolism and understanding their effects is of key importance, not only in the channels specifically designed to control their passage but also in other multiionic channels. In particular, in porin channels like OmpF, divalent cations modulate the efficiency of molecules having antimicrobial activity. Taking advantage of the fact that the OmpF channel atomic structure has been resolved both in water and in MgCl2 aqueous solutions, we analyze the single channel conductance and the channel selectivity inversion aiming to separate the role of the electrolyte itself, and the counterion accumulation induced by the protein channel charges and other factors (binding, steric effects, etc. that being of minor importance in salts of monovalent cations become crucial in the case of divalent cations.

Frequency-Wavenumber (FK)-Based Data Selection in High-Frequency Passive Surface Wave Survey

Science.gov (United States)

Cheng, Feng; Xia, Jianghai; Xu, Zongbo; Hu, Yue; Mi, Binbin

2018-04-01

Passive surface wave methods have gained much attention from geophysical and civil engineering communities because of the limited application of traditional seismic surveys in highly populated urban areas. Considering that they can provide high-frequency phase velocity information up to several tens of Hz, the active surface wave survey would be omitted and the amount of field work could be dramatically reduced. However, the measured dispersion energy image in the passive surface wave survey would usually be polluted by a type of "crossed" artifacts at high frequencies. It is common in the bidirectional noise distribution case with a linear receiver array deployed along roads or railways. We review several frequently used passive surface wave methods and derive the underlying physics for the existence of the "crossed" artifacts. We prove that the "crossed" artifacts would cross the true surface wave energy at fixed points in the f-v domain and propose a FK-based data selection technique to attenuate the artifacts in order to retrieve the high-frequency information. Numerical tests further demonstrate the existence of the "crossed" artifacts and indicate that the well-known wave field separation method, FK filter, does not work for the selection of directional noise data. Real-world applications manifest the feasibility of the proposed FK-based technique to improve passive surface wave methods by a priori data selection. Finally, we discuss the applicability of our approach.

Frequency-Wavenumber (FK)-Based Data Selection in High-Frequency Passive Surface Wave Survey

Science.gov (United States)

Cheng, Feng; Xia, Jianghai; Xu, Zongbo; Hu, Yue; Mi, Binbin

2018-07-01

Passive surface wave methods have gained much attention from geophysical and civil engineering communities because of the limited application of traditional seismic surveys in highly populated urban areas. Considering that they can provide high-frequency phase velocity information up to several tens of Hz, the active surface wave survey would be omitted and the amount of field work could be dramatically reduced. However, the measured dispersion energy image in the passive surface wave survey would usually be polluted by a type of "crossed" artifacts at high frequencies. It is common in the bidirectional noise distribution case with a linear receiver array deployed along roads or railways. We review several frequently used passive surface wave methods and derive the underlying physics for the existence of the "crossed" artifacts. We prove that the "crossed" artifacts would cross the true surface wave energy at fixed points in the f- v domain and propose a FK-based data selection technique to attenuate the artifacts in order to retrieve the high-frequency information. Numerical tests further demonstrate the existence of the "crossed" artifacts and indicate that the well-known wave field separation method, FK filter, does not work for the selection of directional noise data. Real-world applications manifest the feasibility of the proposed FK-based technique to improve passive surface wave methods by a priori data selection. Finally, we discuss the applicability of our approach.

Mode-Selective Photon Counting Via Quantum Frequency Conversion Using Spectrally-Engineered Pump Pulses

Science.gov (United States)

Manurkar, Paritosh

Most of the existing protocols for quantum communication operate in a two-dimensional Hilbert space where their manipulation and measurement have been routinely investigated. Moving to higher-dimensional Hilbert spaces is desirable because of advantages in terms of longer distance communication capabilities, higher channel capacity and better information security. We can exploit the spatio-temporal degrees of freedom for the quantum optical signals to provide the higher-dimensional signals. But this necessitates the need for measurement and manipulation of multidimensional quantum states. To that end, there have been significant theoretical studies based on quantum frequency conversion (QFC) in recent years even though the experimental progress has been limited. QFC is a process that allows preservation of the quantum information while changing the frequency of the input quantum state. It has deservedly garnered a lot of attention because it serves as the connecting bridge between the communications band (C-band near 1550 nm) where the fiber-optic infrastructure is already established and the visible spectrum where high efficiency single-photon detectors and optical memories have been demonstrated. In this experimental work, we demonstrate mode-selective frequency conversion as a means to measure and manipulate photonic signals occupying d -dimensional Hilbert spaces where d=2 and 4. In the d=2 case, we demonstrate mode contrast between two temporal modes (TMs) which serves as the proof-of-concept demonstration. In the d=4 version, we employ six different TMs for our detailed experimental study. These TMs also include superposition modes which are a crucial component in many quantum key distribution protocols. Our method is based on producing pump pulses which allow us to upconvert the TM of interest while ideally preserving the other modes. We use MATLAB simulations to determine the pump pulse shapes which are subsequently produced by controlling the amplitude and

Iterative Frequency-Domain Channel Estimation and Equalization for Ultra-Wideband Systems with Short Cyclic Prefix

Directory of Open Access Journals (Sweden)

Salim Bahçeci

2010-01-01

Full Text Available In impulse radio ultra-wideband (IR-UWB systems where the channel lengths are on the order of a few hundred taps, conventional use of frequency-domain (FD processing for channel estimation and equalization may not be feasible because the need to add a cyclic prefix (CP to each block causes a significant reduction in the spectral efficiency. On the other hand, using no or short CP causes the interblock interference (IBI and thus degradation in the receiver performance. Therefore, in order to utilize FD receiver processing UWB systems without a significant loss in the spectral efficiency and the performance, IBI cancellation mechanisms are needed in both the channel estimation and equalization operations. For this reason, in this paper, we consider the joint FD channel estimation and equalization for IR-UWB systems with short cyclic prefix (CP and propose a novel iterative receiver employing soft IBI estimation and cancellation within both its FD channel estimator and FD equalizer components. We show by simulation results that the proposed FD receiver attains performances close to that of the full CP case in both line-of-sight (LOS and non-line-of-sight (NLOS UWB channels after only a few iterations.

Spectro-temporal modulation masking patterns reveal frequency selectivity.

Science.gov (United States)

Oetjen, Arne; Verhey, Jesko L

2015-02-01

The present study investigated the possibility that the human auditory system demonstrates frequency selectivity to spectro-temporal amplitude modulations. Threshold modulation depth for detecting sinusoidal spectro-temporal modulations was measured using a generalized masked threshold pattern paradigm with narrowband masker modulations. Four target spectro-temporal modulations were examined, differing in their temporal and spectral modulation frequencies: a temporal modulation of -8, 8, or 16 Hz combined with a spectral modulation of 1 cycle/octave and a temporal modulation of 4 Hz combined with a spectral modulation of 0.5 cycles/octave. The temporal center frequencies of the masker modulation ranged from 0.25 to 4 times the target temporal modulation. The spectral masker-modulation center-frequencies were 0, 0.5, 1, 1.5, and 2 times the target spectral modulation. For all target modulations, the pattern of average thresholds for the eight normal-hearing listeners was consistent with the hypothesis of a spectro-temporal modulation filter. Such a pattern of modulation-frequency sensitivity was predicted on the basis of psychoacoustical data for purely temporal amplitude modulations and purely spectral amplitude modulations. An analysis of separability indicates that, for the present data set, selectivity in the spectro-temporal modulation domain can be described by a combination of a purely spectral and a purely temporal modulation filter function.

Energy and spectral efficiency analysis for selective ARQ multi-channel systems

KAUST Repository

Shafique, Taniya

2017-07-31

In this paper, we develop selective retransmission schemes for multiple-channel systems. The proposed schemes are selective automatic repeat request with fixed bandwidth (SARQ-FB), selective chase combining with fixed bandwidth (SCC-FB) and selective automatic repeat request with variable bandwidth (SARQ-VB). The main objective of the proposed schemes is to use the available power and bandwidth budget effectively along with the selective retransmission to deliver the required data successfully within a limited number of transmissions. To investigate the performance of each scheme, we first analyze the average spectral and energy efficiency and derive closed form expressions for each scheme. Then, we compare the EE and SE of each scheme through numerical results.

A Micromechanical RF Channelizer

Science.gov (United States)

Akgul, Mehmet

The power consumption of a radio generally goes as the number and strength of the RF signals it must process. In particular, a radio receiver would consume much less power if the signal presented to its electronics contained only the desired signal in a tiny percent bandwidth frequency channel, rather than the typical mix of signals containing unwanted energy outside the desired channel. Unfortunately, a lack of filters capable of selecting single channel bandwidths at RF forces the front-ends of contemporary receivers to accept unwanted signals, and thus, to operate with sub-optimal efficiency. This dissertation focuses on the degree to which capacitive-gap transduced micromechanical resonators can achieve the aforementioned RF channel-selecting filters. It aims to first show theoretically that with appropriate scaling capacitive-gap transducers are strong enough to meet the needed coupling requirements; and second, to fully detail an architecture and design procedure needed to realize said filters. Finally, this dissertation provides an actual experimentally demonstrated RF channel-select filter designed using the developed procedures and confirming theoretical predictions. Specifically, this dissertation introduces four methods that make possible the design and fabrication of RF channel-select filters. The first of these introduces a small-signal equivalent circuit for parallel-plate capacitive-gap transduced micromechanical resonators that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates the analysis of micromechanical circuits loaded with arbitrary electrical impedances. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive-gap transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for

On channel selection and shape co-existence

International Nuclear Information System (INIS)

Dracoulis, G.D.

1993-08-01

Ambivalence with respect to a favoured shape is emerging as a ubiquitous phenomenon in nuclei. Multiple minima in the nuclear potential well occur because of the delicate balance in nuclei between the long and short-range properties of the nuclear force and the contribution specific particle orbitals make in forcing the nucleus to a decision. Exploration of the dependence of the resulting shape co-existence on particle number and orbital is a prominent area of research. Experimental aspects of spectroscopy studies using heavy ion fusion, evaporation reactions and channel selection are discussed, with focus on shape co-existence in the light Os-Pt-Hg-Pb region. 42 refs., 8 figs

Adaptive Space-Time-Spreading-Assisted Wideband CDMA Systems Communicating over Dispersive Nakagami- Fading Channels

Directory of Open Access Journals (Sweden)

Yang Lie-Liang

2005-01-01

Full Text Available In this contribution, the performance of wideband code-division multiple-access (W-CDMA systems using space-time-spreading- (STS- based transmit diversity is investigated, when frequency-selective Nakagami- fading channels, multiuser interference, and background noise are considered. The analysis and numerical results suggest that the achievable diversity order is the product of the frequency-selective diversity order and the transmit diversity order. Furthermore, both the transmit diversity and the frequency-selective diversity have the same order of importance. Since W-CDMA signals are subjected to frequency-selective fading, the number of resolvable paths at the receiver may vary over a wide range depending on the transmission environment encountered. It can be shown that, for wireless channels where the frequency selectivity is sufficiently high, transmit diversity may be not necessitated. Under this case, multiple transmission antennas can be leveraged into an increased bitrate. Therefore, an adaptive STS-based transmission scheme is then proposed for improving the throughput of W-CDMA systems. Our numerical results demonstrate that this adaptive STS-based transmission scheme is capable of significantly improving the effective throughput of W-CDMA systems. Specifically, the studied W-CDMA system's bitrate can be increased by a factor of three at the modest cost of requiring an extra 0.4 dB or 1.2 dB transmitted power in the context of the investigated urban or suburban areas, respectively.

Selective and lithography-independent fabrication of 20 nm nano-gap electrodes and nano-channels for nanoelectrofluidics applications

International Nuclear Information System (INIS)

Zhang, J Y; Wang, X F; Wang, X D; Fan, Z C; Li, Y; Ji, An; Yang, F H

2010-01-01

A new method has been developed to selectively fabricate nano-gap electrodes and nano-channels by conventional lithography. Based on a sacrificial spacer process, we have successfully obtained sub-100-nm nano-gap electrodes and nano-channels and further reduced the dimensions to 20 nm by shrinking the sacrificial spacer size. Our method shows good selectivity between nano-gap electrodes and nano-channels due to different sacrificial spacer etch conditions. There is no length limit for the nano-gap electrode and the nano-channel. The method reported in this paper also allows for wafer scale fabrication, high throughput, low cost, and good compatibility with modern semiconductor technology.

Objective ARX Model Order Selection for Multi-Channel Human Operator Identification

NARCIS (Netherlands)

Roggenkämper, N; Pool, D.M.; Drop, F.M.; van Paassen, M.M.; Mulder, M.

2016-01-01

In manual control, the human operator primarily responds to visual inputs but may elect to make use of other available feedback paths such as physical motion, adopting a multi-channel control strategy. Hu- man operator identification procedures generally require a priori selection of the model

[Amplitude Changes of Low Frequency Fluctuation in Brain Spontaneous Nervous Activities Induced by Needling at Hand Taiyin Lung Channel].

Science.gov (United States)

Zhou, You-long; Su, Cheng-guo; Liu, Shou-fang; Jin, Xiang-yu; Duan, Yan-li; Chen, Xiao-yan; Zhao, Shu-hua; Wang, Quan-liang; Dang, Chang-lin

2016-05-01

To observe amplitude changes of low frequency fluctuation in brain spontaneous nervous activities induced by needling at Hand Taiyin Lung Channel, and to preliminarily explore the possible brain function network of Hand Taiyin Lung Channel. By using functional magnetic resonance imaging (fMRI), 16 healthy volunteers underwent resting-state scanning (R1) and scanning with retained acupuncture at Hand Taiyin Lung Channel (acupuncture, AP). Data of fMRI collected were statistically calculated using amplitude of low frequency fluctuations (ALFF). Under R1 significantly enhanced ALFF occurred in right precuneus, left inferior parietal lobule, bilateral superior temporal gyrus, bilateral middle frontal gyrus, left superior frontal gyrus, left inferior frontal gyrus, left medial frontal gyrus. Under AP significantly enhanced ALFF occurred in right precuneus, bilateral superior frontal gyrus, cerebellum, bilateral middle frontal gyrus, right medial frontal gyrus, and so on. Compared with R1, needing at Hand Taiyin Lung Channel could significantly enhance ALFF in right gyrus subcallosum and right inferior frontal gyrus. Significant decreased ALFF appeared in right postcentral gyrus, left precuneus, left superior temporal gyrus, left middle temporal gyrus, and so on. Needing at Hand Taiyin Lung Channel could significantly change fixed activities of cerebral cortex, especially in right subcallosal gyrus, right inferior frontal gyrus, and so on.

Outage Performance Analysis of Relay Selection Schemes in Wireless Energy Harvesting Cooperative Networks over Non-Identical Rayleigh Fading Channels.

Science.gov (United States)

Do, Nhu Tri; Bao, Vo Nguyen Quoc; An, Beongku

2016-02-26

In this paper, we study relay selection in decode-and-forward wireless energy harvesting cooperative networks. In contrast to conventional cooperative networks, the relays harvest energy from the source's radio-frequency radiation and then use that energy to forward the source information. Considering power splitting receiver architecture used at relays to harvest energy, we are concerned with the performance of two popular relay selection schemes, namely, partial relay selection (PRS) scheme and optimal relay selection (ORS) scheme. In particular, we analyze the system performance in terms of outage probability (OP) over independent and non-identical (i.n.i.d.) Rayleigh fading channels. We derive the closed-form approximations for the system outage probabilities of both schemes and validate the analysis by the Monte-Carlo simulation. The numerical results provide comprehensive performance comparison between the PRS and ORS schemes and reveal the effect of wireless energy harvesting on the outage performances of both schemes. Additionally, we also show the advantages and drawbacks of the wireless energy harvesting cooperative networks and compare to the conventional cooperative networks.

Selective Dirac voltage engineering of individual graphene field-effect transistors for digital inverter and frequency multiplier integrations

Science.gov (United States)

Sul, Onejae; Kim, Kyumin; Jung, Yungwoo; Choi, Eunsuk; Lee, Seung-Beck

2017-09-01

The ambipolar band structure of graphene presents unique opportunities for novel electronic device applications. A cycle of gate voltage sweep in a conventional graphene transistor produces a frequency-doubled output current. To increase the frequency further, we used various graphene doping control techniques to produce Dirac voltage engineered graphene channels. The various surface treatments and substrate conditions produced differently doped graphene channels that were integrated on a single substrate and multiple Dirac voltages were observed by applying a single gate voltage sweep. We applied the Dirac voltage engineering techniques to graphene field-effect transistors on a single chip for the fabrication of a frequency multiplier and a logic inverter demonstrating analog and digital circuit application possibilities.

Selective Dirac voltage engineering of individual graphene field-effect transistors for digital inverter and frequency multiplier integrations.

Science.gov (United States)

Sul, Onejae; Kim, Kyumin; Jung, Yungwoo; Choi, Eunsuk; Lee, Seung-Beck

2017-09-15

The ambipolar band structure of graphene presents unique opportunities for novel electronic device applications. A cycle of gate voltage sweep in a conventional graphene transistor produces a frequency-doubled output current. To increase the frequency further, we used various graphene doping control techniques to produce Dirac voltage engineered graphene channels. The various surface treatments and substrate conditions produced differently doped graphene channels that were integrated on a single substrate and multiple Dirac voltages were observed by applying a single gate voltage sweep. We applied the Dirac voltage engineering techniques to graphene field-effect transistors on a single chip for the fabrication of a frequency multiplier and a logic inverter demonstrating analog and digital circuit application possibilities.

Performance analysis of selective cooperation with fixed gain relays in Nakagami-m channels

KAUST Repository

Hussain, Syed Imtiaz; Hasna, Mazen Omar; Alouini, Mohamed-Slim

2012-01-01

Selecting the best relay using the maximum signal to noise ratio (SNR) among all the relays ready to cooperate saves system resources and utilizes the available bandwidth more efficiently compared to the regular all-relay cooperation. In this paper, we analyze the performance of the best relay selection scheme with fixed gain relays operating in Nakagami-. m channels. We first derive the probability density function (PDF) of upper bounded end-to-end SNR of the relay link. Using this PDF, we derive some key performance parameters for the system including average bit error probability and average channel capacity. The analytical results are verified through Monte Carlo simulations. © 2012 Elsevier B.V.

Performance analysis of selective cooperation with fixed gain relays in Nakagami-m channels

KAUST Repository

Hussain, Syed Imtiaz

2012-09-01

Selecting the best relay using the maximum signal to noise ratio (SNR) among all the relays ready to cooperate saves system resources and utilizes the available bandwidth more efficiently compared to the regular all-relay cooperation. In this paper, we analyze the performance of the best relay selection scheme with fixed gain relays operating in Nakagami-. m channels. We first derive the probability density function (PDF) of upper bounded end-to-end SNR of the relay link. Using this PDF, we derive some key performance parameters for the system including average bit error probability and average channel capacity. The analytical results are verified through Monte Carlo simulations. © 2012 Elsevier B.V.

Transmit selection algorithms for imperfect threshold-based receive MRC in the presence of co-channel interference

KAUST Repository

Radaydeh, Redha Mahmoud Mesleh; Alouini, Mohamed-Slim

2010-01-01

The performance of transmit antenna selection for threshold-based maximal ratio combining (MRC) diversity receivers in the presence of multiple co-channel interfering signals is studied. The impact of imperfect channel estimation of desired user

Mutational jackpot events generate effective frequency-dependent selection in adapting populations

Science.gov (United States)

Hallatschek, Oskar

The site-frequency spectrum is one the most easily measurable quantities that characterize the genetic diversity of a population. While most neutral models predict that site frequency spectra should decay with increasing frequency, a high-frequency uptick has been reported in many populations. Anomalies in the high-frequency tail are particularly unsettling because the highest frequencies can be measured with greatest accuracy. Here, we show that an uptick in the spectrum of neutral mutations generally arises when mutant frequencies are dominated by rare jackpot events, mutational events with large descendant numbers. This leads to an effective pattern of frequency-dependent selection (or unstable internal equilibrium at one half frequency) that causes an accumulation of high-frequency polymorphic sites. We reproduce the known uptick occurring for recurrent hitchhiking (genetic draft) as well as rapid adaptation, and (in the future) generalize the shape of the high-frequency tail to other scenarios that are dominated by jackpot events, such as frequent range expansions. We also tackle (in the future) the inverse approach to use the high-frequency uptick for learning about the tail of the offspring number distribution. Positively selected alleles need to surpass, typically, an u NSF Career Award (PoLS), NIH NIGMS R01, Simons Foundation.

12.5 Gb/s multi-channel broadcasting transmission for free-space optical communication based on the optical frequency comb module.

Science.gov (United States)

Tan, Jun; Zhao, Zeping; Wang, Yuehui; Zhang, Zhike; Liu, Jianguo; Zhu, Ninghua

2018-01-22

A wide-spectrum, ultra-stable optical frequency comb (OFC) module with 100 GHz frequency intervals based on a quantum dot mode locked (QDML) laser is fabricated by our lab, and a scheme with 12.5 Gb/s multi-channel broadcasting transmission for free-space optical (FSO) communication is proposed based on the OFC module. The output power of the OFC is very stable, with the specially designed circuit and the flatness of the frequency comb over the span of 6 nm, which can be limited to 1.5 dB. Four channel wavelengths are chosen to demonstrate one-to-many channels for FSO communication, like optical wireless broadcast. The outdoor experiment is established to test the bit error rate (BER) and eye diagrams with 12.5 Gb/s on-off keying (OOK). The indoor experiment is used to test the highest traffic rate, which is up to 21 Gb/s for one-hop FSO communication. To the best of our knowledge, this scheme is the first to propose the realization of one-to-many broadcasting transmission for FSO communication based on the OFC module. The advantages of integration, miniaturization, channelization, low power consumption, and unlimited bandwidth of one-to-many broadcasting communication scheme, shows promising results on constructing the future space-air-ground-ocean (SAGO) FSO communication networks.

Spatial Tuning of a RF Frequency Selective Surface through Origami (Postprint)

Science.gov (United States)

2016-05-12

computational tools to systematically predict optimal folds. 15. SUBJECT TERMS origami, frequency selective surface, tuning, radio frequency 16...experimental study and motivates the development of computational tools to systematically predict optimal fold patterns for targeted frequency response...folding motions. The precise mapping of origami presents a novel method to spatially tune radio frequency (RF) devices, including adaptive antennas

Performance Analysis of Secrecy Outage Probability for AF-Based Partial Relay Selection with Outdated Channel Estimates

Directory of Open Access Journals (Sweden)

Kyu-Sung Hwang

2017-01-01

Full Text Available We study the secrecy outage probability of the amplify-and-forward (AF relaying protocol, which consists of one source, one destination, multiple relays, and multiple eavesdroppers. In this system, the aim is to transmit the confidential messages from a source to a destination via the selected relay in presence of eavesdroppers. Moreover, partial relay selection scheme is utilized for relay selection based on outdated channel state information where only neighboring channel information (source-relays is available and passive eavesdroppers are considered where a transmitter does not have any knowledge of eavesdroppers’ channels. Specifically, we offer the exact secrecy outage probability of the proposed system in a one-integral form as well as providing the asymptotic secrecy outage probability in a closed-form. Numerical examples are given to verify our provided analytical results for different system conditions.

Sub-micron resolution selected area electron channeling patterns.

Science.gov (United States)

Guyon, J; Mansour, H; Gey, N; Crimp, M A; Chalal, S; Maloufi, N

2015-02-01

Collection of selected area channeling patterns (SACPs) on a high resolution FEG-SEM is essential to carry out quantitative electron channeling contrast imaging (ECCI) studies, as it facilitates accurate determination of the crystal plane normal with respect to the incident beam direction and thus allows control the electron channeling conditions. Unfortunately commercial SACP modes developed in the past were limited in spatial resolution and are often no longer offered. In this contribution we present a novel approach for collecting high resolution SACPs (HR-SACPs) developed on a Gemini column. This HR-SACP technique combines the first demonstrated sub-micron spatial resolution with high angular accuracy of about 0.1°, at a convenient working distance of 10mm. This innovative approach integrates the use of aperture alignment coils to rock the beam with a digitally calibrated beam shift procedure to ensure the rocking beam is maintained on a point of interest. Moreover a new methodology to accurately measure SACP spatial resolution is proposed. While column considerations limit the rocking angle to 4°, this range is adequate to index the HR-SACP in conjunction with the pattern simulated from the approximate orientation deduced by EBSD. This new technique facilitates Accurate ECCI (A-ECCI) studies from very fine grained and/or highly strained materials. It offers also new insights for developing HR-SACP modes on new generation high-resolution electron columns. Copyright © 2014 Elsevier B.V. All rights reserved.

Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity

Directory of Open Access Journals (Sweden)

Aitor del Coso

2007-11-01

Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of N wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, 𝒞=log⁡2(W0(N. Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.

Outage Performance Analysis of Relay Selection Schemes in Wireless Energy Harvesting Cooperative Networks over Non-Identical Rayleigh Fading Channels †

Science.gov (United States)

Do, Nhu Tri; Bao, Vo Nguyen Quoc; An, Beongku

2016-01-01

In this paper, we study relay selection in decode-and-forward wireless energy harvesting cooperative networks. In contrast to conventional cooperative networks, the relays harvest energy from the source’s radio-frequency radiation and then use that energy to forward the source information. Considering power splitting receiver architecture used at relays to harvest energy, we are concerned with the performance of two popular relay selection schemes, namely, partial relay selection (PRS) scheme and optimal relay selection (ORS) scheme. In particular, we analyze the system performance in terms of outage probability (OP) over independent and non-identical (i.n.i.d.) Rayleigh fading channels. We derive the closed-form approximations for the system outage probabilities of both schemes and validate the analysis by the Monte-Carlo simulation. The numerical results provide comprehensive performance comparison between the PRS and ORS schemes and reveal the effect of wireless energy harvesting on the outage performances of both schemes. Additionally, we also show the advantages and drawbacks of the wireless energy harvesting cooperative networks and compare to the conventional cooperative networks. PMID:26927119

Outage performance of Decode-and-Forward partial selection in Nakagami-m fading channels

KAUST Repository

Benjillali, Mustapha

2010-01-01

In this paper, we investigate the outage performance of Decode-and-Forward with partial selection relaying in dualhop cooperative Nakagami-m fading links. The source, based on the unique knowledge of local first hop channel state information, selects the best relay to increase the chances of successful decoding and hence the possibility of cooperation when the direct link is also available. After deriving the exact distribution of the sum of two gamma variates with the same shape parameter, the outage probability of the system-with and without the direct link-is obtained in closed-form. We also derive the ε-outage capacity in different particular cases, and the obtained results- when the channel model is reduced to a Rayleigh fading-are either new or correspond to those previously obtained in other works. Simulation results confirm the accuracy of our analysis for a large selection of system and fading parameters. © 2009 IEEE.

Cavity-soliton laser with frequency-selective feedback

International Nuclear Information System (INIS)

Scroggie, A. J.; Firth, W. J.; Oppo, G.-L.

2009-01-01

We present a coupled-cavity model of a laser with frequency-selective feedback, and use it to analyze and explain the existence of stationary and dynamic spatial solitons in the device. Particular features of soliton addressing in this system are discussed. We demonstrate the advantages of our model with respect to the common Lang-Kobayashi approximation.

Transmit selection for imperfect threshold-based receive MRC in Rayleigh fading channels

KAUST Repository

Radaydeh, Redha Mahmoud Mesleh

2010-01-01

The performance of multiple-antenna diversity systems in which the receiver combines signal replicas per thresholdbased maximal ratio combining (MRC) and the transmitter uses only a single antenna according to receive combined signal strength is studied. The impact of imperfect channel estimation is considered when the received signal replicas undergo independent and flat multipath fading. The analysis is applicable for arbitrary transmit antenna selection when the multiple-antenna channels experience identically distributed and non-identically distributed Rayleigh fading conditions. New closed-form expressions for the combined SNR statistics and some performance measures are presented. The system models adopted herein and the presented analytical results can be used to study the performance of different system architectures under various channel conditions when the implementation complexity is of interest. © 2009 IEEE.

Channel Selection Policy in Multi-SU and Multi-PU Cognitive Radio Networks with Energy Harvesting for Internet of Everything

Directory of Open Access Journals (Sweden)

Feng Hu

2016-01-01

Full Text Available Cognitive radio, which will become a fundamental part of the Internet of Everything (IoE, has been identified as a promising solution for the spectrum scarcity. In a multi-SU and multi-PU cognitive radio network, selecting channels is a fundamental problem due to the channel competition among secondary users (SUs and packet collision between SUs and primary users (PUs. In this paper, we adopt cooperative sensing method to avoid the packet collision between SUs and PUs and focus on how to collect the spectrum sensing data of SUs for cooperative sensing. In order to reduce the channel competition among SUs, we first consider the hybrid transmission model for single SU where a SU can opportunistically access both idle channels operating either the Overlay or the Underlay model and the busy channels by using the energy harvesting technology. Then we propose a competitive set based channel selection policy for multi-SU where all SUs competing for data transmission or energy harvesting in the same channel will form a competitive set. Extensive simulations show that the proposed cooperative sensing method and the channel selection policy outperform previous solutions in terms of false alarm, average throughput, average waiting time, and energy harvesting efficiency of SUs.

User Adapted Motor-Imaginary Brain-Computer Interface by means of EEG Channel Selection Based on Estimation of Distributed Algorithms

Directory of Open Access Journals (Sweden)

Aitzol Astigarraga

2016-01-01

Full Text Available Brain-Computer Interfaces (BCIs have become a research field with interesting applications, and it can be inferred from published papers that different persons activate different parts of the brain to perform the same action. This paper presents a personalized interface design method, for electroencephalogram- (EEG- based BCIs, based on channel selection. We describe a novel two-step method in which firstly a computationally inexpensive greedy algorithm finds an adequate search range; and, then, an Estimation of Distribution Algorithm (EDA is applied in the reduced range to obtain the optimal channel subset. The use of the EDA allows us to select the most interacting channels subset, removing the irrelevant and noisy ones, thus selecting the most discriminative subset of channels for each user improving accuracy. The method is tested on the IIIa dataset from the BCI competition III. Experimental results show that the resulting channel subset is consistent with motor-imaginary-related neurophysiological principles and, on the other hand, optimizes performance reducing the number of channels.

Mapping of Residues Forming the Voltage Sensor of the Voltage-Dependent Anion-Selective Channel

Science.gov (United States)

Thomas, Lorie; Blachly-Dyson, Elizabeth; Colombini, Marco; Forte, Michael

1993-06-01

Voltage-gated ion-channel proteins contain "voltage-sensing" domains that drive the conformational transitions between open and closed states in response to changes in transmembrane voltage. We have used site-directed mutagenesis to identify residues affecting the voltage sensitivity of a mitochondrial channel, the voltage-dependent anion-selective channel (VDAC). Although charge changes at many sites had no effect, at other sites substitutions that increased positive charge also increased the steepness of voltage dependance and substitutions that decreased positive charge decreased voltage dependance by an appropriate amount. In contrast to the plasma membrane K^+ and Na^+ channels, these residues are distributed over large parts of the VDAC protein. These results have been used to define the conformational transitions that accompany voltage gating of an ion channel. This gating mechanism requires the movement of large portions of the VDAC protein through the membrane.

