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Electrical Pulses (electrical + pulse)
Selected AbstractsEffects of stimulation frequency and pulse duration on fatigue and metabolic cost during a single bout of neuromuscular electrical stimulationMUSCLE AND NERVE, Issue 5 2010Julien Gondin PhD Abstract We have investigated the effects of stimulation frequency and pulse duration on fatigue and energy metabolism in rat gastrocnemius muscle during a single bout of neuromuscular electrical stimulation (NMES). Electrical pulses were delivered at 100 Hz (1-ms pulse duration) and 20 Hz (5-ms pulse duration) for the high (HF) and low (LF) frequency protocols, respectively. As a standardization procedure, the averaged stimulation intensity, the averaged total charge, the initial peak torque, the duty cycle, the contraction duration and the torque-time integral were similar in both protocols. Fatigue was assessed using two testing trains delivered at a frequency of 100 Hz and 20 Hz before and after each protocol. Metabolic changes were investigated in vivo using 31P-magnetic resonance spectroscopy (31P-MRS) and in vitro in freeze-clamped muscles. Both LF and HF NMES protocols induced the same decrease in testing trains and metabolic changes. We conclude that, under carefully controlled and comparable conditions, the use of low stimulation frequency and long pulse duration do not minimize the occurrence of muscle fatigue or affect the corresponding stimulation-induced metabolic changes so that this combination of stimulation parameters would not be adequate in the context of rehabilitation. Muscle Nerve, 2010 [source] Conductivity switching effect in Cd1,xZnxTe filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006T. Wojciechowski Abstract We report an experimental study of the conductivity switching effect in mono and polycrystalline layers of Cd1,xZnxTe grown by MBE on the Si(001)/Au and n+ - GaAs(001) substrates. The current-voltage (I-V) characteristics of metal-semiconductor junctions show that the conductivity of the Cd1,xZnxTe structures exhibit two states: high- and low-resistive. Electrical pulses applied to the layers trigger the switching effect between these two states. The coefficient of resistivity switching is of the order of 104 while its reproducibility is repetitive about 100 switching cycles. The bistablity of the conductance in Cd1,xZnxTe layers supports the hypothesis of the ferroelectricity in this material. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermally Activated Delayed Fluorescence from Sn4+,Porphyrin Complexes and Their Application to Organic Light Emitting Diodes , A Novel Mechanism for ElectroluminescenceADVANCED MATERIALS, Issue 47 2009Ayataka Endo Electroluminescence based on TADF, that is, thermally activated delayed fluorescence, is demonstrated in Sn4+,porphyrin complexes. On excitation by a short electrical pulse, prompt and delayed electroluminescence components were clearly observed. The delayed component was composed of both TADF and phosphorescence (see figure), and the TADF component significantly increased with increasing temperature. [source] Effect of conditioning electrical stimuli on temporalis electromyographic activity during sleepJOURNAL OF ORAL REHABILITATION, Issue 3 2008F. JADIDI Summary, Inhibitory reflexes during voluntary contractions are well described; however, few studies have attempted to use such reflex-mechanisms to modulate electromyographic (EMG) activity in jaw-closing muscles during sleep. The aim was to apply a new intelligent biofeedback device (Grindcare®) using electrical pulses to inhibit EMG activity in the temporalis muscle during sleep. Fourteen volunteers participated who were aware of jaw-clenching activity as indicated by complaints from sleep partner, soreness or pain in the jaw-muscle upon awakening and tooth wear facets. The EMG activity was recorded from the temporalis muscle, online analysed and the frequency content determined using a signal recognition algorithm. Based on specific individual parameters for pattern recognition, an electrical square-wave pulse train, which was adjusted to a clear, but non-painful intensity (range 1,7 mA) was applied through the EMG electrodes, if jaw-clenching activity was detected. All volunteers had baseline EMG recordings for five to seven consecutive nights, followed by 3-weeks EMG recordings with the feedback turned on, 2 weeks without the feedback and finally 3 weeks with the biofeedback on. There were no session effects on the average duration of sleep hours (P = 0·626). The number of EMG episodes/hour sleep was significantly reduced during the two sessions with biofeedback (54 ± 14%; 55 ± 17%, P < 0·001) compared with baseline EMG activity and the session without biofeedback. The present study suggests that biofeedback with electrical pulses does not cause major disruption in sleep and is associated with pronounced reduction in temporalis EMG activity during sleep. [source] Optically and electrically induced dissipation in quantum Hall systemsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2008G. Nachtwei Abstract We have studied the onset of dissipation in quantum Hall systems (QHSs), patterned in various geometries (Hall bars, meanders and Corbino rings) from wafers with heterojunctions (GaAs/GaAlAs) and HgTe quantum wells with adjacent HgCdTe barriers. The QH samples were excited by electrical pulses with pulse durations tP of 0.5 ns , tP , 180 ns or by illumination with electromagnetic waves of 1.7 THz , f , 2.5 THz. These waves were either emitted coherently by a pulsed p-Ge laser system or by a thermal source. In the case of excitation by electric pulses, it is necessary to exceed a certain critical pulse length which is a function of various extrinsic parameters and sample properties. For no dissipation occurs inside the QHSs. Also, using THz illumination, the QHSs can be driven to dissipation. We found different mechanisms to be responsible for the photoresponse (PR) of the QHSs: non-resonant (bolometric) and resonant (cyclotron resonance) contributions to the PR of the QHSs. First attempts to develop a quantitative model for the observed data are made. We are able to describe a part of the observations by either a drift model or a two-level model. The quantitative agreement of these calculations with the measured data is, however, limited. This is due to the simplicity of the models applied so far and to the complex behaviour of QHSs when nonlinearly excited. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Early events of electroporation-mediated intramuscular DNA vaccination potentiate Th1-directed immune responsesTHE JOURNAL OF GENE MEDICINE, Issue 9 2005Eirik Grønevik Abstract Background Application of electrical pulses after DNA injection into muscle increases expression of the encoded genes, and is shown to improve antigen-specific immune responses when used for DNA vaccination. In addition, electroporation causes tissue injury and inflammatory reactions. Together with immune stimulatory motifs in the injected DNA these factors may potentiate the immune response by acting as adjuvants for the antigen. Here, we have examined the role of these factors in promoting the efficiency of DNA vaccination. Methods We injected a plasmid DNA vector containing the gene Ag85B from M. tuberculosis into mouse quadriceps muscles followed by electroporation. Ag85B was under control of a Tet-responsive promoter, and was expressed either immediately or up to 28 days later by administrating doxycycline to the mice. Delayed expression was combined with injection of non-coding DNA or saline with or without electroporation to examine the ability of these factors to enhance the Ag85B-specific antibody response in the blood and cellular responses in the spleen. Blood samples were analysed with ELISA, while the number of Ag85B-specific IFN-,- and IL-4-producing spleenocytes was analysed with ELISpot. Results Delaying Ag85B expression by 5 or 28 days caused lower anti-Ag85B-specific IgG2a levels. In contrast, the IgG1 antibody response was not significantly affected. Injection of non-coding DNA followed by electroporation moderately increased the IgG2a response. Delaying the Ag85B expression by 28 days reduced the average number of Ag85B-specific IFN-,-producing spleenocytes by over 60%. No significant change in the number of IL-4-producing Ag85B-specific spleenocytes was observed. Conclusions These results suggest that DNA and electroporation per se may act as good adjuvants in promoting efficient Th1-directed responses during DNA vaccination. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||