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Electrical Changes (electrical + change)
Selected AbstractsPreparation of High-Performance Conductive Polymer Fibers through Morphological Control of Networks Formed by NanofillersADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Hua Deng Abstract A general method is described to prepare high-performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower-melting-temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt-based process. Morphological control of the conductive network formed by nanofillers is realized by solid-state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275,S,m,1 with tensile strengths of around 500,MPa. To the best of the authors' knowledge, it is the most conductive, high-strength polymer fiber produced by melt-processing reported in literature, despite the fact that only ,5,wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ,0.5,wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers. [source] Effects of acute vagal nerve stimulation on the early passive electrical changes induced by myocardial ischaemia in dogs: heart rate-mediated attenuationEXPERIMENTAL PHYSIOLOGY, Issue 8 2008Carlos L. Del Rio Parasympathetic activity during acute coronary artery occlusion (CAO) can protect against ischaemia-induced malignant arrhythmias; nonetheless, the mechanism mediating this protection remains unclear. During CAO, myocardial electrotonic uncoupling is associated with autonomically mediated immediate (i.e. type 1A) arrhythmias and can modulate pro-arrhythmic dispersion of repolarization. Therefore, the effects of acutely enhanced or decreased cardiac parasympathetic activity on early electrotonic coupling during CAO, as measured by myocardial electrical impedance (MEI), were investigated. Anaesthetized dogs were instrumented for MEI measurements, and left circumflex coronary arterial occlusions were performed in intact (CTRL) and vagotomized (VAG) animals. The CAO was followed by either vagotomy (CTRL) or vagal nerve stimulation (VNS, 10 Hz, 10 V) in the VAG dogs. Vagal nerve stimulation was studied in two additional sets of animals. In one set heart rate (HR) was maintained by pacing (220 beats min,1), while in the other set bilateral stellectomy preceded CAO. The MEI increased after CAO in all animals. A larger MEI increase was observed in vagotomized animals (+85 ± 9 ,, from 611 ± 24 ,, n= 16) when compared with intact control dogs (+43 ± 5 ,, from 620 ± 20 ,, n= 7). Acute vagotomy during ischaemia abruptly increased HR (from 155 ± 11 to 193 ± 15 beats min,1) and MEI (+12 ± 1.1 ,, from 663 ± 18 ,). In contrast, VNS during ischaemia (n= 11) abruptly reduced HR (from 206 ± 6 to 73 ± 9 beats min,1) and MEI (,16 ± 2 ,, from 700 ± 44 ,). These effects of VNS were eliminated by pacing but not by bilateral stellectomy. Vagal nerve stimulation during CAO also attenuated ECG-derived indices of ischaemia (e.g. ST segment, 0.22 ± 0.03 versus 0.15 ± 0.03 mV) and of rate-corrected repolarization dispersion [terminal portion of T wave (TPEc), 84.5 ± 4.2 versus 65.8 ± 5.9 ms; QTc, 340 ± 8 versus 254 ± 16 ms]. Vagal nerve stimulation during myocardial ischaemia exerts negative chronotropic effects, limiting early ischaemic electrotonic uncoupling and dispersion of repolarization, possibly via a decreased myocardial metabolic demand. [source] Noninvasive dynamic imaging of seizures in epileptic patientsHUMAN BRAIN MAPPING, Issue 12 2009Louise Tyvaert Abstract Epileptic seizures are due to abnormal synchronized neuronal discharges. Techniques measuring electrical changes are commonly used to analyze seizures. Neuronal activity can be also defined by concomitant hemodynamic and metabolic changes. Simultaneous electroencephalogram (EEG)-functional MRI (fMRI) measures noninvasively with a high-spatial resolution BOLD changes during seizures in the whole brain. Until now, only a static image representing the whole seizure was provided. We report in 10 focal epilepsy patients a new approach to dynamic imaging of seizures including the BOLD time course of seizures and the identification of brain structures involved in seizure onset and discharge propagation. The first activation was observed in agreement with the expected location of the focus based on clinical and EEG data (three intracranial recordings), thus providing validity to this approach. The BOLD signal preceded ictal EEG changes in two cases. EEG-fMRI may detect changes in smaller and deeper structures than scalp EEG, which can only record activity form superficial cortical areas. This method allowed us to demonstrate that seizure onset zone was limited to one structure, thus supporting the concept of epileptic focus, but that a complex neuronal network was involved during propagation. Deactivations were also found during seizures, usually appearing after the first activation in areas close or distant to the activated regions. Deactivations may correspond to actively inhibited regions or to functional disconnection from normally active regions. This new noninvasive approach should open the study of seizure generation and propagation mechanisms in the whole brain to groups of patients with focal epilepsies. