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Electrical
Terms modified by Electrical Selected AbstractsDIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] Multi-Agent Distributed Coordination of Project Schedule ChangesCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2003Keesoo Kim This article presents the design and implementation of a multi-agent system called Distributed Subcontractor Agent System (DSAS), which consists of multiple subcontractor agents, multiple Graphic User Interfaces (GUIs), and an Agent Message Router. In the DSAS, subcontractors interact with their software agents to evaluate the impact of changes, simulate decisions, and get the negotiation results that they need to reschedule the project. This also presents the design and results of DSAS charrette tests, which demonstrated that DSAS produces the lower-cost results faster than manual centralized processes. DSAS can be useful for other domains, such as Mechanical, Electrical, and Plumbing (MEP) coordination and workspace management, if the appropriate agents are designed. [source] Industry responses to EU WEEE and ROHS Directives: perspectives from ChinaCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 5 2006Jieqiong Yu Abstract The electrical and electronics (EE) industry has come under increasing pressure to adopt extended producer responsibility (EPR) policies through the introduction of the European Union's Directives on Waste Electrical and Electronic Equipment (WEEE) and the Restriction of Use of Certain Hazardous Substances (ROHS). Based on the findings of 50 questionnaires and in-depth interviews with China's EE manufacturers, this paper investigates the perception of and readiness of companies for implementation of WEEE and ROHS in China. It identifies key difficulties encountered by manufacturers in fulfilling the requirements and evaluates the effectiveness of these two directives in promoting environmental reform. The findings indicate that the extent of companies' responses largely depends on their market structure and client requirements. Supply chain management, raw material testing and cost implications appear to be key challenges in addressing issues surrounding the directives. There is little evidence to suggest that these directives have effectively driven China's EE manufacturers towards systematic eco-design. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment. [source] Electrical and optical properties of CdS nanocrystalline semiconductorsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006Shikha Tiwari Abstract II-VI semiconductor nanoparticles have recently attracted a lot of attention due to the possibility of their application in various devices. In the present study, chemical method has been used in synthesis of CdS nanoparticles and thiophenol was used as capping agent. X-ray diffraction studies of both samples were done. The dc conductivity of CdS increases at a lower rate or is approximately constant upto 500K and thereafter the conductivity increases at a rapid rate. Beyond Tc it is seen that the portion of the ,dc versus 1000/T is almost a straight line showing an Arrehenious behaviour. The dielectric constant of nanoparticles of CdS is found to be larger than the corresponding values of CdS crystals. It is clearly observed that at lower wavelengths nanocrystalline samples show a blue-shift. The three peaks of sample (S2), A, Band C can be ascribed to the transition from Cd-O complex donor formed by adsorbed oxygen to the valance band, Cd - excess acceptor and the surface states, respectively. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole-Poly(HEMA) CompositesELECTROANALYSIS, Issue 7 2005Sean Brahim Abstract Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2-hydroxyethyl methacrylate)-based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ,472,mV for electropolymerized polypyrrole to ,636,mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100,,, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3,M Cl,) for typically 100,min. (conditioning) to reduce the background amperometric current to <1.0,,A, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (Dappt=7.97×10,5,cm2,s,1) compared to electropolymerized PPy (Dappt=5.56×10,5,cm2,s,1), however a marked reduction in diffusivity (Dappt=1.01×10,5,cm2,s,1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H2O2 showed an absence of redox peaks for electrodes coated with PPy-containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant [source] Electrical and Chemical Long-term Depression Do Not Attenuate Low-Mg2+,induced Epileptiform Activity in the Entorhinal CortexEPILEPSIA, Issue 4 2005Jörg Solger Summary:,Purpose: Low-frequency electrical and magnetic stimulation of cortical brain regions has been shown to reduce cortical excitability and to decrease the susceptibility to seizures in humans and in vivo models of epilepsy. The induction of long-term depression (LTD) or depotentiation of a seizure-related long-term potentiation has been