Feasibility Studies on the Use of Higher Frequency Bands and Beamforming Selection Scheme for High Speed Train Communication

Directory of Open Access Journals (Sweden)

Ayotunde O. Laiyemo

2017-01-01

Full Text Available With increasing popularity of high speed trains and traffic forecast for future cellular networks, the need to provide improved data rates using higher frequency bands (HFBs for train passengers is becoming crucial. In this paper, we modify the OFDM frame structure for HST, taking into account the increasing sensitivity to speed at HFBs. A lower bound on the SNR/SINR for a given rate for reliable communication was derived considering the physical layer parameters from the OFDM frame. We also analyze different pathloss models in the context of examining the required gain needed to achieve the same performance as with microwave bands. Finally, we present a time-based analogue beamforming selection approach for HST. We observed that, irrespective of the pathloss models used, the required gains are within the same range. For the same SNR/SINR at different frequency bands, the achievable data rate varies with respect to the frequency bands. Our results show the potential of the use of HFBs. However, due to the increased sensitivity of some channel parameters, a maximum frequency band of 38 GHz is suggested. Evaluation of our proposed beamforming scheme indicates a close performance to the optimal SVD scheme with a marginal rate gap of less than 2 b/s/Hz.

High-Frequency Ground-Motion Parameters from Weak-Motion Data in the Sicily Channel and Surrounding Regions

Science.gov (United States)

D'Amico, Sebastiano; Akinci, Aybige; Pischiutta, Marta

2018-03-01

In this paper we characterize the high frequency (1.0 - 10 Hz) seismic wave crustal attenuation and the source excitation in the Sicily Channel and surrounding regions using background seismicity from weak-motion database. The data set includes 15995 waveforms related to earthquakes having local magnitude ranging from 2.0 to 4.5 recorded between 2006 and 2012. The observed and predicted ground motions form the weak-motion data are evaluated in several narrow frequency bands from 0.25 to 20.0 Hz. The filtered observed peaks are regressed to specify a proper functional form for the regional attenuation, excitation and site specific term separately. The results are then used to calibrate effective theoretical attenuation and source excitation models using the Random Vibration Theory (RVT). In the log-log domain, the regional seismic wave attenuation and the geometrical spreading coefficient are modeled together. The geometrical spreading coefficient, g (r), modeled with a bilinear piecewise functional form and given as g (r) ∝ r-1.0 for the short distances (r selected reference distance with a magnitude independent roll-off spectral parameter, κ 0.04 s and with a Brune stress drop parameter increasing with moment magnitude, from Δσ = 2 MPa for Mw = 2.0 to Δσ = 13 MPa for Mw = 4.5. For events M≤4.5 (being Mwmax = 4.5 available in the dataset) the stress parameters are obtained by correlating the empirical/excitation source spectra with the Brune spectral model as function of magnitude. For the larger magnitudes (Mw>4.5) outside the range available in the calibration dataset where we do not have recorded data, we extrapolate our results through the calibration of the stress parameters of the Brune source spectrum over the Bindi et al. (2011) ground motion prediction equation (GMPE) selected as a reference model (hereafter also ITA10).

Full Waveform Inversion with Multisource Frequency Selection of Marine Streamer Data

KAUST Repository

Huang, Yunsong

2017-10-27

The theory and practice of multisource full waveform inversion of marine supergathers are described with a frequency-selection strategy. The key enabling property of frequency selection is that it eliminates the crosstalk among sources, thus overcoming the aperture mismatch of marine multisource inversion. Tests on multisource full waveform inversion of synthetic marine data and Gulf of Mexico data show speedups of 4× and 8×, respectively, compared to conventional full waveform inversion.

Full Waveform Inversion with Multisource Frequency Selection of Marine Streamer Data

KAUST Repository

Huang, Yunsong; Schuster, Gerard T.

2017-01-01

The theory and practice of multisource full waveform inversion of marine supergathers are described with a frequency-selection strategy. The key enabling property of frequency selection is that it eliminates the crosstalk among sources, thus overcoming the aperture mismatch of marine multisource inversion. Tests on multisource full waveform inversion of synthetic marine data and Gulf of Mexico data show speedups of 4× and 8×, respectively, compared to conventional full waveform inversion.

Least-squares reverse time migration of marine data with frequency-selection encoding

KAUST Repository

Dai, Wei

2013-08-20

The phase-encoding technique can sometimes increase the efficiency of the least-squares reverse time migration (LSRTM) by more than one order of magnitude. However, traditional random encoding functions require all the encoded shots to share the same receiver locations, thus limiting the usage to seismic surveys with a fixed spread geometry. We implement a frequency-selection encoding strategy that accommodates data with a marine streamer geometry. The encoding functions are delta functions in the frequency domain, so that all the en- coded shots have unique non-overlapping frequency content, and the receivers can distinguish the wavefield from each shot with a unique frequency band. Since the encoding functions are orthogonal to each other, there will be no crosstalk between different shots during modeling and migration. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is compara- ble to conventional RTM for both the Marmousi2 model and a marine data set recorded in the Gulf of Mexico. With more iterations, the LSRTM image quality is further improved. We conclude that LSRTM with frequency-selection is an efficient migration method that can sometimes produce more focused images than conventional RTM.

MONETARY TRANSMISSION CHANNELS IN FLEXIBLE MONETARY AND EXCHANGE RATE REGIMES: THE CASE OF SELECTED TRANSITION ECONOMIES

OpenAIRE

JOSIFIDIS, Kosta; PUCAR, Emilija Beker; SUPIĆ, Novica

2010-01-01

The paper explores selected monetary transmission channels in the case of transition economies. Namely, an exchange rate channel, an interest rate channel, direct and indirect influence to an exchange rate, are focused. Specific (former) transition economies are differentiated according the combination of implemented monetary and exchange rate regimes: exchange rate as a nominal anchor and rigid exchange rate regimes, exchange rate as a nominal anchor and intermediate exchange rate regimes, a...

Mechanical stress-controlled tunable active frequency-selective surface

Science.gov (United States)

Huang, Bo-Cin; Hong, Jian-Wei; Lo, Cheng-Yao

2017-01-01

This study proposes a tunable active frequency-selective surface (AFSS) realized by mechanically expanding or contracting a split-ring resonator (SRR) array. The proposed AFSS transfers mechanical stress from its elastic substrate to the top of the SRR, thereby achieving electromagnetic (EM) modulation without the need for an additional external power supply, meeting the requirements for the target application: the invisibility cloak. The operating mechanism of the proposed AFSS differs from those of other AFSSs, supporting modulations in arbitrary frequencies in the target range. The proposed stress-controlled or strain-induced EM modulation proves the existence of an identical and linear relationship between the strain gradient and the frequency shift, implying its suitability for other EM modulation ranges and applications.

Adaptive Modulation with Best User Selection over Non-Identical Nakagami Fading Channels

KAUST Repository

Rao, Anlei

2012-09-08

In this paper, we analyze the performance of adaptive modulation with single-cell multiuser scheduling over independent but not identical distributed (i.n.i.d.) Nakagami fading channels. Closed-form expressions are derived for the average channel capacity, spectral efficiency, and bit-error-rate (BER) for both constant-power variable-rate and variable-power variable-rate uncoded M-ary quadrature amplitude modulation (M-QAM) schemes. We also study the impact of time delay on the average BER of adaptive M-QAM. Selected numerical results show that the multiuser diversity brings a considerably better performance even over i.n.i.d. fading environments.

47 CFR 90.315 - Special provisions governing use of frequencies in the 476-494 MHz band (TV Channels 15, 16, 17...

Science.gov (United States)

2010-10-01

... in the 476-494 MHz band (TV Channels 15, 16, 17) in the Southern Louisiana-Texas Offshore Zone. 90... RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Authorization in the Band 470-512 MHz (UHF-TV Sharing) § 90.315 Special provisions governing use of frequencies in the 476-494 MHz band (TV Channels 15, 16...

A Novel Partial Discharge Ultra-High Frequency Signal De-Noising Method Based on a Single-Channel Blind Source Separation Algorithm

Directory of Open Access Journals (Sweden)

Liangliang Wei

2018-02-01

Full Text Available To effectively de-noise the Gaussian white noise and periodic narrow-band interference in the background noise of partial discharge ultra-high frequency (PD UHF signals in field tests, a novel de-noising method, based on a single-channel blind source separation algorithm, is proposed. Compared with traditional methods, the proposed method can effectively de-noise the noise interference, and the distortion of the de-noising PD signal is smaller. Firstly, the PD UHF signal is time-frequency analyzed by S-transform to obtain the number of source signals. Then, the single-channel detected PD signal is converted into multi-channel signals by singular value decomposition (SVD, and background noise is separated from multi-channel PD UHF signals by the joint approximate diagonalization of eigen-matrix method. At last, the source PD signal is estimated and recovered by the l1-norm minimization method. The proposed de-noising method was applied on the simulation test and field test detected signals, and the de-noising performance of the different methods was compared. The simulation and field test results demonstrate the effectiveness and correctness of the proposed method.

A selectivity filter at the intracellular end of the acid-sensing ion channel pore

DEFF Research Database (Denmark)

Lynagh, Timothy; Flood, Emelie; Boiteux, Céline

2017-01-01

Increased extracellular proton concentrations during neurotransmission are converted to excitatory sodium influx by acid-sensing ion channels (ASICs). 10-fold sodium/potassium selectivity in ASICs has long been attributed to a central constriction in the channel pore, but experimental verificatio...... at the "GAS belt" in the central constriction. Instead, we identified a band of glutamate and aspartate side chains at the lower end of the pore that enables preferential sodium conduction....

Adaptive Equalizer Using Selective Partial Update Algorithm and Selective Regressor Affine Projection Algorithm over Shallow Water Acoustic Channels

Directory of Open Access Journals (Sweden)

Masoumeh Soflaei

2014-01-01

Full Text Available One of the most important problems of reliable communications in shallow water channels is intersymbol interference (ISI which is due to scattering from surface and reflecting from bottom. Using adaptive equalizers in receiver is one of the best suggested ways for overcoming this problem. In this paper, we apply the family of selective regressor affine projection algorithms (SR-APA and the family of selective partial update APA (SPU-APA which have low computational complexity that is one of the important factors that influences adaptive equalizer performance. We apply experimental data from Strait of Hormuz for examining the efficiency of the proposed methods over shallow water channel. We observe that the values of the steady-state mean square error (MSE of SR-APA and SPU-APA decrease by 5.8 (dB and 5.5 (dB, respectively, in comparison with least mean square (LMS algorithm. Also the families of SPU-APA and SR-APA have better convergence speed than LMS type algorithm.

Joint beam design and user selection over non-binary coded MIMO interference channel

Science.gov (United States)

Li, Haitao; Yuan, Haiying

2013-03-01

In this paper, we discuss the problem of sum rate improvement for coded MIMO interference system, and propose joint beam design and user selection over interference channel. Firstly, we have formulated non-binary LDPC coded MIMO interference networks model. Then, the least square beam design for MIMO interference system is derived, and the low complexity user selection is presented. Simulation results confirm that the sum rate can be improved by the joint user selection and beam design comparing with single interference aligning beamformer.

Performance analysis of best relay selection scheme for amplify-and-forward cooperative networks in identical Nakagami-m channels

KAUST Repository

Hussain, Syed Imtiaz

2010-06-01

In cooperative communication networks, the use of multiple relays between the source and the destination was proposed to increase the diversity gain. Since the source and all the relays must transmit on orthogonal channels, multiple relay cooperation is considered inefficient in terms of channel resources and bandwidth utilization. To overcome this problem, the concept of best relay selection was recently proposed. In this paper, we analyze the performance of the best relay selection scheme for a cooperative network with multiple relays operating in amplify-and-forward (AF) mode over identical Nakagami-m channels using exact source-relay-destination signal to noise ratio (SNR) expression. We derive accurate closed form expressions for various system parameters including probability density function (pdf) of end-to-end SNR, average output SNR, average probability of bit error and average channel capacity. T he analytical results are verified through extensive simulations. It is shown that the best relay selection scheme performs better than the regular all relay cooperation.

Consequences of peripheral frequency selectivity for nonsimultaneous masking

NARCIS (Netherlands)

Duifhuis, H.

1973-01-01

The frequency selectivity of the peripheral ear (e.g., at the VIIIth nerve level) is so acute that onset and offset transients in responses to short signals produce a nonnegligible extension of the signal duration. Thus, peripheral excitation patterns produced by signals which were separated in time

Iterative Pilot-Layer Aided Channel Estimation with Emphasis on Interleave-Division Multiple Access Systems

Directory of Open Access Journals (Sweden)

Schoeneich Hendrik

2006-01-01

Full Text Available Channel estimation schemes suitable for interleave-division multiple access (IDMA systems are presented. Training and data are superimposed. Training-based and semiblind linear channel estimators are derived and their performance is discussed and compared. Monte Carlo simulation results are presented showing that the derived channel estimators in conjunction with a superimposed pilot sequence and chip-by-chip processing are able to track fast-fading frequency-selective channels. As opposed to conventional channel estimation techniques, the BER performance even improves with increasing Doppler spread for typical system parameters. An error performance close to the case of perfect channel knowledge can be achieved with high power efficiency.

A structural, functional, and computational analysis suggests pore flexibility as the base for the poor selectivity of CNG channels.

Science.gov (United States)

Napolitano, Luisa Maria Rosaria; Bisha, Ina; De March, Matteo; Marchesi, Arin; Arcangeletti, Manuel; Demitri, Nicola; Mazzolini, Monica; Rodriguez, Alex; Magistrato, Alessandra; Onesti, Silvia; Laio, Alessandro; Torre, Vincent

2015-07-07

Cyclic nucleotide-gated (CNG) ion channels, despite a significant homology with the highly selective K(+) channels, do not discriminate among monovalent alkali cations and are permeable also to several organic cations. We combined electrophysiology, molecular dynamics (MD) simulations, and X-ray crystallography to demonstrate that the pore of CNG channels is highly flexible. When a CNG mimic is crystallized in the presence of a variety of monovalent cations, including Na(+), Cs(+), and dimethylammonium (DMA(+)), the side chain of Glu66 in the selectivity filter shows multiple conformations and the diameter of the pore changes significantly. MD simulations indicate that Glu66 and the prolines in the outer vestibule undergo large fluctuations, which are modulated by the ionic species and the voltage. This flexibility underlies the coupling between gating and permeation and the poor ionic selectivity of CNG channels.

Performance Analysis of Wavelet Channel Coding in COST207-based Channel Models on Simulated Radio-over-Fiber Systems at the W-Band

DEFF Research Database (Denmark)

Cavalcante, Lucas Costa Pereira; Silveira, Luiz F. Q.; Rommel, Simon

2016-01-01

Millimeter wave communications based on photonic technologies have gained increased attention to provide optic fiber-like capacity in wireless environments. However, the new hybrid fiber-wireless channel represents new challenges in terms of signal transmission performance analysis. Traditionally......, such systems use diversity schemes in combination with digital signal processing (DSP) techniques to overcome effects such as fading and inter-symbol interference (ISI). Wavelet Channel Coding (WCC) has emerged as a technique to minimize the fading effects of wireless channels, which is a mayor challenge...... in systems operating in the millimeter wave regime. This work takes the WCC one step beyond by performance evaluation in terms of bit error probability, over time-varying, frequency-selective multipath Rayleigh fading channels. The adopted propagation model follows the COST207 norm, the main international...

Substituted N-(biphenyl-4'-yl)methyl (R)-2-acetamido-3-methoxypropionamides: potent anticonvulsants that affect frequency (use) dependence and slow inactivation of sodium channels.

Science.gov (United States)

Lee, Hyosung; Park, Ki Duk; Torregrosa, Robert; Yang, Xiao-Fang; Dustrude, Erik T; Wang, Yuying; Wilson, Sarah M; Barbosa, Cindy; Xiao, Yucheng; Cummins, Theodore R; Khanna, Rajesh; Kohn, Harold

2014-07-24

We prepared 13 derivatives of N-(biphenyl-4'-yl)methyl (R)-2-acetamido-3-methoxypropionamide that differed in type and placement of a R-substituent in the terminal aryl unit. We demonstrated that the R-substituent impacted the compound's whole animal and cellular pharmacological activities. In rodents, select compounds exhibited excellent anticonvulsant activities and protective indices (PI=TD50/ED50) that compared favorably with clinical antiseizure drugs. Compounds with a polar, aprotic R-substituent potently promoted Na+ channel slow inactivation and displayed frequency (use) inhibition of Na+ currents at low micromolar concentrations. The possible advantage of affecting these two pathways to decrease neurological hyperexcitability is discussed.

Least-squares reverse time migration of marine data with frequency-selection encoding

KAUST Repository

Dai, Wei

2013-06-24

The phase-encoding technique can sometimes increase the efficiency of the least-squares reverse time migration (LSRTM) by more than one order of magnitude. However, traditional random encoding functions require all the encoded shots to share the same receiver locations, thus limiting the usage to seismic surveys with a fixed spread geometry. We implement a frequency-selection encoding strategy that accommodates data with a marine streamer geometry. The encoding functions are delta functions in the frequency domain, so that all the encoded shots have unique nonoverlapping frequency content, and the receivers can distinguish the wavefield from each shot with a unique frequency band. Because the encoding functions are orthogonal to each other, there will be no crosstalk between different shots during modeling and migration. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is comparable to conventional RTM for the Marmousi2 model and a marine data set recorded in the Gulf of Mexico. With more iterations, the LSRTM image quality is further improved by suppressing migration artifacts, balancing reflector amplitudes, and enhancing the spatial resolution. We conclude that LSRTM with frequency-selection is an efficient migration method that can sometimes produce more focused images than conventional RTM. © 2013 Society of Exploration Geophysicists.

Evaluation and selection of hot channel (peaking) factors for research reactor applications

International Nuclear Information System (INIS)

Woodruff, W.L.

1987-01-01

A proposed method for selecting and applying hot channel factors is presented along with some justification for these selections. The method is illustrated by example, and the sensitivity to some of the choices is examined. The uncertainty in the heat transfer coefficient is a major contributor to the reduction in thermal-hydraulic safety margins. The uncertainty introduced by the heterogeneity in the fuel is another important contributor and an area where more information may be useful in reducing this uncertainty. (Author)

Performance of Antenna Selection in MIMO System Using Channel Reciprocity with Measured Data

Directory of Open Access Journals (Sweden)

Peerapong Uthansakul

2011-01-01

Full Text Available The channel capacity of MIMO system increases as a function of antenna pairs between transmitter and receiver but it suffers from multiple expensive RF chains. To reduce cost of RF chains, antenna selection (AS method can offer a good tradeoff between expense and performance. For a transmitting AS system, channel state information (CSI feedback is required to choose the best subset of available antennas. However, the delay and error in feedback channel are the most dominant factors to degrade performances. In this paper, the concept of AS method using reciprocal CSI instead of feedback channel is proposed. The capacity performance of proposed system is investigated by own developing Testbed. The obtained results indicate that the reciprocity technique offers a capacity close to a system with perfect CSI and gains a higher capacity than a system without AS method. This benefit is from 0.9 to 2.2 bps/Hz at SNR 10 dB.

Individual Alpha Peak Frequency Predicts 10 Hz Flicker Effects on Selective Attention.

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Gulbinaite, Rasa; van Viegen, Tara; Wieling, Martijn; Cohen, Michael X; VanRullen, Rufin

2017-10-18

Rhythmic visual stimulation ("flicker") is primarily used to "tag" processing of low-level visual and high-level cognitive phenomena. However, preliminary evidence suggests that flicker may also entrain endogenous brain oscillations, thereby modulating cognitive processes supported by those brain rhythms. Here we tested the interaction between 10 Hz flicker and endogenous alpha-band (∼10 Hz) oscillations during a selective visuospatial attention task. We recorded EEG from human participants (both genders) while they performed a modified Eriksen flanker task in which distractors and targets flickered within (10 Hz) or outside (7.5 or 15 Hz) the alpha band. By using a combination of EEG source separation, time-frequency, and single-trial linear mixed-effects modeling, we demonstrate that 10 Hz flicker interfered with stimulus processing more on incongruent than congruent trials (high vs low selective attention demands). Crucially, the effect of 10 Hz flicker on task performance was predicted by the distance between 10 Hz and individual alpha peak frequency (estimated during the task). Finally, the flicker effect on task performance was more strongly predicted by EEG flicker responses during stimulus processing than during preparation for the upcoming stimulus, suggesting that 10 Hz flicker interfered more with reactive than proactive selective attention. These findings are consistent with our hypothesis that visual flicker entrained endogenous alpha-band networks, which in turn impaired task performance. Our findings also provide novel evidence for frequency-dependent exogenous modulation of cognition that is determined by the correspondence between the exogenous flicker frequency and the endogenous brain rhythms. SIGNIFICANCE STATEMENT Here we provide novel evidence that the interaction between exogenous rhythmic visual stimulation and endogenous brain rhythms can have frequency-specific behavioral effects. We show that alpha-band (10 Hz) flicker impairs stimulus

Safety and efficacy of a Nav1.7 selective sodium channel blocker in patients with trigeminal neuralgia

DEFF Research Database (Denmark)

Zakrzewska, Joanna M; Palmer, Joanne; Morisset, Valerie

2017-01-01

BACKGROUND: Current standard of care for trigeminal neuralgia is treatment with the sodium channel blockers carbamazepine and oxcarbazepine, which although effective are associated with poor tolerability and the need for titration. BIIB074, a Nav1.7-selective, state-dependent sodium-channel blocker...

Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers

Science.gov (United States)

Oliver, A. E.; Deamer, D. W.

1994-01-01

Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two

TWIK-1 two-pore domain potassium channels change ion selectivity and conduct inward leak sodium currents in hypokalemia.

Science.gov (United States)

Ma, Liqun; Zhang, Xuexin; Chen, Haijun

2011-06-07

Background potassium (K+) channels, which are normally selectively permeable to K+, maintain the cardiac resting membrane potential at around -80 mV. In subphysiological extracellular K+ concentrations ([K+]o), which occur in pathological hypokalemia, the resting membrane potential of human cardiomyocytes can depolarize to around -50 mV, whereas rat and mouse cardiomyocytes become hyperpolarized, consistent with the Nernst equation for K+. This paradoxical depolarization of cardiomyocytes in subphysiological [K+]o, which may contribute to cardiac arrhythmias, is thought to involve an inward leak sodium (Na+) current. Here, we show that human cardiac TWIK-1 (also known as K2P1) two-pore domain K+ channels change ion selectivity, becoming permeable to external Na+, and conduct inward leak Na+ currents in subphysiological [K+]o. A specific threonine residue (Thr118) within the pore selectivity sequence TxGYG was required for this altered ion selectivity. Mouse cardiomyocyte-derived HL-1 cells exhibited paradoxical depolarization with ectopic expression of TWIK-1 channels, whereas TWIK-1 knockdown in human spherical primary cardiac myocytes eliminated paradoxical depolarization. These findings indicate that ion selectivity of TWIK-1 K+ channels changes during pathological hypokalemia, elucidate a molecular basis for inward leak Na+ currents that could trigger or contribute to cardiac paradoxical depolarization in lowered [K+]o, and identify a mechanism for regulating cardiac excitability.

The mechanosensory calcium-selective ion channel: key component of a plasmalemmal control centre?

Science.gov (United States)

Pickard, B. G.; Ding, J. P.

1993-01-01

Mechanosensory calcium-selective ion channels probably serve to detect not only mechanical stress but also electrical, thermal, and diverse chemical stimuli. Because all stimuli result in a common output, most notably a shift in second messenger calcium concentration, the channels are presumed to serve as signal integrators. Further, insofar as second messenger calcium in turn gives rise to mechanical, electrical, and diverse chemical changes, the channels are postulated to initiate regulatory feedbacks. It is proposed that the channels and the feedback loops play a wide range of roles in regulating normal plant function, as well as in mediating disturbance of normal function by environmental stressors and various pathogens. In developing evidence for the physiological performance of the channel, a model for a cluster of regulatory plasmalemmal proteins and cytoskeletal elements grouped around a set of wall-to-membrane and transmembrane linkers has proved useful. An illustration of how the model might operate is presented. It is founded on the demonstration that several xenobiotics interfere both with normal channel behaviour and with gravitropic reception. Accordingly, the first part of the illustration deals with how the channels and the control system within which they putatively operate might initiate gravitropism. Assuming that gravitropism is an asymmetric expression of growth, the activities of the channels and the plasmalemmal control system are extrapolated to account for regulation of both rate and allometry of cell expansion. Finally, it is discussed how light, hormones, redox agents and herbicides could in principle affect growth via the putative plasmalemmal control cluster or centre.

The yule approximation for the site frequency spectrum after a selective sweep.

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Sebastian Bossert

Full Text Available In the area of evolutionary theory, a key question is which portions of the genome of a species are targets of natural selection. Genetic hitchhiking is a theoretical concept that has helped to identify various such targets in natural populations. In the presence of recombination, a severe reduction in sequence diversity is expected around a strongly beneficial allele. The site frequency spectrum is an important tool in genome scans for selection and is composed of the numbers S(1,...,S(n-1, where S(k is the number of single nucleotide polymorphisms (SNPs present in k from n individuals. Previous work has shown that both the number of low- and high-frequency variants are elevated relative to neutral evolution when a strongly beneficial allele fixes. Here, we follow a recent investigation of genetic hitchhiking using a marked Yule process to obtain an analytical prediction of the site frequency spectrum in a panmictic population at the time of fixation of a highly beneficial mutation. We combine standard results from the neutral case with the effects of a selective sweep. As simulations show, the resulting formula produces predictions that are more accurate than previous approaches for the whole frequency spectrum. In particular, the formula correctly predicts the elevation of low- and high-frequency variants and is significantly more accurate than previously derived formulas for intermediate frequency variants.

Selective injection locking of a multi-mode semiconductor laser to a multi-frequency reference beam

Science.gov (United States)

Pramod, Mysore Srinivas; Yang, Tao; Pandey, Kanhaiya; Giudici, Massimo; Wilkowski, David

2014-07-01

Injection locking is a well known and commonly used method for coherent light amplification. Usually injection locking is obtained on a single-mode laser injected by a single-frequency seeding beam. In this work we show that selective injection locking of a single-frequency may also be achieved on a multi-mode semiconductor laser injected by a multi-frequency seeding beam, if the slave laser provides sufficient frequency filtering. This selective injection locking condition depends critically on the frequency detuning between the free-running slave emission frequency and each injected frequency component. Stable selective injection locking to a set of three seeding components separated by 1.2 GHz is obtained. This system provides an amplification up to 37 dB of each component. This result suggests that, using distinct slave lasers for each frequency line, a set of mutually coherent high-power radiation modes can be tuned in the GHz frequency domain.

Bit Error Rate Performance Analysis of a Threshold-Based Generalized Selection Combining Scheme in Nakagami Fading Channels

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Kousa Maan

2005-01-01

Full Text Available The severity of fading on mobile communication channels calls for the combining of multiple diversity sources to achieve acceptable error rate performance. Traditional approaches perform the combining of the different diversity sources using either the conventional selective diversity combining (CSC, equal-gain combining (EGC, or maximal-ratio combining (MRC schemes. CSC and MRC are the two extremes of compromise between performance quality and complexity. Some researches have proposed a generalized selection combining scheme (GSC that combines the best branches out of the available diversity resources ( . In this paper, we analyze a generalized selection combining scheme based on a threshold criterion rather than a fixed-size subset of the best channels. In this scheme, only those diversity branches whose energy levels are above a specified threshold are combined. Closed-form analytical solutions for the BER performances of this scheme over Nakagami fading channels are derived. We also discuss the merits of this scheme over GSC.

Pacemaker rate and depolarization block in nigral dopamine neurons: a somatic sodium channel balancing act

Science.gov (United States)

Tucker, Kristal R.; Huertas, Marco A.; Horn, John P.; Canavier, Carmen C.; Levitan, Edwin S.

2012-01-01

Midbrain dopamine (DA) neurons are slow intrinsic pacemakers that undergo depolarization (DP) block upon moderate stimulation. Understanding DP block is important because it has been correlated with the clinical efficacy of chronic antipsychotic drug treatment. Here we describe how voltage-gated sodium (NaV) channels regulate DP block and pacemaker activity in DA neurons of the substantia nigra using rat brain slices. The distribution, density and gating of NaV currents were manipulated by blocking native channels with tetrodotoxin and by creating virtual channels and anti-channels with dynamic clamp. Although action potentials initiate in the axon initial segment (AIS) and NaV channels are distributed in multiple dendrites, selective reduction of NaV channel activity in the soma was sufficient to decrease pacemaker frequency and increase susceptibility to DP block. Conversely, increasing somatic NaV current density raised pacemaker frequency and lowered susceptibility to DP block. Finally, when NaV currents were restricted to the soma, pacemaker activity occurred at abnormally high rates due to excessive local subthreshold NaV current. Together with computational simulations, these data show that both the slow pacemaker rate and the sensitivity to DP block that characterizes DA neurons result from the low density of somatic NaV channels. More generally, we conclude that the somatodendritic distribution of NaV channels is a major determinant of repetitive spiking frequency. PMID:23077037

Selection of the wavelet function for the frequencies estimation

International Nuclear Information System (INIS)

Garcia R, A.

2007-01-01

At the moment the signals are used to diagnose the state of the systems, by means of the extraction of their more important characteristics such as the frequencies, tendencies, changes and temporary evolutions. This characteristics are detected by means of diverse analysis techniques, as Autoregressive methods, Fourier Transformation, Fourier transformation in short time, Wavelet transformation, among others. The present work uses the one Wavelet transformation because it allows to analyze stationary, quasi-stationary and transitory signals in the time-frequency plane. It also describes a methodology to select the scales and the Wavelet function to be applied the one Wavelet transformation with the objective of detecting to the dominant system frequencies. (Author)

Direct Frequency Comb Spectroscopy of Alkali Atoms

Science.gov (United States)

Pradhananga, Trinity; Palm, Christopher; Nguyen, Khoa; Guttikonda, Srikanth; Kimball, Derek Jackson

2011-11-01

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Channel selective tunnelling through a nanographene assembly

International Nuclear Information System (INIS)

Wong, H S; Durkan, C; Feng, X; Müllen, K; Chandrasekhar, N

2012-01-01

We report selective tunnelling through a nanographene intermolecular tunnel junction achieved via scanning tunnelling microscope tip functionalization with hexa-peri-hexabenzocoronene (HBC) molecules. This leads to an offset in the alignment between the energy levels of the tip and the molecular assembly, resulting in the imaging of a variety of distinct charge density patterns in the HBC assembly, not attainable using a bare metallic tip. Different tunnelling channels can be selected by the application of an electric field in the tunnelling junction, which changes the condition of the HBC on the tip. Density functional theory-based calculations relate the imaged HBC patterns to the calculated molecular orbitals at certain energy levels. These patterns bear a close resemblance to the π-orbital states of the HBC molecule calculated at the relevant energy levels, mainly below the Fermi energy of HBC. This correlation demonstrates the ability of an HBC functionalized tip as regards accessing an energy range that is restricted to the usual operating bias range around the Fermi energy with a normal metallic tip at room temperature. Apart from relating to molecular orbitals, some patterns could also be described in association with the Clar aromatic sextet formula. Our observations may help pave the way towards the possibility of controlling charge transport between organic interfaces. (paper)

Low-frequency 1/f noise in MoS2 transistors: Relative contributions of the channel and contacts

Science.gov (United States)

Renteria, J.; Samnakay, R.; Rumyantsev, S. L.; Jiang, C.; Goli, P.; Shur, M. S.; Balandin, A. A.

2014-04-01

We report on the results of the low-frequency (1/f, where f is frequency) noise measurements in MoS2 field-effect transistors revealing the relative contributions of the MoS2 channel and Ti/Au contacts to the overall noise level. The investigation of the 1/f noise was performed for both as fabricated and aged transistors. It was established that the McWhorter model of the carrier number fluctuations describes well the 1/f noise in MoS2 transistors, in contrast to what is observed in graphene devices. The trap densities extracted from the 1/f noise data for MoS2 transistors, are 2 × 1019 eV-1cm-3 and 2.5 × 1020 eV-1cm-3 for the as fabricated and aged devices, respectively. It was found that the increase in the noise level of the aged MoS2 transistors is due to the channel rather than the contact degradation. The obtained results are important for the proposed electronic applications of MoS2 and other van der Waals materials.

