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Noise Analysis (noise + analysis)

Distribution by Scientific Domains
Life Sciences50%
Engineering40%

Kinds of Noise Analysis

  • non-stationary noise analysis
    		•

    Selected Abstracts

    Analytical noise model of a high-electron-mobility transistor for microwave-frequency application

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2004
    Vandana Guru
    Abstract Noise analysis for AlGaAs/GaAs HEMT and AlGaAs/InGaAs/GaAs PHEMT is developed at microwave frequency using an accurate charge control approach. The small-signal parameters and the drain and gate-noise sources are calculated to determine the noise coefficients and correlation coefficients. Finally, the minimum noise figure is evaluated by incorporating the extrinsic noise sources and compared with the experimental data, which is in excellent agreement. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 410,417, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11396 [source]

    Diversity of GABAA receptor synaptic currents on individual pyramidal cortical neurons

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2007
    Timothy Ing
    Abstract Miniature GABAA receptor-mediated inhibitory postsynaptic currents (mIPSCs) in cortical pyramidal neurons have previously been categorized into two types: small amplitude mIPSCs with a mono-exponential deactivation (mono-mIPSCs) and relatively larger mIPSCs with bi-exponential deactivation (bi-mIPSCs). The aim of this study was to determine if the GABAA channels that underlie these mIPSCSs are molecularly distinct. We found, using non-stationary noise analysis, that the difference in their amplitude could be not accounted for by their single channel conductance (both were 40 pS). Next, using , subunit selective GABAA receptor modulators, we examined the identity of the , subunits that may be expressed in the synapses that give rise to these mIPSCs. Zolpidem (100 and 500 nm, ,1 selective) affected the deactivation of a subset of the mono-mIPSCs, indicating that ,1 subunits are not highly expressed in these synapses. However, zolpidem (100 nm) prolonged the deactivation of all bi-mIPSCs, indicating a high abundance of ,1 subunits in these synapses. SB-205384 (,3 selective) had no effect on the mono-mIPSCs but the bi-mIPSCs were prolonged. Furosemide (,4 selective) reduced the amplitude of only the mono-mIPSCs. L655,708 (,5 selective) reduced the amplitude of both populations and shortened the duration of the mono-mIPSCs. Finally, we found that the neuroactive steroid pregesterone sulphate reduced the amplitude of both mIPSC types. These results provide pharmacological evidence that synapses on cortical pyramidal neurons are molecularly distinct. The purpose of these different types of synapses may be to provide different inhibitory timing patterns on these cells. [source]

    Periodic noise analysis of electric circuits: Artifacts, singularities and a numerical method

    INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 7 2010
    Angelo Brambilla
    Abstract In this paper it is shown that a numerical method largely adopted for the simulation of noise in autonomous circuits is affected by singularities that manifest when the frequency at which the noise analysis is carried out approaches a harmonic of the autonomous circuit. The resulting noise power spectral density (PSD) is thus characterized by spurious spikes. The presence of these singularities is for the first time justified from an analytical standpoint and their effects are shown by simulating some oscillators, employed as benchmarks. Furthermore, the presented approach justifies the 1/(fs,f)2 shape of the PSD of noise at the output when the fs frequency approaches the f fundamental of a stable oscillator and the 1/|fs,f|3 shape when the effects of flicker noise are manifest. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Evaluation of 08CH18N10T stainless steel corrosion in subcritical water by electrochemical noise analysis

    MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2008
    P. Ku
    Abstract The corrosion behaviour of pressurized water reactor (PWR) steam generator tube material (08CH18N10T steel) was studied by electrochemical noise (EN) measurements and electrochemical impedance spectroscopy in high-temperature water at 280,°C and 8 MPa. Long-term measurements were performed in two electrolytes: (i) deionised water alkalized to pH25,=,9.5 by KOH; (ii) the same electrolyte with 200 ppm of chlorides added (as KCl). The noise data were processed by two filtering methods and the noise resistance and spectral noise resistance values were calculated. Different contributions to the total impedance were identified and the polarization resistance values were calculated from EIS data. Noise and polarization resistances were compared and the influence of filtering methods was discussed. Instantaneous corrosion data were transformed to integral ones and comparison with mean corrosion current estimated from the oxide thickness was made. It was confirmed that the crucial point of EN analysis is selection of proper cut-off frequency in high-pass fast Fourier transform (HP-FFT). [source]

    Microphotonic wideband tapped optical delay line FIR filter noise analysis

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2005
    R. D. Jeffery
    Abstract MicroPhotonic broadband RF signal processors utilize true-time-delay methods to perform processing functions that cannot be achieved by conventional electronic methods. Using a tapped optical-delay line, a low-cost adaptive wideband FIR filter can be realized. We analyse the sources of noise for such a filter using commercially available VCSEL sources, PIN diodes, and transimpedance amplifiers. The power at each tap can be equal by using a suitably graded coating, or if the reflectivity is constant, there is an optimum reflectivity that maximizes the signal-to-noise ratio for a given number of taps, as we show in this paper. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 476,480, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20857 [source]

    Properties of glycine receptors underlying synaptic currents in presynaptic axon terminals of rod bipolar cells in the rat retina