proposed to be part of the underlying mechanism. With the low-Mg2+ -model of epilepsy, this study investigated the effect of electrical LTD, chemical LTD, and depotentiation on the susceptibility of the entorhinal cortex to epileptiform activity. Methods: The experiments were performed on isolated entorhinal cortex slices obtained from adult Wistar rats and mice. With extracellular recording techniques, we studied whether LTD induced by (a) three episodes of low-frequency paired-pulse stimulation (3 × 900 paired pulses at 1 Hz), and by (b) bath-applied N -methyl- d -aspartate (NMDA, 20 ,M) changes time-to-onset, duration, and frequency of seizure-like events (SLEs) induced by omitting MgSO4 from the artificial cerebrospinal fluid. Next we investigated the consequences of depotentiation on SLEs themselves by applying low-frequency stimulation after onset of low-Mg2+,induced epileptiform activity. Results: LTD, induced either by low-frequency stimulation or by bath-applied NMDA, had no effect on time-to-onset, duration, and frequency of SLEs compared with unconditioned slices. Low-frequency stimulation after onset of SLEs did not suppress but induced SLEs that lasted for the time of stimulation and were associated with a simultaneous increase of the extracellular K+ concentration. Conclusions: Our study demonstrates that neither conditioning LTD nor brief low-frequency stimulation decreases the susceptibility of the entorhinal cortex to low-Mg2+,induced epileptiform activity. The present study does not support the hypothesis that low-frequency brain stimulation exerts its anticonvulsant effect via the induction of LTD or depotentiation. [source] Electrical and neurotransmitter activity of mature neurons derived from mouse embryonic stem cells by Sox-1 lineage selection and directed differentiationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2004R. J. Lang Abstract Sx1TV2/16C is a mouse embryonic stem (ES) cell line in which one copy of the Sox1 gene, an early neuroectodermal marker, has been targeted with a neomycin (G418) selection cassette. A combination of directed differentiation with retinoic acid and G418 selection results in an enriched neural stem cell population that can be further differentiated into neurons. After 6,7 days post-plating (D6,7PP) most neurons readily fired tetrodotoxin (TTX)-sensitive action potentials due to the expression of TTX-sensitive Na+ and tetraethylammonium (TEA)-sensitive K+ channels. Neurons reached their maximal cell capacitance after D6,7PP; however, ion channel expression continued until at least D21PP. The percentage of cells receiving spontaneous synaptic currents (s.s.c.) increased with days in culture until 100% of cells received a synaptic input by D20PP. Spontaneous synaptic currents were reduced in amplitude and frequency by TTX, or upon exposure to a Ca2+ -free, 2.5 mm Mg2+ saline. S.s.c. of rapid decay time constants were preferentially blocked by the nonNMDA glutamatergic receptor antagonists CNQX or NBQX. Ca2+ levels within ES cell-derived neurons increased in response to glutamate receptor agonists l -glutamate, AMPA, N -methyl- d -aspartate (NMDA) and kainic acid and to acetylcholine, ATP and dopamine. ES cell-derived neurons also generated cationic and Cl, -selective currents in response to NMDA and glycine or GABA, respectively. It was concluded that ES-derived neurons fire action potentials, receive excitatory and inhibitory synaptic input and respond to various neurotransmitters in a manner akin to primary central neurons. [source] Repeated long-term potentiation induces mossy fibre sprouting and changes the sensibility of hippocampal granule cells to subconvulsive doses of pentylenetetrazolEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000Hadir Hassan Abstract Electrical and chemical kindling induces sprouting of the mossy fibre system and potentiation of evoked field potentials in the dentate gyrus. It has been postulated that such changes may also be induced by repeated induction of long-term potentiation (LTP) with tetanic stimulation of the perforant pathway. LTP was induced in rats chronically implanted with stimulation electrodes in the ipsilateral and contralateral angular bundles and with a recording electrode in the ipsilateral dorsal dentate gyrus. The animals were stimulated 10 times on 10 consecutive days but with different tetanization strengths. Sprouting of the mossy fibres terminating in the CA3 region was significantly induced only in the group of ,strongly' tetanized animals, but not in that of ,weakly' tetanized animals, or in low-frequency stimulated animals. Additionally, a novel form of potentiation which was previously found in pentylenetetrazol (PTZ)-kindled animals was also observed in the group of ,strongly' and ,weakly' tetanized rats. Differences in duration of this potentiation were found between the two groups of animals tetanized with different strengths. The results further demonstrate that morphological and functional changes in the