Integral criterion for selecting nonlinear crystals for frequency conversion

International Nuclear Information System (INIS)

Grechin, Sergei G

2009-01-01

An integral criterion, which takes into account all parameters determining the conversion efficiency, is offered for selecting nonlinear crystals for frequency conversion. The angular phase-matching width is shown to be related to the beam walk-off angle. (nonlinear optical phenomena)

A Smartphone Application for Customized Frequency Table Selection in Cochlear Implants.

Science.gov (United States)

Jethanamest, Daniel; Azadpour, Mahan; Zeman, Annette M; Sagi, Elad; Svirsky, Mario A

2017-09-01

A novel smartphone-based software application can facilitate self-selection of frequency allocation tables (FAT) in postlingually deaf cochlear implant (CI) users. CIs use FATs to represent the tonotopic organization of a normal cochlea. Current CI fitting methods typically use a standard FAT for all patients regardless of individual differences in cochlear size and electrode location. In postlingually deaf patients, different amounts of mismatch can result between the frequency-place function they experienced when they had normal hearing and the frequency-place function that results from the standard FAT. For some CI users, an alternative FAT may enhance sound quality or speech perception. Currently, no widely available tools exist to aid real-time selection of different FATs. This study aims to develop a new smartphone tool for this purpose and to evaluate speech perception and sound quality measures in a pilot study of CI subjects using this application. A smartphone application for a widely available mobile platform (iOS) was developed to serve as a preprocessor of auditory input to a clinical CI speech processor and enable interactive real-time selection of FATs. The application's output was validated by measuring electrodograms for various inputs. A pilot study was conducted in six CI subjects. Speech perception was evaluated using word recognition tests. All subjects successfully used the portable application with their clinical speech processors to experience different FATs while listening to running speech. The users were all able to select one table that they judged provided the best sound quality. All subjects chose a FAT different from the standard FAT in their everyday clinical processor. Using the smartphone application, the mean consonant-nucleus-consonant score with the default FAT selection was 28.5% (SD 16.8) and 29.5% (SD 16.4) when using a self-selected FAT. A portable smartphone application enables CI users to self-select frequency allocation

Chloride channels as tools for developing selective insecticides.

Science.gov (United States)

Bloomquist, Jeffrey R

2003-12-01

Ligand-gated chloride channels underlie inhibition in excitable membranes and are proven target sites for insecticides. The gamma-aminobutyric acid (GABA(1)) receptor/chloride ionophore complex is the primary site of action for a number of currently used insecticides, such as lindane, endosulfan, and fipronil. These compounds act as antagonists by stabilizing nonconducting conformations of the chloride channel. Blockage of the GABA-gated chloride channel reduces neuronal inhibition, which leads to hyperexcitation of the central nervous system, convulsions, and death. We recently investigated the mode of action of the silphinenes, plant-derived natural compounds that structurally resemble picrotoxinin. These materials antagonize the action of GABA on insect neurons and block GABA-mediated chloride uptake into mouse brain synaptoneurosomes in a noncompetitive manner. In mammals, avermectins have a blocking action on the GABA-gated chloride channel consistent with a coarse tremor, whereas at longer times and higher concentrations, activation of the channel suppresses neuronal activity. Invertebrates display ataxia, paralysis, and death as the predominant signs of poisoning, with a glutamate-gated chloride channel playing a major role. Additional target sites for the avermectins or other chloride channel-directed compounds might include receptors gated by histamine, serotonin, or acetylcholine.The voltage-sensitive chloride channels form another large gene family of chloride channels. Voltage-dependent chloride channels are involved in a number of physiological processes including: maintenance of electrical excitability, chloride ion secretion and resorption, intravesicular acidification, and cell volume regulation. A subset of these channels is affected by convulsants and insecticides in mammals, although the role they play in acute lethality in insects is unclear. Given the wide range of functions that they mediate, these channels are also potential targets for

Ferrite Film Loaded Frequency Selective Metamaterials for Sub-GHz Applications

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Bo Gao

2016-12-01

Full Text Available Electromagnetic metamaterials are constructed with sub-wavelength structures that exhibit particular electromagnetic properties under a certain frequency range. Because the form-factor of the substructures has to be comparable to the wavelength of the operating frequency, few papers have discussed the metamaterials under GHz frequency. In this paper, we developed an innovative method to reduce the resonant frequency of metamaterals. By integrating the meta-structures with ferrite materials of higher permeability, the cell size of the meta-structure can be scaled down. This paper describes the methodology, design, and development of low-profile GHz ferrite loaded metamaterials. A ferrite film with a permeability of 20 could reduce the resonant frequency of metamaterials by up to 50%. A prototype has been fabricated and the measurement data align well with the simulation results. Because of the lowered operational frequency, the proposed ferrite loaded metamaterials offer more flexibility for various sub-GHz microwave applications, such as cloaks, absorbers, and frequency selective surfaces.

Membrane-tethered peptides patterned after the TRP domain (TRPducins) selectively inhibit TRPV1 channel activity.

Science.gov (United States)

Valente, Pierluigi; Fernández-Carvajal, Asia; Camprubí-Robles, María; Gomis, Ana; Quirce, Susana; Viana, Félix; Fernández-Ballester, Gregorio; González-Ros, José M; Belmonte, Carlos; Planells-Cases, Rosa; Ferrer-Montiel, Antonio

2011-05-01

The transient receptor potential vanilloid 1 (TRPV1) channel is a thermosensory receptor implicated in diverse physiological and pathological processes. The TRP domain, a highly conserved region in the C terminus adjacent to the internal channel gate, is critical for subunit tetramerization and channel gating. Here, we show that cell-penetrating, membrane-anchored peptides patterned after this protein domain are moderate and selective TRPV1 antagonists both in vitro and in vivo, blocking receptor activity in intact rat primary sensory neurons and their peripheral axons with mean decline time of 30 min. The most potent lipopeptide, TRP-p5, blocked all modes of TRPV1 gating with micromolar efficacy (IC(50)100 μM). TRP-p5 did not affect the capsaicin sensitivity of the vanilloid receptor. Our data suggest that TRP-p5 interferes with protein-protein interactions at the level of the TRP domain that are essential for the "conformational" change that leads to gate opening. Therefore, these palmitoylated peptides, which we termed TRPducins, are noncompetitive, voltage-independent, sequence-specific TRPV1 blockers. Our findings indicate that TRPducin-like peptides may embody a novel molecular strategy that can be exploited to generate a selective pharmacological arsenal for the TRP superfamily of ion channels.

Theoretical analysis and simulation of a code division multiple access system (cdma for secure signal transmission in wideband channels

Directory of Open Access Journals (Sweden)

Stevan M. Berber

2014-06-01

Full Text Available Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system.  The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used. Introduction Over the past years, the demand for wireless communications has increased substantially due to advancements in mobile communication systems and networks. Following these increasing demands, modern communication systems require the ability to handle a large number of users to process and transmit wideband signals through complex frequency selective channels. One of the techniques for transmission of multi-user signals is the

Differential Regulation of Action Potential Shape and Burst-Frequency Firing by BK and Kv2 Channels in Substantia Nigra Dopaminergic Neurons.

Science.gov (United States)

Kimm, Tilia; Khaliq, Zayd M; Bean, Bruce P

2015-12-16

Little is known about the voltage-dependent potassium currents underlying spike repolarization in midbrain dopaminergic neurons. Studying mouse substantia nigra pars compacta dopaminergic neurons both in brain slice and after acute dissociation, we found that BK calcium-activated potassium channels and Kv2 channels both make major contributions to the depolarization-activated potassium current. Inhibiting Kv2 or BK channels had very different effects on spike shape and evoked firing. Inhibiting Kv2 channels increased spike width and decreased the afterhyperpolarization, as expected for loss of an action potential-activated potassium conductance. BK inhibition also increased spike width but paradoxically increased the afterhyperpolarization. Kv2 channel inhibition steeply increased the slope of the frequency-current (f-I) relationship, whereas BK channel inhibition had little effect on the f-I slope or decreased it, sometimes resulting in slowed firing. Action potential clamp experiments showed that both BK and Kv2 current flow during spike repolarization but with very different kinetics, with Kv2 current activating later and deactivating more slowly. Further experiments revealed that inhibiting either BK or Kv2 alone leads to recruitment of additional current through the other channel type during the action potential as a consequence of changes in spike shape. Enhancement of slowly deactivating Kv2 current can account for the increased afterhyperpolarization produced by BK inhibition and likely underlies the very different effects on the f-I relationship. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. This work shows that BK calcium-activated potassium channels and Kv2 voltage-activated potassium channels both regulate action potentials in dopamine neurons of the substantia nigra pars compacta. Although both

Molecular Dynamics Simulations of Orai Reveal How the Third Transmembrane Segment Contributes to Hydration and Ca2+ Selectivity in Calcium Release-Activated Calcium Channels.

Science.gov (United States)

Alavizargar, Azadeh; Berti, Claudio; Ejtehadi, Mohammad Reza; Furini, Simone

2018-04-26

Calcium release-activated calcium (CRAC) channels open upon depletion of Ca 2+ from the endoplasmic reticulum, and when open, they are permeable to a selective flux of calcium ions. The atomic structure of Orai, the pore domain of CRAC channels, from Drosophila melanogaster has revealed many details about conduction and selectivity in this family of ion channels. However, it is still unclear how residues on the third transmembrane helix can affect the conduction properties of the channel. Here, molecular dynamics and Brownian dynamics simulations were employed to analyze how a conserved glutamate residue on the third transmembrane helix (E262) contributes to selectivity. The comparison between the wild-type and mutated channels revealed a severe impact of the mutation on the hydration pattern of the pore domain and on the dynamics of residues K270, and Brownian dynamics simulations proved that the altered configuration of residues K270 in the mutated channel impairs selectivity to Ca 2+ over Na + . The crevices of water molecules, revealed by molecular dynamics simulations, are perfectly located to contribute to the dynamics of the hydrophobic gate and the basic gate, suggesting a possible role in channel opening and in selectivity function.

Frequency selective bolometer development at Argonne National Laboratory

Science.gov (United States)

Datesman, Aaron; Pearson, John; Wang, Gensheng; Yefremenko, Volodymyr; Divan, Ralu; Downes, Thomas; Chang, Clarence; McMahon, Jeff; Meyer, Stephan; Carlstrom, John; Logan, Daniel; Perera, Thushara; Wilson, Grant; Novosad, Valentyn

2008-07-01

We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

Practical implementation of Channelized Hotelling Observers: Effect of ROI size.

Science.gov (United States)

Ferrero, Andrea; Favazza, Christopher P; Yu, Lifeng; Leng, Shuai; McCollough, Cynthia H

2017-03-01

Fundamental to the development and application of channelized Hotelling observer (CHO) models is the selection of the region of interest (ROI) to evaluate. For assessment of medical imaging systems, reducing the ROI size can be advantageous. Smaller ROIs enable a greater concentration of interrogable objects in a single phantom image, thereby providing more information from a set of images and reducing the overall image acquisition burden. Additionally, smaller ROIs may promote better assessment of clinical patient images as different patient anatomies present different ROI constraints. To this end, we investigated the minimum ROI size that does not compromise the performance of the CHO model. In this study, we evaluated both simulated images and phantom CT images to identify the minimum ROI size that resulted in an accurate figure of merit (FOM) of the CHO's performance. More specifically, the minimum ROI size was evaluated as a function of the following: number of channels, spatial frequency and number of rotations of the Gabor filters, size and contrast of the object, and magnitude of the image noise. Results demonstrate that a minimum ROI size exists below which the CHO's performance is grossly inaccurate. The minimum ROI size is shown to increase with number of channels and be dictated by truncation of lower frequency filters. We developed a model to estimate the minimum ROI size as a parameterized function of the number of orientations and spatial frequencies of the Gabor filters, providing a guide for investigators to appropriately select parameters for model observer studies.

Two-photon direct frequency comb spectroscopy of alkali atoms

Science.gov (United States)

Palm, Christopher; Pradhananga, Trinity; Nguyen, Khoa; Montcrieffe, Caitlin; Kimball, Derek

2012-11-01

We have studied transition frequencies and excited state hyperfine structure in rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the rubidium vapor. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. An interesting dependence of the 2-photon spectrum on the energy of the intermediate state of the 2-photon transition is discussed. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Optimal Superimposed Training Sequences for Channel Estimation in MIMO-OFDM Systems

Directory of Open Access Journals (Sweden)

Ratnam V. Raja Kumar

2010-01-01

Full Text Available In this work an iterative time domain Least Squares (LS based channel estimation method using superimposed training (ST for a Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM system over time varying frequency selective fading channels is proposed. The performance of the channel estimator is analyzed in terms of the Mean Square Estimation Error (MSEE and its impact on the uncoded Bit Error Rate (BER of the MIMO-OFDM system is studied. A new selection criterion for the training sequences that jointly optimizes the MSEE and the BER of the OFDM system is proposed. Chirp based sequences are proposed and shown to satisfy the same. These are compared with the other sequences proposed in the literature and are found to yield a superior performance. The sequences, one for each transmitting antenna, offers fairness through providing equal interference in all the data carriers unlike earlier proposals. The effectiveness of the mathematical analysis presented is demonstrated through a comparison with the simulation studies. Experimental studies are carried out to study and validate the improved performance of the proposed scheme. The scheme is applied to the IEEE 802.16e OFDM standard and a case is made with the required design of the sequence.

Multi-frequency Defect Selective Imaging via Nonlinear Ultrasound

Science.gov (United States)

Solodov, Igor; Busse, Gerd

The concept of defect-selective ultrasonic nonlinear imaging is based on visualization of strongly nonlinear inclusions in the form of localized cracked defects. For intense excitation, the ultrasonic response of defects is affected by mechanical constraint between their fragments that makes their vibrations extremely nonlinear. The cracked flaws, therefore, efficiently generate multiple new frequencies, which can be used as a nonlinear "tag" to detect and image them. In this paper, the methodologies of nonlinear scanning laser vibrometry (NSLV) and nonlinear air-coupled emission (NACE) are applied for nonlinear imaging of various defects in hi-tech and constructional materials. A broad database obtained demonstrates evident advantages of the nonlinear approach over its linear counterpart. The higher-order nonlinear frequencies provide increase in signal-to-noise ratio and enhance the contrast of imaging. Unlike conventional ultrasonic instruments, the nonlinear approach yields abundant multi-frequency information on defect location. The application of image recognition and processing algorithms is described and shown to improve reliability and quality of ultrasonic imaging.

Harnessing mode-selective nonlinear optics for on-chip multi-channel all-optical signal processing

Directory of Open Access Journals (Sweden)

Ming Ma

2016-11-01

Full Text Available All-optical signal processing based on nonlinear optical effects allows for the realization of important functions in telecommunications including wavelength conversion, optical multiplexing/demultiplexing, Fourier transformation, and regeneration, amongst others, on ultrafast time scales to support high data rate transmission. In integrated photonic subsystems, the majority of all-optical signal processing systems demonstrated to date typically process only a single channel at a time or perform a single processing function, which imposes a serious limitation on the functionality of integrated solutions. Here, we demonstrate how nonlinear optical effects can be harnessed in a mode-selective manner to perform simultaneous multi-channel (two and multi-functional optical signal processing (i.e., regenerative wavelength conversion in an integrated silicon photonic device. This approach, which can be scaled to a higher number of channels, opens up a new degree of freedom for performing a broad range of multi-channel nonlinear optical signal processing functions using a single integrated photonic device.

Compressive Sensing Based Bayesian Sparse Channel Estimation for OFDM Communication Systems: High Performance and Low Complexity

Science.gov (United States)

Xu, Li; Shan, Lin; Adachi, Fumiyuki

2014-01-01

In orthogonal frequency division modulation (OFDM) communication systems, channel state information (CSI) is required at receiver due to the fact that frequency-selective fading channel leads to disgusting intersymbol interference (ISI) over data transmission. Broadband channel model is often described by very few dominant channel taps and they can be probed by compressive sensing based sparse channel estimation (SCE) methods, for example, orthogonal matching pursuit algorithm, which can take the advantage of sparse structure effectively in the channel as for prior information. However, these developed methods are vulnerable to both noise interference and column coherence of training signal matrix. In other words, the primary objective of these conventional methods is to catch the dominant channel taps without a report of posterior channel uncertainty. To improve the estimation performance, we proposed a compressive sensing based Bayesian sparse channel estimation (BSCE) method which cannot only exploit the channel sparsity but also mitigate the unexpected channel uncertainty without scarifying any computational complexity. The proposed method can reveal potential ambiguity among multiple channel estimators that are ambiguous due to observation noise or correlation interference among columns in the training matrix. Computer simulations show that proposed method can improve the estimation performance when comparing with conventional SCE methods. PMID:24983012

Optically transparent frequency selective surfaces on flexible thin plastic substrates

Energy Technology Data Exchange (ETDEWEB)

Dewani, Aliya A., E-mail: a.ashraf@griffith.edu.au; O’Keefe, Steven G.; Thiel, David V.; Galehdar, Amir [School Of Electrical Engineering, Griffith University, Brisbane, 4111 (Australia)

2015-02-15

A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

Optically transparent frequency selective surfaces on flexible thin plastic substrates

Directory of Open Access Journals (Sweden)

Aliya A. Dewani

2015-02-01

Full Text Available A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm, flexible transparent plastic substrate (relative permittivity 3.2. It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

Optically transparent frequency selective surfaces on flexible thin plastic substrates

Science.gov (United States)

Dewani, Aliya A.; O'Keefe, Steven G.; Thiel, David V.; Galehdar, Amir

2015-02-01

A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

Wideband optical vector network analyzer based on optical single-sideband modulation and optical frequency comb.

Science.gov (United States)

Xue, Min; Pan, Shilong; He, Chao; Guo, Ronghui; Zhao, Yongjiu

2013-11-15

A novel approach to increase the measurement range of the optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation is proposed and experimentally demonstrated. In the proposed system, each comb line in an optical frequency comb (OFC) is selected by an optical filter and used as the optical carrier for the OSSB-based OVNA. The frequency responses of an optical device-under-test (ODUT) are thus measured channel by channel. Because the comb lines in the OFC have fixed frequency spacing, by fitting the responses measured in all channels together, the magnitude and phase responses of the ODUT can be accurately achieved in a large range. A proof-of-concept experiment is performed. A measurement range of 105 GHz and a resolution of 1 MHz is achieved when a five-comb-line OFC with a frequency spacing of 20 GHz is applied to measure the magnitude and phase responses of a fiber Bragg grating.

Microwave frequency sensor for detection of biological cells in microfluidic channels.

Science.gov (United States)

Nikolic-Jaric, M; Romanuik, S F; Ferrier, G A; Bridges, G E; Butler, M; Sunley, K; Thomson, D J; Freeman, M R

2009-08-12

We present details of an apparatus for capacitive detection of biomaterials in microfluidic channels operating at microwave frequencies where dielectric effects due to interfacial polarization are minimal. A circuit model is presented, which can be used to adapt this detection system for use in other microfluidic applications and to identify ones where it would not be suitable. The detection system is based on a microwave coupled transmission line resonator integrated into an interferometer. At 1.5 GHz the system is capable of detecting changes in capacitance of 650 zF with a 50 Hz bandwidth. This system is well suited to the detection of biomaterials in a variety of suspending fluids, including phosphate-buffered saline. Applications involving both model particles (polystyrene microspheres) and living cells-baker's yeast (Saccharomyces cerevisiae) and Chinese hamster ovary cells-are presented.

Study of Internal Channel Surface Roughnesses Manufactured by Selective Laser Melting in Aluminum and Titanium Alloys

Science.gov (United States)

Pakkanen, Jukka; Calignano, Flaviana; Trevisan, Francesco; Lorusso, Massimo; Ambrosio, Elisa Paola; Manfredi, Diego; Fino, Paolo

2016-08-01

Interest in additive manufacturing (AM) has gained considerable impetus over the past decade. One of the driving factors for AM success is the ability to create unique designs with intrinsic characteristics as, e.g., internal channels used for hydraulic components, cooling channels, and heat exchangers. However, a couple of the main problems in internal channels manufactured by AM technologies are the high surface roughness obtained and the distortion of the channel shape. There is still much to understand in these design aspects. In this study, a cylindrical geometry for internal channels to be built with different angles with respect to the building plane in AlSi10Mg and Ti6Al4V alloys by selective laser melting was considered. The internal surfaces of the channels produced in both materials were analyzed by means of a surface roughness tester and by optical and electron microscopy to evaluate the effects of the material and design choices.

An adaptation method to improve secret key rates of time-frequency QKD in atmospheric turbulence channels

Science.gov (United States)

Sun, Xiaole; Djordjevic, Ivan B.; Neifeld, Mark A.

2016-03-01

Free-space optical (FSO) channels can be characterized by random power fluctuations due to atmospheric turbulence, which is known as scintillation. Weak coherent source based FSO quantum key distribution (QKD) systems suffer from the scintillation effect because during the deep channel fading the expected detection rate drops, which then gives an eavesdropper opportunity to get additional information about protocol by performing photon number splitting (PNS) attack and blocking single-photon pulses without changing QBER. To overcome this problem, in this paper, we study a large-alphabet QKD protocol, which is achieved by using pulse-position modulation (PPM)-like approach that utilizes the time-frequency uncertainty relation of the weak coherent photon state, called here TF-PPM-QKD protocol. We first complete finite size analysis for TF-PPM-QKD protocol to give practical bounds against non-negligible statistical fluctuation due to finite resources in practical implementations. The impact of scintillation under strong atmospheric turbulence regime is studied then. To overcome the secure key rate performance degradation of TF-PPM-QKD caused by scintillation, we propose an adaptation method for compensating the scintillation impact. By changing source intensity according to the channel state information (CSI), obtained by classical channel, the adaptation method improves the performance of QKD system with respect to the secret key rate. The CSI of a time-varying channel can be predicted using stochastic models, such as autoregressive (AR) models. Based on the channel state predictions, we change the source intensity to the optimal value to achieve a higher secret key rate. We demonstrate that the improvement of the adaptation method is dependent on the prediction accuracy.

47 CFR 87.475 - Frequencies.

Science.gov (United States)

2010-10-01

... with simultaneous radiotelephone channels and their associated glide path station frequency from the...) VHF omni-range (VOR) stations are to be assigned frequencies in the 112.050-117.950 MHz band (50 kHz channel spacing) and the following frequencies in the 108-112 MHz band: 108.200 108.250 108.400 108.450...

ASIC and ENaC type sodium channels: conformational states and the structures of the ion selectivity filters.

Science.gov (United States)

Hanukoglu, Israel

2017-02-01

The acid-sensing ion channels (ASICs) and epithelial sodium channels (ENaC) are members of a superfamily of channels that play critical roles in mechanosensation, chemosensation, nociception, and regulation of blood volume and pressure. These channels look and function like a tripartite funnel that directs the flow of Na + ions into the cytoplasm via the channel pore in the membrane. The subunits that form these channels share a common structure with two transmembrane segments (TM1 and TM2) and a large extracellular part. In most vertebrates, there are five paralogous genes that code for ASICs (ASIC1-ASIC5), and four for ENaC subunits alpha, beta, gamma, and delta (α, β, γ, and δ). While ASICs can form functional channels as a homo- or heterotrimer, ENaC functions as an obligate heterotrimer composed of α-β-γ or β-γ-δ subunits. The structure of ASIC has been determined in several conformations, including desensitized and open states. This review presents a comparison of the structures of these states using easy-to-understand molecular models of the full complex, the central tunnel that includes an outer vestibule, the channel pore, and ion selectivity filter. The differences in the secondary, tertiary, and quaternary structures of the states are summarized to pinpoint the conformational changes responsible for channel opening. Results of site-directed mutagenesis studies of ENaC subunits are examined in light of ASIC1 models. Based on these comparisons, a molecular model for the selectivity filter of ENaC is built by in silico mutagenesis of an ASIC1 structure. These models suggest that Na + ions pass through the filter in a hydrated state. © 2016 Federation of European Biochemical Societies.

Eight channel fast scalar

Energy Technology Data Exchange (ETDEWEB)

Waddoup, W D; Stubbs, R J [Durham Univ. (UK)

1977-11-01

An eight channel 64-bit scaler has been constructed with a static CMOS memory. Scaling frequencies are independently variable, at each channel, as are the number of bits/channel. The scaler, when used in conjunction with a multichannel charge to time converter results in a very flexible, gated multichannel ADC.

Low-frequency 1/f noise in MoS2 transistors: Relative contributions of the channel and contacts

International Nuclear Information System (INIS)

Renteria, J.; Jiang, C.; Samnakay, R.; Rumyantsev, S. L.; Goli, P.; Balandin, A. A.; Shur, M. S.

2014-01-01

We report on the results of the low-frequency (1/f, where f is frequency) noise measurements in MoS 2 field-effect transistors revealing the relative contributions of the MoS 2 channel and Ti/Au contacts to the overall noise level. The investigation of the 1/f noise was performed for both as fabricated and aged transistors. It was established that the McWhorter model of the carrier number fluctuations describes well the 1/f noise in MoS 2 transistors, in contrast to what is observed in graphene devices. The trap densities extracted from the 1/f noise data for MoS 2 transistors, are 2 × 10 19  eV −1 cm −3 and 2.5 × 10 20  eV −1 cm −3 for the as fabricated and aged devices, respectively. It was found that the increase in the noise level of the aged MoS 2 transistors is due to the channel rather than the contact degradation. The obtained results are important for the proposed electronic applications of MoS 2 and other van der Waals materials

Channel-morphology data for the Tongue River and selected tributaries, southeastern Montana, 2001-02

Science.gov (United States)

Chase, Katherine J.

2004-01-01

Coal-bed methane exploration and production have begun within the Tongue River watershed in southeastern Montana. The development of coal-bed methane requires production of large volumes of ground water, some of which may be discharged to streams, potentially increasing stream discharge and sediment load. Changes in stream discharge or sediment load may result in changes to channel morphology through changes in erosion and vegetation. These changes might be subtle and difficult to detect without baseline data that indicate stream-channel conditions before extensive coal-bed methane development began. In order to provide this baseline channel-morphology data, the U.S. Geological Survey, in cooperation with the Bureau of Land Management, collected channel-morphology data in 2001-02 to document baseline conditions for several reaches along the Tongue River and selected tributaries. This report presents channel-morphology data for five sites on the mainstem Tongue River and four sites on its tributaries. Bankfull, water-surface, and thalweg elevations, channel sections, and streambed-particle sizes were measured along reaches near streamflow-gaging stations. At each site, the channel was classified using methods described by Rosgen. For six sites, bankfull discharge was determined from the stage- discharge relation at the gage for the stage corresponding to the bankfull elevation. For three sites, the step-backwater computer model HEC-RAS was used to estimate bankfull discharge. Recurrence intervals for the bankfull discharge also were estimated for eight of the nine sites. Channel-morphology data for each site are presented in maps, tables, graphs, and photographs.

LOCO - a linearised model for analysing the onset of coolant oscillations and frequency response of boiling channels

International Nuclear Information System (INIS)

Romberg, T.M.

1982-12-01

Industrial plant such as heat exchangers and nuclear and conventional boilers are prone to coolant flow oscillations which may not be detected. In this report, a hydrodynamic model is formulated in which the one-dimensional, non-linear, partial differential equations for the conservation of mass, energy and momentum are perturbed with respect to time, linearised, and Laplace-transformed into the s-domain for frequency response analysis. A computer program has been developed to integrate numerically the resulting non-linear ordinary differential equations by finite difference methods. A sample problem demonstrates how the computer code is used to analyse the frequency response and flow stability characteristics of a heated channel

Vast Volatility Matrix Estimation using High Frequency Data for Portfolio Selection*

Science.gov (United States)

Fan, Jianqing; Li, Yingying; Yu, Ke

2012-01-01

Portfolio allocation with gross-exposure constraint is an effective method to increase the efficiency and stability of portfolios selection among a vast pool of assets, as demonstrated in Fan et al. (2011). The required high-dimensional volatility matrix can be estimated by using high frequency financial data. This enables us to better adapt to the local volatilities and local correlations among vast number of assets and to increase significantly the sample size for estimating the volatility matrix. This paper studies the volatility matrix estimation using high-dimensional high-frequency data from the perspective of portfolio selection. Specifically, we propose the use of “pairwise-refresh time” and “all-refresh time” methods based on the concept of “refresh time” proposed by Barndorff-Nielsen et al. (2008) for estimation of vast covariance matrix and compare their merits in the portfolio selection. We establish the concentration inequalities of the estimates, which guarantee desirable properties of the estimated volatility matrix in vast asset allocation with gross exposure constraints. Extensive numerical studies are made via carefully designed simulations. Comparing with the methods based on low frequency daily data, our methods can capture the most recent trend of the time varying volatility and correlation, hence provide more accurate guidance for the portfolio allocation in the next time period. The advantage of using high-frequency data is significant in our simulation and empirical studies, which consist of 50 simulated assets and 30 constituent stocks of Dow Jones Industrial Average index. PMID:23264708

Vast Volatility Matrix Estimation using High Frequency Data for Portfolio Selection.

Science.gov (United States)

Fan, Jianqing; Li, Yingying; Yu, Ke

2012-01-01

Portfolio allocation with gross-exposure constraint is an effective method to increase the efficiency and stability of portfolios selection among a vast pool of assets, as demonstrated in Fan et al. (2011). The required high-dimensional volatility matrix can be estimated by using high frequency financial data. This enables us to better adapt to the local volatilities and local correlations among vast number of assets and to increase significantly the sample size for estimating the volatility matrix. This paper studies the volatility matrix estimation using high-dimensional high-frequency data from the perspective of portfolio selection. Specifically, we propose the use of "pairwise-refresh time" and "all-refresh time" methods based on the concept of "refresh time" proposed by Barndorff-Nielsen et al. (2008) for estimation of vast covariance matrix and compare their merits in the portfolio selection. We establish the concentration inequalities of the estimates, which guarantee desirable properties of the estimated volatility matrix in vast asset allocation with gross exposure constraints. Extensive numerical studies are made via carefully designed simulations. Comparing with the methods based on low frequency daily data, our methods can capture the most recent trend of the time varying volatility and correlation, hence provide more accurate guidance for the portfolio allocation in the next time period. The advantage of using high-frequency data is significant in our simulation and empirical studies, which consist of 50 simulated assets and 30 constituent stocks of Dow Jones Industrial Average index.

λ-Selection Strategy in C+L Band 1-Pbit/s (448 WDM/19-Core/128 Gbit/s/channel) Flex-Grid Space Division Multiplexed Transmission

DEFF Research Database (Denmark)

Asif, Rameez; Ye, Feihong; Morioka, Toshio

2015-01-01

In this paper, an inter-core crosstalk based wavelength selection scheme has been proposed for flex-grid superchannels in space division multiplexed transmission. The two λ-selection strategies are categorized as: (a) aligned wavelength super-channels (Aλ-SCs), where all super-channels are placed...... at same λ in all the cores and (b) interleaved wavelength super-channels (Iλ-SCs), where all super-channels are placed at different λ in all the neighboring cores. It is depicted that system performance is improved for DP-16QAM channels in 1-Pbit/s (448 WDM/19 Core/128 Gbit/s/channel) 60 km fiber link...

Frequency Selective Surfaces for extended Bandwidth backing reflector functions

NARCIS (Netherlands)

Pasian, M.; Neto, A.; Monni, S.; Ettorre, M.; Gerini, G.

