Current Signals (current + signal)

Distribution by Scientific Domains


Selected Abstracts


EVOLUTION OF BIRD SONG AFFECTS SIGNAL EFFICACY: AN EXPERIMENTAL TEST USING HISTORICAL AND CURRENT SIGNALS

EVOLUTION, Issue 8 2007
Elizabeth P. Derryberry
Mating signals act as behavioral barriers to gene flow in many animal taxa, yet little is known about how signal evolution within populations contributes to the formation of these barriers. Although variation in mating signals among populations is known to affect mating behavior, there is no direct evidence that the evolution of mating signals changes signal effectiveness within a natural population. Making use of historical recordings of bird song, I found that both male and female white-crowned sparrows (Zonotrichia leucophrys) respond more strongly to current than to historical songs, indicating that historical songs are less effective as signals in the current contexts of both mate choice and male,male competition. Finding that historical signals are less effective suggests that signal evolution within populations may ultimately contribute to the formation of behavioral barriers to gene flow between populations. [source]


Study of Factors Affecting Molecular Behaviors in Phenothiazine-Mediated Biosensing by Electrochemical and Spectroscopic Methods

ELECTROANALYSIS, Issue 23 2006
Yetunde
Abstract Reagentless glucose-detecting biosensors were constructed by incorporating a series of phenothiazine derivatives as mediators onto chitosan (CHIT) matrix via different covalent bonds, wherein glucose oxidase (GOx) was employed as the enzyme. Electrochemical studies show significant decrease in the electrocatalytic current during cyclic voltammetric and amperometric measurements, resulting from complexes formation between GOx and phenothiazine molecules. This behavior was further verified by spectroscopic studies. The decrease in the peak intensity at 258,nm is due to the gradual complexes formation over time, consistent to the decrease in the current signal in electrochemical investigations. Correlation with the molecular structures of phenothiazine derivatives reveals a strong relationship between the hydrophobicity of the mediators and the stability of the biosensor electrodes. [source]


Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films

JOURNAL OF MICROSCOPY, Issue 3 2003
F. Iwata
Summary A novel technique for scanning near-field optical microscopy capable of point-contact current-sensing was developed in order to investigate the nanometre-scale optical and electrical properties of electrochromic materials. An apertureless bent-metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p -polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high-sensitive current amplifier. Using the current-sensing scanning near-field optical microscopy, the surface topography, optical and current images of coloured WO3 thin films were observed simultaneously. Furthermore, nanometre-scale electrochromic modification of local bleaching could be performed using the current-sensing scanning near-field optical microscopy. The current-sensing scanning near-field optical microscopy has potential use in various fields of nanometre-scale optoelectronics. [source]


Gold electrodes modified with poly(4-aminophenol): incorporation of nitrogenated bases and an oligonucleotide

POLYMER INTERNATIONAL, Issue 4 2008
Lucas F Ferreira
Abstract BACKGROUND: Investigations of chemical modification of electrode surfaces and immobilization of nitrogenated bases and oligonucleotides are considered essential for the construction of DNA electrochemical nanodevices. Modification of gold electrode surfaces with poly(4-aminophenol) was carried out in order to produce polymers capable of immobilizing purine bases and oligonucleotides. RESULTS: Gold electrodes coated with poly(4-aminophenol) showed improved analytical characteristics and considerably enhanced the electrochemical signals associated with the detection of adenine and guanine by factors of ca 3 and ca 6, respectively, when compared with non-coated gold surfaces. Impedance studies indicated higher charge transfer impedance to modified electrodes containing adenosine monophosphate. Atomic force microscopy images showed that nitrogenated bases have a strong influence over the morphology of the modified electrode surface. It was observed that the modified electrode containing guanine presents globular morphology. CONCLUSION: The modified electrodes increased the amplitude of the current signal of nitrogenated bases when compared to non-coated gold surfaces and produced good response and peaks to the detection of an oligonucleotide. This work presents, for the first time, the electropolymerization of 4-aminophenol on gold electrodes, as well as the detection of nitrogenated bases and an oligonucleotide incorporated on these modified electrodes. Copyright 2007 Society of Chemical Industry [source]