hippocampus, similar to those seen after kindling, can also occur in an activation paradigm leading to long-lasting synaptic plasticity but not accompanied by seizure activity. [source] Environmental issues related to end-of-life options of plastics containing brominated flame retardantsFIRE AND MATERIALS, Issue 5 2004Lein Tange Abstract Bromine is used as the building block for some of the most effective flame retarding agents available to the plastics industry today. They are used to protect against the risk of accidental fires in a wide range of Electrical and Electronic Equipment (EEE). Brominated flame retardants (BFRs), as all flame retardants, act to decrease the risk of fire by increasing the fire resistance of the materials in which they are applied. There is a perception that BFRs affect adversely the end-of-life management of plastics through formation of Polybrominated Dibenzo Dioxins and Dibenzo Furans (PBDD/F). In fact, there exists a wide range of data and practical experience demonstrating that the end-of-life management of plastics containing BFRs is fully compliant with legislation setting the strictest limit values for PBDD/F and is fully compatible with an integrated waste management concept. Copyright © 2004 John Wiley & Sons, Ltd. [source] Evolution of Electrical, Chemical, and Structural Properties of Transparent and Conducting Chemically Derived Graphene Thin FilmsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Cecilia Mattevi Abstract A detailed description of the electronic properties, chemical state, and structure of uniform single and few-layered graphene oxide (GO) thin films at different stages of reduction is reported. The residual oxygen content and structure of GO are monitored and these chemical and structural characteristics are correlated to electronic properties of the thin films at various stages of reduction. It is found that the electrical characteristics of reduced GO do not approach those of intrinsic graphene obtained by mechanical cleaving because the material remains significantly oxidized. The residual oxygen forms sp3 bonds with carbon atoms in the basal plane such that the carbon sp2 bonding fraction in fully reduced GO is ,0.80. The minority sp3 bonds disrupt the transport of carriers delocalized in the sp2 network, limiting the mobility, and conductivity of reduced GO thin films. Extrapolation of electrical conductivity data as a function of oxygen content reveals that complete removal of oxygen should lead to properties that are comparable to graphene. [source] Shaping Carbon Nanotubes and the Effects on Their Electrical and Mechanical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006S. Wang Abstract A method is developed and shown to be able to shape a carbon nanotube (CNT) into a desired morphology while maintaining its excellent electrical and mechanical properties. Single, freestanding nanotubes are bent by a scanning tunneling microscopy probe, and their morphology is fixed by electron-beam-induced deposition (inside a transmission electron microscope) of amorphous carbon on the bent area. It is shown that the mechanical strength of the bent CNT may be greatly enhanced by increasing the amount of carbon glue or the deposition area, and the electrical conduction of the nanotube shows hardly any dependence on the bending deformation or on the deposition of amorphous carbon. Our findings suggest that CNTs might be manipulated and processed as interconnections between electronic devices without much degradation in their electrical conductance, and be used in areas requiring complex morphology, such as nanometer-scale transport carriers and nanoelectromechanical systems. [source] Cover Picture: Fabrication and Electrical and Mechanical Properties of Carbon Nanotube Interconnections (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005Mater. Abstract The fabrication of carbon nanotube (CNT) structures, including simple tube,tube connections, crossed junctions, T-junctions, zigzag structures, and even nanotube networks, has been achieved by cutting and soldering CNTs using electron-beam-induced deposition of amorphous carbon (a-C), as detailed in the work of Peng and co-workers on p.,1825. These CNT structures have been constructed with a high degree of control, and it is found that the electric conductance and mechanical strength of the junctions can be improved by the deposition of a-C and by increasing the contact area of the junctions. Individual carbon nanotubes (CNTs) have been cut, manipulated, and soldered via electron-beam-induced deposition of amorphous carbon (a-C) and using a scanning tunneling microscope inside a transmission electron microscope. All CNT structures, including simple tube,tube connections, crossed junctions, T-junctions, zigzag structures, and even nanotube networks, have been successfully constructed with a high degree of control, and their electrical and mechanical properties have been measured in situ inside the transmission electron microscope. It is found