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Characterization of Charge Collection in Photodiodes under Mechanical Strain: Comparison between Organic Bulk Heterojunction and Amorphous SiliconADVANCED MATERIALS, Issue 18 2009Tse Nga Ng Both gradual electrical changes and device failure mechanisms caused by mechanical strain in organic photodiodes are investigated and compared to a-Si:H deposited on plastic substrates. [source] Changes in afferent activity after spinal cord injury,NEUROUROLOGY AND URODYNAMICS, Issue 1 2010William C. de Groat Abstract Aims To summarize the changes that occur in the properties of bladder afferent neurons following spinal cord injury. Methods Literature review of anatomical, immunohistochemical, and pharmacologic studies of normal and dysfunctional bladder afferent pathways. Results Studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through coordination centers (periaqueductal gray and pontine micturition center) located in the rostral brain stem. This reflex pathway, which is activated by small myelinated (A,) bladder afferent nerves, is in turn modulated by higher centers in the cerebral cortex involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary voiding, as well as the normal reflex pathways that coordinate bladder and sphincter function. Following spinal cord injury, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. The recovery of bladder function after spinal cord injury is dependent in part on the plasticity of bladder afferent pathways and the unmasking of reflexes triggered by unmyelinated, capsaicin-sensitive, C-fiber bladder afferent neurons. Plasticity is associated with morphologic, chemical, and electrical changes in bladder afferent neurons and appears to be mediated in part by neurotrophic factors released in the spinal cord and the peripheral target organs. Conclusions Spinal cord injury at sites remote from the lumbosacral spinal cord can indirectly influence properties of bladder afferent neurons by altering the function and chemical environment in the bladder or the spinal cord. Neurourol. Urodynam. 29: 63,76, 2010. © 2009 Wiley-Liss, Inc. [source] Morphological and electrical changes in TiO2 memristive devices induced by electroforming and switchingPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010Ruth Münstermann Abstract Combining delamination technique with conductive AFM, we have been able to reveal spatially resolved morphology and conductance changes in TiO2 memristive junctions after electroforming and switching. Being able to distinguish between effects caused by electroforming and switching, respectively, we could demonstrate that electroforming results in the creation of localized conductance channels induced by oxygen evolution while subsequent resistive switching causes an additional conducting structure next to the forming spot. We observe that the lateral extent of this structure depends on the number of switching cycles indicating an ongoing breaking of existing and creation of neighbouring current channels during subsequent switching. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Aberrant processing of deviant stimuli in schizophrenia revealed by fusion of fMRI and EEG dataACTA NEUROPSYCHIATRICA, Issue 3 2010Vince D. Calhoun Calhoun VD, Wu L, Kiehl KA, Eichele T, Pearlson GD. Aberrant processing of deviant stimuli in schizophrenia revealed by fusion of fMRI and EEG data. Background: Aberrant electrophysiological and haemodynamic processing of auditory oddball stimuli is among the most robustly documented findings in patients with schizophrenia. However, no study to date has directly examined linked patterns of electrical and haemodynamic differences in patients and controls. Methods: In a recent paper we demonstrated a data-driven approach, joint independent component analysis (jICA) to fuse together functional magnetic resonance imaging (fMRI) and event-related potential (ERP) data and elucidated the chronometry of auditory oddball target detection in healthy control subjects. In this paper we extend our fusion method to identify specific differences in the neuronal chronometry of target detection for chronic schizophrenia patients compared to healthy controls. Results: We found one linked source, consistent with the N2 response, known to be related to cognitive processing of deviant stimuli, spatially localized to bilateral fronto-temporal regions. This source showed significant between-group differences both in amplitude response and in the fMRI/ERP distribution pattern. These findings are consistent with previous work showing N2 amplitude and latency abnormalities in schizophrenia, and provide new information about the linkage between the two. Conclusions: In summary, we use a novel approach to isolate and identify a linked fMRI/ERP component which shows marked differences in chronic schizophrenia patients. We also show that jointly using both fMRI and ERP measures provides a fully picture of the underlying haemodynamic and electrical changes which are present in patients. Our approach also has broad applicability to other diseases such as autism, Alzheimer's disease, or bipolar disorder. [source] | ||||||||||||||||