Symmetric Window Research Articles

GABAergic synaptic transmission regulates calcium influx during spike-timing dependent plasticity

Coincident pre- and postsynaptic activity of hippocampal neurons alters the strength of gamma-aminobutyric acid (GABAA)-mediated inhibition through a Ca2+-dependent regulation of cation-chloride cotransporters. This long-term synaptic modulation is termed GABAergic spike-timing dependent plasticity (STDP). In the present study, we examined whether the properties of the GABAergic synapses themselves modulate the required postsynaptic Ca2+ influx during GABAergic STDP induction. To do this we first identified GABAergic synapses between cultured hippocampal neurons based on their relatively long decay time constants and their reversal potentials which lay close to the resting membrane potential. GABAergic STDP was then induced by coincidentally (±1 ms) firing the pre- and postsynaptic neurons at 5 Hz for 30 s, while postsynaptic Ca2+ was imaged with the Ca2+-sensitive fluorescent dye Fluo4-AM. In all cases, the induction of GABAergic STDP increased postsynaptic Ca2+ above resting levels. We further found that the magnitude of this increase correlated with the amplitude and polarity of the GABAergic postsynaptic current (GPSC); hyperpolarizing GPSCs reduced the Ca2+ influx in comparison to both depolarizing GPSCs, and postsynaptic neurons spiked alone. This relationship was influenced by both the driving force for Cl− and GABAA conductance (which had positive correlations with the Ca2+ influx). The spike-timing order during STDP induction did not influence the correlation between GPSC amplitude and Ca2+ influx, which is likely accounted for by the symmetrical GABAergic STDP window.

Enhancing Binary Change Detection Performance Using A Moving Threshold Window (MTW) Approach

This study introduced a new concept, the Moving Threshold Window (MTW), for binary change detection. An automated MTW-based calibration model was developed and evaluated using a case study. The MTW-based model is free from the assumption of symmetry for difference and ratio types of change-enhanced images, unlike traditional binary change detection methods. The MTW-based calibration model outperformed the traditional binary change detection methods based on the Symmetric Threshold Window (STW) for both single and multiple change-enhanced images of the study area. In most of the calibrations, the optimum thresholds resulting in the highest Kappa coefficient were asymmetric. Three major factors may explain the asymmetric characteristics of the optimum thresholds, including: different atmospheric conditions found in the two dates of imagery, different look angles associated with the two dates of imagery, and the nature of the change information. Multiple change-enhanced images generally produced higher accuracies than single changeenhanced images using both the MTW- and STW-based models.

Matching the temporal window and the fine‐structure.

Research in psychological and physiological acoustics requires careful stimulus generation. This is especially true for research in binaural hearing because of the importance of interaural phase relationships. Knowing the stimulus precisely becomes even more important when the experiment employs reproducible noise because there is less averaging over stimulus variations. The discrete Fourier transform can be used to generate noise bursts with precise timing. Although the bursts are not band limited, the amplitude and phase spectra are well characterized within any chosen band if the fine‐structure is matched to the temporal window. For the example, with a 100‐ms rectangular window, the components are taken to be integer multiples of a fundamental frequency of 10 Hz. With this ideal fundamental frequency, the long‐term spectrum is predictable. If the window is not rectangular, the ideal fundamental frequency depends on the temporal parameters of the window. The ideal frequency can be found from the Fourier transform of the window itself. For trapezoidal and Hann (raised‐cosine) symmetrical windows, the ideal frequency turns out to be the reciprocal of the total (nonsilent) duration minus the rise time (only). Windows that are not symmetrical about their center lead to phase shifts and should be avoided.

What marks the beat of speech?

Which acoustic properties of the speech signal differ between rhythmically prominent syllables and non-prominent ones? A production experiment was conducted to identify these acoustic properties. Subjects read out repetitive text to a metronome, trying to match stressed syllables to its beat. The analysis searched for the function of the speech signal that best predicts the timing of the metronome ticks. The most important factor in this function is found to be the contrast in loudness between a syllable and its neighbors. The prominence of a syllable can be deduced from the specific loudness in an (approximately) 360 ms window centered on the syllable in question relative to an (approximately) 800-ms-wide symmetric window.