that multiple CNTs may be readily soldered together with moderate junction resistance and excellent mechanical resilience and strength, and the junction resistance may be further reduced by current-induced graphitization of the deposited a-C on the junction. [source] ERRATUM: IEEJ Transactions on Electrical and Electronic Engineering, 4, 6IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2010Article first published online: 22 DEC 200 The original article to which this Erratum refers was published in IEEJ Transactions on Electrical and Electronic Engineering Vol.4, No. 6 [source] Highly Bendable, Transparent Thin-Film Transistors That Use Carbon-Nanotube-Based Conductors and Semiconductors with Elastomeric Dielectrics,ADVANCED MATERIALS, Issue 3 2006Q. Cao Transparent flexible thin-film transistors (see Figure) have been made using single-walled carbon nanotube networks of high and moderate coverages as the conducting and semiconducting layers. Electrical (e.g., good performance on plastic), optical (e.g. transparency to visible wavelengths), and mechanical (e.g. extreme flexibility) characteristics that would be difficult, or impossible, to achieve with conventional materials are reported. [source] Fabrication of Polypyrrole, Poly(N -vinylcarbazole) Core,Shell Nanoparticles with Excellent Electrical and Optical Properties,ADVANCED MATERIALS, Issue 11 2005J. Jang Polypyrrole,poly(N -vinylcarbazole) (PPy,PVK) core,shell nanoparticles have been fabricated by nanoparticle-seeded dispersion polymerization. The monodisperse PPy nanoseeds are fabricated by micelle templating, and the PVK shell thickness is easily tuned by varying the amount of N -vinylcarbazole monomer. The PPy core and PVK shell produce superior conductivity and fluorescence, respectively (see Figure). [source] Electrical and thermal properties of nylon 6/calcium carbonate compositesADVANCES IN POLYMER TECHNOLOGY, Issue 4 2009M. A. Moussa Abstract Several polymer composites formed from nylon 6/CaCO3 with different ratios and particle sizes were prepared using modified and unmodified CaCO3 as inorganic filler. The modification of CaCO3 surfaces was carried out by adsorption of oleic acid from toluene. TGA and DSC measurements show that the glass transition temperatures reduced by the presence of inorganic filler, whereas the melting temperature did not influenced. In all prepared polymer composites, the presence of filler accelerates the degradation process of the polymer. Dielectric properties of the investigated samples were studied in the frequency range from 45 Hz to 1 MHz and at temperatures ranging between 50 and 200°C. The presence of CaCO3 led to a remarkable decrease in the conductivity of nylon 6. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 28:257,266, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20165 [source] Demonstration of Electrical and Anatomic Connections Between Marshall Bundles and Left Atrium in Dogs: Implications on the Generation of P Waves on Surface ElectrocardiogramJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2002CHIKAYA OMICHI M.D. Marshall Bundle and P Wave.Introduction: The muscle bundles within the ligament of Marshall (LOM) are electrically active. The importance of these muscle bundles (Marshall bundle [MB]) to atrial activation and the generation of the ECG P wave is unclear. Methods and Results: We used optical mapping techniques to study epicardial activation patterns in isolated perfused left atrium in four dogs. In another seven dogs, P waves were studied before and after in vivo radiofrequency (RF) ablation of the connection between coronary sinus (CS) and the LOM. Computerized mapping was performed before and after RF ablation. Optical mapping studies showed that CS pacing resulted in broad wavefronts propagating from the middle and distal LOM directly to the adjacent left atrium (LA). Serial sections showed direct connection between MB and LA near the orifice of the left superior pulmonary vein in two dogs. In vivo studies showed that MB potentials were recorded in three dogs. After ablation, the duration of P waves remained unchanged. In the other four dogs, MB potentials were not recorded. Computerized mapping showed that LA wavefronts propagated to the MB region via LA-MB connection and then excited the CS. After ablation, the activation of CS muscle sleeves is delayed, and P wave duration increased from 65.3 ± 14.9 msec to 70.5 ± 17.2 msec (P = 0.025). Conclusion: In about half of the normal dogs, MB provides an electrical conduit between LA free wall and CS. Severing MB alters the atrial activation and lengthens the P wave. MB contributes to generation of the P wave on surface ECG. [source] Effect of Electrical and Structural Remodeling on Spatiotemporal Organization in Acute and Persistent Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2002JOSEPH G. AKAR M.D. Spatiotemporal Organization in Atrial Fibrillation.Introduction: Atrial fibrillation (AF) may originate from discrete sites of periodic activity. We