2008-01-01

This paper deals with the use of Frequency Selective Surfaces (FSS) to increase the Efficiency × Bandwidth product in Ultra-Wide Band (UWB) antenna arrays whose efficiency is limited by the front-to-back ratio. If the backing reflector is realized in one metal plane solution its location will be

Selective blockade of TRPA1 channel attenuates pathological pain without altering noxious cold sensation or body temperature regulation.

Science.gov (United States)

Chen, Jun; Joshi, Shailen K; DiDomenico, Stanley; Perner, Richard J; Mikusa, Joe P; Gauvin, Donna M; Segreti, Jason A; Han, Ping; Zhang, Xu-Feng; Niforatos, Wende; Bianchi, Bruce R; Baker, Scott J; Zhong, Chengmin; Simler, Gricelda H; McDonald, Heath A; Schmidt, Robert G; McGaraughty, Steve P; Chu, Katharine L; Faltynek, Connie R; Kort, Michael E; Reilly, Regina M; Kym, Philip R

2011-05-01

Despite the increasing interest in TRPA1 channel as a pain target, its role in cold sensation and body temperature regulation is not clear; the efficacy and particularly side effects resulting from channel blockade remain poorly understood. Here we use a potent, selective, and bioavailable antagonist to address these issues. A-967079 potently blocks human (IC(50): 51 nmol/L, electrophysiology, 67 nmol/L, Ca(2+) assay) and rat TRPA1 (IC(50): 101 nmol/L, electrophysiology, 289 nmol/L, Ca(2+) assay). It is >1000-fold selective over other TRP channels, and is >150-fold selective over 75 other ion channels, enzymes, and G-protein-coupled receptors. Oral dosing of A-967079 produces robust drug exposure in rodents, and exhibits analgesic efficacy in allyl isothiocyanate-induced nocifensive response and osteoarthritic pain in rats (ED(50): 23.2 mg/kg, p.o.). A-967079 attenuates cold allodynia produced by nerve injury but does not alter noxious cold sensation in naive animals, suggesting distinct roles of TRPA1 in physiological and pathological states. Unlike TRPV1 antagonists, A-967079 does not alter body temperature. It also does not produce locomotor or cardiovascular side effects. Collectively, these data provide novel insights into TRPA1 function and suggest that the selective TRPA1 blockade may present a viable strategy for alleviating pain without untoward side effects. Copyright © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Multi-Channel Electroencephalogram (EEG) Signal Acquisition and its Effective Channel selection with De-noising Using AWICA for Biometric System

OpenAIRE

B.Sabarigiri; D.Suganyadevi

2014-01-01

the embedding of low cost electroencephalogram (EEG) sensors in wireless headsets gives improved authentication based on their brain wave signals has become a practical opportunity. In this paper signal acquisition along with effective multi-channel selection from a specific area of the brain and denoising using AWICA methods are proposed for EEG based personal identification. At this point, to develop identification system the steps are as follows. (i) the high-quality device with the least ...

Alcohol marketing in televised international football: frequency analysis.

Science.gov (United States)

Adams, Jean; Coleman, James; White, Martin

2014-05-20

Alcohol marketing includes sponsorship of individuals, organisations and sporting events. Football (soccer) is one of the most popular spectator sports worldwide. No previous studies have quantified the frequency of alcohol marketing in a high profile international football tournament. The aims were to determine: the frequency and nature of visual references to alcohol in a representative sample of EURO2012 matches broadcast in the UK; and if frequency or nature varied between matches broadcast on public service and commercial channels, or between matches that did and did not feature England. Eight matches selected by stratified random sampling were recorded. All visual references to alcohol were identified using a tool with high inter-rater reliability. 1846 visual references to alcohol were identified over 1487 minutes of broadcast--an average of 1.24 references per minute. The mean number of references per minute was higher in matches that did vs did not feature England (p = 0.004), but did not differ between matches broadcast on public service vs commercial channels (p = 0.92). The frequency of visual references to alcohol was universally high and higher in matches featuring the only UK home team--England--suggesting that there may be targeting of particularly highly viewed matches. References were embedded in broadcasts, and not particular to commercial channels including paid-for advertising. New UK codes-of-conduct on alcohol marketing at sporting events will not reduce the level of marketing reported here.

Effects of high frequency fluctuations on DNS of turbulent open-channel flow with high Pr passive scalar transport

International Nuclear Information System (INIS)

Yamamoto, Yoshinobu; Kunugi, Tomoaki; Serizawa, Akimi

2002-01-01

In this study, investigation on effects of high frequency fluctuations on DNS of turbulent open-channel flows with high Pr passive scalar transport was conducted. As the results, although significant differences of energy spectra behaviors in temperature fields, are caused at high wave number region where insignificant area for velocity components, large difference dose not caused in mean and statistic behaviors in temperature component. But, if the buoyancy were considered, this temperature high-frequency fluctuations would be greatly changed mean and statistics behaviors from the difference of the accuracy and resolution at high wave number region. (author)

Drainage basins, channels, and flow characteristics of selected streams in central Pennsylvania

Science.gov (United States)

Brush, Lucien M.

1961-01-01

The hydraulic, basin, and geologic characteristics of 16 selected streams in central Pennsylvania were measured for the purpose of studying the relations among these general characteristics and their process of development. The basic parameters which were measured include bankfull width and depth, channel slope, bed material size and shape, length of stream from drainage divide, and size of drainage area. The kinds of bedrock over which the streams flow were noted. In these streams the bankfull channel is filled by flows approximating the 2.3-year flood. By measuring the breadth and mean depth of the channel, it was possible to compute the bankfull mean velocity for each of the 119 sampling stations. These data were then used to compute the downstream changes in hydraulic geometry of the streams studied. This method has been called an indirect computation of the hydraulic geometry. The results obtained by the indirect method are similar to those of the direct method of other workers. The basins were studied by examining the relations of drainage area, discharge, and length of stream from drainage divide. For the streams investigated, excellent correlations were found to exist between drainage area and the 2.3-year flood, as well as between length of stream from the basin divide and drainage area. From these correlations it is possible to predict the discharge for the 2.3-year flood at any arbitrary point along the length of the stream. The long, intermediate, and short axes of pebbles sampled from the bed of the stream were recorded to study both size and sphericity changes along individual streams and among the streams studied. No systematic downstream changes in sphericity were found. Particle size changes are erratic and show no consistent relation to channel slope. Particle size decreases downstream in many streams but remains constant or increases in others. Addition of material by tributaries is one factor affecting particle size and another is the parent

Effect of efferent activation on binaural frequency selectivity.

Science.gov (United States)

Verhey, Jesko L; Kordus, Monika; Drga, Vit; Yasin, Ifat

2017-07-01

Binaural notched-noise experiments indicate a reduced frequency selectivity of the binaural system compared to monaural processing. The present study investigates how auditory efferent activation (via the medial olivocochlear system) affects binaural frequency selectivity in normal-hearing listeners. Thresholds were measured for a 1-kHz signal embedded in a diotic notched-noise masker for various notch widths. The signal was either presented in phase (diotic) or in antiphase (dichotic), gated with the noise. Stimulus duration was 25 ms, in order to avoid efferent activation due to the masker or the signal. A bandpass-filtered noise precursor was presented prior to the masker and signal stimuli to activate the efferent system. The silent interval between the precursor and the masker-signal complex was 50 ms. For comparison, thresholds for detectability of the masked signal were also measured in a baseline condition without the precursor and, in addition, without the masker. On average, the results of the baseline condition indicate an effectively wider binaural filter, as expected. For both signal phases, the addition of the precursor results in effectively wider filters, which is in agreement with the hypothesis that cochlear gain is reduced due to the presence of the precursor. Copyright © 2017 Elsevier B.V. All rights reserved.

Selective spider toxins reveal a role for Nav1.1 channel in mechanical pain

Science.gov (United States)

Osteen, Jeremiah D.; Herzig, Volker; Gilchrist, John; Emrick, Joshua J.; Zhang, Chuchu; Wang, Xidao; Castro, Joel; Garcia-Caraballo, Sonia; Grundy, Luke; Rychkov, Grigori Y.; Weyer, Andy D.; Dekan, Zoltan; Undheim, Eivind A. B.; Alewood, Paul; Stucky, Cheryl L.; Brierley, Stuart M.; Basbaum, Allan I.; Bosmans, Frank; King, Glenn F.; Julius, David

2016-01-01

Voltage-gated sodium (Nav) channels initiate action potentials in most neurons, including primary afferent nerve fibers of the pain pathway. Local anesthetics block pain through non-specific actions at all Nav channels, but the discovery of selective modulators would facilitate the analysis of individual subtypes and their contributions to chemical, mechanical, or thermal pain. Here, we identify and characterize spider toxins that selectively activate the Nav1.1 subtype, whose role in nociception and pain has not been explored. We exploit these probes to demonstrate that Nav1.1-expressing fibers are modality-specific nociceptors: their activation elicits robust pain behaviors without neurogenic inflammation and produces profound hypersensitivity to mechanical, but not thermal, stimuli. In the gut, high-threshold mechanosensitive fibers also express Nav1.1 and show enhanced toxin sensitivity in a model of irritable bowel syndrome. Altogether, these findings establish an unexpected role for Nav1.1 in regulating the excitability of sensory nerve fibers that underlie mechanical pain. PMID:27281198

Analysis of Various Frequency Selective Shielding Glass by FDTD method

OpenAIRE

笠嶋, 善憲; Kasashima, Yoshinori

2012-01-01

A frequency Selective shielding (FSS) glass is a print of many same size antennas on a sheet of glass, and it has high shielding properties for one specific frequency. This time, the author analyzed characteristics of various FSSs whose antenna types are different by FDTD method. The antenna types are cross dipole, circular loop, square loop, circular patch, and square patch. As the result, the FSSs can be composed of the various types of the antennas, and the FSSs have broad-band shielding c...

Some characteristic features of the construction of the amplifying channel for working with semiconductor detectors in the charged particle energy spectrometer. [noise minimization at preamplifier input

Science.gov (United States)

Kuzyuta, E. I.

1974-01-01

A transistorized spectrometric amplifier with a shaper is reported that selects the shape of the frequency characteristic of the amplifying channel for which the primary frequency spectrum of the signal will pass, but where the noise spectrum is limited to the maximum. A procedure is presented for selecting the shaping circuits and their inclusion principles.

The effect of training frequency on selected physical and ...

African Journals Online (AJOL)

They were randomly selected into 3 groups of 20 each. Groups A and B served as the training groups while group C formed the control group which remained sedentary, and followed their normal lifestyle. The experimental groups (A & B) initially trained for 12 weeks at a training frequency of 3 times a week. This was ...

Activity of the anticonvulsant lacosamide in experimental and human epilepsy via selective effects on slow Na+ channel inactivation.

Science.gov (United States)

Holtkamp, Dominik; Opitz, Thoralf; Niespodziany, Isabelle; Wolff, Christian; Beck, Heinz

2017-01-01

In human epilepsy, pharmacoresistance to antiepileptic drug therapy is a major problem affecting ~30% of patients with epilepsy. Many classical antiepileptic drugs target voltage-gated sodium channels, and their potent activity in inhibiting high-frequency firing has been attributed to their strong use-dependent blocking action. In chronic epilepsy, a loss of use-dependent block has emerged as a potential cellular mechanism of pharmacoresistance for anticonvulsants acting on voltage-gated sodium channels. The anticonvulsant drug lacosamide (LCM) also targets sodium channels, but has been shown to preferentially affect sodium channel slow inactivation processes, in contrast to most other anticonvulsants. We used whole-cell voltage clamp recordings in acutely isolated cells to investigate the effects of LCM on transient Na + currents. Furthermore, we used whole-cell current clamp recordings to assess effects on repetitive action potential firing in hippocampal slices. We show here that LCM exerts its effects primarily via shifting the slow inactivation voltage dependence to more hyperpolarized potentials in hippocampal dentate granule cells from control and epileptic rats, and from patients with epilepsy. It is important to note that this activity of LCM was maintained in chronic experimental and human epilepsy. Furthermore, we demonstrate that the efficacy of LCM in inhibiting high-frequency firing is undiminished in chronic experimental and human epilepsy. Taken together, these results show that LCM exhibits maintained efficacy in chronic epilepsy, in contrast to conventional use-dependent sodium channel blockers such as carbamazepine. They also establish that targeting slow inactivation may be a promising strategy for overcoming target mechanisms of pharmacoresistance. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

Directory of Open Access Journals (Sweden)

Roman Kusche

2017-10-01

Full Text Available Bioimpedance measurements have become a useful technique in the past several years in biomedical engineering. Especially, multi-channel measurements facilitate new imaging and patient monitoring techniques. While most instrumentation research has focused on signal acquisition and signal processing, this work proposes the design of an excitation current source module that can be easily implemented in existing or upcoming bioimpedance measurement systems. It is galvanically isolated to enable simultaneous multi-channel bioimpedance measurements with a very low channel-coupling. The system is based on a microcontroller in combination with a voltage-controlled current source circuit. It generates selectable sinusoidal excitation signals between 0.12 and 1.5 mA in a frequency range from 12 to 250 kHz, whereas the voltage compliance range is ±3.2 V. The coupling factor between two current sources, experimentally galvanically connected with each other, is measured to be less than −48 dB over the entire intended frequency range. Finally, suggestions for developments in the future are made.

Application of a Channel Estimation Algorithm to Spectrum Sensing in a Cognitive Radio Context

Directory of Open Access Journals (Sweden)

Vincent Savaux

2014-01-01

Full Text Available This paper deals with spectrum sensing in an orthogonal frequency division multiplexing (OFDM context, allowing an opportunistic user to detect a vacant spectrum resource in a licensed band. The proposed method is based on an iterative algorithm used for the joint estimation of noise variance and frequency selective channel. It can be seen as a second-order detector, since it is performed by means of the minimum mean square error criterion. The main advantage of the proposed algorithm is its capability to perform spectrum sensing, noise variance estimation, and channel estimation in the presence of a signal. Furthermore, the sensing duration is limited to only one OFDM symbol. We theoretically show the convergence of the algorithm, and we derive its analytical detection and false alarm probabilities. Furthermore, we show that the detector is very efficient, even for low SNR values, and is robust against a channel uncertainty.

Monitoring Voltage-Dependent Charge Displacement of Shaker B-IR K+ Ion Channels Using Radio Frequency Interrogation

OpenAIRE

Dharia, Sameera; Rabbitt, Richard D.

2011-01-01

Here we introduce a new technique that probes voltage-dependent charge displacements of excitable membrane-bound proteins using extracellularly applied radio frequency (RF, 500 kHz) electric fields. Xenopus oocytes were used as a model cell for these experiments, and were injected with cRNA encoding Shaker B-IR (ShB-IR) K(+) ion channels to express large densities of this protein in the oocyte membranes. Two-electrode voltage clamp (TEVC) was applied to command whole-cell membrane potential a...

On the possibility of a quantum bremsstrahlung induced self-modulation of a relativistic beam channeling in crystals

International Nuclear Information System (INIS)

Vysotskij, V.I.; Vorontsov, V.I.; Kuz'min, R.N.

1987-01-01

Physical predictions and quantitative estimations of a new physical effect - the phenomenon of quantum bremsstrahlung induced selfmodulation of a fast beam channeling in the crystals are considered and carried out. The occurrence of induced self-modulation results from nonstationary interference of proper waves of a channeled particle in the range of mutual coherence and with account of difference of selective bremsstrahlung losses of these waves. The modulation frequency for superrelativistic particles is shown to lie within the range from soft X-ray to hard gamma range. It proceeds from the estimations that modulation at these frequencies is preserved within the limits of macroscopically large ranges after the crystal attaining several meters. The maximum frequency of modulation for nonrelativistic heavy particles (protons) corresponds to the optical range

Efficient and Robust Detection of GFSK Signals under Dispersive Channel, Modulation Index, and Carrier Frequency Offset Conditions

Directory of Open Access Journals (Sweden)

Stephan Weiss

2005-09-01

Full Text Available Gaussian frequency shift keying is the modulation scheme specified for Bluetooth. Signal adversities typical in Bluetooth networks include AWGN, multipath propagation, carrier frequency, and modulation index offsets. In our effort to realise a robust but efficient Bluetooth receiver, we adopt a high-performance matched-filter-based detector, which is near optimal in AWGN, but requires a prohibitively costly filter bank for processing of K bits worth of the received signal. However, through filtering over a single bit period and performing phase propagation of intermediate results over successive single-bit stages, we eliminate redundancy involved in providing the matched filter outputs and reduce its complexity by up to 90% (for K=9. The constant modulus signal characteristic and the potential for carrier frequency offsets make the constant modulus algorithm (CMA suitable for channel equalisation, and we demonstrate its effectiveness in this paper. We also introduce a stochastic gradient-based algorithm for carrier frequency offset correction, and show that the relative rotation between successive intermediate filter outputs enables us to detect and correct offsets in modulation index.

EEG Channel Selection Using Particle Swarm Optimization for the Classification of Auditory Event-Related Potentials

Directory of Open Access Journals (Sweden)

Alejandro Gonzalez

2014-01-01

Full Text Available Brain-machine interfaces (BMI rely on the accurate classification of event-related potentials (ERPs and their performance greatly depends on the appropriate selection of classifier parameters and features from dense-array electroencephalography (EEG signals. Moreover, in order to achieve a portable and more compact BMI for practical applications, it is also desirable to use a system capable of accurate classification using information from as few EEG channels as possible. In the present work, we propose a method for classifying P300 ERPs using a combination of Fisher Discriminant Analysis (FDA and a multiobjective hybrid real-binary Particle Swarm Optimization (MHPSO algorithm. Specifically, the algorithm searches for the set of EEG channels and classifier parameters that simultaneously maximize the classification accuracy and minimize the number of used channels. The performance of the method is assessed through offline analyses on datasets of auditory ERPs from sound discrimination experiments. The proposed method achieved a higher classification accuracy than that achieved by traditional methods while also using fewer channels. It was also found that the number of channels used for classification can be significantly reduced without greatly compromising the classification accuracy.

A New Quantum Key Distribution Scheme Based on Frequency and Time Coding

International Nuclear Information System (INIS)

Chang-Hua, Zhu; Chang-Xing, Pei; Dong-Xiao, Quan; Jing-Liang, Gao; Nan, Chen; Yun-Hui, Yi

2010-01-01

A new scheme of quantum key distribution (QKD) using frequency and time coding is proposed, in which the security is based on the frequency-time uncertainty relation. In this scheme, the binary information sequence is encoded randomly on either the central frequency or the time delay of the optical pulse at the sender. The central frequency of the single photon pulse is set as ω 1 for bit 0 and set as ω 2 for bit 1 when frequency coding is selected. However, the single photon pulse is not delayed for bit 0 and is delayed in τ for 1 when time coding is selected. At the receiver, either the frequency or the time delay of the pulse is measured randomly, and the final key is obtained after basis comparison, data reconciliation and privacy amplification. With the proposed method, the effect of the noise in the fiber channel and environment on the QKD system can be reduced effectively

Efficient coding schemes with power allocation using space-time-frequency spreading

Institute of Scientific and Technical Information of China (English)

Jiang Haining; Luo Hanwen; Tian Jifeng; Song Wentao; Liu Xingzhao

2006-01-01

An efficient space-time-frequency (STF) coding strategy for multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is presented for high bit rate data transmission over frequency selective fading channels. The proposed scheme is a new approach to space-time-frequency coded OFDM (COFDM) that combines OFDM with space-time coding, linear precoding and adaptive power allocation to provide higher quality of transmission in terms of the bit error rate performance and power efficiency. In addition to exploiting the maximum diversity gain in frequency, time and space, the proposed scheme enjoys high coding advantages and low-complexity decoding. The significant performance improvement of our design is confirmed by corroborating numerical simulations.

Human Commercial Models' Eye Colour Shows Negative Frequency-Dependent Selection.

Directory of Open Access Journals (Sweden)

Isabela Rodrigues Nogueira Forti

Full Text Available In this study we investigated the eye colour of human commercial models registered in the UK (400 female and 400 male and Brazil (400 female and 400 male to test the hypothesis that model eye colour frequency was the result of negative frequency-dependent selection. The eye colours of the models were classified as: blue, brown or intermediate. Chi-square analyses of data for countries separated by sex showed that in the United Kingdom brown eyes and intermediate colours were significantly more frequent than expected in comparison to the general United Kingdom population (P<0.001. In Brazil, the most frequent eye colour brown was significantly less frequent than expected in comparison to the general Brazilian population. These results support the hypothesis that model eye colour is the result of negative frequency-dependent selection. This could be the result of people using eye colour as a marker of genetic diversity and finding rarer eye colours more attractive because of the potential advantage more genetically diverse offspring that could result from such a choice. Eye colour may be important because in comparison to many other physical traits (e.g., hair colour it is hard to modify, hide or disguise, and it is highly polymorphic.

Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel.

Science.gov (United States)

Gurnev, Philip A; Bezrukov, Sergey M

2012-11-13

We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the "charge inversion" phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification, which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations, which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine.

Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

Directory of Open Access Journals (Sweden)

Alexandre Lehmann

Full Text Available Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

Asymptotic Performance Analysis of the k-th Best Link Selection over Wireless Fading Channels: An Extreme Value Theory Approach

KAUST Repository

Al-Badarneh, Yazan Hussein

2018-01-25

We consider a general selection-diversity (SD) scheme in which the k-th best link is selected from a number of links. We use extreme value theory (EVT) to derive simple closed-form asymptotic expressions for the average throughput, effective throughput and average bit error probability (BEP) for the k-th best link over various channel models that are widely used to characterize fading in wireless communication systems. As an application example, we consider the Weibull fading channel model and verify the accuracy of the derived asymptotic expressions through Monte Carlo simulations.

Asymptotic Performance Analysis of the k-th Best Link Selection over Wireless Fading Channels: An Extreme Value Theory Approach

KAUST Repository

Al-Badarneh, Yazan Hussein; Georghiades, Costas; Alouini, Mohamed-Slim

2018-01-01

We consider a general selection-diversity (SD) scheme in which the k-th best link is selected from a number of links. We use extreme value theory (EVT) to derive simple closed-form asymptotic expressions for the average throughput, effective throughput and average bit error probability (BEP) for the k-th best link over various channel models that are widely used to characterize fading in wireless communication systems. As an application example, we consider the Weibull fading channel model and verify the accuracy of the derived asymptotic expressions through Monte Carlo simulations.

The transport kinetics and selectivity of HpUreI, the urea channel from Helicobacter pylori†

Science.gov (United States)

Gray, Lawrence R; Gu, Sean X; Quick, Matthias; Khademi, Shahram

2017-01-01

Helicobacter pylori’s unique ability to colonize and survive in the acidic environment of the stomach is critically dependent on uptake of urea through the urea channel, HpUreI. Hence, HpUreI may represent a promising target for the development of specific drugs against this human pathogen. To obtain insight into the structure/function relationship of this channel, we have developed conditions for the high-yield expression and purification of stable recombinant HpUreI that allowed its detailed kinetic characterization in solubilized form and reconstituted into liposomes. Detergent-solubilized HpUreI forms homo-trimer, as determined by chemical cross-linking. Urea dissociation kinetics of purified HpUreI were determined by means of the scintillation proximity assay (SPA), whereas urea efflux was measured in HpUreI-containing proteoliposomes using stopped-flow spectrometry to determine the kinetics and selectivity of the urea channel. The kinetic analyses revealed that urea conduction in HpUreI is pH sensitive and saturable with a half-saturation concentration (or K0.5) of ~163 mM. Binding of urea by HpUreI was increased at lower pH; however, the apparent affinity of urea binding (~150 mM) was not significantly pH dependent. The solute selectivity analysis indicated that HpUreI is highly selective for urea and hydroxyurea. Removing either amino group of urea molecules diminishes their permeability through HpUreI. Similar to urea conduction, water diffusion through HpUreI is pH-dependent with low water permeability at neutral pH. PMID:21877689

Gating of a pH-sensitive K(2P potassium channel by an electrostatic effect of basic sensor residues on the selectivity filter.

Directory of Open Access Journals (Sweden)

Leandro Zúñiga

2011-01-01

Full Text Available K(+ channels share common selectivity characteristics but exhibit a wide diversity in how they are gated open. Leak K(2P K(+ channels TASK-2, TALK-1 and TALK-2 are gated open by extracellular alkalinization. The mechanism for this alkalinization-dependent gating has been proposed to be the neutralization of the side chain of a single arginine (lysine in TALK-2 residue near the pore of TASK-2, which occurs with the unusual pK(a of 8.0. We now corroborate this hypothesis by transplanting the TASK-2 extracellular pH (pH(o sensor in the background of a pH(o-insensitive TASK-3 channel, which leads to the restitution of pH(o-gating. Using a concatenated channel approach, we also demonstrate that for TASK-2 to open, pH(o sensors must be neutralized in each of the two subunits forming these dimeric channels with no apparent cross-talk between the sensors. These results are consistent with adaptive biasing force analysis of K(+ permeation using a model selectivity filter in wild-type and mutated channels. The underlying free-energy profiles confirm that either a doubly or a singly charged pH(o sensor is sufficient to abolish ion flow. Atomic detail of the associated mechanism reveals that, rather than a collapse of the pore, as proposed for other K(2P channels gated at the selectivity filter, an increased height of the energetic barriers for ion translocation accounts for channel blockade at acid pH(o. Our data, therefore, strongly suggest that a cycle of protonation/deprotonation of pH(o-sensing arginine 224 side chain gates the TASK-2 channel by electrostatically tuning the conformational stability of its selectivity filter.

Gating of a pH-sensitive K(2P) potassium channel by an electrostatic effect of basic sensor residues on the selectivity filter.

Science.gov (United States)

Zúñiga, Leandro; Márquez, Valeria; González-Nilo, Fernando D; Chipot, Christophe; Cid, L Pablo; Sepúlveda, Francisco V; Niemeyer, María Isabel

2011-01-25

K(+) channels share common selectivity characteristics but exhibit a wide diversity in how they are gated open. Leak K(2P) K(+) channels TASK-2, TALK-1 and TALK-2 are gated open by extracellular alkalinization. The mechanism for this alkalinization-dependent gating has been proposed to be the neutralization of the side chain of a single arginine (lysine in TALK-2) residue near the pore of TASK-2, which occurs with the unusual pK(a) of 8.0. We now corroborate this hypothesis by transplanting the TASK-2 extracellular pH (pH(o)) sensor in the background of a pH(o)-insensitive TASK-3 channel, which leads to the restitution of pH(o)-gating. Using a concatenated channel approach, we also demonstrate that for TASK-2 to open, pH(o) sensors must be neutralized in each of the two subunits forming these dimeric channels with no apparent cross-talk between the sensors. These results are consistent with adaptive biasing force analysis of K(+) permeation using a model selectivity filter in wild-type and mutated channels. The underlying free-energy profiles confirm that either a doubly or a singly charged pH(o) sensor is sufficient to abolish ion flow. Atomic detail of the associated mechanism reveals that, rather than a collapse of the pore, as proposed for other K(2P) channels gated at the selectivity filter, an increased height of the energetic barriers for ion translocation accounts for channel blockade at acid pH(o). Our data, therefore, strongly suggest that a cycle of protonation/deprotonation of pH(o)-sensing arginine 224 side chain gates the TASK-2 channel by electrostatically tuning the conformational stability of its selectivity filter.

Strategies for sustainable channel relations in mobile telecom sector

Directory of Open Access Journals (Sweden)

Githa Heggde

2011-01-01

Full Text Available The telecom sector in India largely comprises of wireless connections for phones. As of today, there are approximately 21 network providers in the country with about 7 per each circle, each offering competitive pricing to the consumers. The main objective of the study is to provide an accurate role for the company executive in developing channel relations. Further to this, the study explores the strategies which can sustain a good working relationship between the company and its channel members in the mobile telecom sector. The constructs identified for developing sustainable relationships were Setting distribution objectives, Channel design, Logistics, Image Building, Inventory management, Channel management, Payment & credit, Promotional assistance, Setting targets, Coverage frequency , Motivating channel members to perform. The sample selected contained distributors from the Mobile telecom sector and company executives/channel managers of leading telecom companies. Factor analysis and Friedman’s test was applied. The findings revealed a correlation in attitude between distributors and the executives. Motivating distributors was rated as the most important strategy by the company. The distributors felt that all channel partners needed to have positive attitude towards the channel while company executives felt that aggression made channel members perform effectively. Such findings will be of use to mobile telecom companies who are new entrants to the Indian market and to existing companies who plan to expand their coverage.

Use of navigation channels by Lake Sturgeon: Does channelization increase vulnerability of fish to ship strikes?

Directory of Open Access Journals (Sweden)

Darryl W Hondorp

Full Text Available Channelization for navigation and flood control has altered the hydrology and bathymetry of many large rivers with unknown consequences for fish species that undergo riverine migrations. In this study, we investigated whether altered flow distributions and bathymetry associated with channelization attracted migrating Lake Sturgeon (Acipenser fulvescens into commercial navigation channels, potentially increasing their exposure to ship strikes. To address this question, we quantified and compared Lake Sturgeon selection for navigation channels vs. alternative pathways in two multi-channel rivers differentially affected by channelization, but free of barriers to sturgeon movement. Acoustic telemetry was used to quantify Lake Sturgeon movements. Under the assumption that Lake Sturgeon navigate by following primary flow paths, acoustic-tagged Lake Sturgeon in the more-channelized lower Detroit River were expected to choose navigation channels over alternative pathways and to exhibit greater selection for navigation channels than conspecifics in the less-channelized lower St. Clair River. Consistent with these predictions, acoustic-tagged Lake Sturgeon in the more-channelized lower Detroit River selected the higher-flow and deeper navigation channels over alternative migration pathways, whereas in the less-channelized lower St. Clair River, individuals primarily used pathways alternative to navigation channels. Lake Sturgeon selection for navigation channels as migratory pathways also was significantly higher in the more-channelized lower Detroit River than in the less-channelized lower St. Clair River. We speculated that use of navigation channels over alternative pathways would increase the spatial overlap of commercial vessels and migrating Lake Sturgeon, potentially enhancing their vulnerability to ship strikes. Results of our study thus demonstrated an association between channelization and the path use of migrating Lake Sturgeon that could prove

On Optimal Input Design and Model Selection for Communication Channels

Energy Technology Data Exchange (ETDEWEB)

Li, Yanyan [ORNL; Djouadi, Seddik M [ORNL; Olama, Mohammed M [ORNL

2013-01-01

In this paper, the optimal model (structure) selection and input design which minimize the worst case identification error for communication systems are provided. The problem is formulated using metric complexity theory in a Hilbert space setting. It is pointed out that model selection and input design can be handled independently. Kolmogorov n-width is used to characterize the representation error introduced by model selection, while Gel fand and Time n-widths are used to represent the inherent error introduced by input design. After the model is selected, an optimal input which minimizes the worst case identification error is shown to exist. In particular, it is proven that the optimal model for reducing the representation error is a Finite Impulse Response (FIR) model, and the optimal input is an impulse at the start of the observation interval. FIR models are widely popular in communication systems, such as, in Orthogonal Frequency Division Multiplexing (OFDM) systems.

Predicting the impact of selection for scrapie resistance on PRNP genotype frequencies in goats.

