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Electrical Responses (electrical + response)
Selected AbstractsVapor Sorption and Electrical Response of Au-Nanoparticle, Dendrimer Composites,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007N. Krasteva Abstract Films comprising Au nanoparticles and polyphenylene dendrimers (first and second generation) are deposited onto transducer substrates via layer-by-layer self-assembly and characterized by atomic force microscopy and X-ray photoelectron spectroscopy. Their sorption behavior is studied by measuring the uptake of solvents from the vapor phase with quartz crystal microbalances (QCMs). The resistance of the films is simultaneously monitored. Both sensor types, QCMs and chemiresistors, give qualitatively very similar response isotherms that are consistent with a combination of Henry- and Langmuir-type sorption processes. The sorption-induced increase in relative differential resistance scales linearly with the amount of analyte accumulated in the films. This result is in general agreement with an activated tunneling process for charge transport, if little swelling and only small changes in the permittivity of the film occur during analyte sorption (a first-order approximation). The relative sensitivity of the films to different solvents decreases in the order toluene,,,tetrachloroethylene,>,1-propanol,,,water. Films containing the larger second-generation dendrimers show higher sensitivity than films containing first-generation dendrimers. [source] Electrical Response to Organic Vapor of Conductive Composites from Amorphous Polymer/Carbon Black Prepared by Polymerization FillingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2003Jun Rong Li Abstract In recent years, conductive polymer composites have found applications as gas sensors because of their sudden change in electric resistance of several orders of magnitude when the materials are exposed to certain solvent vapors. However, the composites having this function reported so far are mostly based on crystalline polymeric matrices, which factually sets a limit to materials selection. The present work prepares polystyrene/carbon black composites through polymerization filling and proves that the amorphous polymer composites can also serve as gas sensing materials. The composites' percolation threshold is much lower than that of the composites produced by dispersive mixing. In addition, high responsivity to some organic vapors coupled with sufficient reproducibility is acquired. The experimental data show that molecular weight and molecular weight distribution of the matrix polymer and conducting filler content exert great influence on the electrical response behavior of the composites. As a result, composites performance can be purposely tailored accordingly. Compared with the approaches of melt-blending and solution-blending, the current technique is characterized by many advantages, such as simplicity, low cost, and easy to be controlled. Effect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content,=,10.35 vol.-%). [source] Adenylyl cyclase encoded by AC78C participates in sugar perception in Drosophila melanogasterEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2008Kohei Ueno Abstract In gustatory receptor neurons (GRNs) in Drosophila melanogaster, Gr5a and one of the Gr64s encode sugar receptors with seven transmembrane domains. Previously, we have shown that the responses to various sugars are depressed in DGs, mutant flies (Ueno et al., 2006). Because DGs, is a homolog of Gs, we hypothesized that the sugar receptors are coupled to adenylyl cyclase (AC) in Drosophila. The aim of this study was to identify the AC that participates in sugar perception. Here, we found that an AC inhibitor, MDL-12330A, depressed the response in GRNs to trehalose as well as sucrose; that an AC gene, AC78C, was expressed in the sugar-sensitive GRNs; that RNAi against AC78C depressed the electrical response in GRNs to sucrose; and that the sugar response in GRNs, as well as sugar intake in a behavioral assay in an AC78C mutant, was depressed at low sugar concentrations. We conclude that AC78C, via cAMP, participates in the sugar-taste signaling pathway at the low concentration range. [source] Artificial neural network modeling of RF MEMS resonatorsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2004Yongjae Lee Abstract In this article, a novel and efficient approach for modeling radio-frequency microelectromechanical system (RF MEMS) resonators by using artificial neural network (ANN) modeling is presented. In the proposed methodology, the relationship between physical-input parameters and corresponding electrical-output parameters is obtained by combined circuit/full-wave/ANN modeling. More specifically, in order to predict the electrical responses from a resonator, an analytical representation of the electrical equivalent-network model (EENM) is developed from the well-known electromechanical analogs. Then, the reduced-order, nonlinear, dynamic macromodels from 3D finite-element method (FEM) simulations are generated to provide training, validating, and testing datasets for the ANN model. The developed ANN model provides an accurate prediction of an electrical response for various sets of driving parameters and it is suitable for integration with an RF/microwave circuit simulator. Although the proposed approach is demonstrated on a clamped-clamped (C-C) beam resonator, it can be readily adapted for the analysis of other micromechanical resonators. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 302,316, 2004. [source] Simulation of Protective Zones During Quatrefoil Reentry in Cardiac TissueJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001MARISA C. HILDEBRANDT Protective Zones During Quatrefoil Reentry.Introduction: An S3 stimulus can exert a protective effect by terminating reentry induced by an S2 stimulus. Our goal was to examine the mechanism by which an S3 pulse terminates reentry and the role that virtual electrodes and break excitation play in this process. Methods and Results: In our simulation, the bidomain model represents the electrical properties of the tissue and the Beeler-Reuter model represents the membrane kinetics. Quatrefoil reentry is initiated by S1-S2 stimulation, and then a third stimulus S3 is applied at different intervals after S2. All stimuli are applied through the same unipolar electrode. For some S2-S3 intervals, the S2 and S3 wavefronts interact destructively, terminating reentry (protective zones). For other S2-S3 intervals, S2 and S3 wavefronts interact constructively, and reentry continues. Protective zones appear recurrently, with approximately the period of the S2 reentrant circuit. The protective zones are wider for anodal stimulation than for cathodal stimulation. Conclusion: Virtual electrodes, break excitation, and S2-S3 timing all play important roles in determining the electrical response of the tissue. [source] Preparation, characterization, and electrical properties of dual-emissive Langmuir-Blodgett films of some europium-substituted polyoxometalates and a platinum polyyne polymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010Li Liu Abstract A new series of organometallic/inorganic composite Langmuir-Blodgett (LB) films consisting of a rigid-rod polyplatinyne polymer coordinated with 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene (denoted as PtP) as the ,-conjugated organometallic molecule, an europium-substituted polyoxometalate (POM; POM = Na9EuW10O36, K13[Eu(SiW11O39)2] and K5[Eu(SiW11O39)(H2O)2]) as the inorganic component, and an amphiphilic behenic acid (BA) as the auxiliary film-forming agent were prepared. Structural and photophysical characterization of these LB films were achieved by ,,A isotherms, absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low-angle X-ray diffraction. Our experimental results indicate that stable, well-defined, and well-organized Langmuir and LB films are formed in pure water and POM subphases, and the presence of Eu-based POM in the subphase causes an area expansion. It is proposed that a lamellar layered structure exists for the PtP/BA/POM LB film in which the POM and PtP molecules can lay down with the interfacial planes. Luminescence spectra of the prepared hybrid LB films show that near-white emission spectra can be obtained due to the dual-emissive nature of the mixed PtP/POM blends. These Pt-polyyne-based LB films displayed interesting electric conductivity behavior. Among them, PtP/BA/POM 13-layer films showed a good electrical response, with the tunneling current up to ±100 nA when the voltage was monitored between ,1 and 7 V. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 879,888, 2010 [source] Modeling Mach,Zehnder LiNbO3 external modulators in microwave optical systemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2001J. M. Fuster Abstract A novel modeling approach for Mach,Zehnder electro-optic modulators (MZ,EOMs) in microwave optical systems is presented. MZ,EOM traveling-wave electrodes are fully characterized by an electrode transfer function (ETF) which considers internal design parameters. This ETF is approximated by the modulator electrical response that, jointly with the half-wave voltage at dc and the optical insertion loss, are the three parameters on which the model is based. Frequency- and time-domain models are provided. An excellent agreement between theoretical and experimental results validates the proposed modeling approach, useful in simulating microwave optical systems. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 85,90, 2001. [source] Electrical and magnetic response of archaeological features at the early neolithic site of Movila lui Deciov, western RomaniaARCHAEOLOGICAL PROSPECTION, Issue 4 2004J. M. Maillol Abstract An archaeological geophysics survey was conducted on the early neolithic site of Movila lui Deciov, in the Province of Banat, Romania. Magnetometry and electromagnetic terrain conductivity were used for the main prospection effort, and a test of electrical resistivity imaging was conducted on a selected profile. In addition, magnetic susceptibility measurements were obtained from excavation pit samples. The magnetic survey was successful in determining the extent of the site, in delimiting zones rich in structures and artefacts, and in confirming the presence of a ditched enclosure that could be the earliest known in the region. The electromagnetic survey was limited by a lack of resolution of electrical property contrast. Detailed joint modelling of the magnetic and electrical response of the subsurface was used to confirm that electrical resistivity imaging can provide depth information to complement magnetic mapping. One of very few reported in Romania, this survey paves the way for an increased use of geophysical techniques in the cultural heritage management of this country. From a methodological viewpoint, this work further demonstrates the potential of electrical resistivity imaging in archaeology Copyright © 2004 John Wiley & Sons, Ltd. [source] Ions, genes and insulin release: from basic science to clinical disease Based on the 1998 R. D. Lawrence LectureDIABETIC MEDICINE, Issue 2 2000M. J. Dunne Summary In 1968, reports of the first microelectrode recordings of insulin-secreting