studied the effect of structural and electrical remodeling on spatiotemporal organization in acute and persistent AF. Methods and Results: Atrial effective refractory periods (AERPs) were recorded from five different sites at baseline and after pacing in acute AF (n = 8 dogs) and persistent AF (n = 8). Four persistent AF dogs subsequently were cardioverted to sinus rhythm to allow AERP recovery. Periodicity was quantified by calculating power spectra on left atrial electrograms obtained from a 64-electrode basket catheter. Left atrial size was measured by intracardiac echocardiography and structural changes were assessed by electron microscopy. Mean AERPs decreased after pacing in acute (128 ± 16 msec to 108 ± 29 msec, P < 0.001) and persistent AF (135 ± 16 msec to 104 ± 24 msec, P < 0.0001). AERP recovery was established after 7 days of sinus rhythm. Structural changes were mild in acute AF, severe in persistent AF, and remained severe after AERP recovery. A single dominant frequency was identified in 94% of acute AF bipoles, 57% in persistent AF, and 76% after AERP recovery. Average correlation coefficient was 0.82 among acute AF bipoles, 0.63 in persistent AF, and 0.73 after AERP recovery. Conclusion: Transition from acute to persistent AF is associated with loss of spatiotemporal organization. A single dominant frequency recruits the majority of the left atrium in acute AF. Persistent AF, however, is associated with structural remodeling and dominant frequency dispersion. Recovery of refractoriness only partially restores spatiotemporal organization, indicating a major role for structural remodeling in the maintenance of persistent AF. [source] Effect of Multiwall Carbon Nanotubes on Electrical and Dielectric Properties of Yttria-Stabilized Zirconia CeramicJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Sui-Lin Shi MWCNT/3Y-TZP (3 mol% yttria-stabilized tetragonal polycrystalline zirconia) composites with different multiwall carbon nanotube (MWCNT) contents were prepared by the spark plasma sintering technique. The effect of MWCNT addition on the electrical and dielectric properties of the composites at room temperature was studied. The experimental results showed that the DC conductivity of the composites demonstrated a typical percolation behavior with a very low percolation threshold between 1.0 and 2.0 wt% MWCNT content, and the dielectric constant was greatly increased when the MWCNT concentration was close to the percolation threshold, which was attributed to dielectric relaxation, the space charge polarization effect, and the percolation effect. [source] Electrical and optical low frequency noises in multimodal vertical cavity surface emitting lasersLASER PHYSICS LETTERS, Issue 10 2006F. Principato Abstract Experimental investigations of the low frequency noise of multimode 780 nm vertical cavity surface emitting lasers are reported. Electrical noise, optical noise and their correlation have been measured in the frequency range 1 Hz,95 kHz. The results show that the main contribution to the electrical noise is located in the distributed Bragg reflector layers of the laser. The optical power and pump current noise sources are strongly correlated below and around the threshold, while are weakly correlated above threshold. It is argued that the noise in the optical power is due to both free injection carrier noise and optical gain fluctuations. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Structural, Electrical, Mechanical, and Thermal Properties of Electrospun Poly(lactic acid)/Polyaniline Blend FibersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2010Paulo H. S. Picciani Abstract Conducting electrospun fiber mats based on PLA and PAni blends were obtained with average diameter values between 87 and 1 006,nm with PAni quantities from 0 to 5.6 wt.-%. Structural characteristics of fiber mats were compared to cast films with the same amount of PAni and studied by SEM, SAXS, and AFM. Thermal properties of fiber mats and cast films were compared by DSC analyses. Mechanical properties of fiber mats were also evaluated. It was found that electrospinning process governs the crystal structure of the fibers and strongly affects fiber properties. New properties of PLA/PAni blends are reported due to the size fiber reduction. [source] pH Tailoring Electrical and Mechanical Behavior of Polymer,Clay,Nanotube AerogelsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2009Matthew D. Gawryla Abstract Aerogels are low density (<0.1,g,·,cm,3), highly porous materials that are especially interesting for insulating applications. Combinations of clay and water-soluble polymers are commonly used to produce aerogels, but these materials are often mechanically weak. Single-walled carbon nanotubes (SWNT) were combined with clay and found to significantly improve mechanical behavior and impart electrical conductivity to these aerogels. Poly(acrylic acid) (PAA) as the matrix polymer provides a means of tailoring the electrical conductivity and mechanical behavior by altering the pH of the aqueous aerogel precursor suspensions prior to freeze drying. An aerogel, made from a pH 9 aqueous suspension containing 0.5,wt.