Science.gov (United States)

Sacchi, Paola; Rasero, Roberto; Ru, Giuseppe; Aiassa, Eleonora; Colussi, Silvia; Ingravalle, Francesco; Peletto, Simone; Perrotta, Maria Gabriella; Sartore, Stefano; Soglia, Dominga; Acutis, Pierluigi

2018-03-06

The European Union has implemented breeding programmes to increase scrapie resistance in sheep. A similar approach can be applied also in goats since the K222 allele provides a level of resistance equivalent to that of ARR in sheep. The European Food Safety Authority stated that breeding for resistance could be offered as an option for Member States to control classical scrapie in goats. We assessed the impact of different breeding strategies on PRNP genotype frequencies using a mathematical model that describes in detail the evolution of K222 in two goat breeds, Chamois Coloured and Saanen. Different patterns of age structure and replacement rate were modelled as factors affecting response to selection. Breeding for scrapie resistance can be implemented in goats, even though the initial K222 frequencies in these breeds are not particularly favourable and the rate at which the resistant animals increase, both breeding and slaughtered for meat production, is slow. If the goal is not to achieve the fixation of resistance allele, it is advisable to carry out selection only until a desired frequency of K222-carriers has been attained. Nucleus selection vs. selection on the overall populations is less expensive but takes longer to reach the desired output. The programme performed on the two goat breeds serves as a model of the response the selection could have in other breeds that show different initial frequencies and population structure. In this respect, the model has a general applicability.

An improved method for estimating the frequency correlation function

KAUST Repository

Chelli, Ali; Pä tzold, Matthias

2012-01-01

For time-invariant frequency-selective channels, the transfer function is a superposition of waves having different propagation delays and path gains. In order to estimate the frequency correlation function (FCF) of such channels, the frequency averaging technique can be utilized. The obtained FCF can be expressed as a sum of auto-terms (ATs) and cross-terms (CTs). The ATs are caused by the autocorrelation of individual path components. The CTs are due to the cross-correlation of different path components. These CTs have no physical meaning and leads to an estimation error. We propose a new estimation method aiming to improve the estimation accuracy of the FCF of a band-limited transfer function. The basic idea behind the proposed method is to introduce a kernel function aiming to reduce the CT effect, while preserving the ATs. In this way, we can improve the estimation of the FCF. The performance of the proposed method and the frequency averaging technique is analyzed using a synthetically generated transfer function. We show that the proposed method is more accurate than the frequency averaging technique. The accurate estimation of the FCF is crucial for the system design. In fact, we can determine the coherence bandwidth from the FCF. The exact knowledge of the coherence bandwidth is beneficial in both the design as well as optimization of frequency interleaving and pilot arrangement schemes. © 2012 IEEE.

An improved method for estimating the frequency correlation function

KAUST Repository

Chelli, Ali

2012-04-01

For time-invariant frequency-selective channels, the transfer function is a superposition of waves having different propagation delays and path gains. In order to estimate the frequency correlation function (FCF) of such channels, the frequency averaging technique can be utilized. The obtained FCF can be expressed as a sum of auto-terms (ATs) and cross-terms (CTs). The ATs are caused by the autocorrelation of individual path components. The CTs are due to the cross-correlation of different path components. These CTs have no physical meaning and leads to an estimation error. We propose a new estimation method aiming to improve the estimation accuracy of the FCF of a band-limited transfer function. The basic idea behind the proposed method is to introduce a kernel function aiming to reduce the CT effect, while preserving the ATs. In this way, we can improve the estimation of the FCF. The performance of the proposed method and the frequency averaging technique is analyzed using a synthetically generated transfer function. We show that the proposed method is more accurate than the frequency averaging technique. The accurate estimation of the FCF is crucial for the system design. In fact, we can determine the coherence bandwidth from the FCF. The exact knowledge of the coherence bandwidth is beneficial in both the design as well as optimization of frequency interleaving and pilot arrangement schemes. © 2012 IEEE.

MMSE-NP-RISIC-Based Channel Equalization for MIMO-SC-FDE Troposcatter Communication Systems

Directory of Open Access Journals (Sweden)

Zedong Xie

2016-01-01

Full Text Available The impact of intersymbol interference (ISI on single-carrier frequency-domain equalization with multiple input multiple output (MIMO-SC-FDE troposcatter communication systems is severe. Most of the channel equalization methods fail to solve it completely. In this paper, given the disadvantages of the noise-predictive (NP MMSE-based and the residual intersymbol interference cancellation (RISIC equalization in the single input single output (SISO system, we focus on the combination of both equalization schemes mentioned above. After extending both of them into MIMO system for the first time, we introduce a novel MMSE-NP-RISIC equalization method for MIMO-SC-FDE troposcatter communication systems. Analysis and simulation results validate the performance of the proposed method in time-varying frequency-selective troposcatter channel at an acceptable computational complexity cost.

Performance analysis of selective cooperation in amplify-and-forward relay networks over identical Nakagami-m channels

KAUST Repository

Hussain, Syed Imtiaz; Alouini, Mohamed-Slim; Hasna, Mazen Omar

2011-01-01

In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple-relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify-and-forward mode over identical Nakagami-m channels using an exact source-relay-destination signal-to-noise ratio (SNR).We derived accurate closed-form expressions for various system parameters including the probability density function of end-to-end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.

Performance analysis of selective cooperation in amplify-and-forward relay networks over identical Nakagami-m channels

KAUST Repository

Hussain, Syed Imtiaz

2011-05-02

In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple-relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify-and-forward mode over identical Nakagami-m channels using an exact source-relay-destination signal-to-noise ratio (SNR).We derived accurate closed-form expressions for various system parameters including the probability density function of end-to-end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.

Distinct interactions of Na+ and Ca2+ ions with the selectivity filter of the bacterial sodium channel NaVAb

International Nuclear Information System (INIS)

Ke, Song; Zangerl, Eva-Maria; Stary-Weinzinger, Anna

2013-01-01

Highlights: ► Ca 2+ translocates slowly in the filter, due to lack of “loose” knock-on mechanism. ► Identification of a high affinity binding site in Na V Ab selectivity filter. ► Changes of EEEE locus triggered by electrostatic interactions with Ca 2+ ions. -- Abstract: Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. In this study, we use molecular dynamics simulations and free energy calculations to investigate how the bacterial sodium channel Na V Ab (Arcobacter butzleri) differentiates between Na + and Ca 2+ ions. Multiple nanosecond molecular dynamics simulations revealed distinct binding patterns for these two cations in the selectivity filter and suggested a high affinity calcium binding site formed by backbone atoms of residues Leu-176 and Thr-175 (S CEN ) in the sodium channel selectivity filter

Bit Error Rate Analysis for MC-CDMA Systems in Nakagami- Fading Channels

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Li Zexian

2004-01-01

Full Text Available Multicarrier code division multiple access (MC-CDMA is a promising technique that combines orthogonal frequency division multiplexing (OFDM with CDMA. In this paper, based on an alternative expression for the -function, characteristic function and Gaussian approximation, we present a new practical technique for determining the bit error rate (BER of multiuser MC-CDMA systems in frequency-selective Nakagami- fading channels. The results are applicable to systems employing coherent demodulation with maximal ratio combining (MRC or equal gain combining (EGC. The analysis assumes that different subcarriers experience independent fading channels, which are not necessarily identically distributed. The final average BER is expressed in the form of a single finite range integral and an integrand composed of tabulated functions which can be easily computed numerically. The accuracy of the proposed approach is demonstrated with computer simulations.

Integrated synchronous receiver channel for optical instrumentation applications

Science.gov (United States)

Benten, Harold G. P. H.; Ruotsalainen, Tarmo; Maekynen, Anssi J.; Rahkonen, Timo E.; Kopola, Harri K.

1997-09-01

A two-channel synchronous receiver circuit for optical instrumentation applications has been designed and implemented. Each receiver channel comprises a.o. transimpedance preamplifier, voltage amplifiers, programmable feedback networks, and a synchronous detector. The function of the channel is to extract the slowly varying information carrying signal from a modulated carrier which is accompanied by relatively high levels of noise. As a whole, the channel can be characterized as a narrow band filter around the frequency of interest. Medical applications include arterial oxygen saturation (SaO2) measurement and dental pulp vitality measurement. In both cases, two optical signals with different frequencies are received by a single photodiode. The measured performance of the optical receiver shows its suitability for the above mentioned applications. Therefore the circuit will be used in a small sized, battery-operated sensor prototype to test the sensing method in a clinical environment. Other applications include the signal processing of optical position-sensitive detectors. A summary of measured receiver channel performance: input reduced noise current spectral density between 0.20 and 0.30 pA/(root)Hz at all relevant frequencies, total programmable channel transimpedance between 7 M(Omega) and 500 M(Omega) , lower -3 dB frequency of at least 50 Hz, upper -3 dB frequency of 40 kHz, maximum voltage swing at the demodulator output of 2.4 V.

Terbinafine is a novel and selective activator of the two-pore domain potassium channel TASK3.

Science.gov (United States)

Wright, Paul D; Veale, Emma L; McCoull, David; Tickle, David C; Large, Jonathan M; Ococks, Emma; Gothard, Gemma; Kettleborough, Catherine; Mathie, Alistair; Jerman, Jeffrey

2017-11-04

Two-pore domain potassium channels (K2Ps) are characterized by their four transmembrane domain and two-pore topology. They carry background (or leak) potassium current in a variety of cell types. Despite a number of important roles there is currently a lack of pharmacological tools with which to further probe K2P function. We have developed a cell-based thallium flux assay, using baculovirus delivered TASK3 (TWIK-related acid-sensitive K + channel 3, KCNK9, K2P9.1) with the aim of identifying novel, selective TASK3 activators. After screening a library of 1000 compounds, including drug-like and FDA approved molecules, we identified Terbinafine as an activator of TASK3. In a thallium flux assay a pEC50 of 6.2 ( ±0.12) was observed. When Terbinafine was screened against TASK2, TREK2, THIK1, TWIK1 and TRESK no activation was observed in thallium flux assays. Several analogues of Terbinafine were also purchased and structure activity relationships examined. To confirm Terbinafine's activation of TASK3 whole cell patch clamp electrophysiology was carried out and clear potentiation observed in both the wild type channel and the pathophysiological, Birk-Barel syndrome associated, G236R TASK3 mutant. No activity at TASK1 was observed in electrophysiology studies. In conclusion, we have identified the first selective activator of the two-pore domain potassium channel TASK3. Copyright © 2017 Elsevier Inc. All rights reserved.

Channel capacity of TDD-OFDM-MIMO for multiple access points in a wireless single-frequency-network

DEFF Research Database (Denmark)

Takatori, Y.; Fitzek, Frank; Tsunekawa, K.

2005-01-01

MIMO data transmission scheme, which combines Single-Frequency-Network (SFN) with TDD-OFDM-MIMO applied for wireless LAN networks. In our proposal, we advocate to use SFN for multiple access points (MAP) MIMO data transmission. The goal of this approach is to achieve very high channel capacity in both......The multiple-input-multiple-output (MIMO) technique is the most attractive candidate to improve the spectrum efficiency in the next generation wireless communication systems. However, the efficiency of MIMO techniques reduces in the line of sight (LOS) environments. In this paper, we propose a new...

Top down and bottom up selection drives variations in frequency and form of a visual signal.

Science.gov (United States)

Yeh, Chien-Wei; Blamires, Sean J; Liao, Chen-Pan; Tso, I-Min

2015-03-30

The frequency and form of visual signals can be shaped by selection from predators, prey or both. When a signal simultaneously attracts predators and prey selection may favour a strategy that minimizes risks while attracting prey. Accordingly, varying the frequency and form of the silken decorations added to their web may be a way that Argiope spiders minimize predation while attracting prey. Nonetheless, the role of extraneous factors renders the influences of top down and bottom up selection on decoration frequency and form variation difficult to discern. Here we used dummy spiders and decorations to simulate four possible strategies that the spider Argiope aemula may choose and measured the prey and predator attraction consequences for each in the field. The strategy of decorating at a high frequency with a variable form attracted the most prey, while that of decorating at a high frequency with a fixed form attracted the most predators. These results suggest that mitigating the cost of attracting predators while maintaining prey attraction drives the use of variation in decoration form by many Argiope spp. when decorating frequently. Our study highlights the importance of considering top-down and bottom up selection pressure when devising evolutionary ecology experiments.

Isotachophoresis system having larger-diameter channels flowing into channels with reduced diameter and with selectable counter-flow

Energy Technology Data Exchange (ETDEWEB)

Mariella, Jr., Raymond P.

2018-03-06

An isotachophoresis system for separating a sample containing particles into discrete packets including a flow channel, the flow channel having a large diameter section and a small diameter section; a negative electrode operably connected to the flow channel; a positive electrode operably connected to the flow channel; a leading carrier fluid in the flow channel; a trailing carrier fluid in the flow channel; and a control for separating the particles in the sample into discrete packets using the leading carrier fluid, the trailing carrier fluid, the large diameter section, and the small diameter section.

Low-frequency 1/f noise in MoS{sub 2} transistors: Relative contributions of the channel and contacts

Energy Technology Data Exchange (ETDEWEB)

Renteria, J.; Jiang, C. [Nano-Device Laboratory, Department of Electrical Engineering, Bourns College of Engineering, University of California – Riverside, Riverside, California 92521 (United States); Samnakay, R. [Materials Science and Engineering Program, Bourns College of Engineering, University of California – Riverside, Riverside, California 92521 (United States); Rumyantsev, S. L. [Department of Electrical, Computer, and Systems Engineering, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Goli, P.; Balandin, A. A., E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory, Department of Electrical Engineering, Bourns College of Engineering, University of California – Riverside, Riverside, California 92521 (United States); Materials Science and Engineering Program, Bourns College of Engineering, University of California – Riverside, Riverside, California 92521 (United States); Shur, M. S. [Department of Electrical, Computer, and Systems Engineering, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2014-04-14

We report on the results of the low-frequency (1/f, where f is frequency) noise measurements in MoS{sub 2} field-effect transistors revealing the relative contributions of the MoS{sub 2} channel and Ti/Au contacts to the overall noise level. The investigation of the 1/f noise was performed for both as fabricated and aged transistors. It was established that the McWhorter model of the carrier number fluctuations describes well the 1/f noise in MoS{sub 2} transistors, in contrast to what is observed in graphene devices. The trap densities extracted from the 1/f noise data for MoS{sub 2} transistors, are 2 × 10{sup 19} eV{sup −1}cm{sup −3} and 2.5 × 10{sup 20} eV{sup −1}cm{sup −3} for the as fabricated and aged devices, respectively. It was found that the increase in the noise level of the aged MoS{sub 2} transistors is due to the channel rather than the contact degradation. The obtained results are important for the proposed electronic applications of MoS{sub 2} and other van der Waals materials.

Analysis of Broad-band Frequency Selective Shielding Glass by FDTD method

OpenAIRE

笠嶋, 善憲; Kasashima, Yoshinori

2010-01-01

A frequency Selective shielding (FSS) glass is a print of many same size antennas on a sheet of glass, and it has high shielding properties for one specific frequency. In the past, the author analyzed theoretically the characteristics of the FSS, as a large scale array antenna. The FSS has narrow-band shielding characteristics. This time, the author analyzed accurately the characteristics of a FSS glass being a print of many same size dipole antennas on a sheet of glass by FDTD method. As the...

Orthogonal Multi-Carrier DS-CDMA with Frequency-Domain Equalization

Science.gov (United States)

Tanaka, Ken; Tomeba, Hiromichi; Adachi, Fumiyuki

Orthogonal multi-carrier direct sequence code division multiple access (orthogonal MC DS-CDMA) is a combination of orthogonal frequency division multiplexing (OFDM) and time-domain spreading, while multi-carrier code division multiple access (MC-CDMA) is a combination of OFDM and frequency-domain spreading. In MC-CDMA, a good bit error rate (BER) performance can be achieved by using frequency-domain equalization (FDE), since the frequency diversity gain is obtained. On the other hand, the conventional orthogonal MC DS-CDMA fails to achieve any frequency diversity gain. In this paper, we propose a new orthogonal MC DS-CDMA that can obtain the frequency diversity gain by applying FDE. The conditional BER analysis is presented. The theoretical average BER performance in a frequency-selective Rayleigh fading channel is evaluated by the Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the orthogonal MC DS-CDMA signal transmission.

Receptor model for the molecular basis of tissue selectivity of 1,4-dihydropyridine calcium channel drugs

Science.gov (United States)

Langs, David A.; Strong, Phyllis D.; Triggle, David J.

1990-09-01

Our analysis of the solid state conformations of nifedipine [dimethyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinecarboxylate] and its 1,4-dihydropyridine (1,4-DHP) analogues produced a cartoon description of the important interactions between these drugs and their voltage-dependent calcium channel receptor. In the present study a molecular-level detailed model of the 1,4-DHP receptor binding site has been built from the published amino acid sequence of the 215-1 subunit of the voltage-dependent calcium channel isolated from rabbit skeletal muscle transverse tubule membranes. The voltage-sensing component of the channel described in this work differs from others reported for the homologous sodium channel in that it incorporates a water structure and a staggered, rather than eclipsed, hydrogen bonded S4 helix conformation. The major recognition surfaces of the receptor lie in helical grooves on the S4 or voltagesensing α-helix that is positioned in the center of the bundle of transmembrane helices that define each of the four calcium channel domains. Multiple binding clefts defined by Arg-X-X-Arg-P-X-X-S `reading frames' exist on the S4 strand. The tissue selectivity of nifedipine and its analogues may arise, in part, from conservative changes in the amino acid residues at the P and S positions of the reading frame that define the ester-binding regions of receptors from different tissues. The crystal structures of two tissue-selective nifedipine analogues, nimodipine [isopropyl (2-methoxyethyl) 1,4-dihydro-2,6- dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] and nitrendipine [ethyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] are reported. Nimodipine was observed to have an unusual ester side chain conformation that enhances the fit to the proposed ester-sensing region of the receptor.

Discovery and characterization of a potent and selective inhibitor of Aedes aegypti inward rectifier potassium channels.

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Rene Raphemot

Full Text Available Vector-borne diseases such as dengue fever and malaria, which are transmitted by infected female mosquitoes, affect nearly half of the world's population. The emergence of insecticide-resistant mosquito populations is reducing the effectiveness of conventional insecticides and threatening current vector control strategies, which has created an urgent need to identify new molecular targets against which novel classes of insecticides can be developed. We previously demonstrated that small molecule inhibitors of mammalian Kir channels represent promising chemicals for new mosquitocide development. In this study, high-throughput screening of approximately 30,000 chemically diverse small-molecules was employed to discover potent and selective inhibitors of Aedes aegypti Kir1 (AeKir1 channels heterologously expressed in HEK293 cells. Of 283 confirmed screening 'hits', the small-molecule inhibitor VU625 was selected for lead optimization and in vivo studies based on its potency and selectivity toward AeKir1, and tractability for medicinal chemistry. In patch clamp electrophysiology experiments of HEK293 cells, VU625 inhibits AeKir1 with an IC50 value of 96.8 nM, making VU625 the most potent inhibitor of AeKir1 described to date. Furthermore, electrophysiology experiments in Xenopus oocytes revealed that VU625 is a weak inhibitor of AeKir2B. Surprisingly, injection of VU625 failed to elicit significant effects on mosquito behavior, urine excretion, or survival. However, when co-injected with probenecid, VU625 inhibited the excretory capacity of mosquitoes and was toxic, suggesting that the compound is a substrate of organic anion and/or ATP-binding cassette (ABC transporters. The dose-toxicity relationship of VU625 (when co-injected with probenecid is biphasic, which is consistent with the molecule inhibiting both AeKir1 and AeKir2B with different potencies. This study demonstrates proof-of-concept that potent and highly selective inhibitors of mosquito

Experimental study of the helicopter-mobile radioelectrical channel and possible extension to the satellite-mobile channel

Science.gov (United States)

Blanchetiere-Ciarletti, V.; Sylvain, M.; Lemenn, P.

1994-07-01

The use of satellite seems to be an answer to the radioelectrical covering problem for the mobile communications, particularly in the low populated areas. Frequency bands at 1.5 and 2.5 GHz have been dedicated to these future services. Satellite-mobile links will be much more affected by propagation phenomena than the existing links between satellites and fixed stations. The reasons for that are twofold: The probable use of LEO (Low-Earth-Orbit) satellites instead of GEO; such satellites will have to be received at relatively low elevation to limit their number; the use of mobile communication terminals with small and non directive antennas that must work in various environments instead of terrestrian stations located at carefully chosen places and equipped with large diameter paraboloids. These propagation phenomena mainly consist in the fading of the signal level (shadowing of the link), and a frequency selective fading due to multipath propagation. The experience run by C.R.P.E. is aimed at a better understanding of the satellite-mobile propagation channel at fixed frequency as well as on a large band. In this paper, we discuss preliminary results from a series of propagation measurements performed (by lack of any experimental satellite) on an experimental radio link at 1.45 GHz on a of 20 MHz bandwidth between a helicopter flying at a height of 2 km and a mobile receiver. The whole experiment has been run in a rural environment in Brittany (France). In a first part, we illustrate the quality of the data collected during the experiment on a typical case study and give a possible physical interpretation of the observed phenomena. Then we present statistical results concerning the various characteristics (attenuation and delay spreads) of the propagation channel. Finally, we discuss the problem of using a helicopter (flying at a height of 2 km) as a substitute for a satellite at about 1000 km and try to estimate to what extent it is possible to use the data

Pharmacological modulation of SK3 channels

DEFF Research Database (Denmark)

Grunnet, M; Jespersen, Thomas; Angelo, K

2001-01-01

Small-conductance, calcium-activated K+ channels (SK channels) are voltage-insensitive channels that have been identified molecularly within the last few years. As SK channels play a fundamental role in most excitable cells and participate in afterhyperpolarization (AHP) and spike-frequency adapt...... at concentrations of 3 microM and above. Amitriptyline, a tricyclic antidepressive widely used clinically, inhibits SK3 channels with an IC50 of 39.1 +/- 10 microM (n=6)....

Switches of stimulus tagging frequencies interact with the conflict-driven control of selective attention, but not with inhibitory control.

Science.gov (United States)

Scherbaum, Stefan; Frisch, Simon; Dshemuchadse, Maja

2016-01-01

Selective attention and its adaptation by cognitive control processes are considered a core aspect of goal-directed action. Often, selective attention is studied behaviorally with conflict tasks, but an emerging neuroscientific method for the study of selective attention is EEG frequency tagging. It applies different flicker frequencies to the stimuli of interest eliciting steady state visual evoked potentials (SSVEPs) in the EEG. These oscillating SSVEPs in the EEG allow tracing the allocation of selective attention to each tagged stimulus continuously over time. The present behavioral investigation points to an important caveat of using tagging frequencies: The flicker of stimuli not only produces a useful neuroscientific marker of selective attention, but interacts with the adaptation of selective attention itself. Our results indicate that RT patterns of adaptation after response conflict (so-called conflict adaptation) are reversed when flicker frequencies switch at once. However, this effect of frequency switches is specific to the adaptation by conflict-driven control processes, since we find no effects of frequency switches on inhibitory control processes after no-go trials. We discuss the theoretical implications of this finding and propose precautions that should be taken into account when studying conflict adaptation using frequency tagging in order to control for the described confounds. Copyright © 2015 Elsevier B.V. All rights reserved.

Temperature dependency of cupular mechanics and hair cell frequency selectivity in the fish canal lateral line organ

NARCIS (Netherlands)

Wiersinga-Post, JEC; van Netten, SM

2000-01-01

The mechanical frequency selectivity of the cupula located in the supraorbital lateral line canal and the frequency selectivity of the hair cells driven by the cupula were measured simultaneously in vivo. Laser interferometry was used to measure cupular mechanics and extracellular receptor

Selective ablation of dental calculus with a frequency-doubled Alexandrite laser

Science.gov (United States)

Rechmann, Peter; Hennig, Thomas

1996-01-01

The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.

High Guanidinium Permeability Reveals Dehydration-Dependent Ion Selectivity in the Plasmodial Surface Anion Channel

Directory of Open Access Journals (Sweden)

Abdullah A. B. Bokhari

2014-01-01

Full Text Available Malaria parasites grow within vertebrate erythrocytes and increase host cell permeability to access nutrients from plasma. This increase is mediated by the plasmodial surface anion channel (PSAC, an unusual ion channel linked to the conserved clag gene family. Although PSAC recognizes and transports a broad range of uncharged and charged solutes, it must efficiently exclude the small Na+ ion to maintain infected cell osmotic stability. Here, we examine possible mechanisms for this remarkable solute selectivity. We identify guanidinium as an organic cation with high permeability into human erythrocytes infected with Plasmodium falciparum, but negligible uptake by uninfected cells. Transport characteristics and pharmacology indicate that this uptake is specifically mediated by PSAC. The rank order of organic and inorganic cation permeabilities suggests cation dehydration as the rate-limiting step in transport through the channel. The high guanidinium permeability of infected cells also allows rapid and stringent synchronization of parasite cultures, as required for molecular and cellular studies of this pathogen. These studies provide important insights into how nutrients and ions are transported via PSAC, an established target for antimalarial drug development.

Multi-Channel Capacitive Sensor Arrays

Directory of Open Access Journals (Sweden)

Bingnan Wang

2016-01-01

Full Text Available In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved.

Point mutations in the transmembrane region of the clic1 ion channel selectively modify its biophysical properties.

Directory of Open Access Journals (Sweden)

Stefania Averaimo

Full Text Available Chloride intracellular Channel 1 (CLIC1 is a metamorphic protein that changes from a soluble cytoplasmic protein into a transmembrane protein. Once inserted into membranes, CLIC1 multimerises and is able to form chloride selective ion channels. Whilst CLIC1 behaves as an ion channel both in cells and in artificial lipid bilayers, its structure in the soluble form has led to some uncertainty as to whether it really is an ion channel protein. CLIC1 has a single putative transmembrane region that contains only two charged residues: arginine 29 (Arg29 and lysine 37 (Lys37. As charged residues are likely to have a key role in ion channel function, we hypothesized that mutating them to neutral alanine to generate K37A and R29A CLIC1 would alter the electrophysiological characteristics of CLIC1. By using three different electrophysiological approaches: i single channel Tip-Dip in artificial bilayers using soluble recombinant CLIC1, ii cell-attached and iii whole-cell patch clamp recordings in transiently transfected HEK cells, we determined that the K37A mutation altered the single-channel conductance while the R29A mutation affected the single-channel open probability in response to variation in membrane potential. Our results show that mutation of the two charged amino acids (K37 and R29 in the putative transmembrane region of CLIC1 alters the biophysical properties of the ion channel in both artificial bilayers and cells. Hence these charged residues are directly involved in regulating its ion channel activity. This strongly suggests that, despite its unusual structure, CLIC1 itself is able to form a chloride ion channel.

Spatial Frequency Selectivity Is Impaired in Dopamine D2 Receptor Knockout Mice

Science.gov (United States)

Souza, Bruno Oliveira Ferreira; Abou Rjeili, Mira; Quintana, Clémentine; Beaulieu, Jean M.; Casanova, Christian

2018-01-01

Dopamine is a neurotransmitter implicated in several brain functions, including vision. In the present study, we investigated the impacts of the lack of D2 dopamine receptors on the structure and function of the primary visual cortex (V1) of D2-KO mice using optical imaging of intrinsic signals. Retinotopic maps were generated in order to measure anatomo-functional parameters such as V1 shape, cortical magnification factor, scatter, and ocular dominance. Contrast sensitivity and spatial frequency selectivity (SF) functions were computed from responses to drifting gratings. When compared to control mice, none of the parameters of the retinotopic maps were affected by D2 receptor loss of function. While the contrast sensitivity function of D2-KO mice did not differ from their wild-type counterparts, SF selectivity function was significantly affected as the optimal SF and the high cut-off frequency (p D2-KO than in WT mice. These findings show that the lack of function of D2 dopamine receptors had no influence on cortical structure whereas it had a significant impact on the spatial frequency selectivity and high cut-off. Taken together, our results suggest that D2 receptors play a specific role on the processing of spatial features in early visual cortex while they do not seem to participate in its development. PMID:29379422

Statistical model of natural stimuli predicts edge-like pooling of spatial frequency channels in V2

Directory of Open Access Journals (Sweden)

Gutmann Michael

2005-02-01

Full Text Available Abstract Background It has been shown that the classical receptive fields of simple and complex cells in the primary visual cortex emerge from the statistical properties of natural images by forcing the cell responses to be maximally sparse or independent. We investigate how to learn features beyond the primary visual cortex from the statistical properties of modelled complex-cell outputs. In previous work, we showed that a new model, non-negative sparse coding, led to the emergence of features which code for contours of a given spatial frequency band. Results We applied ordinary independent component analysis to modelled outputs of complex cells that span different frequency bands. The analysis led to the emergence of features which pool spatially coherent across-frequency activity in the modelled primary visual cortex. Thus, the statistically optimal way of processing complex-cell outputs abandons separate frequency channels, while preserving and even enhancing orientation tuning and spatial localization. As a technical aside, we found that the non-negativity constraint is not necessary: ordinary independent component analysis produces essentially the same results as our previous work. Conclusion We propose that the pooling that emerges allows the features to code for realistic low-level image features related to step edges. Further, the results prove the viability of statistical modelling of natural images as a framework that produces quantitative predictions of visual processing.

Decisions about design and selection of marketing channels

OpenAIRE

Marjanova Jovanov, Tamara; Temjanovski, Riste

2016-01-01

The significance of the distribution strategy stems from its participation in the costs included in the price, the conditioning of the information in the promotional message, the connection with the desired market position of the product. The distribution includes management of all functions (physical flow, promotion, ordering and payment information, negotiation, risk taking) involved in the channel. Distribution channel...

Soliton generation from a multi-frequency optical signal

International Nuclear Information System (INIS)

Panoiu, N-C; Mel'nikov, I V; Mihalache, D; Etrich, C; Lederer, F

2002-01-01

We present a comprehensive analysis of the generation of optical solitons in a monomode optical fibre from a superposition of soliton-like optical pulses at different frequencies. It is demonstrated that the structure of the emerging optical field is highly dependent on the number of input channels, the inter-channel frequency separation, the time shift between the pulses belonging to adjacent channels, and the polarization of the pulses. Also, it is found that there exists a critical frequency separation above which wavelength-division multiplexing with solitons is feasible and that this critical frequency increases with the number of transmission channels. Moreover, for the case in which only two channels are considered, we analyse the propagation of the emerging two-soliton solutions in the presence of several perturbations important for optical networks: bandwidth-limited amplification, nonlinear amplification, and amplitude and phase modulation. Finally, the influence of the birefringence of the fibre on the structure of the emerging optical field is discussed. (review article)

On Secrecy Outage of Relay Selection in Underlay Cognitive Radio Networks over Nakagami-m Fading Channels

KAUST Repository

Lei, Hongjiang; Zhang, Huan; Ansari, Imran Shafique; Ren, Zhi; Pan, Gaofeng; Qaraqe, Khalid A.; Alouini, Mohamed-Slim

2017-01-01

In this paper, the secrecy outage performance of an underlay cognitive decode-and-forward relay network over independent but not necessarily identical distributed (i.n.i.d) Nakagami-m fading channels is investigated, in which the secondary user transmitter communicates with the secondary destination via relays, and an eavesdropper attempts to overhear the information. Based on whether the channel state information (CSI) of the wiretap links is available or not, we analyze the secrecy outage performance with optimal relay selection (ORS) and suboptimal relay selection (SRS) schemes, and multiple relays combining scheme (MRC) scheme is considered for comparison purpose. The exact and asymptotic closed-form expressions for the secrecy outage probability with three different relay selection schemes are derived and verified by Monte-Carlo simulations. The numerical results illustrate that ORS scheme always outperforms SRS and MRC schemes, and SRS scheme is better than MRC scheme in the lower fading parameters scenario. Furthermore, through asymptotic analysis, we find that these three different schemes achieve the same secrecy diversity order, which is determined by the number of the relays, and the fading parameters of the links among the relays and the destination.