cells were published. Thirty years later it is now established that electrical responses of ,-cells play a critical role in stimulus-secretion coupling. It is now also clear that defects in ion channel genes compromise the mechanisms which govern secretion and lead to the onset of disease. Here, the physiology of insulin release is reviewed in the context of ion channels, the ionic control of insulin release and the pathophysiology of hyperinsulinism of infancy. [source] Single olfactory sensory neurons simultaneously integrate the components of an odour mixtureEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003Patricia Duchamp-Viret Abstract Most odours are complex mixtures. However, the capacities of olfactory sensory neurons (OSNs) to process complex odour stimuli have never been explored in air-breathing vertebrates. To face this issue, the present study compares the electrical responses of single OSNs to two odour molecules, delivered singly and mixed together, in rats in vivo. This work is the first aimed at demonstrating that single OSNs simultaneously integrate several chemical signals and which, furthermore, attempts to describe such processes for the whole concentration range over which single OSNs can work. The results stress that complex interactions occur between components in odour mixtures and that OSN responses to such mixtures are not simply predictable from the responses to their components. Three types of interactions are described. They are termed suppression, hypoadditivity and synergy, in accord with psychophysical terminology. This allows us to draw links between peripheral odour reception and central odour coding. Indeed, events occurring in single OSNs may account for the dominating or even the masking effects of odour molecules in complex mixtures, i.e. for the prevailing action of a minor component in the final qualitative perception of a mixture. We conclude that our observations with binary mixtures anticipate the complexity of processes which may rise at the level of a single OSN in physiological conditions. Following this hypothesis, a natural odour would induce a multi-chemical integration at the level of single OSNs which may result in refining their individual odour-coding properties, leading them to play a crucial role in the final performance of the olfactory system. [source] Artificial neural network modeling of RF MEMS resonatorsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2004Yongjae Lee Abstract In this article, a novel and efficient approach for modeling radio-frequency microelectromechanical system (RF MEMS) resonators by using artificial neural network (ANN) modeling is presented. In the proposed methodology, the relationship between physical-input parameters and corresponding electrical-output parameters is obtained by combined circuit/full-wave/ANN modeling. More specifically, in order to predict the electrical responses from a resonator, an analytical representation of the electrical equivalent-network model (EENM) is developed from the well-known electromechanical analogs. Then, the reduced-order, nonlinear, dynamic macromodels from 3D finite-element method (FEM) simulations are generated to provide training, validating, and testing datasets for the ANN model. The developed ANN model provides an accurate prediction of an electrical response for various sets of driving parameters and it is suitable for integration with an RF/microwave circuit simulator. Although the proposed approach is demonstrated on a clamped-clamped (C-C) beam resonator, it can be readily adapted for the analysis of other micromechanical resonators. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 302,316, 2004. [source] Detecting amine vapours with thermally carbonized porous silicon gas sensorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009Mikko Björkqvist Abstract A capacitive type porous silicon based gas sensor for detecting amine vapours has been developed. The sensor is highly sensitive, e.g., to methylamine and trimethylamine vapours, and its electrical parameters recover totally after exposure to studied gases. Thermal carbonization of porous silicon under acetylene atmosphere was carried out to produce stable and attractive surface to amine vapours. The sensor response to studied amine vapours can be separated from its response to humidity changes since their electrical responses act reversely. In addition to the vapours of methylamine/water and trimethylamine/water solutions, the sensor was also used to detect different amines, which are generated during spoilage of raw shrimps and Baltic herring fillets at room temperature. Fourier Transform Infrared spectroscopy was used to detect the amine vapours and other volatile compounds simultaneously with sensor measurements. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow troutTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2006W. Ted Allison Abstract Ultraviolet-sensitive (UVS) cones disappear from the retina of salmonid fishes during a metamorphosis that prepares them for deeper/marine waters. UVS cones subsequently reappear in the retina near sexual maturation and the return migration to natal streams. Cellular mechanisms of this UVS cone ontogeny were investigated using electroretinograms, in situ hybridization, and immunohistochemistry against opsins during and after thyroid hormone (TH) treatments of rainbow trout (Oncorhynchus mykiss). Increasing TH levels led to UVS cone degeneration. Labeling demonstrated that UVS cone degeneration occurs via programmed cell death and caspase inhibitors can inhibit this death. After the cessation of TH treatment, UVS cones regenerated in the retina. Bromodeoxyuridine (BrdU) was applied after the termination of TH treatment and was detected in the nuclei of cells expressing UVS opsin. BrdU was found in UVS cones but not other cone types. The most parsimonious explanation for the data is that UVS cones degenerated and UVS cones were regenerated from intrinsic retinal progenitor cells. Regenerating UVS cones were functionally integrated such that they were able to elicit electrical responses from second-order neurons. This is the first report of cones regenerating during natural development. Both the death and regeneration of cones in retinae represent novel mechanisms for tuning visual systems to new visual tasks or environments. J. Comp. Neurol. 