-% PAA, 5,wt.-% clay, and 0.05,wt.-% SWNT, has a compressive modulus of 373,kPa. In the absence of nanotubes, this modulus is reduced to 43,kPa. Reducing suspension pH to 3, prior to freeze drying, also reduces modulus for these aerogels, but electrical conductivity is increased when nanotubes are present. It was found that bundled nanotubes provide better reinforcement for these low-density composites, which may provide some new insight into the use of nanotubes in materials that will be exposed to compressive loading. [source] Cardioversion for Atrial Fibrillation: Treatment Options and AdvancesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2009JAMES A. REIFFEL M.D. Atrial fibrillation (AF) is associated with significant morbidity and mortality. There are two basic approaches to managing AF: slowing the ventricular rate, while allowing the arrhythmia to continue (the rate-control approach), and restoring and maintaining sinus rhythm (the rhythm-control approach) with antiarrhythmic drugs (AADs) and/or ablation, electrical cardioversion (CV), if needed, or both. Strategy trials comparing rate and rhythm control have found no survival advantage of one approach over the other, but other considerations, such as symptom reduction, often necessitate pursuit of rhythm control. Electrical, or direct current, CV is a widely used and effective method for termination of nonparoxysmal AF, although its success can be affected by patient- and technique-related variables. Pharmacological CV options also exist and are preferable in specific circumstances. Both pharmacological and electrical CV are associated with the risk of proarrhythmia. Many AADs are under development for both CV and maintenance of sinus rhythm. Some are atrioselective, such as vernakalant, and target ion channels in the atria, with little or no effects in the ventricle. Vernakalant, currently under Food and Drug Administration review, appears to offer a safer profile than current CV agents and is likely to expand the role of pharmacological CV. Other new AADs that provide increased efficacy or safety while maintaining normal sinus rhythm may also be better than current drugs; if so, rate-rhythm comparisons will differ from those of previous studies. In conclusion, further trials should clarify the long-term safety profiles of new atrioselective agents and other investigational drugs and define their role in the treatment of AF. [source] Cardiac Safety of Electrical Stun Guns: Letting Science and Reason Advance the DebatePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2008MARK S. LINK M.D. No abstract is available for this article. [source] Cardiac Effects of Electrical Stun Guns: Does Position of Barbs Contact Make a Difference?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2008DHANUNJAYA LAKKIREDDY M.D. Background:The use of electrical stun guns has been rising among law enforcement authorities for subduing violent subjects. Multiple reports have raised concerns over their safety. The cardiovascular safety profile of these devices in relationship to the position of delivery on the torso has not been well studied. Methods:We tested 13 adult pigs using a custom device built to deliver neuromuscular incapacitating (NMI) discharge of increasing intensity that matched the waveform of a commercially available stun gun (TASER® X-26, TASER International, Scottsdale, AZ, USA). Discharges with increasing multiples of output capacitances were applied in a step-up and step-down fashion, using two-tethered barbs at five locations: (1) Sternal notch to cardiac apex (position-1), (2) sternal notch to supraumbilical area (position-2), (3) sternal notch to infraumbilical area (position-3), (4) side to side on the chest (position-4), and (5) upper to lower mid-posterior torso (position-5). Endpoints included determination of maximum safe multiple (MaxSM), ventricular fibrillation threshold (VFT), and minimum ventricular fibrillation induction multiple (MinVFIM). Results:Standard TASER discharges repeated three times did not cause ventricular fibrillation (VF) at any of the five locations. When the barbs were applied in the axis of the heart (position-1), MaxSM and MinVFIM were significantly lower than when applied away from the heart, on the dorsum (position-5) (4.31 ± 1.11 vs 40.77 ± 9.54, P< 0.001 and 8.31 ± 2.69 vs 50.77 ± 9.54, P< 0.001, respectively). The values of these endpoints at position-2, position-3, and position-4 were progressively higher and ranged in between those of position-1 and position-5. Presence of ventricular capture at a 2:1 ratio to the delivered TASER impulses correlated with induction of VF. No significant metabolic changes were seen after standard NMI TASER discharge. There was no evidence of myocardial damage based on serum cardiac markers, electrocardiography, echocardiography, and