Characterization and performance analysis of a TOAD switch employing a dual control pulse scheme in high-speed OTDM demultiplexer

This letter presents the characterization, analysis and simulation of a novel dual control pulse (CP) scheme for the Terahertz Optical Asymmetric Demultiplexer (TOAD) switch used as a demultiplexer in optical time division multiplexing (OTDM) system. The dual-CP TOAD offers symmetrical switching window (SW) which reduces inter-channel crosstalk (CXT) in switched/demultiplexed channels, thus significantly improving the bit-error-rate (BER) and received power penalty. The improvements in CXT and received power penalty are 5 and 1.5 dB (at BER = 10-9), respectively, for demultiplexing high bit rates of 200 and 300-to-10 Gb/s.

Small Angle Gamma Ray Scatter: What Is The Impact On Image Quality

Not unlike the potential small translocation errors associated with the angle of variation from perpendicular defined by the collimator 'hole' length and diameter, limitations of energy discrimination in scintigraphy might also result in a small degradation of resolution and/or contrast. Methods: A series of 99mTc line sources were acquired with multiple energy windows to provide simultaneous acquisition of data. Each energy window combination was acquired with the line source on the collimator surface, against 4.0cm of water attenuation and against 8.0cm of water attenuation. A series of 99mTc thyroid and brain phantoms were also acquired using dual energy windows positioned to capture a 10% window below 140keV and a 10% window above 140keV. The thyroid and the brain phantoms were each positioned on the collimator surface, against 4.0cm of water attenuation and against 8.0cm of water attenuation. Results: The mean improvement in FWHM for 140keV + 10% over 140keV – 10% was 0.26mm (95% CI: 0.16 – 0.36) or 4.0% (95% CI: 2.5 – 5.5) which showed a statistically significant variation from the hypothetical zero difference (P < 0.001). While a 15% window centred on 144keV provided superior image contrast compared to both 15% and 20% centred on 140keV, the improvement is associated with a decrease in accumulated counts. The increase in sampling error associated with these decreased counts, however, is 0.1% to 0.2%. Conclusion: Energy discrimination with a symmetric window about the photopeak is ineffective in eliminating photons scattered by as much as 45 to 60 degrees. While the direct impact on image resolution is perhaps negligible, low angle scatter is a major source of potential artifact and contrast degradation. A 15% energy window centered on 144keV might provide an optimized trade-off between contrast and total counts.

Detecting rhythmical prominence in speech by an optimized convolution kernel

We present an approach for detecting rhythmical prominence in read speech. A production experiment was conducted during which subjects repetitively read out speech to a metronome, trying to match stressed syllables to its beat. In the analysis, we compute a function from the speech waveform, related to acoustic properties of speech such as specific loudness, pitch, voicing, and spectral slope. The function is then convolved with a Mexican Hat convolution kernel. Taking large maxima in the function to be predictions of the metronome ticks, we adjust the parameters of the signal to maximize the accuracy of the predictions. The parameters are adjusted by minimizing the phase variation between metronome ticks and ticks predicted from the audio, over a specified time interval. We confirm the results by Bootstrap resampling. We find that the most important factor is the contrast in specific loudness between a syllable and its neighbors. The prominence can be deduced from the specific loudness in an (approximately) 360 ms window centered on the syllable in question relative to an (approximately) 800 ms-wide symmetric window.

Synthesis of a benzoxazine monomer containing maleimide and allyloxy groups

A novel benzoxazine monomer 3-(4-allyloxy)phenyl-3,4-dihydro-2 H-6-( N-maleimido)-1,3-benzoxazine (AMB) was synthesized and structure was confirmed by FT-IR, 1H NMR. Thermal analysis (DSC) of AMB showed the introduction of allyloxy group decreased melting point and exhibited a narrow and symmetric curing exothermic window.

A CMOS circuit for STDP with a symmetric time window

In some spiking neuron models, analog information is expressed by the timing of neuronal spike firing events, and synaptic weights change depending on the relative timing between asynchronous spikes, which is called spike-timing dependent synaptic plasticity (STDP). In this paper, we propose an analog CMOS circuit for STDP with a symmetric time window and a Hopfield-type VLSI neural network using the synapse circuit. We have confirmed by circuit simulations that the network can perform autocorrelation learning from input spike patterns.