High-Temperature Electrochemistry: A Review

ELECTROANALYSIS, Issue 6 2004
Gregory
Abstract High-temperature electrochemistry remains a relatively unexplored field of research, although in recent years significant developments have been made. This report details the main experimental methods and approaches to heating an electrochemical system under both isothermal and non-isothermal conditions and gives an insight into the experimental and electroanalytical results obtainable under such conditions. It has been shown that the promotion of mass transport at high-temperatures, through diffusion or convection, often results in increased current signals. This increase benefits electroanalytical measurements by lowering detection limits. High temperatures also usefully enhance the sensitivity of systems with sluggish kinetics. [source]


Hydrodynamic Modulation Voltammetry with a Dual Disk Chopped Flow-Microjet Electrode (CF-MJE)

ELECTROANALYSIS, Issue 18 2003
Nafeesa Simjee
Abstract A novel form of hydrodynamic modulation voltammetry (HMV) is described, based on the periodic variation of mass transport in a microjet electrode (MJE) system, in combination with phase-sensitive detection techniques. In the configuration developed, a jet of solution is fired from a nozzle that is aligned directly over the surface of a dual disk Pt-Pt ultramicroelectrode (UME). The potential at each electrode is controlled separately. A rotating blade, positioned between the nozzle and the UME probe, is used to periodically interrupt flow to the electrode surface, resulting in modulation of the overall mass transfer rate between two defined extremes. The use of a dual disk UME enables two transport-limited current signals to be recorded simultaneously, one for the analyte of interest, and the other for a ,reference species' (oxygen for the studies described herein). The latter current response corresponds to the variation in mass transport rate in the chopped flow (CF) arrangement and is used as the signal for phase sensitive detection of the analyte current. Studies of potassium hexachloroiridate (III) [IrCl] oxidation in aqueous solution are used to demonstrate the capabilities of the technique. HMV in the CF-MJE arrangement allows quantitative concentration measurements, down to at least 510,7,M. [source]


Design and implementation of a new neural network-based high speed distance relay

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2008
M. Sanaye-Pasand
Abstract This paper presents a new neural network-based transmission line distance protection module. The proposed module uses samples of voltage and current signals to learn the hidden relationship existing in the input patterns. Using a power system model, simulation studies are preformed and influence of changing system parameters such as fault resistance and power flow direction is studied. The proposed neural network has also been implemented on a digital signal processor (DSP) board and its behavior is investigated using suitable developed hardware. Details of the implementation and experimental studies are given in the paper. Performance studies results show that the proposed algorithm is able to distinguish various transmission line faults rapidly and correctly. It shows that the proposed network is fast, reliable, and accurate. Copyright 2007 John Wiley & Sons, Ltd. [source]


Light- and Touch-Point Localization using Flexible Large Area Organic Photodiodes and Elastomer Waveguides

ADVANCED MATERIALS, Issue 34 2009
Robert Koeppe
A homogeneous large area photodiode with high resistance electrodes can be used to trace the position of a localized light signal, thus allowing the easy fabrication of large area light- and touch-point sensors. A readout scheme is presented that allows a direct and simple recalculation of the coordinates from four current signals picked up at the edges of the device. [source]


Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films

JOURNAL OF MICROSCOPY, Issue 3 2003
F. Iwata
Summary A novel technique for scanning near-field optical microscopy capable of point-contact current-sensing was developed in order to investigate the nanometre-scale optical and electrical properties of electrochromic materials. An apertureless bent-metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p -polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high-sensitive current amplifier. Using the current-sensing scanning near-field optical microscopy, the surface topography, optical and current images of coloured WO3 thin films were observed simultaneously. Furthermore, nanometre-scale electrochromic modification of local bleaching could be performed using the current-sensing scanning near-field optical microscopy. The current-sensing scanning near-field optical microscopy has potential use in various fields of nanometre-scale optoelectronics. [source]