On Secrecy Outage of Relay Selection in Underlay Cognitive Radio Networks over Nakagami-m Fading Channels

KAUST Repository

Lei, Hongjiang

2017-10-02

In this paper, the secrecy outage performance of an underlay cognitive decode-and-forward relay network over independent but not necessarily identical distributed (i.n.i.d) Nakagami-m fading channels is investigated, in which the secondary user transmitter communicates with the secondary destination via relays, and an eavesdropper attempts to overhear the information. Based on whether the channel state information (CSI) of the wiretap links is available or not, we analyze the secrecy outage performance with optimal relay selection (ORS) and suboptimal relay selection (SRS) schemes, and multiple relays combining scheme (MRC) scheme is considered for comparison purpose. The exact and asymptotic closed-form expressions for the secrecy outage probability with three different relay selection schemes are derived and verified by Monte-Carlo simulations. The numerical results illustrate that ORS scheme always outperforms SRS and MRC schemes, and SRS scheme is better than MRC scheme in the lower fading parameters scenario. Furthermore, through asymptotic analysis, we find that these three different schemes achieve the same secrecy diversity order, which is determined by the number of the relays, and the fading parameters of the links among the relays and the destination.

Effects of feeding frequency on apparent energy and nutrient digestibility/availability of channel catfish, Ictalurus punctatus, reared at optimal and suboptimal temperatures

Science.gov (United States)

This study examined the effects of feeding frequency (daily versus every other day [EOD]) on nutrient digestibility/availability of channel catfish, Ictalurus punctatus, reared at optimal (30 C) and suboptimal (24 C) temperatures. A 28% protein practical diet was used as the test diet, and chromic o...

Baseline Channel Geometry and Aquatic Habitat Data for Selected Streams in the Matanuska-Susitna Valley, Alaska

Science.gov (United States)

Curran, Janet H.; Rice, William J.

2009-01-01

Small streams in the rapidly developing Matanuska-Susitna Valley in south-central Alaska are known to support anadromous and resident fish but little is known about their hydrologic and riparian conditions, or their sensitivity to the rapid development of the area or climate variability. To help address this need, channel geometry and aquatic habitat data were collected in 2005 as a baseline of stream conditions for selected streams. Three streams were selected as representative of various stream types, and one drainage network, the Big Lake drainage basin, was selected for a systematic assessment. Streams in the Big Lake basin were drawn in a Geographic Information System (GIS), and 55 reaches along 16 miles of Meadow Creek and its primary tributary Little Meadow Creek were identified from orthoimagery and field observations on the basis of distinctive physical and habitat parameters, most commonly gradient, substrate, and vegetation. Data-collection methods for sites at the three representative reaches and the 55 systematically studied reaches consisted of a field survey of channel and flood-plain geometry and collection of 14 habitat attributes using published protocols or slight modifications. Width/depth and entrenchment ratios along the Meadow-Little Meadow Creek corridor were large and highly variable upstream of Parks Highway and lower and more consistent downstream of Parks Highway. Channel width was strongly correlated with distance, increasing downstream in a log-linear relation. Runs formed the most common habitat type, and instream vegetation dominated the habitat cover types, which collectively covered 53 percent of the channel. Gravel suitable for spawning covered isolated areas along Meadow Creek and about 29 percent of Little Meadow Creek. Broad wetlands were common along both streams. For a comprehensive assessment of small streams in the Mat-Su Valley, critical additional data needs include hydrologic, geologic and geomorphic, and biologic data

Extracting time-frequency feature of single-channel vastus medialis EMG signals for knee exercise pattern recognition.

Directory of Open Access Journals (Sweden)

Yi Zhang

Full Text Available The EMG signal indicates the electrophysiological response to daily living of activities, particularly to lower-limb knee exercises. Literature reports have shown numerous benefits of the Wavelet analysis in EMG feature extraction for pattern recognition. However, its application to typical knee exercises when using only a single EMG channel is limited. In this study, three types of knee exercises, i.e., flexion of the leg up (standing, hip extension from a sitting position (sitting and gait (walking are investigated from 14 healthy untrained subjects, while EMG signals from the muscle group of vastus medialis and the goniometer on the knee joint of the detected leg are synchronously monitored and recorded. Four types of lower-limb motions including standing, sitting, stance phase of walking, and swing phase of walking, are segmented. The Wavelet Transform (WT based Singular Value Decomposition (SVD approach is proposed for the classification of four lower-limb motions using a single-channel EMG signal from the muscle group of vastus medialis. Based on lower-limb motions from all subjects, the combination of five-level wavelet decomposition and SVD is used to comprise the feature vector. The Support Vector Machine (SVM is then configured to build a multiple-subject classifier for which the subject independent accuracy will be given across all subjects for the classification of four types of lower-limb motions. In order to effectively indicate the classification performance, EMG features from time-domain (e.g., Mean Absolute Value (MAV, Root-Mean-Square (RMS, integrated EMG (iEMG, Zero Crossing (ZC and frequency-domain (e.g., Mean Frequency (MNF and Median Frequency (MDF are also used to classify lower-limb motions. The five-fold cross validation is performed and it repeats fifty times in order to acquire the robust subject independent accuracy. Results show that the proposed WT-based SVD approach has the classification accuracy of 91.85%±0

Reduced feedback selective cluster index scheduling with user pre-selection for next-generation multi-input multi-output orthogonal frequency division multiple access system

OpenAIRE

Nicolaou, M; Doufexi, A; Armour, SMD; Sun, Y

2011-01-01

The joint use of opportunistic scheduling and orthogonal frequency division multiple access (OFDMA) provide significant gains in environments of low mobility and scatter for which channel variations are low. The downside of opportunistic scheduling in multicarrier systems such as OFDMA, lies in the substantial uplink overhead required to feed back by the mobile stations (MSs) describing users' instantaneous link conditions. This study presents a novel approach towards multicarrier opportunist...

Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes.

Science.gov (United States)

Shen, Yue-Xiao; Song, Woochul C; Barden, D Ryan; Ren, Tingwei; Lang, Chao; Feroz, Hasin; Henderson, Codey B; Saboe, Patrick O; Tsai, Daniel; Yan, Hengjing; Butler, Peter J; Bazan, Guillermo C; Phillip, William A; Hickey, Robert J; Cremer, Paul S; Vashisth, Harish; Kumar, Manish

2018-06-12

Synthetic polymer membranes, critical to diverse energy-efficient separations, are subject to permeability-selectivity trade-offs that decrease their overall efficacy. These trade-offs are due to structural variations (e.g., broad pore size distributions) in both nonporous membranes used for Angstrom-scale separations and porous membranes used for nano to micron-scale separations. Biological membranes utilize well-defined Angstrom-scale pores to provide exceptional transport properties and can be used as inspiration to overcome this trade-off. Here, we present a comprehensive demonstration of such a bioinspired approach based on pillar[5]arene artificial water channels, resulting in artificial water channel-based block copolymer membranes. These membranes have a sharp selectivity profile with a molecular weight cutoff of ~ 500 Da, a size range challenging to achieve with current membranes, while achieving a large improvement in permeability (~65 L m -2  h -1  bar -1  compared with 4-7 L m -2  h -1  bar -1 ) over similarly rated commercial membranes.

Electrostatic tuning of permeation and selectivity in aquaporin water channels

DEFF Research Database (Denmark)

Jensen, Mogens O Stibius; Tajkhorshid, E.; Schulten, K.

2003-01-01

Water permeation and electrostatic interactions between water and channel are investigated in the Escherichia coli glycerol uptake facilitator GlpF, a member of the aquaporin water channel family, by molecular dynamics simulations. A tetrameric model of the channel embedded in a 16:0/ 18:1c9...... with the protein electrostatic fields enforce a bipolar water configuration inside the channel with dipole inversion at the NPA motifs. At the NPA motifs water-protein electrostatic interactions facilitate this inversion. Furthermore, water-water electrostatic interactions are in all regions inside the channel...... stronger than water-protein interactions, except near a conserved, positively charged Arg residue. We find that variations of the protein electrostatic field through the channel, owing to preserved structural features, completely explain the bipolar orientation of water. This orientation persists despite...

Whether and How to Select Inertia and Acceleration of Discrete Particle Swarm Optimization Algorithm: A Study on Channel Assignment

Directory of Open Access Journals (Sweden)

Min Jin

2014-01-01

Full Text Available There is recently a great deal of interest and excitement in understanding the role of inertia and acceleration in the motion equation of discrete particle swarm optimization (DPSO algorithms. It still remains unknown whether the inertia section should be abandoned and how to select the appropriate acceleration in order for DPSO to show the best convergence performance. Adopting channel assignment as a case study, this paper systematically conducts experimental filtering research on this issue. Compared with other channel assignment schemes, the proposed scheme and the selection of inertia and acceleration are verified to have the advantage to channel assignment in three respects of convergence rate, convergence speed, and the independency of the quality of initial solution. Furthermore, the experimental result implies that DSPO might have the best convergence performance when its motion equation includes an inertia section in a less medium weight, a bigger acceleration coefficient for global-search optimum, and a smaller acceleration coefficient for individual-search optimum.

Thermal responsive ion selectivity of uranyl peroxide nanocages: an inorganic mimic of K{sup +} ion channels

Energy Technology Data Exchange (ETDEWEB)

Gao, Yunyi; Sun, Xinyu; Liu, Tianbo [Department of Polymer Science, University of Akron, Akron, OH (United States); Szymanowski, Jennifer E.S.; Burns, Peter C. [Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN (United States)

2016-06-06

An actinyl peroxide cage cluster, Li{sub 48+m}K{sub 12}(OH){sub m}[UO{sub 2}(O{sub 2})(OH)]{sub 60} (H{sub 2}O){sub n} (m∼20 and n∼310; U{sub 60}), discriminates precisely between Na{sup +} and K{sup +} ions when heated to certain temperatures, a most essential feature for K{sup +} selective filters. The U{sub 60} clusters demonstrate several other features in common with K{sup +} ion channels, including passive transport of K{sup +} ions, a high flux rate, and the dehydration of U{sub 60} and K{sup +} ions. These qualities make U{sub 60} (a pure inorganic cluster) a promising ion channel mimic in an aqueous environment. Laser light scattering (LLS) and isothermal titration calorimetry (ITC) studies revealed that the tailorable ion selectivity of U{sub 60} clusters is a result of the thermal responsiveness of the U{sub 60} hydration shells. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Thermal responsive ion selectivity of uranyl peroxide nanocages. An inorganic mimic of K{sup +} ion channels

Energy Technology Data Exchange (ETDEWEB)

Gao, Yunyi; Sun, Xinyu; Liu, Tianbo [Akron Univ., OH (United States). Dept. of Polymer Science; Szymanowski, Jennifer E.S.; Burns, Peter C. [Notre Dame Univ., IN (United States). Dept. of Civil Engineering and Geological Sciences

2016-06-06

An actinyl peroxide cage cluster, Li{sub 48+m}K{sub 12}(OH){sub m}[UO{sub 2}(O{sub 2})(OH)]{sub 60} (H{sub 2}O){sub n} (m∼20 and n∼310; U{sub 60}), discriminates precisely between Na{sup +} and K{sup +} ions when heated to certain temperatures, a most essential feature for K{sup +} selective filters. The U{sub 60} clusters demonstrate several other features in common with K{sup +} ion channels, including passive transport of K{sup +} ions, a high flux rate, and the dehydration of U{sub 60} and K{sup +} ions. These qualities make U{sub 60} (a pure inorganic cluster) a promising ion channel mimic in an aqueous environment. Laser light scattering (LLS) and isothermal titration calorimetry (ITC) studies revealed that the tailorable ion selectivity of U{sub 60} clusters is a result of the thermal responsiveness of the U{sub 60} hydration shells.

A guinea pig model of selective severe high-frequency hearing loss.

Science.gov (United States)

Havenith, Sarah; Klis, Sjaak F L; Versnel, Huib; Grolman, Wilko

2013-10-01

Using an appropriate dose of an aminoglycoside antibiotic cotreated with a loop diuretic a guinea pig model of high-frequency loss can be obtained mimicking cochlear implant candidates with low-frequency residual hearing. We examined the stability of this model over time. A well-established method to create an animal model for profound deafness is cotreatment with an aminoglycoside antibiotic and a loop diuretic. Recent data indicated that reduction of the aminoglycoside dose might yield selective high-frequency hearing loss. Such a model is relevant for studies related to hybrid cochlear implant devices, for example, with respect to preservation of residual hearing. Guinea pigs received an electrode for chronic recording of compound action potentials to tones to assess thresholds. They were treated with a coadministration of kanamycin (200 mg/kg) and furosemide (100 mg/kg), after which, the animals were sacrificed for histologic analysis at 2, 4, or 7 weeks. After 2 to 7 weeks threshold shifts were greater than 50 dB for 8 to 16 kHz in 15 of 17 animals, whereas threshold shifts at 2 kHz or lower were less than 50 dB in 13 animals. Major threshold shifts occurred the first 2 to 4 days; subsequently, some spontaneous recovery occurred and, after 2-3 weeks thresholds, remained stable. Inner hair cell loss still progressed between 2 and 4 weeks in the most basal cochlear region; thereafter, hair cell loss was stable. An appropriate animal model for selective severe high-frequency hearing loss was obtained, which is stable at 4 weeks after ototoxic treatment.

Maitotoxin Is a Potential Selective Activator of the Endogenous Transient Receptor Potential Canonical Type 1 Channel in Xenopus laevis Oocytes

Directory of Open Access Journals (Sweden)

Pedro L. Flores

2017-06-01

Full Text Available Maitotoxin (MTX is the most potent marine toxin known to date. It is responsible for a particular human intoxication syndrome called ciguatera fish poisoning (CFP. Several reports indicate that MTX is an activator of non-selective cation channels (NSCC in different cell types. The molecular identity of these channels is still an unresolved topic, and it has been proposed that the transient receptor potential (TRP channels are involved in this effect. In Xenopus laevis oocytes, MTX at picomolar (pM concentrations induces the activation of NSCC with functional and pharmacological properties that resemble the activity of TRP channels. The purpose of this study was to characterize the molecular identity of the TRP channel involved in the MTX response, using the small interference RNA (siRNA approach and the two-electrode voltage-clamp technique (TEVC. The injection of a specifically designed siRNA to silence the transient receptor potential canonical type 1 (TRPC1 protein expression abolished the MTX response. MTX had no effect on oocytes, even at doses 20-fold higher compared to cells without injection. Total mRNA and protein levels of TRPC1 were notably diminished. The TRPC4 siRNA did not change the MTX effect, even though it was important to note that the protein level was reduced by the silencing of TRPC4. Our results suggest that MTX could be a selective activator of TRPC1 channels in X. laevis oocytes and a useful pharmacological tool for further studies on these TRP channels.

Environmental testing of an experimental digital safety channel

International Nuclear Information System (INIS)

Korsah, K.; Tanaka, T.J.; Wilson, T.L. Jr.; Wood, R.T.

1996-09-01

This document presents the results of environmental stress tests performed on an experimental digital safety channel (EDSC) assembled at the Oak Ridge National Laboratory (ORNL) as part of the NRC-sponsored Qualification of Advanced Instrumentation and Controls (W) System program. The objective of this study is to investigate failure modes and vulnerabilities of microprocessor-based technologies when subjected to environmental stressors. The study contributes to the technical basis for environmental qualification of safety-related digital I ampersand C systems. The EDSC employs technologies and digital subsystems representative of those proposed for use in advanced light-water reactors (ALWRs) or for retrofits in existing plants. Subsystems include computers, electrical and optical serial communication links, fiber-optic network links, analog-to-digital and digital-to-analog converters, and multiplexers. The EDSC was subjected to selected stressors that are a potential risk to digital equipment in a mild environment. The selected stressors were electromagnetic and radio-frequency interference (EMYRFI), temperature, humidity, and smoke exposure. The stressors were applied over ranges that were considerably higher than what the channel is likely to experience in a normal nuclear power plant environment. Ranges of stress were selected at a sufficiently high level to induce errors so that failure modes that are characteristic of the technologies employed could be identified

Evaluation of Dynamic Channel and Power Assignment for Cognitive Networks

Energy Technology Data Exchange (ETDEWEB)

Syed A. Ahmad; Umesh Shukla; Ryan E. Irwin; Luiz A. DaSilva; Allen B. MacKenzie

2011-03-01

In this paper, we develop a unifying optimization formulation to describe the Dynamic Channel and Power Assignment (DCPA) problem and evaluation method for comparing DCPA algorithms. DCPA refers to the allocation of transmit power and frequency channels to links in a cognitive network so as to maximize the total number of feasible links while minimizing the aggregate transmit power. We apply our evaluation method to five algorithms representative of DCPA used in literature. This comparison illustrates the tradeoffs between control modes (centralized versus distributed) and channel/power assignment techniques. We estimate the complexity of each algorithm. Through simulations, we evaluate the effectiveness of the algorithms in achieving feasible link allocations in the network, as well as their power efficiency. Our results indicate that, when few channels are available, the effectiveness of all algorithms is comparable and thus the one with smallest complexity should be selected. The Least Interfering Channel and Iterative Power Assignment (LICIPA) algorithm does not require cross-link gain information, has the overall lowest run time, and highest feasibility ratio of all the distributed algorithms; however, this comes at a cost of higher average power per link.

The long-term evolution of multilocus traits under frequency-dependent disruptive selection

NARCIS (Netherlands)

Van Doorn, G. Sander; Dieckmann, Ulf

Frequency-dependent disruptive selection is widely recognized as an important source of genetic variation. Its evolutionary consequences have been extensively studied using phenotypic evolutionary models, based on quantitative genetics, game theory, or adaptive dynamics. However, the genetic

Modeling and characterization of different channels based on human body communication.

Science.gov (United States)

Jingzhen Li; Zedong Nie; Yuhang Liu; Lei Wang

2017-07-01

Human body communication (HBC), which uses the human body as a transmission medium for electrical signals, provides a prospective communication solution for body sensor networks (BSNs). In this paper, an inhomogeneous model which includes the tissue layers of skin, fat, and muscle is proposed to study the propagation characteristics of different HBC channels. Specifically, the HBC channels, namely, the on-body to on-body (OB-OB)channel, on-body to in-body (OB-IB) channel, in-body to on-body (IB-OB) channel, and in-body to in-body (IB-IB)channel, are studied over different frequencies (from 1MHz to 100MHz) through numerical simulations with finite-difference time-domain (FDTD) method. The results show that the gain of OB-IB channel and IB-OB channel is almost the same. The gain of IB-IB channel is greater than other channels in the frequency range 1MHz to 70MHz. In addition, the gain of all channels is associated with the channel length and communication frequency. The simulations are verified by experimental measurements in a porcine tissue sample. The results show that the simulations are in agreement with the measurements.

Channel-aware multi-user uplink transmission scheme for SIMO-OFDM systems

Institute of Scientific and Technical Information of China (English)

PAN ChengKang; CAI YueMing; XU YouYun

2009-01-01

The problem of medium access control (MAC) in wireless single-Input multiple-output-orthogonal frequency division multiplexing (SIMO-OFOM) systems is addressed.Traditional random access protocols have low overheads and inferior performance.Centralized methods have superior performance and high overheads.To achieve the tradeoff between overhead and performance,we propose a channelaware uplink transmission (CaUT) scheme for SIMO-OFDM systems.In CaUT,users transmit requestto-send (RTS) at some subcarriers whose channel gains are above a predetermined threshold.Using the channel state information provided by RTS,access point performs user selection with receive beamforming to decide which users can access and then broadcasts the selection results via clear-to-send (CTS) to users.We present a distributed power control scheme by using a simple fixed modulation mode.We optimize the modulation order and channel gain thresholds to maximize the separable packets subject to the bit-error-rate (BER) and temporal fairness requirements and the Individual average transmit power constraints.The performance of CaUT scheme is analyzed analytically and evaluated by simulations.Simulation results show that CaUT can achieve more significant throughput performance than traditional random access protocols.

Monitoring voltage-dependent charge displacement of Shaker B-IR K+ ion channels using radio frequency interrogation.

Directory of Open Access Journals (Sweden)

Sameera Dharia

2011-02-01

Full Text Available Here we introduce a new technique that probes voltage-dependent charge displacements of excitable membrane-bound proteins using extracellularly applied radio frequency (RF, 500 kHz electric fields. Xenopus oocytes were used as a model cell for these experiments, and were injected with cRNA encoding Shaker B-IR (ShB-IR K(+ ion channels to express large densities of this protein in the oocyte membranes. Two-electrode voltage clamp (TEVC was applied to command whole-cell membrane potential and to measure channel-dependent membrane currents. Simultaneously, RF electric fields were applied to perturb the membrane potential about the TEVC level and to measure voltage-dependent RF displacement currents. ShB-IR expressing oocytes showed significantly larger changes in RF displacement currents upon membrane depolarization than control oocytes. Voltage-dependent changes in RF displacement currents further increased in ShB-IR expressing oocytes after ∼120 µM Cu(2+ addition to the external bath. Cu(2+ is known to bind to the ShB-IR ion channel and inhibit Shaker K(+ conductance, indicating that changes in the RF displacement current reported here were associated with RF vibration of the Cu(2+-linked mobile domain of the ShB-IR protein. Results demonstrate the use of extracellular RF electrodes to interrogate voltage-dependent movement of charged mobile protein domains--capabilities that might enable detection of small changes in charge distribution associated with integral membrane protein conformation and/or drug-protein interactions.

Monitoring voltage-dependent charge displacement of Shaker B-IR K+ ion channels using radio frequency interrogation.

Science.gov (United States)

Dharia, Sameera; Rabbitt, Richard D

2011-02-28

Here we introduce a new technique that probes voltage-dependent charge displacements of excitable membrane-bound proteins using extracellularly applied radio frequency (RF, 500 kHz) electric fields. Xenopus oocytes were used as a model cell for these experiments, and were injected with cRNA encoding Shaker B-IR (ShB-IR) K(+) ion channels to express large densities of this protein in the oocyte membranes. Two-electrode voltage clamp (TEVC) was applied to command whole-cell membrane potential and to measure channel-dependent membrane currents. Simultaneously, RF electric fields were applied to perturb the membrane potential about the TEVC level and to measure voltage-dependent RF displacement currents. ShB-IR expressing oocytes showed significantly larger changes in RF displacement currents upon membrane depolarization than control oocytes. Voltage-dependent changes in RF displacement currents further increased in ShB-IR expressing oocytes after ∼120 µM Cu(2+) addition to the external bath. Cu(2+) is known to bind to the ShB-IR ion channel and inhibit Shaker K(+) conductance, indicating that changes in the RF displacement current reported here were associated with RF vibration of the Cu(2+)-linked mobile domain of the ShB-IR protein. Results demonstrate the use of extracellular RF electrodes to interrogate voltage-dependent movement of charged mobile protein domains--capabilities that might enable detection of small changes in charge distribution associated with integral membrane protein conformation and/or drug-protein interactions.

Secure Degrees of Freedom of the Gaussian Z Channel with Single Antenna

Directory of Open Access Journals (Sweden)

Xianzhong XIE

2014-03-01

Full Text Available This paper presents the secrecy capacity and the secure degrees of freedom of Gaussian Z channel with single antenna and confidential information. Firstly, we analysis the secrecy capacity and the upper bound of secure degrees of freedom of this channel in theory. Then, we respectively discuss the security pre-coding scheme for real Gaussian channel model and frequency selection channel model. Under the first model, through real interference alignment and cooperative jamming, we obtain the secrecy capacity and secure degrees of freedom, proving that it can reach the upper bound of secure degrees of freedom in theory. While, under the second one, a strong security pre-coding algorithm is proposed, which is based on the fact that sparse matrix has strong hash property. Next, we arrange interference with interference alignment and the receivers process their received signal through zero forcing algorithm. At last, the messages are reconstructed with maximum likelihood decoding, where it shows that the algorithm can asymptotically achieve the optimal secrecy capacity.

Blind Channel Equalization Using Constrained Generalized Pattern Search Optimization and Reinitialization Strategy

Directory of Open Access Journals (Sweden)

Charles Tatkeu

2008-12-01

Full Text Available We propose a global convergence baud-spaced blind equalization method in this paper. This method is based on the application of both generalized pattern optimization and channel surfing reinitialization. The potentially used unimodal cost function relies on higher- order statistics, and its optimization is achieved using a pattern search algorithm. Since the convergence to the global minimum is not unconditionally warranted, we make use of channel surfing reinitialization (CSR strategy to find the right global minimum. The proposed algorithm is analyzed, and simulation results using a severe frequency selective propagation channel are given. Detailed comparisons with constant modulus algorithm (CMA are highlighted. The proposed algorithm performances are evaluated in terms of intersymbol interference, normalized received signal constellations, and root mean square error vector magnitude. In case of nonconstant modulus input signals, our algorithm outperforms significantly CMA algorithm with full channel surfing reinitialization strategy. However, comparable performances are obtained for constant modulus signals.

Blind Channel Equalization Using Constrained Generalized Pattern Search Optimization and Reinitialization Strategy

Science.gov (United States)

Zaouche, Abdelouahib; Dayoub, Iyad; Rouvaen, Jean Michel; Tatkeu, Charles

2008-12-01

We propose a global convergence baud-spaced blind equalization method in this paper. This method is based on the application of both generalized pattern optimization and channel surfing reinitialization. The potentially used unimodal cost function relies on higher- order statistics, and its optimization is achieved using a pattern search algorithm. Since the convergence to the global minimum is not unconditionally warranted, we make use of channel surfing reinitialization (CSR) strategy to find the right global minimum. The proposed algorithm is analyzed, and simulation results using a severe frequency selective propagation channel are given. Detailed comparisons with constant modulus algorithm (CMA) are highlighted. The proposed algorithm performances are evaluated in terms of intersymbol interference, normalized received signal constellations, and root mean square error vector magnitude. In case of nonconstant modulus input signals, our algorithm outperforms significantly CMA algorithm with full channel surfing reinitialization strategy. However, comparable performances are obtained for constant modulus signals.

A propagation-measurement-based evaluation of channel characteristics and models pertinent to the expansion of mobile radio systems to frequencies beyond 2 GHz

NARCIS (Netherlands)

Bultitude, R.J.C.; Schenk, T.C.W.; Op de Kamp, N.A.A.; Adnani, N.

2007-01-01

64This paper concerns the measurement-based comparison of urban microcellular mobile radio channel characteristics at 1.9 GHz and a higher frequency, i.e., 5.8 GHz, where future wireless systems could operate. Characteristics that are reported include transmission loss, root-mean-square delay

Mechanical frequency selectivity of an artificial basilar membrane using a beam array with narrow supports

International Nuclear Information System (INIS)

Kim, Sangwon; Jang, Jongmoon; Choi, Hongsoo; Song, Won Joon; Jang, Jeong Hun

2013-01-01

The study presented in this paper assessed the frequency selectivity of an artificial basilar membrane (ABM) constructed using a piezoelectric beam array with narrow supports. Three ABM samples were constructed. Each ABM contained 16 beams with various lengths in a one-dimensional array. To experimentally assess the frequency selectivity of the ABM, mechanical vibration induced either by an electrical or an acoustic stimulus was measured with a scanning laser-Doppler vibrometer. The electro-mechanical and acousto-mechanical transfer functions were defined for the same purpose. The tonotopy of each beam array was visualized by post-processing the experimental results. Finite element analyses were conducted to numerically compute the resonance frequencies, identify the associated vibrational modes, and evaluate the harmonic responses of the beams. The influence of the residual stresses existing in the beams was reflected in the geometric models by introducing three different levels of arc-shaped lateral deformations in the beams. The harmonic analyses revealed that each beam of the ABM samples presented independent band-pass characteristics. The experiments and simulations commonly showed a frequency selectivity of the fabricated ABMs in the range of 2–20 kHz. Therefore, the device is suitable for development of a totally implantable artificial cochlea, implementing a mechanical frequency analyzer. This work is part of research to develop a prototype of a totally implantable artificial cochlea. (paper)

Distributed Channel Estimation and Pilot Contamination Analysis for Massive MIMO-OFDM Systems

KAUST Repository

Zaib, Alam

2016-07-22

By virtue of large antenna arrays, massive MIMO systems have a potential to yield higher spectral and energy efficiency in comparison with the conventional MIMO systems. This paper addresses uplink channel estimation in massive MIMO-OFDM systems with frequency selective channels. We propose an efficient distributed minimum mean square error (MMSE) algorithm that can achieve near optimal channel estimates at low complexity by exploiting the strong spatial correlation among antenna array elements. The proposed method involves solving a reduced dimensional MMSE problem at each antenna followed by a repetitive sharing of information through collaboration among neighboring array elements. To further enhance the channel estimates and/or reduce the number of reserved pilot tones, we propose a data-aided estimation technique that relies on finding a set of most reliable data carriers. Furthermore, we use stochastic geometry to quantify the pilot contamination, and in turn use this information to analyze the effect of pilot contamination on channel MSE. The simulation results validate our analysis and show near optimal performance of the proposed estimation algorithms.

Multicarrier chaotic communications in multipath fading channels without channel estimation

Energy Technology Data Exchange (ETDEWEB)

Wang, Shilian, E-mail: wangsl@nudt.edu.cn; Zhang, Zhili [College of Electrical Science and Engineering, National University of Defense Technology, Changsha, 410073, P R China (China)

2015-01-15

A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

Multicarrier chaotic communications in multipath fading channels without channel estimation

Directory of Open Access Journals (Sweden)

Shilian Wang

2015-01-01

Full Text Available A multi-carrier chaotic shift keying(MC-CSK communication scheme with low probability of interception(LPI is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

Escitalopram block of hERG potassium channels.

Science.gov (United States)

Chae, Yun Ju; Jeon, Ji Hyun; Lee, Hong Joon; Kim, In-Beom; Choi, Jin-Sung; Sung, Ki-Wug; Hahn, Sang June

2014-01-01

Escitalopram, a selective serotonin reuptake inhibitor, is the pharmacologically active S-enantiomer of the racemic mixture of RS-citalopram and is widely used in the treatment of depression. The effects of escitalopram and citalopram on the human ether-a-go-go-related gene (hERG) channels expressed in human embryonic kidney cells were investigated using voltage-clamp and Western blot analyses. Both drugs blocked hERG currents in a concentration-dependent manner with an IC50 value of 2.6 μM for escitalopram and an IC50 value of 3.2 μM for citalopram. The blocking of hERG by escitalopram was voltage-dependent, with a steep increase across the voltage range of channel activation. However, voltage independence was observed over the full range of activation. The blocking by escitalopram was frequency dependent. A rapid application of escitalopram induced a rapid and reversible blocking of the tail current of hERG. The extent of the blocking by escitalopram during the depolarizing pulse was less than that during the repolarizing pulse, suggesting that escitalopram has a high affinity for the open state of the hERG channel, with a relatively lower affinity for the inactivated state. Both escitalopram and citalopram produced a reduction of hERG channel protein trafficking to the plasma membrane but did not affect the short-term internalization of the hERG channel. These results suggest that escitalopram blocked hERG currents at a supratherapeutic concentration and that it did so by preferentially binding to both the open and the inactivated states of the channels and by inhibiting the trafficking of hERG channel protein to the plasma membrane.

A hybrid polarization-selective atomic sensor for radio-frequency field detection with a passive resonant-cavity field amplifier

OpenAIRE

Anderson, David A.; Paradis, Eric G.; Raithel, Georg

2018-01-01

We present a hybrid atomic sensor that realizes radio-frequency electric field detection with intrinsic field amplification and polarization selectivity for robust high-sensitivity field measurement. The hybrid sensor incorporates a passive resonator element integrated with an atomic vapor cell that provides amplification and polarization selectivity for detection of incident radio-frequency fields. The amplified intra-cavity radio-frequency field is measured by atoms using a quantum-optical ...

