Comparison of phase effects in masking obtained from broad‐band and narrow‐band frozen noise waveforms

An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA). The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle) azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591) with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH) in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.

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Thalamic inputs determine functionally distinct gamma bands in mouse primary visual cortex

10.1101/2020.07.09.194811 ◽

2020 ◽

Author(s):

Nicolò Meneghetti ◽

Chiara Cerri ◽

Elena Tantillo ◽

Eleonora Vannini ◽

Matteo Caleo ◽

...

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Visual Information ◽

Narrow Band ◽

Broad Band ◽

Gamma Band ◽

Neuron Network ◽

Sensory Stimuli ◽

Thalamic Input ◽

Visual Contrast

AbstractGamma band is known to be involved in the encoding of visual features in the primary visual cortex (V1). Recent results in rodents V1 highlighted the presence, within a broad gamma band (BB) increasing with contrast, of a narrow gamma band (NB) peaking at ∼60 Hz suppressed by contrast and enhanced by luminance. However, the processing of visual information by the two channels still lacks a proper characterization. Here, by combining experimental analysis and modeling, we prove that the two bands are sensitive to specific thalamic inputs associated with complementary contrast ranges. We recorded local field potentials from V1 of awake mice during the presentation of gratings and observed that NB power progressively decreased from low to intermediate levels of contrast. Conversely, BB power was insensitive to low levels of contrast but it progressively increased going from intermediate to high levels of contrast. Moreover, BB response was stronger immediately after contrast reversal, while the opposite held for NB. All the aforementioned dynamics were accurately reproduced by a recurrent excitatory-inhibitory leaky integrate-and-fire network, mimicking layer IV of mouse V1, provided that the sustained and periodic component of the thalamic input were modulated over complementary contrast ranges. These results shed new light on the origin and function of the two V1 gamma bands. In addition, here we propose a simple and effective model of response to visual contrast that might help in reconstructing network dysfunction underlying pathological alterations of visual information processing.Significance StatementGamma band is a ubiquitous hallmark of cortical processing of sensory stimuli. Experimental evidence shows that in the mouse visual cortex two types of gamma activity are differentially modulated by contrast: a narrow band (NB), that seems to be rodent specific, and a standard broad band (BB), observed also in other animal models.We found that narrow band correlates and broad band anticorrelates with visual contrast in two complementary contrast ranges (low and high respectively). Moreover, BB displayed an earlier response than NB. A thalamocortical spiking neuron network model reproduced the aforementioned results, suggesting they might be due to the presence of two complementary but distinct components of the thalamic input into visual cortical circuitry.

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Argon Matrix Infrared Spectroscopic Evidence for the Generation of Pentatetraenone by Flash Pyrolysis of Suitable Precursors

Australian Journal of Chemistry ◽

10.1071/ch9880225 ◽

1988 ◽

Vol 41 (2) ◽

pp. 225 ◽

Cited By ~ 7

Author(s):

RFC Brown ◽

KJ Coulston ◽

FW Eastwood ◽

MJ Irvine ◽

ADE Pullin

Keyword(s):

Carbon Atom ◽

Infrared Spectra ◽

Spectral Region ◽

Narrow Band ◽

Broad Band ◽

Carbonyl Carbon Atom ◽

Carbonyl Carbon ◽

Argon Matrix ◽

Spectroscopic Evidence ◽

Argon Mixture

Five compounds were investigated as precursors for the pyrolytic generation of pentatetraenone, H2C=C=C=C=C=O. These were (1)-(4): 3- ethenylidenebicyclo [2.2.1]hept-5-ene with the following 2,2 substituents : H, COOCOCF3 (1); H, 13COOCOCF3 (1′); (COOCOCF3)2 (2); (COO)2C(CH3)(OCH3) (3); (COO)2Si(CH3)2 (4) and 5-(3′- methylenebicyclo [2.2.1]hept-5′-en-2′-ylidene)-2,2-dimethyl-1,3-dioxan-4,6-dione (5). The five precursors were pyrolysed in a stream of argon at temperatures in the range 350-725°C and the pyrolysate -argon mixture condensed on a CsI plate at c. 10 K. Infrared spectra were obtained between 4000 and 250 cm-1. All five precursors gave two strong bands in the spectral region 2070-2250 cm-1, possibly attributable to pentatetraenone. At lower pyrolytic temperatures the more intense of the two bands was a broad band centred at c. 2128 cm-1 [precursors (1)- (4)] or at c. 2094 cm-1 [precursor (5)]. At higher pyrolytic temperatures these bands were diminished in intensity and replaced by a narrow band at 2207 cm-1 for all five precursors. Bands due to the expected other products for each pyrolysis reaction to form pentatetraenone were observed. H2C413CO ( pentatetraenone substituted by 13C at the carbonyl carbon atom) was prepared by pyrolysis of precursor (1′). We assign the broad bands at c. 2128 cm-1 [precursors (1)-(4)] and at c. 2094 [precursor (5)] to incompletely pyrolysed precursor in which cyclopentadiene has been retained but decomposition in the rest of the molecule has resulted in formation of a =C=C=O group. Bands at 2207, 2068 and 1726 cm-1 we assign to v2-v4 of pentatetraenone. Corresponding bands at 2168, 2056 and 1720 cm-1 are observed in the spectrum of H2C413CO.

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Narrow Band and Broad Band Step-recovery Diode Frequency Multipliers for Microwave Power Generation

IETE Journal of Research ◽

10.1080/03772063.1972.11487043 ◽

1972 ◽

Vol 18 (10) ◽

pp. 457-463

Author(s):

V. P. Kodali

Keyword(s):

Power Generation ◽

Microwave Power ◽

Narrow Band ◽

Broad Band ◽

Frequency Multipliers

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SUPPRESSION OF JAMMING IN EXCITABLE SYSTEMS BY APERIODIC STOCHASTIC RESONANCE

International Journal of Bifurcation and Chaos ◽

10.1142/s0218127404011454 ◽

2004 ◽

Vol 14 (10) ◽

pp. 3519-3539 ◽

Cited By ~ 17

Author(s):

YING-CHENG LAI ◽

ZONGHUA LIU ◽

ARJE NACHMAN ◽

LIQIANG ZHU

Keyword(s):

Dynamical Systems ◽

Stochastic Resonance ◽

Narrow Band ◽

Broad Band ◽

Effective Mechanism ◽

Strong Broad Band ◽

Chaotic Signals ◽

Input Signals ◽

Excitable Systems ◽

Processing Information

To suppress undesirable noise (jamming) associated with signals is important for many applications. Here we explore the idea of jamming suppression with realistic, aperiodic signals by stochastic resonance. In particular, we consider weak amplitude-modulated (AM), frequency-modulated (FM), and chaotic signals with strong, broad-band or narrow-band jamming, and show that aperiodic stochastic resonance occurring in an array of excitable dynamical systems can be effective to counter jamming. We provide formulas for quantitative measures characterizing the resonance. As excitability is ubiquitous in biological systems, our work suggests that aperiodic stochastic resonance may be a universal and effective mechanism for reducing noise associated with input signals for transmitting and processing information.

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