    THE JOURNAL OF PHYSIOLOGY, Issue 15 2009
    Svein Harald Mørkve
    The excitability of presynaptic terminals can be controlled by synaptic input that directly targets the terminals. Retinal rod bipolar axon terminals receive presynaptic input from different types of amacrine cells, some of which are glycinergic. Here, we have performed patch-clamp recordings from rod bipolar axon terminals in rat retinal slices. We used whole-cell recordings to study glycinergic inhibitory postsynaptic currents (IPSCs) under conditions of adequate local voltage clamp and outside-out patch recordings to study biophysical and pharmacological properties of the glycine receptors with ultrafast application. Glycinergic IPSCs, recorded in both intact cells and isolated terminals, were strychnine sensitive and displayed fast kinetics with a double-exponential decay. Ultrafast application of brief (,1 ms) pulses of glycine (3 mm) to patches evoked responses with fast, double-exponential deactivation kinetics, no evidence of desensitization in double-pulse experiments, relatively low apparent affinity (EC50,100 ,m), and high maximum open probability (,0.9). Longer pulses evoked slow, double-exponential desensitization and double-pulse experiments indicated slow, double-exponential recovery from desensitization. Non-stationary noise analysis of IPSCs and patch responses yielded single-channel conductances of ,41 pS and ,64 pS, respectively. Directly observed single-channel gating occurred at ,40,50 pS and ,80,90 pS in both types of responses, suggesting a mixture of heteromeric and homomeric receptors. Synaptic release of glycine leads to transient receptor activation, with about eight receptors available to bind transmitter after release of a single vesicle. With a low intracellular chloride concentration, this leads to either hyperpolarizing or shunting inhibition that will counteract passive and regenerative depolarization and depolarization-evoked transmitter release. [source]

    Spontaneous IPSCs and glycine receptors with slow kinetics in wide-field amacrine cells in the mature rat retina

    THE JOURNAL OF PHYSIOLOGY, Issue 1 2007
    Margaret Lin Veruki
    The functional properties of glycine receptors were analysed in different types of wide-field amacrine cells, narrowly stratifying cells considered to play a role in larger-scale integration across the retina. The patch-clamp technique was used to record spontaneous IPSCs (spIPSCs) and glycine-evoked patch responses from mature rat retinal slices (4,7 weeks postnatal). Glycinergic spIPSCs were blocked reversibly by strychnine (300 nm). Compared to previously described spIPSCs in AII amacrine cells, the spIPSCs in wide-field amacrine cells displayed a very slow decay time course (,fast, 15 ms; ,slow, 57 ms). The kinetic properties of spIPSCs in whole-cell recordings were paralleled by even slower deactivation kinetics of responses evoked by brief pulses of glycine (3 mm) to outside-out patches from wide-field amacrine cells (,fast, 45 ms; ,slow, 350 ms). Non-stationary noise analysis of patch responses and spIPSCs yielded similar average single-channel conductances (,31 and ,34 pS, respectively). Similar, as well as both lower- and higher-conductance levels could be identified from directly observed single-channel gating during the decay phase of spIPSCs and patch responses. These results suggest that the slow glycinergic spIPSCs in wide-field amacrine cells involve ,2, heteromeric receptors. Taken together with previous work, the kinetic properties of glycine receptors in different types of amacrine cells display a considerable range that is probably a direct consequence of differential expression of receptor subunits. Unique kinetic properties are likely to differentially shape the glycinergic input to different types of amacrine cells and thereby contribute to distinct integrative properties among these cells. [source]

    Functional segregation of synaptic GABAA and GABAC receptors in goldfish bipolar cell terminals

    THE JOURNAL OF PHYSIOLOGY, Issue 1 2006
    Mary J. Palmer
    The transmission of light responses to retinal ganglion cells is regulated by inhibitory input from amacrine cells to bipolar cell (BC) synaptic terminals. GABAA and GABAC receptors in BC terminals mediate currents with different kinetics and are likely to have distinct functions in limiting BC output; however, the synaptic properties and localization of the receptors are currently poorly understood. By recording endogenous GABA receptor currents directly from BC terminals in goldfish retinal slices, I show that spontaneous GABA release activates rapid GABAA receptor miniature inhibitory postsynaptic currents (mIPSCs) (predominant decay time constant (,decay), 1.0 ms) in addition to a tonic GABAC receptor current. The GABAC receptor antagonist (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) has no effect on the amplitude or kinetics of the rapid GABAA mIPSCs. In addition, inhibition of the GAT-1 GABA transporter, which strongly regulates GABAC receptor currents in BC terminals, fails to reveal a GABAC component in the mIPSCs. These data suggest that GABAA and GABAC receptors are highly unlikely to be synaptically colocalized. Using non-stationary noise analysis of the mIPSCs, I estimate that GABAA receptors in BC terminals have a single-channel conductance (,) of 17 pS and that an average of just seven receptors mediates a quantal event. From noise analysis of the tonic current, GABAC receptor , is estimated to be 4 pS. Identified GABAC receptor mIPSCs exhibit a slow decay (,decay, 54 ms) and are mediated by approximately 42 receptors. The distinct properties and localization of synaptic GABAA and GABAC receptors in BC terminals are likely to facilitate their specific roles in regulating the transmission of light responses in the retina. [source]