The relation between spike-timing dependent plasticity and Ca2+ dynamics in the hippocampal CA1 network

In our previous study, spike timing dependent synaptic plasticity (STDP) was investigated in the CA1 area of rat hippocampal slices using optical imaging. It was revealed that the profiles of STDP could be classified into two types depending upon layer specific location along the dendrite. The first was characterized by a symmetric time window observed in the proximal region of the stratum radiatum (SR), and the second by an asymmetric time window in the distal region of the SR. Our methods involved the bath-application of bicuculline (GABAA receptor antagonist) to hippocampal slices, which revealed that GABAergic interneuron projections were responsible for the symmetry of a time window. In this study, the intracellular Ca2+ increase of hippocampal CA1 neurons, induced by the protocol of timing between pre- and post-synaptic excitation (i.e. STDP protocol), was measured spatially by using optical imaging to investigate how the triggering of STDP is dependant on intracellular calcium concentration. We found that the magnitude of STDP was closely related to the rate of Ca2+ increase (“velocity”) of calcium transient during application of induction stimuli. Location dependency was also analyzed in terms of Ca2+ influx. Furthermore, it was shown that decay time constant of Ca2+ dynamics during the application of STDP-inducing stimuli was also significantly correlated with STDP.

The binaural temporal window in adults and children

This study investigated the binaural temporal window in adults and children 5-10.5 years of age. Detection thresholds were estimated for a brief, interaurally out-of-phase (Spi) 500 Hz pure tone signal masked by bandpass, 100-2000 Hz Gaussian noise. In one set of conditions, the masker was consistently either in phase (No) or out of phase (Npi). In another set of conditions, the masker changed abruptly in interaural phase (NoNpi or NpiNo), and threshold was estimated at a range of delays with respect to the phase transition. Masked thresholds were also obtained in further conditions where the masker interaural phase was steady and the signal was of long duration. Age effects obtained with dynamic maskers could be accounted for by positing that children have a binaural temporal window with a relatively prolonged leading edge or that the children position the binaural temporal window relatively late with respect to the signal. Modeling of the reduced masking-level difference shown by children for a brief Spi signal presented in a steady No or Npi masker was more consistent with late placement of a symmetrical binaural temporal window than a binaural temporal window having a relatively prolonged leading edge.

Spectral Estimation of Wideband Noise in Delta–Sigma Modulators

Spectral leakage is a well-known phenomenon induced by the windowing process and usually revealed in the frequency domain. Scientific literature has deeply investigated the spectral leakage of narrow-band components. However, the problem of windowing a wide-band colored noise has not yet been fully characterized. In this paper, the effect of the windowing process on the estimate of the in-band DeltaSigma-shaped quantization-noise power spectral density is investigated. The reported analysis holds for any modulator order and for any kind of real and symmetric window and proves the necessity of the windowing process in order to reduce the in-band noise power estimation bias. Moreover, an a priori criterion for designing the optimal window that reduces the shaped-noise spectral leakage and for choosing the minimum number of acquired samples to be employed is derived

An Approach To Discrete Spectrum Correction Based on Energy Centroid

This paper proves that the energy centre of symmetric window function is the coordinate origin in discrete spectrum analysis. The correction formula of frequency, amplitude and phase can be obtained using this character. Simulation demonstrates that this method can correct averaged power spectrum directly with simple algorithm and fast processing speed, and the interference of negative or narrow interval frequencies has little influence on correction precision. This method is suitable for all kinds of symmetric window. But it is not suited with dense frequencies signal or continuous spectrum.

Low-voltage operation of metal-ferroelectric-insulator-semiconductor diodes incorporating a ferroelectric polyvinylidene fluoride copolymer Langmuir-Blodgett film

We report the electrical characteristics of metal-ferroelectric-insulator-semiconductor structures, where the ferroelectric layer is a Langmuir-Blodgett film of a copolymer of 70% vinylidene fluoride and 30% trifluoroethylene. The 36-nm thick copolymer films were deposited on thermally oxidized (10nm SiO2) p-type silicon and covered with a gold gate electrode. Polarization-field hysteresis loops indicate polarization switching in the polymer film. The device capacitance shows hysteresis when cycling the applied voltage between ±3V, exhibiting a zero-bias on/off capacitance ratio of over 3:1 and a symmetric memory window 1V wide, with little evidence of bias that can arise from traps in the oxide. Model calculations are in good agreement with the data and show that film polarization was not saturated. The capacitance hysteresis vanishes above the ferroelectric-paraelectric transition temperature, showing that it is due to polarization hysteresis. The retention time of both the on and off states was approximately 15min at room temperature, possibly limited by leakage or by polarization instability in the unsaturated film. These devices provide a basis for nonvolatile data storage devices with fast nondestructive readout.