histopathologic findings confirming the absence of significant cardiac effects. Conclusions: Standard TASER discharges did not cause VF at any of the positions. Induction of VF at higher output multiples appear to be sensitive to electrode distance from the heart, giving highest ventricular fibrillation safety margin when the electrodes are placed on the dorsum. Rapid ventricular capture appears to be a likely mechanism of VF induction by higher output TASER discharges. [source] Electrical and microstructural properties of low-resistance Ti/Re/Au ohmic contacts to n-type GaNPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2007V. Rajagopal Reddy Abstract The microstructural and electrical properties of Ti/Re/Au (10 nm/10 nm/50 nm) ohmic contacts to moderately doped n-type GaN (4.0 × 1018 cm,3) have been investigated by current,voltage (I ,V), Auger electron microscopy (AES) and transmission electron microscopy (TEM). The electrical characteristics of as-deposited and annealing at temperatures below 800 °C samples exhibit non-linear behaviour. However, the sample showed ohmic behaviour when the contact is annealed at 900 °C for 1 min in nitrogen ambient. The Ti/Re/Au contacts give specific contact resistance as low as 8.6 × 10,6 , cm2 after annealing at 900 °C. It is shown that the surface of the as-deposited contact is fairly smooth and slightly degraded when the contact is annealed at 900 °C. The Ti/Re/Au ohmic contact showed good edge acuity after annealing at 900 °C for 1 min. Based on the Auger electron microscopy and transmission electron microscopy results, possible ohmic formation mechanisms for the Ti/Re/Au contacts to the n-type GaN are described and discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical and structural properties of p -type nanocrystalline silicon grown by LEPECVD for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Gabriel Micard Abstract p-doped hydrogenated nanocrystalline silicon (p-nc-Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc-Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p-nc-Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical and optical properties of thick highly doped p-type GaN layers grown by HVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008A. Usikov Abstract In this paper we report 3-7 ,m thick p-GaN growth by hydride vapor phase epitaxy (HVPE) on sapphire substrates. Mg impurity was used for doping. As-grown GaN layers had p-type conductivity with concentration NA -ND up to 3×1019 cm,3. Mg atom concentration was varied from 1017 to 1020 cm,3. Hydrogen concentration was about 10 times less than that for Mg, which may explain effective p-type doping for as-grown GaN layers. Micro-cathodoluminescence revealed a columnar-like structure of the GaN layers with a non-uniform distribution of material regions having dominant 362 nm or 430 nm luminescence. Use of these thick p-GaN layers to grow InGaN-based blue and green LEDs by the HVPE is demonstrated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mimosa pudica: Electrical and mechanical stimulation of plant movementsPLANT CELL & ENVIRONMENT, Issue 2 2010ALEXANDER G. VOLKOV ABSTRACT Thigmonastic movements in the sensitive plant Mimosa pudica L., associated with fast responses to environmental stimuli, appear to be regulated through electrical and chemical signal transductions. The thigmonastic responses of M. pudica can be considered in three stages: stimulus perception, electrical signal transmission and induction of mechanical, hydrodynamical and biochemical responses. We investigated the mechanical movements of the pinnae and petioles in M. pudica induced by the electrical stimulation of a pulvinus, petiole, secondary pulvinus or pinna by a low electrical voltage and charge. The threshold value was 1.3,1.5 V of applied voltage and 2 to 10 µC of charge for the closing of the pinnules. Both voltage and electrical charge are responsible for the electro-stimulated closing of a leaf. The mechanism behind closing the leaf in M. pudica is discussed. The hydroelastic curvature mechanism closely describes the kinetics of M. pudica leaf movements. [source] Effects of Electrode Protrusion Length, Pre-Existing Bubbles, Solution Conductivity and Temperature, on Liquid Phase Pulsed Electrical DischargePLASMA PROCESSES AND POLYMERS, Issue 11 2009Kai-Yuan Shih Abstract The effects of high voltage electrode needle protrusion length and the presence of low density pre-existing bubbles on liquid phase pulsed electrical discharge were investigated. Liquid phase pulsed corona discharge was operated with two different protrusion length needle electrodes (short , 2,mm and long , 20,mm) with different bulk solution conductivities (5,µS,·,cm,1 and 150,µS,·,cm,1) at room temperature (25,°C) and near boiling (95,°C). Chemical reactions formed in the discharge were also investigated by measuring the generation rates of hydrogen (H2), oxygen (O2) and hydrogen peroxide (H2O2). [source] | ||||||||||||||||||||||||||||||||||||||||||||||