499:702,715, 2006. © 2006 Wiley-Liss, Inc. [source] Millimeter wave effects on electrical responses of the sural nerve in vivoBIOELECTROMAGNETICS, Issue 3 2010Stanislav I. Alekseev Abstract Millimeter wave (MMW, 42.25,GHz)-induced changes in electrical activity of the murine sural nerve were studied in vivo using external electrode recordings. MMW were applied to the receptive field of the sural nerve in the hind paw. We found two types of responses of the sural nerve to MMW exposure. First, MMW exposure at the incident power density ,45,mW/cm2 inhibited the spontaneous electrical activity. Exposure with lower intensities (10,30,mW/cm2) produced no detectable changes in the firing rate. Second, the nerve responded to the cessation of MMW exposure with a transient increase in the firing rate. The effect lasted 20,40,s. The threshold intensity for this effect was 160,mW/cm2. Radiant heat exposure reproduced only the inhibitory effect of MMW but not the transient excitatory response. Depletion of mast cells by compound 48/80 eliminated the transient response of the nerve. It was suggested that the cold sensitive fibers were responsible for the inhibitory effect of MMW and radiant heat exposures. However, the receptors and mechanisms involved in inducing the transient response to MMW exposure are not clear. The hypothesis of mast cell involvement was discussed. Bioelectromagnetics 31:180,190, 2010. © 2009 Wiley-Liss, Inc. [source] Continence and some properties of the urethral striated muscle of male greyhoundsBJU INTERNATIONAL, Issue 3 2000B.A. Van Der Werf Objective To determine the properties of the striated muscle of the greyhound (dog) urethra and to consider its role in maintaining continence. Materials and methods The thickness of the muscle layers and the muscle types were determined by examining sections stained with haematoxylin and eosin or Masson's trichrome. These factors were correlated with the mechanical and electrical responses of muscle strips to nerve stimulation, and compared with muscle from other breeds of dog and other parts of the animal. Results The striated muscle formed ,70% of the membranous urethra and was predominantly (68%) type IIa muscle (i.e. fast but fatigue-resistant). The mean resting membrane potential was ,74 mV; nerve stimulation produced an action potential with a mean amplitude of 97 mV and contraction lasting about 200 ms. All responses were abolished by d -tubocurarine. The contractions were well maintained with continuous or intermittent stimulation. The properties were intermediate between those of the anconeus (slow) and the extensor carpi radialis (fast) muscles. Conclusions The distribution, fibre type and contractile characteristics would enable the striated urethral muscle to maintain tension for continence at rest and provide additional continence during sprints. [source] Evolving mechanisms of action of alverine citrate on phasic smooth musclesBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2007M Hayase Background and purpose: We have investigated the mechanisms underlying the paradoxical ability of the antispasmodic, alverine, to enhance spontaneous activity in smooth muscles while suppressing evoked activity. Experimental approach: The effects of alverine on spontaneous and induced contractile activity were examined in preliminary experiments with various smooth muscles. More detailed effects were also investigated by recording membrane potential, intracellular Ca2+ concentration ([Ca2+]i) and tension from single-bundle detrusor smooth muscle (DSM) of the guinea-pig urinary bladder. Key results: Alverine (10 ,M) increased the frequency and amplitude of spontaneous action potentials, transient increases in [Ca2+]i and associated contractions. Alverine also decreased action potential rate of decay, suggesting inhibition of L -type Ca channel inactivation. Charybdotoxin (50 nM) but neither cyclopiazonic acid (10 ,M) nor Bay K 8644 (10 ,M) attenuated alverine-induced enhancement of spontaneous contractions. Alverine suppressed contractions produced by high K (40 mM) or ACh (10 ,M), without affecting electrical responses and with little suppression of increases in [Ca2+]i. This feature was very similar to that of the effects of the Rho kinase inhibitor Y-27632 (10 ,M). Conclusions and implications: Alverine may increase Ca influx during action potentials due to inhibition of the inactivation of L -type Ca channels, but may also suppress evoked activity by inhibiting the sensitivity of contractile proteins to Ca2+. The proportional contribution of Ca-dependent and Ca-independent contractions in DSM may differ between spontaneous and evoked activity, necessitating further investigations into the interactions between these pathways for assessing the therapeutic potential of alverine to treat DSM dysfunction. British Journal of Pharmacology (2007) 152, 1228,1238; doi:10.1038/sj.bjp.0707496; published online 15 October 2007 [source] | |||||||||||||||||||