Reduction of variance in spectral estimates for correction of ultrasonic aberration

A variance reduction factor is defined to describe the rate of convergence and accuracy of spectra estimated from overlapping ultrasonic scattering volumes when the scattering is from a spatially uncorrelated medium. Assuming that the individual volumes are localized by a spherically symmetric Gaussian window and that centers of the volumes are located on orbits of an icosahedral rotation group, the factor is minimized by adjusting the weight and radius of each orbit. Conditions necessary for the application of the variance reduction method, particularly for statistical estimation of aberration, are examined. The smallest possible value of the factor is found by allowing an unlimited number of centers constrained only to be within a ball rather than on icosahedral orbits. Computations using orbits formed by icosahedral vertices, face centers, and edge midpoints with a constraint radius limited to a small multiple of the Gaussian width show that a significant reduction of variance can be achieved from a small number of centers in the confined volume and that this reduction is nearly the maximum obtainable from an unlimited number of centers in the same volume.

Spatial analysis of spike-timing-dependent LTP and LTD in the CA1 area of hippocampal slices using optical imaging.

Spike-timing-dependent long-term potentiation (LTP) and long-term depression (LTD) were investigated in the CA1 area of hippocampal slices using optical imaging. A pair of electrical pulses were used to stimulate the Schaffer-commissural collateral and the stratum oriens with various sets of relative timing (tau) between the two stimuli. These sets of paired pulses gave rise to LTP/LTD, whose induction was closely related to tau, and their profiles were classified into two types depending on their layer specific location along the dendrite. One was characterized by a symmetric time window observed in the proximal region of the stratum radiatum (SR) and the other by an asymmetric time window in the distal region of the SR. Bath application of bicuculline (gamma-aminobutyric acid [GABA] receptor antagonist) to hippocampal slices revealed that GABAergic interneuron projections were responsible for the symmetry of a time window.

New Algorithm for Modulated Complex Lapped Transform With Symmetrical Window Function

An algorithm for the fast computation of modulated complex lapped transform (MCLT) with symmetrical window function is proposed. The method is based on two discrete cosine transforms (DCTs), two stages of butterfly operations and additional multiplications. The real or imaginary part of the MCLT coefficients can be independently obtained from one of the two blocks of DCT coefficients. The proposed algorithm not only reduces the computational complexity compared with previous algorithms, but also has regular architecture which is suitable for hardware implementations.

Numerical analysis of waveguide bandpass filters using singular integral equations and construction of simple design formulas

AbstractA powerful numerical solution is presented for bandpass filters in rectangular waveguides. The filters are composed of cascading of perfectly conducting inductive obstacles with zero thickness: asymmetrical windows, symmetrical windows, or symmetrical strips. The problem is reduced to a set of singular integral equations, which is solved by an extension of Lewin's quasi‐static procedure. After the accuracy of the classical formulas for the equivalent reactance is investigated, the simple inverse formulas are constructed to yield proper window widths for desired equivalent parameters. Their effectiveness is demonstrated by designing practical filters having maximally flat or equal‐ripple characteristics. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 17–25, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10251

The Bi-Gaussian S-Transform

The S-transform kernel is derived from the kernel of the Fourier transform through the introduction of a scalable, translating window. The width of the window is a function of inverse frequency. In effect the S-transform is a method of spectral localization, with some similarities to wavelet transforms but using the concept of frequency rather than the concept of scale. An important property of the S-transform is that it collapses into the Fourier transform when integrated over the time axis; this property requires the window to satisfy a normalizing condition. The window which has been used in the majority of previous S-transform research is the symmetric Gaussian window introduced by Stockwell, Mansinha, and Lowe [IEEE Trans. Signal Process., 44 (1996), pp. 998--1001]. One problem with the use of a Gaussian, however, is degradation of time resolution in the time-frequency spectrum due to the long front taper. In this paper, a bi-Gaussian window is introduced, constructed through the welding of two half Gaussian windows. The asymmetry of the bi-Gaussian introduces asymmetry in the resultant time-frequency spectrum, with time resolution better in the "front" direction, as compared with the "back" direction. The bi-Gaussian S-transform is better at resolving the sharp onset of events in a time series.

Time-shifting correcting method of phase difference on discrete spectrum

A general method called time-shifting correcting method of phase difference on discrete spectrum is presented. That is, the second discrete-time sequence lags behind the first one with L points, then performing N-point FFT analysis on both sequences, and finally correcting spectrum by making use of the phase difference of two corresponding peak lines. The method proposed by XIE Ming et al. is just the particular case of this method in the case that L is equal to N. Simulation result shows that this method is easily carried out with high precision, applicable for all kinds of symmetrical window functions and having high ability of anti-noise.