Generation of radio vortex beams with designable polarization using anisotropic frequency selective surface

Science.gov (United States)

Yang, Jin; Zhang, Cheng; Ma, Hui Feng; Zhao, Jie; Dai, Jun Yan; Yuan, Wei; Yang, Liu Xi; Cheng, Qiang; Cui, Tie Jun

2018-05-01

We propose a strategy to convert a linearly polarized wave from a single point source to an orbital angular momentum (OAM) wave by arbitrary polarization via an anisotropic frequency selective surface (FSS) in the microwave frequency. By tailoring the geometries of FSS elements, reflection-phases in x and y polarizations are engineered and encoded independently, which allows us to design the eventual polarization state of the generated OAM vortex beam by elaborately selecting individual coding sequences for each polarization. Two types of FSSs are designed and experimentally characterized to demonstrate the capability of OAM generation with circular and linear polarizations, respectively, showing excellent performance in a wide bandwidth from 14 to 16 GHz. This method provides opportunities for polarization multiplexing in microwave OAM communication systems.

Mechanism underlying selective regulation of G protein-gated inwardly rectifying potassium channels by the psychostimulant-sensitive sorting nexin 27

Science.gov (United States)

Balana, Bartosz; Maslennikov, Innokentiy; Kwiatkowski, Witek; Stern, Kalyn M.; Bahima, Laia; Choe, Senyon; Slesinger, Paul A.

2011-01-01

G protein-gated inwardly rectifying potassium (GIRK) channels are important gatekeepers of neuronal excitability. The surface expression of neuronal GIRK channels is regulated by the psychostimulant-sensitive sorting nexin 27 (SNX27) protein through a class I (-X-Ser/Thr-X-Φ, where X is any residue and Φ is a hydrophobic amino acid) PDZ-binding interaction. The G protein-insensitive inward rectifier channel (IRK1) contains the same class I PDZ-binding motif but associates with a different synaptic PDZ protein, postsynaptic density protein 95 (PSD95). The mechanism by which SNX27 and PSD95 discriminate these channels was previously unclear. Using high-resolution structures coupled with biochemical and functional analyses, we identified key amino acids upstream of the channel's canonical PDZ-binding motif that associate electrostatically with a unique structural pocket in the SNX27-PDZ domain. Changing specific charged residues in the channel's carboxyl terminus or in the PDZ domain converts the selective association and functional regulation by SNX27. Elucidation of this unique interaction site between ion channels and PDZ-containing proteins could provide a therapeutic target for treating brain diseases. PMID:21422294

On Data and Parameter Estimation Using the Variational Bayesian EM-algorithm for Block-fading Frequency-selective MIMO Channels

DEFF Research Database (Denmark)

Christensen, Lars P.B.; Larsen, Jan

2006-01-01

A general Variational Bayesian framework for iterative data and parameter estimation for coherent detection is introduced as a generalization of the EM-algorithm. Explicit solutions are given for MIMO channel estimation with Gaussian prior and noise covariance estimation with inverse-Wishart prior....... Simulation of a GSM-like system provides empirical proof that the VBEM-algorithm is able to provide better performance than the EM-algorithm. However, if the posterior distribution is highly peaked, the VBEM-algorithm approaches the EM-algorithm and the gain disappears. The potential gain is therefore...

In vivo and in vitro attenuation of naloxone-precipitated experimental opioid withdrawal syndrome by insulin and selective KATP channel modulator.

Science.gov (United States)

Singh, Prabhat; Sharma, Bhupesh; Gupta, Surbhi; Sharma, B M

2015-01-01

Opiate exposure for longer duration develops state of dependence in humans and animals, which is revealed by signs and symptoms of withdrawal precipitated by opioid receptor antagonists. The sudden withdrawal of opioids produces a withdrawal syndrome in opioid-dependent subjects. Insulin and ATP-sensitive potassium (KATP) channel-mediated glucose homeostasis have been shown to modulate morphine withdrawal. Present study has been structured to investigate the role of insulin and pharmacological modulator of KATP channel (gliclazide) in experimental morphine withdrawal syndrome, both invivo and invitro. In this study, naloxone-precipitated morphine withdrawal syndrome in mice (invivo) as well as in rat ileum (invitro) were utilized to assess opioid withdrawal phenomenon. Morphine withdrawal syndromes like jumping and rearing frequency, forepaw licking, circling, fore paw tremor, wet dog shake, sneezing, overall morphine withdrawal severity (OMWS), serum glucose, brain malondialdehyde (MDA), glutathione (GSH), nitrite/nitrate, and calcium (Ca(+2)) were assessed. Naloxone has significantly increased morphine withdrawal syndrome, both invivo and invitro. Insulin and gliclazide have significantly attenuated, naloxone induced behavioral changes like jumping and rearing frequency, forepaw licking, wet dog shake, sneezing, straightening, circling, OMWS, and various biochemical impairments such as serum glucose, brain MDA, GSH, nitrite/nitrate, and Ca(+2) in morphine-dependent animals (invivo). In vitro, insulin and gliclazide have significantly reduced naloxone-induced contraction in morphine-withdrawn rat ileum preparation. Insulin and gliclazide (KATP channel blocker) have attenuated naloxone-precipitated morphine withdrawal syndrome, both invivo and invitro. Thus, insulin and KATP channel modulation may provide new avenues for research in morphine withdrawal.

Estimate of Hurricane Wind Speed from AMSR-E Low-Frequency Channel Brightness Temperature Data

Directory of Open Access Journals (Sweden)

Lei Zhang

2018-01-01

Full Text Available Two new parameters (W6H and W6V were defined that represent brightness temperature increments for different low-frequency channels due to ocean wind. We developed a new wind speed retrieval model inside hurricanes based on W6H and W6V using brightness temperature data from AMSR-E. The AMSR-E observations of 12 category 3–5 hurricanes from 2003 to 2011 and corresponding data from the H*wind analysis system were used to develop and validate the AMSR-E wind speed retrieval model. The results show that the mean bias and the overall root-mean-square (RMS difference of the AMSR-E retrieved wind speeds with respect to H*wind (HRD Real-time Hurricane Wind Analysis System analysis data were −0.01 m/s and 2.66 m/s, respectively. One case study showed that W6H and W6V were less sensitive to rain than the observed AMSR-E C-band and X-band brightness temperature data. The AMSR-E retrieval model was further validated by comparing the retrieved wind speeds against stepped-frequency microwave radiometer (SFMR measurements. The comparison showed an RMS difference of 3.41 m/s and a mean bias of 0.49 m/s.

Performance Analysis of Simple Channel Feedback Schemes for a Practical OFDMA System

DEFF Research Database (Denmark)

Pedersen, Klaus, I.; Kolding, Troels; Kovacs, Istvan

2009-01-01

In this paper, we evaluate the tradeoff between the amount of uplink channel feedback information and the orthogonal frequency-division multiple access (OFDMA) downlink performance with opportunistic frequency-domain packet scheduling. Three candidate channel feedback schemes are investigated......, including practical aspects, such as the effects of terminal measurement errors, bandwidth measurement granularity, quantization, and uplink signaling delays. The performance is evaluated by means of system-level simulations with detailed modeling of various radio resource-management algorithms, etc. Our...... results show that the optimal tradeoff between the channel feedback and the downlink OFDMA system performance depends on the radio channel frequency coherence bandwidth. We conclude that the so-called average best-M scheme is the most attractive channel feedback solution, where only the average channel...

Negative frequency-dependent selection between Pasteuria penetrans and its host Meloidogyne arenaria

Science.gov (United States)

In negative frequency-dependant selection (NFDS), parasite genotypes capable of infecting the numerically dominant host genotype are favored, while host genotypes resistant to the dominant parasite genotype are favored, creating a cyclical pattern of resistant genotypes in the host population and, a...

Joint source/channel coding of scalable video over noisy channels

Energy Technology Data Exchange (ETDEWEB)

Cheung, G.; Zakhor, A. [Department of Electrical Engineering and Computer Sciences University of California Berkeley, California94720 (United States)

1997-01-01

We propose an optimal bit allocation strategy for a joint source/channel video codec over noisy channel when the channel state is assumed to be known. Our approach is to partition source and channel coding bits in such a way that the expected distortion is minimized. The particular source coding algorithm we use is rate scalable and is based on 3D subband coding with multi-rate quantization. We show that using this strategy, transmission of video over very noisy channels still renders acceptable visual quality, and outperforms schemes that use equal error protection only. The flexibility of the algorithm also permits the bit allocation to be selected optimally when the channel state is in the form of a probability distribution instead of a deterministic state. {copyright} {ital 1997 American Institute of Physics.}

Fatigue level estimation of monetary bills based on frequency band acoustic signals with feature selection by supervised SOM

Science.gov (United States)

Teranishi, Masaru; Omatu, Sigeru; Kosaka, Toshihisa

Fatigued monetary bills adversely affect the daily operation of automated teller machines (ATMs). In order to make the classification of fatigued bills more efficient, the development of an automatic fatigued monetary bill classification method is desirable. We propose a new method by which to estimate the fatigue level of monetary bills from the feature-selected frequency band acoustic energy pattern of banking machines. By using a supervised self-organizing map (SOM), we effectively estimate the fatigue level using only the feature-selected frequency band acoustic energy pattern. Furthermore, the feature-selected frequency band acoustic energy pattern improves the estimation accuracy of the fatigue level of monetary bills by adding frequency domain information to the acoustic energy pattern. The experimental results with real monetary bill samples reveal the effectiveness of the proposed method.

A Novel OFDM Channel Estimation Algorithm with ICI Mitigation over Fast Fading Channels

Directory of Open Access Journals (Sweden)

C. Tao

2010-06-01

Full Text Available Orthogonal frequency-division multiplexing (OFDM is well-known as a high-bit-rate transmission technique, but the Doppler frequency offset due to the high speed movement destroys the orthogonality of the subcarriers resulting in the intercarrier interference (ICI, and degrades the performance of the system at the same time. In this paper a novel OFDM channel estimation algorithm with ICI mitigation based on the ICI self-cancellation scheme is proposed. With this method, a more accurate channel estimation is obtained by comb-type double pilots and then ICI coefficients can be obtained to mitigate the ICI on each subcarrier under the assumption that the channel impulse response (CIR varies in a linear fashion. The theoretical analysis and simulation results show that the bit error rate (BER and spectral efficiency performances are improved significantly under high-speed mobility conditions (350 km/h – 500 km/h in comparison to ZHAO’s ICI self-cancellation scheme.

Channel Incision Driven by Suburbanization: Impacts to Riparian Groundwater Flow and Overbank Flow Frequency

Science.gov (United States)

Bowles, C. J.; Lawrence, R. L.; Noll, C.; Hancock, G. S.

2005-12-01

Channel incision is a widely observed response to increased flow in urbanized watersheds, but the effects of channel lowering on riparian water tables is not well documented. In a rapidly incising suburban stream in the Virginia Coastal Plain, we hypothesize that stream incision has lowered floodplain water tables and decreased the overbank flow frequency. The monitored stream is a tributary to the James River draining 1.3 km2 of which 15% is impervious cover. Incision has occurred largely through upstream migration of a one meter high knickpoint at a rate of ~1.5 m/yr, primarily during high flow events. We installed 63 wells in six stream-perpendicular transects as well as a cluster of wells around the knickpoint to assess water table elevations beneath the floodplain adjacent to the incising stream. Two transects are located 30 and 50 m upstream of the knickpoint in the unincised floodplain, and the remainder are 5, 30, 70, and 100 m downstream in the incised floodplain. In one transect above and two below, pressure transducers attached to dataloggers provide a high-resolution record of water table changes. Erosion pins were installed and channel cross-sections surveyed to determine streambed stability. Significant differences are observed in bank morphology and groundwater flow above vs. below the knickpoint. Above the knickpoint, the banks are stable, ~3 m wide, and ~0.3 m deep, and widen and deepen slightly toward the knickpoint. The water table is relatively flat and is 0.2-0.4 m below the floodplain surface, and groundwater contours suggest flow is parallel to the stream direction. The water table responds immediately to precipitation events, and rises to the floodplain surface in significant rainfall events. Immediately downstream of the knickpoint, channel width increases by about a meter, and stream depth increases to ~1.5 meters. The water table immediately below the knickpoint possesses a steep gradient, and is up to one meter below the floodplain

Sanshool on The Fingertip Interferes with Vibration Detection in a Rapidly-Adapting (RA Tactile Channel.

Directory of Open Access Journals (Sweden)

Scinob Kuroki

Full Text Available An Asian spice, Szechuan pepper (sanshool, is well known for the tingling sensation it induces on the mouth and on the lips. Electrophysiological studies have revealed that its active ingredient can induce firing of mechanoreceptor fibres that typically respond to mechanical vibration. Moreover, a human behavioral study has reported that the perceived frequency of sanshool-induced tingling matches with the preferred frequency range of the tactile rapidly adapting (RA channel, suggesting the contribution of sanshool-induced RA channel firing to its unique perceptual experience. However, since the RA channel may not be the only channel activated by sanshool, there could be a possibility that the sanshool tingling percept may be caused in whole or in part by other sensory channels. Here, by using a perceptual interference paradigm, we show that the sanshool-induced RA input indeed contributes to the human tactile processing. The absolute detection thresholds for vibrotactile input were measured with and without sanshool application on the fingertip. Sanshool significantly impaired detection of vibrations at 30 Hz (RA channel dominant frequency, but did not impair detection of higher frequency vibrations at 240 Hz (Pacinian-corpuscle (PC channel dominant frequency or lower frequency vibrations at 1 Hz (slowly adapting 1 (SA1 channel dominant frequency. These results show that the sanshool induces a peripheral RA channel activation that is relevant for tactile perception. This anomalous activation of RA channels may contribute to the unique tingling experience of sanshool.

Synchronization and matched filtering in time-frequency using the sunflower spiral

NARCIS (Netherlands)

Korevaar, C.W.; Kokkeler, Andre B.J.; de Boer, Pieter-Tjerk; Smit, Gerardus Johannes Maria

2012-01-01

Synchronization and matched filtering of signals in time dispersive, frequency dispersive and time-frequency dispersive channels are addressed in this paper. The ‘eigenfunctions’ of these channels form the signal sets under investigation. While using channel-eigenfunctions is a first requirement for

Cortical drive of low-frequency oscillations in the human nucleus accumbens during action selection.

Science.gov (United States)

Stenner, Max-Philipp; Litvak, Vladimir; Rutledge, Robb B; Zaehle, Tino; Schmitt, Friedhelm C; Voges, Jürgen; Heinze, Hans-Jochen; Dolan, Raymond J

2015-07-01

The nucleus accumbens is thought to contribute to action selection by integrating behaviorally relevant information from multiple regions, including prefrontal cortex. Studies in rodents suggest that information flow to the nucleus accumbens may be regulated via task-dependent oscillatory coupling between regions. During instrumental behavior, local field potentials (LFP) in the rat nucleus accumbens and prefrontal cortex are coupled at delta frequencies (Gruber AJ, Hussain RJ, O'Donnell P. PLoS One 4: e5062, 2009), possibly mediating suppression of afferent input from other areas and thereby supporting cortical control (Calhoon GG, O'Donnell P. Neuron 78: 181-190, 2013). In this report, we demonstrate low-frequency cortico-accumbens coupling in humans, both at rest and during a decision-making task. We recorded LFP from the nucleus accumbens in six epilepsy patients who underwent implantation of deep brain stimulation electrodes. All patients showed significant coherence and phase-synchronization between LFP and surface EEG at delta and low theta frequencies. Although the direction of this coupling as indexed by Granger causality varied between subjects in the resting-state data, all patients showed a cortical drive of the nucleus accumbens during action selection in a decision-making task. In three patients this was accompanied by a significant coherence increase over baseline. Our results suggest that low-frequency cortico-accumbens coupling represents a highly conserved regulatory mechanism for action selection. Copyright © 2015 the American Physiological Society.

Flow around turbulence promoters in parallel channel, (2)

International Nuclear Information System (INIS)

Shiina, Yasuaki

1983-01-01

Effects of walls on shedding vortex in developed channel flow were investigated putting a cylinder at the center of channels or on a wall for the value of w/d from 2 to 4. Results were compared with the uniform flow result. When a cylinder was put at the center of the channels, non-dimensional frequency plotted against Reynolds number agreed with the uniform flow result at low Reynolds number. However, it increased rapidly with Reynolds number, then it lay considerably above the uniform flow results at high Reynolds number. When a cylinder was put on a wall, non-dimensional frequency was considerably lower than the uniform flow result in the cases of w/d = 3 and 4. In the case of w/d = 2, however, frequency was higher than the uniform flow result at high Reynolds number. In all cases in the present study, the transition Reynolds number increased with decrease in the value of w/d. These results indicate that the increase in shedding frequency was due to the shift in velocity distribution from Poiseuille parabora in the wake region, which obviously increased with Reynolds number and with decrease in channel width. (author)

Top down and bottom up selection drives variations in frequency and form of a visual signal

OpenAIRE

Yeh, Chien-Wei; Blamires, Sean J.; Liao, Chen-Pan; Tso, I.-Min

2015-01-01

The frequency and form of visual signals can be shaped by selection from predators, prey or both. When a signal simultaneously attracts predators and prey, selection may favour a strategy that minimizes risks while attracting prey. Accordingly, varying the frequency and form of the silken decorations added to their web may be a way that Argiope spiders minimize predation while attracting prey. Nonetheless, the role of extraneous factors renders the influences of top down and bottom up selecti...

Hopping control channel MAC protocol for opportunistic spectrum access networks

Institute of Scientific and Technical Information of China (English)

FU Jing-tuan; JI Hong; MAO Xu

2010-01-01

Opportunistic spectrum access （OSA） is considered as a promising approach to mitigate spectrum scarcity by allowing unlicensed users to exploit spectrum opportunities in licensed frequency bands. Derived from the existing channel-hopping multiple access （CHMA） protocol,we introduce a hopping control channel medium access control （MAC） protocol in the context of OSA networks. In our proposed protocol,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Considering primary users＇ occupancy of the channel,we use a primary user （PU） detection model to calculate the channel availability for unlicensed users＇ access. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.

Program scheme using common source lines in channel stacked NAND flash memory with layer selection by multilevel operation

Science.gov (United States)

Kim, Do-Bin; Kwon, Dae Woong; Kim, Seunghyun; Lee, Sang-Ho; Park, Byung-Gook

2018-02-01

To obtain high channel boosting potential and reduce a program disturbance in channel stacked NAND flash memory with layer selection by multilevel (LSM) operation, a new program scheme using boosted common source line (CSL) is proposed. The proposed scheme can be achieved by applying proper bias to each layer through its own CSL. Technology computer-aided design (TCAD) simulations are performed to verify the validity of the new method in LSM. Through TCAD simulation, it is revealed that the program disturbance characteristics is effectively improved by the proposed scheme.

Bathymetric survey of the Cayuga Inlet flood-control channel and selected tributaries in Ithaca, New York, 2016

Science.gov (United States)

Wernly, John F.; Nystrom, Elizabeth A.; Coon, William F.

2017-09-08

From July 14 to July 20, 2016, the U.S. Geological Survey, in cooperation with the City of Ithaca, New York, and the New York State Department of State, surveyed the bathymetry of the Cayuga Inlet flood-control channel and the mouths of selected tributaries to Cayuga Inlet and Cayuga Lake in Ithaca, N.Y. The flood-control channel, built by the U.S. Army Corps of Engineers between 1965 and 1970, was designed to convey flood flows from the Cayuga Inlet watershed through the City of Ithaca and minimize possible flood damages. Since that time, the channel has infrequently been maintained by dredging, and sediment accumulation and resultant shoaling have greatly decreased the conveyance of the channel and its navigational capability.U.S. Geological Survey personnel collected bathymetric data by using an acoustic Doppler current profiler. The survey produced a dense dataset of water depths that were converted to bottom elevations. These elevations were then used to generate a geographic information system bathymetric surface. The bathymetric data and resultant bathymetric surface show the current condition of the channel and provide the information that governmental agencies charged with maintaining the Cayuga Inlet for flood-control and navigational purposes need to make informed decisions regarding future maintenance measures.

Novel role for the transient potential receptor melastatin 4 channel in guinea pig detrusor smooth muscle physiology

Science.gov (United States)

Smith, Amy C.; Hristov, Kiril L.; Cheng, Qiuping; Xin, Wenkuan; Parajuli, Shankar P.; Earley, Scott; Malysz, John

2013-01-01

Members of the transient receptor potential (TRP) channel superfamily, including the Ca2+-activated monovalent cation-selective TRP melastatin 4 (TRPM4) channel, have been recently identified in the urinary bladder. However, their expression and function at the level of detrusor smooth muscle (DSM) remain largely unexplored. In this study, for the first time we investigated the role of TRPM4 channels in guinea pig DSM excitation-contraction coupling using a multidisciplinary approach encompassing protein detection, electrophysiology, live-cell Ca2+ imaging, DSM contractility, and 9-phenanthrol, a recently characterized selective inhibitor of the TRPM4 channel. Western blot and immunocytochemistry experiments demonstrated the expression of the TRPM4 channel in whole DSM tissue and freshly isolated DSM cells with specific localization on the plasma membrane. Perforated whole cell patch-clamp recordings and real-time Ca2+ imaging experiments with fura 2-AM, both using freshly isolated DSM cells, revealed that 9-phenanthrol (30 μM) significantly reduced the cation current and decreased intracellular Ca2+ levels. 9-Phenanthrol (0.1–30 μM) significantly inhibited spontaneous, 0.1 μM carbachol-induced, 20 mM KCl-induced, and nerve-evoked contractions in guinea pig DSM-isolated strips with IC50 values of 1–7 μM and 70–80% maximum inhibition. 9-Phenanthrol also reduced nerve-evoked contraction amplitude induced by continuous repetitive electrical field stimulation of 10-Hz frequency and shifted the frequency-response curve (0.5–50 Hz) relative to the control. Collectively, our data demonstrate the novel finding that TRPM4 channels are expressed in guinea pig DSM and reveal their critical role in the regulation of guinea pig DSM excitation-contraction coupling. PMID:23302778

Degenerated-Inverse-Matrix-Based Channel Estimation for OFDM Systems

Directory of Open Access Journals (Sweden)

Makoto Yoshida

2009-01-01

Full Text Available This paper addresses time-domain channel estimation for pilot-symbol-aided orthogonal frequency division multiplexing (OFDM systems. By using a cyclic sinc-function matrix uniquely determined by Nc transmitted subcarriers, the performance of our proposed scheme approaches perfect channel state information (CSI, within a maximum of 0.4 dB degradation, regardless of the delay spread of the channel, Doppler frequency, and subcarrier modulation. Furthermore, reducing the matrix size by splitting the dispersive channel impulse response into clusters means that the degenerated inverse matrix estimator (DIME is feasible for broadband, high-quality OFDM transmission systems. In addition to theoretical analysis on normalized mean squared error (NMSE performance of DIME, computer simulations over realistic nonsample spaced channels also showed that the DIME is robust for intersymbol interference (ISI channels and fast time-invariant channels where a minimum mean squared error (MMSE estimator does not work well.

Selective visual scaling of time-scale processes facilitates broadband learning of isometric force frequency tracking.

Science.gov (United States)

King, Adam C; Newell, Karl M

2015-10-01

The experiment investigated the effect of selectively augmenting faster time scales of visual feedback information on the learning and transfer of continuous isometric force tracking tasks to test the generality of the self-organization of 1/f properties of force output. Three experimental groups tracked an irregular target pattern either under a standard fixed gain condition or with selectively enhancement in the visual feedback display of intermediate (4-8 Hz) or high (8-12 Hz) frequency components of the force output. All groups reduced tracking error over practice, with the error lowest in the intermediate scaling condition followed by the high scaling and fixed gain conditions, respectively. Selective visual scaling induced persistent changes across the frequency spectrum, with the strongest effect in the intermediate scaling condition and positive transfer to novel feedback displays. The findings reveal an interdependence of the timescales in the learning and transfer of isometric force output frequency structures consistent with 1/f process models of the time scales of motor output variability.

Groundwater controls on river channel pattern

Science.gov (United States)

Bätz, Nico; Colombini, Pauline; Cherubini, Paolo; Lane, Stuart N.

2017-04-01

Braided rivers are characterized by high rates of morphological change. However, despite the potential for frequent disturbance, vegetated patches may develop within this system and influence long-term channel dynamics and channel patterns through the "engineering effects" of vegetation. The stabilizing effect of developing vegetation on morphological change has been widely shown by flume experiments and (historic) aerial pictures analysis. Thus, there is a balance between disturbance and stabilization, mediated through vegetation, that may determine the long-term geomorphic and biogeomorphic evolution of the river. It follows that with a change in disturbance frequency relative to the rate of vegetation establishment, a systematic geomorphological shift could occur. Research has addressed how changes in disturbance frequency affect river channel pattern, but has rarely addressed the way in which the stabilizing effects of biogeomorphic succession interact with disturbance frequency to maintain a river in a more dynamic or a less dynamic state. Here, we quantify how the interplay between groundwater access, disturbance frequency and vegetation succession, drive changes in channel pattern. We studied this complex interplay on a transitional gravel-bed river system (braided, wandering, meandering) close to Geneva (Switzerland) - the Allondon River. Dendroecological analysis demonstrate that vegetation growth is driven by groundwater access. Groundwater access conditions the rate of vegetation stabilization at the sub-reach scale and, due to a reduction in flood-related disturbance frequency over the last 50 years, drives a change in channel pattern. Where groundwater is shallower, vegetation encroachment rates were high and as flood-related disturbance decreased, the river has shifted towards a meandering state. Where groundwater was deeper, vegetation growth was limited by water-access and thus vegetation encroachment rates were low. Even though there was a

Sparse Variational Bayesian SAGE Algorithm With Application to the Estimation of Multipath Wireless Channels

DEFF Research Database (Denmark)

Shutin, Dmitriy; Fleury, Bernard Henri

2011-01-01

In this paper, we develop a sparse variational Bayesian (VB) extension of the space-alternating generalized expectation-maximization (SAGE) algorithm for the high resolution estimation of the parameters of relevant multipath components in the response of frequency and spatially selective wireless...... channels. The application context of the algorithm considered in this contribution is parameter estimation from channel sounding measurements for radio channel modeling purpose. The new sparse VB-SAGE algorithm extends the classical SAGE algorithm in two respects: i) by monotonically minimizing...... parametric sparsity priors for the weights of the multipath components. We revisit the Gaussian sparsity priors within the sparse VB-SAGE framework and extend the results by considering Laplace priors. The structure of the VB-SAGE algorithm allows for an analytical stability analysis of the update expression...

TRPV6 channels.

Science.gov (United States)

Fecher-Trost, Claudia; Weissgerber, Petra; Wissenbach, Ulrich

2014-01-01

TRPV6 (former synonyms ECAC2, CaT1, CaT-like) displays several specific features which makes it unique among the members of the mammalian Trp gene family (1) TRPV6 (and its closest relative, TRPV5) are the only highly Ca(2+)-selective channels of the entire TRP superfamily (Peng et al. 1999; Wissenbach et al. 2001; Voets et al. 2004). (2) Translation of Trpv6 initiates at a non-AUG codon, at ACG, located upstream of the annotated AUG, which is not used for initiation (Fecher-Trost et al. 2013). The ACG codon is nevertheless decoded by methionine. Not only a very rare event in eukaryotic biology, the full-length TRPV6 protein existing in vivo comprises an amino terminus extended by 40 amino acid residues compared to the annotated truncated TRPV6 protein which has been used in most studies on TRPV6 channel activity so far. (In the following numbering occurs according to this full-length protein, with the numbers of the so far annotated truncated protein in brackets). (3) Only in humans a coupled polymorphism of Trpv6 exists causing three amino acid exchanges and resulting in an ancestral Trpv6 haplotype and a so-called derived Trpv6 haplotype (Wissenbach et al. 2001). The ancestral allele encodes the amino acid residues C197(157), M418(378) and M721(681) and the derived alleles R197(157), V418(378) and T721(681). The ancestral haplotype is found in all species, the derived Trpv6 haplotype has only been identified in humans, and its frequency increases with the distance to the African continent. Apparently the Trpv6 gene has been a strong target for selection in humans, and its derived variant is one of the few examples showing consistently differences to the orthologues genes of other primates (Akey et al. 2004, 2006; Stajich and Hahn 2005; Hughes et al. 2008). (4) The Trpv6 gene expression is significantly upregulated in several human malignancies including the most common cancers, prostate and breast cancer (Wissenbach et al. 2001; Zhuang et al. 2002; Fixemer et al

Incorporating Born solvation energy into the three-dimensional Poisson-Nernst-Planck model to study ion selectivity in KcsA K+ channels

Science.gov (United States)

Liu, Xuejiao; Lu, Benzhuo

2017-12-01

Potassium channels are much more permeable to potassium than sodium ions, although potassium ions are larger and both carry the same positive charge. This puzzle cannot be solved based on the traditional Poisson-Nernst-Planck (PNP) theory of electrodiffusion because the PNP model treats all ions as point charges, does not incorporate ion size information, and therefore cannot discriminate potassium from sodium ions. The PNP model can qualitatively capture some macroscopic properties of certain channel systems such as current-voltage characteristics, conductance rectification, and inverse membrane potential. However, the traditional PNP model is a continuum mean-field model and has no or underestimates the discrete ion effects, in particular the ion solvation or self-energy (which can be described by Born model). It is known that the dehydration effect (closely related to ion size) is crucial to selective permeation in potassium channels. Therefore, we incorporated Born solvation energy into the PNP model to account for ion hydration and dehydration effects when passing through inhomogeneous dielectric channel environments. A variational approach was adopted to derive a Born-energy-modified PNP (BPNP) model. The model was applied to study a cylindrical nanopore and a realistic KcsA channel, and three-dimensional finite element simulations were performed. The BPNP model can distinguish different ion species by ion radius and predict selectivity for K+ over Na+ in KcsA channels. Furthermore, ion current rectification in the KcsA channel was observed by both the PNP and BPNP models. The I -V curve of the BPNP model for the KcsA channel indicated an inward rectifier effect for K+ (rectification ratio of ˜3 /2 ) but indicated an outward rectifier effect for Na+ (rectification ratio of ˜1 /6 ) .

How does male–male competition generate negative frequency-dependent selection and disruptive selection during speciation?

Science.gov (United States)

Border, Shana E

2018-01-01

Abstract Natural selection has been shown to drive population differentiation and speciation. The role of sexual selection in this process is controversial; however, most of the work has centered on mate choice while the role of male–male competition in speciation is relatively understudied. Here, we outline how male–male competition can be a source of diversifying selection on male competitive phenotypes, and how this can contribute to the evolution of reproductive isolation. We highlight how negative frequency-dependent selection (advantage of rare phenotype arising from stronger male–male competition between similar male phenotypes compared with dissimilar male phenotypes) and disruptive selection (advantage of extreme phenotypes) drives the evolution of diversity in competitive traits such as weapon size, nuptial coloration, or aggressiveness. We underscore that male–male competition interacts with other life-history functions and that variable male competitive phenotypes may represent alternative adaptive options. In addition to competition for mates, aggressive interference competition for ecological resources can exert selection on competitor signals. We call for a better integration of male–male competition with ecological interference competition since both can influence the process of speciation via comparable but distinct mechanisms. Altogether, we present a more comprehensive framework for studying the role of male–male competition in speciation, and emphasize the need for better integration of insights gained from other fields studying the evolutionary, behavioral, and physiological consequences of agonistic interactions. PMID:29492042

Frequency multiplexing for readout of spin qubits

Energy Technology Data Exchange (ETDEWEB)

Hornibrook, J. M.; Colless, J. I.; Mahoney, A. C.; Croot, X. G.; Blanvillain, S.; Reilly, D. J., E-mail: david.reilly@sydney.edu.au [ARC Centre of Excellence for Engineered Quantum Systems, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Lu, H.; Gossard, A. C. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

2014-03-10

We demonstrate a low loss, chip-level frequency multiplexing scheme for readout of scaled-up spin qubit devices. By integrating separate bias tees and resonator circuits on-chip for each readout channel, we realise dispersive gate-sensing in combination with charge detection based on two radio frequency quantum point contacts. We apply this approach to perform multiplexed readout of a double quantum dot in the few-electron regime and further demonstrate operation of a 10-channel multiplexing device. Limitations for scaling spin qubit readout to large numbers of multiplexed channels are discussed.

Hydraulic modeling of stream channels and structures in Harbor and Crow Hollow Brooks, Meriden, Connecticut

Science.gov (United States)

Weiss, Lawrence A.; Sears, Michael P.; Cervione, Michael A.

1994-01-01

Effects of urbanization have increased the frequency and size of floods along certain reaches of Harbor Brook and Crow Hollow Brook in Meriden, Conn. A floodprofile-modeling study was conducted to model the effects of selected channel and structural modifications on flood elevations and inundated areas. The study covered the reach of Harbor Brook downstream from Interstate 691 and the reach of Crow Hollow Brook downstream from Johnson Avenue. Proposed modifications, which include changes to bank heights, channel geometry, structural geometry, and streambed armoring on Harbor Brook and changes to bank heights on Crow Hollow Brook, significantly lower flood elevations. Results of the modeling indicate a significant reduction of flood elevations for the 10-year, 25-year, 35-year, 50-year, and 100-year flood frequencies using proposed modifications to (1 ) bank heights between Harbor Brook Towers and Interstate 691 on Harbor Brook, and between Centennial Avenue and Johnson Avenue on Crow Hollow Brook; (2) channel geometry between Coe Avenue and Interstate 69 1 on Harbor Brook; (3) bridge and culvert opening geometry between Harbor Brook Towers and Interstate 691 on Harbor Brook; and (4) channel streambed armoring between Harbor Brook Towers and Interstate 691 on Harbor Brook. The proposed modifications were developed without consideration of cost-benefit ratios.

Broadband Reflectionless Metasheets: Frequency-Selective Transmission and Perfect Absorption

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V. S. Asadchy

2015-07-01

Full Text Available Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin resonant absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper, we explore possibilities to realize a thin absorbing layer that produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a thin resonant absorber, invisible in reflection in a very wide frequency range, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cell, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create nonreflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultracompact wave filters and selective multifrequency sensors.

A Channelization-Based DOA Estimation Method for Wideband Signals

Directory of Open Access Journals (Sweden)

Rui Guo

2016-07-01

Full Text Available In this paper, we propose a novel direction of arrival (DOA estimation method for wideband signals with sensor arrays. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using a digital channelization receiver. Based on the output sub-channels, a channelization-based incoherent signal subspace method (Channelization-ISM and a channelization-based test of orthogonality of projected subspaces method (Channelization-TOPS are proposed. Channelization-ISM applies narrowband signal subspace methods on each sub-channel independently. Then the arithmetic mean or geometric mean of the estimated DOAs from each sub-channel gives the final result. Channelization-TOPS measures the orthogonality between the signal and the noise subspaces of the output sub-channels to estimate DOAs. The proposed channelization-based method isolates signals in different bandwidths reasonably and improves the output SNR. It outperforms the conventional ISM and TOPS methods on estimation accuracy and dynamic range, especially in real environments. Besides, the parallel processing architecture makes it easy to implement on hardware. A wideband digital array radar (DAR using direct wideband radio frequency (RF digitization is presented. Experiments carried out in a microwave anechoic chamber with the wideband DAR are presented to demonstrate the performance. The results verify the effectiveness of the proposed method.

Ecological genetics of the Bromus tectorum (Poaceae) - Ustilago Bullata (Ustilaginaceae): A role for frequency dependent selection?

Science.gov (United States)

Susan E. Meyer; David L. Nelson; Suzette Clement; Alisa Ramakrishnan

2010-01-01

Evolutionary processes that maintain genetic diversity in plants are likely to include selection imposed by pathogens. Negative frequency-dependent selection is a mechanism for maintenance of resistance polymorphism in plant - pathogen interactions. We explored whether such selection operates in the Bromus tectorum - Ustilago bullata pathosystem. Gene-for-gene...

Human HDAC isoform selectivity achieved via exploitation of the acetate release channel with structurally unique small molecule inhibitors

Energy Technology Data Exchange (ETDEWEB)

Whitehead, Lewis; Dobler, Markus R.; Radetich, Branko; Zhu, Yanyi; Atadja, Peter W.; Claiborne, Tavina; Grob, Jonathan E.; McRiner, Andrew; Pancost, Margaret R.; Patnaik, Anup; Shao, Wenlin; Shultz, Michael; Tichkule, Ritesh; Tommasi, Ruben A.; Vash, Brian; Wang, Ping; Stams, Travis (Novartis)

2013-11-20

Herein we report the discovery of a family of novel yet simple, amino-acid derived class I HDAC inhibitors that demonstrate isoform selectivity via access to the internal acetate release channel. Isoform selectivity criteria is discussed on the basis of X-ray crystallography and molecular modeling of these novel inhibitors bound to HDAC8, potentially revealing insights into the mechanism of enzymatic function through novel structural features revealed at the atomic level.

Video error concealment using block matching and frequency selective extrapolation algorithms

Science.gov (United States)

P. K., Rajani; Khaparde, Arti

2017-06-01

Error Concealment (EC) is a technique at the decoder side to hide the transmission errors. It is done by analyzing the spatial or temporal information from available video frames. It is very important to recover distorted video because they are used for various applications such as video-telephone, video-conference, TV, DVD, internet video streaming, video games etc .Retransmission-based and resilient-based methods, are also used for error removal. But these methods add delay and redundant data. So error concealment is the best option for error hiding. In this paper, the error concealment methods such as Block Matching error concealment algorithm is compared with Frequency Selective Extrapolation algorithm. Both the works are based on concealment of manually error video frames as input. The parameter used for objective quality measurement was PSNR (Peak Signal to Noise Ratio) and SSIM(Structural Similarity Index). The original video frames along with error video frames are compared with both the Error concealment algorithms. According to simulation results, Frequency Selective Extrapolation is showing better quality measures such as 48% improved PSNR and 94% increased SSIM than Block Matching Algorithm.

On the performance of arbitrary transmit selection for threshold-based receive MRC with and without co-channel interference

KAUST Repository

Radaydeh, Redha Mahmoud Mesleh

2011-11-01

The performance of multiple-antenna diversity systems in which the receiver combines signal replicas per threshold-based maximal ratio combining (MRC) and transmitter uses only a single antenna according to receive combined signal strength is studied. The impact of imperfect channel estimation and the effect of phase and time misalignments between desired and undesired signals are implicitly investigated. It is assumed that the desired signal replicas and interfering signals undergo statistically independent flat Rayleigh fading. The analysis is applicable for arbitrary transmit antenna selection, based either on receive combined signal-to-noise ratio (SNR) or receive combined signal-to-interference-plus-noise ratio (SINR). For the scenario of identical multiple-antenna channels, closed-form analytical results for the combined SNR statistics and some performance measures are first presented. The SNR-based and SINR-based selection algorithms are then employed to obtain expressions for the distribution of combined SINR and outage probability performance, which are applicable for different statistical models of interfering signals. The adopted system models herein as well as the analytical development add enhancements on many existing results, and can be used to study the performance of different architectures under various channel conditions when the implementation complexity is of interest. © 2011 IEEE.

On the performance of arbitrary transmit selection for threshold-based receive MRC with and without co-channel interference

KAUST Repository

Radaydeh, Redha Mahmoud Mesleh; Alouini, Mohamed-Slim

2011-01-01

The performance of multiple-antenna diversity systems in which the receiver combines signal replicas per threshold-based maximal ratio combining (MRC) and transmitter uses only a single antenna according to receive combined signal strength is studied. The impact of imperfect channel estimation and the effect of phase and time misalignments between desired and undesired signals are implicitly investigated. It is assumed that the desired signal replicas and interfering signals undergo statistically independent flat Rayleigh fading. The analysis is applicable for arbitrary transmit antenna selection, based either on receive combined signal-to-noise ratio (SNR) or receive combined signal-to-interference-plus-noise ratio (SINR). For the scenario of identical multiple-antenna channels, closed-form analytical results for the combined SNR statistics and some performance measures are first presented. The SNR-based and SINR-based selection algorithms are then employed to obtain expressions for the distribution of combined SINR and outage probability performance, which are applicable for different statistical models of interfering signals. The adopted system models herein as well as the analytical development add enhancements on many existing results, and can be used to study the performance of different architectures under various channel conditions when the implementation complexity is of interest. © 2011 IEEE.

Broadband Mm-Wave OFDM Communications in Doubly Selective Channel: Performance Evaluation Using Measured Mm-Wave Channel

DEFF Research Database (Denmark)

Chen, Xiaoming; Fan, Wei; Pedersen, Gert F.

2018-01-01

In this work, we evaluate the performance of the broadband millimeter-wave (mm-wave) OFDM system in the presence of phase noise (PN) of phase-locked loop based oscillator and delay spread of measured mm-wave channel. It is shown, using Akaike's information criterion, that the channel tap...... coefficients of the broadband mm-wave channel do not follow Gaussian distribution due to the broad bandwidth. It is also shown that, given a cyclic prefix (CP) length for a certain delay spread, an effective PN mitigation scheme enables a PN corrupted OFDM system to function with small subcarrier spacing and...

Signatures of positive selection: from selective sweeps at individual loci to subtle allele frequency changes in polygenic adaptation.

Science.gov (United States)

Stephan, Wolfgang

2016-01-01

In the past 15 years, numerous methods have been developed to detect selective sweeps underlying adaptations. These methods are based on relatively simple population genetic models, including one or two loci at which positive directional selection occurs, and one or two marker loci at which the impact of selection on linked neutral variation is quantified. Information about the phenotype under selection is not included in these models (except for fitness). In contrast, in the quantitative genetic models of adaptation, selection acts on one or more phenotypic traits, such that a genotype-phenotype map is required to bridge the gap to population genetics theory. Here I describe the range of population genetic models from selective sweeps in a panmictic population of constant size to evolutionary traffic when simultaneous sweeps at multiple loci interfere, and I also consider the case of polygenic selection characterized by subtle allele frequency shifts at many loci. Furthermore, I present an overview of the statistical tests that have been proposed based on these population genetics models to detect evidence for positive selection in the genome. © 2015 John Wiley & Sons Ltd.

Planck 2013 results. VI. High Frequency Instrument data processing

DEFF Research Database (Denmark)

Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.

2013-01-01

We describe the processing of the 531 billion raw data samples from the High Frequency Instrument (HFI), which we performed to produce six temperature maps from the first 473 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143,217, 353, 545......, these two high frequency channels are calibrated to within 5% and the 353 GHz channel to the percent level. The 100 and217 GHz channels, which together with the 143 GHz channel determine the high-multipole part of the CMB power spectrum (50

Automatic pickup of arrival time of channel wave based on multi-channel constraints

Science.gov (United States)

Wang, Bao-Li

2018-03-01

Accurately detecting the arrival time of a channel wave in a coal seam is very important for in-seam seismic data processing. The arrival time greatly affects the accuracy of the channel wave inversion and the computed tomography (CT) result. However, because the signal-to-noise ratio of in-seam seismic data is reduced by the long wavelength and strong frequency dispersion, accurately timing the arrival of channel waves is extremely difficult. For this purpose, we propose a method that automatically picks up the arrival time of channel waves based on multi-channel constraints. We first estimate the Jaccard similarity coefficient of two ray paths, then apply it as a weight coefficient for stacking the multichannel dispersion spectra. The reasonableness and effectiveness of the proposed method is verified in an actual data application. Most importantly, the method increases the degree of automation and the pickup precision of the channel-wave arrival time.

Sound frequency and aural selectivity in sound-contingent visual motion aftereffect.

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Maori Kobayashi

Full Text Available BACKGROUND: One possible strategy to evaluate whether signals in different modalities originate from a common external event or object is to form associations between inputs from different senses. This strategy would be quite effective because signals in different modalities from a common external event would then be aligned spatially and temporally. Indeed, it has been demonstrated that after adaptation to visual apparent motion paired with alternating auditory tones, the tones begin to trigger illusory motion perception to a static visual stimulus, where the perceived direction of visual lateral motion depends on the order in which the tones are replayed. The mechanisms underlying this phenomenon remain unclear. One important approach to understanding the mechanisms is to examine whether the effect has some selectivity in auditory processing. However, it has not yet been determined whether this aftereffect can be transferred across sound frequencies and between ears. METHODOLOGY/PRINCIPAL FINDINGS: Two circles placed side by side were presented in alternation, producing apparent motion perception, and each onset was accompanied by a tone burst of a specific and unique frequency. After exposure to this visual apparent motion with tones for a few minutes, the tones became drivers for illusory motion perception. However, the aftereffect was observed only when the adapter and test tones were presented at the same frequency and to the same ear. CONCLUSIONS/SIGNIFICANCE: These findings suggest that the auditory processing underlying the establishment of novel audiovisual associations is selective, potentially but not necessarily indicating that this processing occurs at an early stage.

128 Channel PCI-based data acquisition system for MDSplus

Energy Technology Data Exchange (ETDEWEB)

Llobet, Xavier E-mail: xavier.llobet@epfl.ch; Duval, Basil P. E-mail: basil.duval@epfl.ch

2002-06-01

With the increasing demand for analogue channel acquisition on the TCV tokamak, a new PCI based acquisition has been specified, designed, built and installed into our MDSplus acquisition environment. The design criteria were to not only improve the cost/channel, as compared to our conventional hub based acquisition (CAMAC), but to provide some distributed processing power to avoid the associated acquisition server saturation, both in terms of CPU and network bandwidth. These units were initially intended to satisfy the requirements of general variable rate acquisition from a variety of sources, and many channel acquisition from modern multi-channel diagnostics. Hosted by a i386-Linux PC in a crate with four available PCI slots, each single-PCI slot 32-channel digitiser features sampling frequencies up to 200 kHz, and 64 MB of memory, providing 1 Msample of 16-bit data per channel. The local hard disk is used for immediate local storage of all the acquired data from the selected channels into a local MDSplus database. The host is then accessed as a MDS/IP server that provides, on demand, down-sampled and software filtered traces. The local hard disk capacity is used for medium to long-term storage and availability of the full data set with optional mirror technology to guard against hard disk failure. We have thus obtained a general solution for high resolution, multi-channel routine acquisition using the multi-platform MDSplus environment, in which different software and hardware architectures are intelligently linked across a standard TCP/IP network. The implementation presented here uses ONLY standard components of the MDSplus environment.

128 Channel PCI-based data acquisition system for MDSplus

International Nuclear Information System (INIS)

Llobet, Xavier; Duval, Basil P.

2002-01-01

With the increasing demand for analogue channel acquisition on the TCV tokamak, a new PCI based acquisition has been specified, designed, built and installed into our MDSplus acquisition environment. The design criteria were to not only improve the cost/channel, as compared to our conventional hub based acquisition (CAMAC), but to provide some distributed processing power to avoid the associated acquisition server saturation, both in terms of CPU and network bandwidth. These units were initially intended to satisfy the requirements of general variable rate acquisition from a variety of sources, and many channel acquisition from modern multi-channel diagnostics. Hosted by a i386-Linux PC in a crate with four available PCI slots, each single-PCI slot 32-channel digitiser features sampling frequencies up to 200 kHz, and 64 MB of memory, providing 1 Msample of 16-bit data per channel. The local hard disk is used for immediate local storage of all the acquired data from the selected channels into a local MDSplus database. The host is then accessed as a MDS/IP server that provides, on demand, down-sampled and software filtered traces. The local hard disk capacity is used for medium to long-term storage and availability of the full data set with optional mirror technology to guard against hard disk failure. We have thus obtained a general solution for high resolution, multi-channel routine acquisition using the multi-platform MDSplus environment, in which different software and hardware architectures are intelligently linked across a standard TCP/IP network. The implementation presented here uses ONLY standard components of the MDSplus environment

Trade-offs between microbial growth phases lead to frequency-dependent and non-transitive selection.

Science.gov (United States)

Manhart, Michael; Adkar, Bharat V; Shakhnovich, Eugene I

2018-02-14

Mutations in a microbial population can increase the frequency of a genotype not only by increasing its exponential growth rate, but also by decreasing its lag time or adjusting the yield (resource efficiency). The contribution of multiple life-history traits to selection is a critical question for evolutionary biology as we seek to predict the evolutionary fates of mutations. Here we use a model of microbial growth to show that there are two distinct components of selection corresponding to the growth and lag phases, while the yield modulates their relative importance. The model predicts rich population dynamics when there are trade-offs between phases: multiple strains can coexist or exhibit bistability due to frequency-dependent selection, and strains can engage in rock-paper-scissors interactions due to non-transitive selection. We characterize the environmental conditions and patterns of traits necessary to realize these phenomena, which we show to be readily accessible to experiments. Our results provide a theoretical framework for analysing high-throughput measurements of microbial growth traits, especially interpreting the pleiotropy and correlations between traits across mutants. This work also highlights the need for more comprehensive measurements of selection in simple microbial systems, where the concept of an ordinary fitness landscape breaks down. © 2018 The Author(s).

Impact of Antenna Placement on Frequency Domain Adaptive Antenna Array in Hybrid FRF Cellular System

Directory of Open Access Journals (Sweden)

Sri Maldia Hari Asti

2012-01-01

Full Text Available Frequency domain adaptive antenna array (FDAAA is an effective method to suppress interference caused by frequency selective fading and multiple-access interference (MAI in single-carrier (SC transmission. However, the performance of FDAAA receiver will be affected by the antenna placement parameters such as antenna separation and spread of angle of arrival (AOA. On the other hand, hybrid frequency reuse can be adopted in cellular system to improve the cellular capacity. However, optimal frequency reuse factor (FRF depends on the channel propagation and transceiver scheme as well. In this paper, we analyze the impact of antenna separation and AOA spread on FDAAA receiver and optimize the cellular capacity by using hybrid FRF.

Analytical Solution for Elliptical Cloaks Based on The Frequency Selective Surface

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E. Ghasemi Mizuji

2015-01-01

Full Text Available In this paper the elliptical dielectric cylinder which is covered with FSS cloak is considered. Frequency selective surface cloak which Alu named it mantle cloak is one of the recent techniques for cloaking. In this method an appropriate FSS can act as cloaking device for suppressing  the scattering of object  in the desired frequency. With using this method the dimension of the cloaks is extremely reduced. By this proposed structure, the RCS of elliptical cylinder  is reduced about 10-20 dB and designed cloak has an appropriate performance.  The analytical solution for the wave in each layer is presented and with using simulation, the electric field and the scattering pattern has been drawn.

Synthesis, structural characterization and selectively catalytic properties of metal-organic frameworks with nano-sized channels: A modular design strategy

International Nuclear Information System (INIS)

Qiu Lingguang; Gu Lina; Hu Gang; Zhang Lide

2009-01-01

Modular design method for designing and synthesizing microporous metal-organic frameworks (MOFs) with selective catalytical activity was described. MOFs with both nano-sized channels and potential catalytic activities could be obtained through self-assembly of a framework unit and a catalyst unit. By selecting hexaaquo metal complexes and the ligand BTC (BTC=1,3,5-benzenetricarboxylate) as framework-building blocks and using the metal complex [M(phen) 2 (H 2 O) 2 ] 2+ (phen=1,10-phenanthroline) as a catalyst unit, a series of supramolecular MOFs 1-7 with three-dimensional nano-sized channels, i.e. [M 1 (H 2 O) 6 ].[M 2 (phen) 2 (H 2 O) 2 ] 2 .2(BTC).xH 2 O (M 1 , M 2 =Co(II), Ni(II), Cu(II), Zn(II), or Mn(II), phen=1,10-phenanthroline, BTC=1,3,5-benzenetricarboxylate, x=22-24), were synthesized through self-assembly, and their structures were characterized by IR, elemental analysis, and single-crystal X-ray diffraction. These supramolecular microporous MOFs showed significant size and shape selectivity in the catalyzed oxidation of phenols, which is due to catalytic reactions taking place in the channels of the framework. Design strategy, synthesis, and self-assembly mechanism for the construction of these porous MOFs were discussed. - Grapical abstract: A modular design strategy has been developed to synthesize microporous metal-organic frameworks with potential catalytic activity by self-assembly of the framework-building blocks and the catalyst unit

Single-Channel Blind Estimation of Reverberation Parameters

DEFF Research Database (Denmark)

Doire, C.S.J.; Brookes, M. D.; Naylor, P. A.

2015-01-01

The reverberation of an acoustic channel can be characterised by two frequency-dependent parameters: the reverberation time and the direct-to-reverberant energy ratio. This paper presents an algorithm for blindly determining these parameters from a single-channel speech signal. The algorithm uses...

AFM imaging reveals the tetrameric structure of the TRPC1 channel

International Nuclear Information System (INIS)

Barrera, Nelson P.; Shaifta, Yasin; McFadzean, Ian; Ward, Jeremy P.T.; Henderson, Robert M.; Edwardson, J. Michael

2007-01-01

We have determined the subunit stoichiometry of the transient receptor potential C1 (TRPC1) channel by imaging isolated channels using atomic force microscopy (AFM). A frequency distribution of the molecular volumes of individual channel particles had two peaks, at 170 and 720 nm 3 , corresponding with the expected sizes of TRPC1 monomers and tetramers, respectively. Complexes were formed between TRPC1 channels and antibodies against a V5 epitope tag present on each subunit. The frequency distribution of angles between pairs of bound antibodies had two peaks, at 88 o and 178 o . This result again indicates that the channel assembles as a tetramer

Energy tunneling through narrow waveguide channel and design of small antennas

Directory of Open Access Journals (Sweden)

Mitrović Miranda

2011-01-01

Full Text Available In this paper we investigate the conditions for energy tunneling through narrow channel obtained by reducing the height of rectangular waveguide. Tunneling of the energy occurs at the frequency for which the effective dielectric permittivity of the channel becomes equal to zero, so it can be treated as an ENZ (epsilon-near-zero metamaterial. We investigated how geometry of the channel and dielectric permittivity affect the transmission coefficient and field density in the channel. Adding slots in the channel, which are placed orthogonally to the wave propagation, we designed a small antenna with directivity of 5.44 dBi at the frequency of 3 GHz.

Planck 2013 results. VI. High Frequency Instrument data processing

CERN Document Server

Ade, P.A.R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J. -P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J.J.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Boulanger, F.; Bowyer, J.W.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J. -F.; Catalano, A.; Chamballu, A.; Chary, R. -R.; Chen, X.; Chiang, L. -Y; Chiang, H.C.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J. -M.; Désert, F. -X.; Dickinson, C.; Diego, J.M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T.A.; Eriksen, H.K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Girard, D.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J.E.; Hansen, F.K.; Hanson, D.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herent, O.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, T.R.; Jaffe, A.H.; Jones, W.C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J. -M.; Lasenby, A.; Laureijs, R.J.; Lawrence, C.R.; Jeune, M. Le; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P.B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P.M.; Macías-Pérez, J.F.; MacTavish, C.J.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P.R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M. -A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Mottet, S.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Nørgaard-Nielsen, H.U.; North, C.; Noviello, F.; Novikov, D.; Novikov, I.; Orieux, F.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prézeau, G.; Prunet, S.; Puget, J. -L.; Rachen, J.P.; Racine, B.; Reach, W.T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sanselme, L.; Santos, D.; Sauvé, A.; Savini, G.; Shellard, E.P.S.; Spencer, L.D.; Starck, J. -L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A. -S.; Sygnet, J. -F.; Tauber, J.A.; Tavagnacco, D.; Techene, S.; Terenzi, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; White, S.D.M.; Yvon, D.; Zacchei, A.; Zonca, A.

2014-01-01

We describe the processing of the 531 billion raw data samples from the High Frequency Instrument (hereafter HFI), which we performed to produce six temperature maps from the first 473 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143, 217, 353, 545, and 857 GHz with an angular resolution ranging from 9.7 to 4.6 arcmin. The detector noise per (effective) beam solid angle is respectively, 10, 6, 12 and 39 microKelvin in HFI four lowest frequency channel (100--353 GHz) and 13 and 14 kJy/sr for the 545 and 857 GHz channels. Using the 143 GHz channel as a reference, these two high frequency channels are intercalibrated within 5% and the 353 GHz relative calibration is at the percent level. The 100 and 217 GHz channels, which together with the 143 GHz channel determine the high-multipole part of the CMB power spectrum (50 < l <2500), are intercalibrated at better than 0.2 %.

Mixed Stimulus-Induced Mode Selection in Neural Activity Driven by High and Low Frequency Current under Electromagnetic Radiation

Directory of Open Access Journals (Sweden)

Lulu Lu

2017-01-01

Full Text Available The electrical activities of neurons are dependent on the complex electrophysiological condition in neuronal system, the three-variable Hindmarsh-Rose (HR neuron model is improved to describe the dynamical behaviors of neuronal activities with electromagnetic induction being considered, and the mode transition of electrical activities in neuron is detected when external electromagnetic radiation is imposed on the neuron. In this paper, different types of electrical stimulus impended with a high-low frequency current are imposed on new HR neuron model, and mixed stimulus-induced mode selection in neural activity is discussed in detail. It is found that mode selection of electrical activities stimulated by high-low frequency current, which also changes the excitability of neuron, can be triggered owing to adding the Gaussian white noise. Meanwhile, the mode selection of the neuron electrical activity is much dependent on the amplitude B of the high frequency current under the same noise intensity, and the high frequency response is selected preferentially by applying appropriate parameters and noise intensity. Our results provide insights into the transmission of complex signals in nerve system, which is valuable in engineering prospective applications such as information encoding.

Selective block of KATP channels: why the anti-diabetic sulphonylureas and rosiglitazone have more in common than we thought

Science.gov (United States)

Dart, Caroline

2012-01-01

Rosiglitazone, the thiazolidinedione class anti-diabetic withdrawn from Europe in 2010 amid reports of adverse cardiovascular effects, is revealed by Yu et al. in this issue of the British Journal of Pharmacology to be a selective blocker of ATP-sensitive potassium (KATP) channels. This seems little cause for excitement given that the closure of pancreatic KATP channels is integral to insulin secretion; and sulphonylureas, which inhibit KATP channels, are widely used to treat type II diabetes. However, rosiglitazone, whose primary targets are nuclear transcription factors that regulate genes involved in lipid metabolism, blocks KATP channels by a novel mechanism different to that of the sulphonylureas and has a worrying preference for blood flow–regulating vascular KATP channels. Identification of a new molecule that modulates KATP channel gating will not only tell us more about how these complex metabolic sensors work but also raises questions as to whether rosiglitazone suppresses the cardiovascular system's ability to cope with metabolic stress – a claim that has dogged the sulphonylureas for many years. LINKED ARTICLE This article is a commentary on Yu et al., pp. 26–36 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2012.01934.x PMID:22506686

Broadband Mm-Wave OFDM Communications in Doubly Selective Channel: Performance Evaluation Using Measured Mm-Wave Channel

DEFF Research Database (Denmark)

Chen, Xiaoming; Fan, Wei; Pedersen, Gert F.

2018-01-01

coefficients of the broadband mm-wave channel do not follow Gaussian distribution due to the broad bandwidth. It is also shown that, given a cyclic prefix (CP) length for a certain delay spread, an effective PN mitigation scheme enables a PN corrupted OFDM system to function with small subcarrier spacing and......In this work, we evaluate the performance of the broadband millimeter-wave (mm-wave) OFDM system in the presence of phase noise (PN) of phase-locked loop based oscillator and delay spread of measured mm-wave channel. It is shown, using Akaike's information criterion, that the channel tap......, therefore, small CP overhead, with only slight degradation of the error rate performance....

An information-guided channel-hopping scheme for block-fading channels with estimation errors

KAUST Repository

Yang, Yuli

2010-12-01

Information-guided channel-hopping technique employing multiple transmit antennas was previously proposed for supporting high data rate transmission over fading channels. This scheme achieves higher data rates than some mature schemes, such as the well-known cyclic transmit antenna selection and space-time block coding, by exploiting the independence character of multiple channels, which effectively results in having an additional information transmitting channel. Moreover, maximum likelihood decoding may be performed by simply decoupling the signals conveyed by the different mapping methods. In this paper, we investigate the achievable spectral efficiency of this scheme in the case of having channel estimation errors, with optimum pilot overhead for minimum meansquare error channel estimation, when transmitting over blockfading channels. Our numerical results further substantiate the robustness of the presented scheme, even with imperfect channel state information. ©2010 IEEE.

An FPGA-Based Adaptable 200 MHz Bandwidth Channel Sounder for Wireless Communication Channel Characterisation

Directory of Open Access Journals (Sweden)

David L. Ndzi

2011-01-01

Full Text Available This paper describes the development of a fast adaptable FPGA-based wideband channel sounder with signal bandwidths of up to 200 MHz and channel sampling rates up to 5.4 kHz. The application of FPGA allows the user to vary the number of real-time channel response averages, channel sampling interval, and duration of measurement. The waveform, bandwidth, and frequency resolution of the sounder can be adapted for any channel under investigation. The design approach and technology used has led to a reduction in size and weight by more than 60%. This makes the sounder ideal for mobile time-variant wireless communication channels studies. Averaging allows processing gains of up to 30 dB to be achieved for measurement in weak signal conditions. The technique applied also improves reliability, reduces power consumption, and has shifted sounder design complexity from hardware to software. Test results show that the sounder can detect very small-scale variations in channels.

Development of in-situ laser cutting technique for removal of single selected coolant channel from pressurized heavy water reactor

International Nuclear Information System (INIS)

Vishwakarma, S.C.; Upadhyaya, B.N.

2016-01-01

We report on the development of a pulsed Nd:YAG laser based cutting technique for removal of single coolant channel from pressurized heavy water reactor (PHWR). It includes development of special tools/manipulators and optimization of laser cutting process parameters for cutting of liner tube, end fitting, bellow lip weld joint, and pressure tube stubs. For each cutting operation, a special tool with precision motion control is utilized. These manipulators/tools hold and move the laser cutting nozzle in the required manner and are fixed on the same coolant channel, which has to be removed. This laser cutting technique has been successfully deployed for removal of selected coolant channels Q-16, Q-15 and N-6 of KAPS-2 reactor with minimum radiation dose consumption and in short time. (author)

Control channels in the brain and their influence on brain executive functions

Science.gov (United States)

Meng, Qinglei; Choa, Fow-Sen; Hong, Elliot; Wang, Zhiguang; Islam, Mohammad

2014-05-01

In a computer network there are distinct data channels and control channels where massive amount of visual information are transported through data channels but the information streams are routed and controlled by intelligent algorithm through "control channels". Recent studies on cognition and consciousness have shown that the brain control channels are closely related to the brainwave beta (14-40 Hz) and alpha (7-13 Hz) oscillations. The high-beta wave is used by brain to synchronize local neural activities and the alpha oscillation is for desynchronization. When two sensory inputs are simultaneously presented to a person, the high-beta is used to select one of the inputs and the alpha is used to deselect the other so that only one input will get the attention. In this work we demonstrated that we can scan a person's brain using binaural beats technique and identify the individual's preferred control channels. The identified control channels can then be used to influence the subject's brain executive functions. In the experiment, an EEG measurement system was used to record and identify a subject's control channels. After these channels were identified, the subject was asked to do Stroop tests. Binaural beats was again used to produce these control-channel frequencies on the subject's brain when we recorded the completion time of each test. We found that the high-beta signal indeed speeded up the subject's executive function performance and reduced the time to complete incongruent tests, while the alpha signal didn't seem to be able to slow down the executive function performance.

Heat Coulomb blockade of one ballistic channel