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Electrode Size (electrode + size)
Selected AbstractsNumerical studies of electrokinetic control of DNA concentration in a closed-end microchannelELECTROPHORESIS, Issue 5 2010Yasaman Daghighi Abstract A major challenge in lab-on-a-chip devices is how to concentrate sample molecules from a dilute solution, which is critical to the effectiveness and the detection limit of on-chip bio-chemical reactions. A numerical study of sample concentration control by electrokinetic microfluidic means in a closed-end microchannel is presented in this paper. The present method provides a simple and efficient way of concentration control by using electrokinetic trapping of a charged species of interest, controlling liquid flow and separating different sample molecules in the microchannel. The electrokinetic-concentration process and the controlled transport of the sample molecules are numerically studied. In this system, in addition to the electroosmotic flow and the electrophoresis, the closed-end of the chamber causes velocity variation at both ends of the channel and induces a pressure gradient and the associated fluid movement in the channel. The combined effects determine the final concentration field of the sample molecules. The influences of a number of parameters such as the channel dimensions, electrode size and the applied electric field are investigated. [source] Optimizing measurement of the electrical anisotropy of muscleMUSCLE AND NERVE, Issue 5 2008Anne B. Chin BS Abstract Skeletal muscle is electrically anisotropic, with applied high-frequency electrical current flowing more easily along than across muscle fibers. As an early step in harnessing this characteristic for clinical use, we studied approaches for maximizing the measured anisotropy by varying electrode size and applied current frequency in the tibialis anterior of 10 normal subjects. The results were compared to those from two patients with amyotrophic lateral sclerosis (ALS). Current was applied percutaneously, first parallel and then perpendicular to the major fiber direction of the muscle at frequencies ranging from 20 kHZ to 1 MHZ, using a fixed voltage,electrode length and varying the current,electrode length. The measured anisotropy was most pronounced using the longest length current electrodes and with a 125-kHZ applied frequency for the major outcome parameter phase. In addition, the two ALS patients showed very distinct anisotropic patterns. These results support the belief that, with the appropriate measurement technique, non-invasive assessment of electrical anisotropy of muscle may have useful clinical application. Muscle Nerve, 2008 [source] Effect of size and pressure of surface recording electrodes on amplitude of sensory nerve action potentialsMUSCLE AND NERVE, Issue 2 2004Antoon A. Ven MSc Abstract The influence of electrode size on sensory nerve action potential (SNAP) amplitude of the lateral antebrachial cutaneous nerve (LACN) and sural nerve (SN) was studied in 63 healthy volunteers. The SNAP amplitudes were measured using surface recording electrodes of three different sizes, positioned across the nerve. Mean amplitudes using a 5-mm electrode were 9.0% (SN) and 15.3% (LACN) higher than with a 20-mm electrode and 19.4% (SN) and 25.8% (LACN) higher than using a 40-mm electrode. To study the influence of pressure on surface recording electrodes, studies were performed on the LACN in 31 healthy volunteers. Light pressure of the recording electrodes on the skin gave lower amplitudes (15.3%) than did greater pressure or pressure applied between active and reference electrodes. These studies demonstrate that standardized surface recording electrode size and pressure are imperative for obtaining valid and reliable results in experimental studies or in clinical follow-up of patients undergoing nerve conduction studies. Muscle Nerve 30: 234,238, 2004 [source] Determinants of Lesion Sizes and Tissue Temperatures During Catheter CryoablationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2007MARK A. WOOD M.D. Background:Factors which influence lesion size from catheter-based cryoablation have not been well described. This study describes factors which influence lesion size during catheter cryoablation. Methods and Results:Cryoablation was delivered to porcine left ventricular myocardium in a saline bath using 4- or 8-mm electrode catheters. Ablation was delivered with the electrodes either vertical or horizontal to the tissue and both with and without superfusate flow over the electrode. The effect of electrode contact pressure was tested. Lesion dimensions were measured. All experiments were duplicated to measure tissue temperatures at 1-, 2-, 3-, and 5-mm deep to the ablation electrode. The 8-mm electrode produced lower tissue temperatures and larger lesion volumes when compared with the 4-mm electrode (all P < 0.05). Superfusate flow slowed the rate of tissue cooling, markedly warmed tissue temperatures, and reduced lesion volume when compared with no flow conditions. By linear regression modeling, lesion sizes and tissue temperatures were related to the presence of superfusate flow, electrode orientation, contact pressure and electrode size, or catheter refrigerant flow rate (r2 for models = 0.90,0.96, all P < 0.001). Electrode temperature predicted lesion size or tissue temperatures only when analyzed independent of electrode size or refrigerant flow rate. Conclusions:Lesion sizes and tissue temperatures during catheter cryoablation are related to convective warming, electrode orientation, electrode contact pressure, and any of the following: electrode size, catheter refrigerant flow rate or electrode temperature. However, electrode temperature may be a poor predictor of lesion size and tissue temperature for a given catheter size. [source] Use of a Single Coil Transvenous Electrode with an Abdominally Placed Implantable Cardioverter Defibrillator in ChildrenPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2000PETER S. FISCHBACH While transvenous defibrillator electrode placement avoiding a thoracotomy is preferable, electrode size, a large intercoil spacing, and the need for subclavicular device placement preclude this approach in most children. We investigated a single RV coil to an abdominally placed active can ICD device. Five children ages 8,16 years (weight 21,50 kg, mean 35 kg) underwent ICD placement. Placement of a single coil Medtronic model 6932 or 6943 electrode was performed via the left subclavian vein approach and the electrode positioned in the RV apex with the coil lying along the RV diaphragmatic surface. The ICD (Medtronic Micro Jewel II model 7223Cx) was implanted in a left abdominal pocket with the lead tunneled from the infraclavicular region to the pocket. Implant DFTs were ± 15 J using a biphasic waveform. DFTs rechecked within 3-month postimplant were unchanged. Lead impedance at implant ranged from 38 to 56 ,, mean 51 ,. Follow-up was 3,21 months (total 82 months) with no electrode dislodgment. lead fractures, or inappropriate discharges. Two of the five patients have had successful appropriate ICD discharges. Transvenous ICD electrode placement can be performed in children as small as 20 kg with the device implanted in a cosmetically acceptable abdominal pocket that is well tolerated. Excellent DFTs can be achieved. This approach avoids a thoracotomy in all but the smallest child, does not require subclavicular placement of the device, and avoids use of a second intravascular coil. [source] Behaviour of a Moving Droplet under Electrowetting Actuation: Numerical SimulationTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2006K. Mohseni Abstract Numerical simulation of droplet transport in microchannels under electrostatic actuation is investigated. Volume-of-Fluid (VOF) technique is employed, in which electrowetting effects are implemented through Lippmann's relation in the form of modified contact angles at the boundary. A velocity of about 35 mm/s is achieved with the actuation of 40 V. The droplet flow under electrowetting actuation is characterized for the majority of the process parameters such as actuation voltage, channel dimension, electrode size, and resultant velocity. On étudie la simulation numérique du transport de gouttelettes dans des microcanaux lors d'une actuation électrostatique. On emploie la technique des volumes de fluide (VOF), dans laquelle les effets de l'électromouillage sont introduits dans la relation de Lippmann sous la forme d'angles de contact modifiés à la frontière. Une vitesse d'environ 35 mm/s est atteinte avec une actuation de 40 V. L'écoulement des gouttelettes dans l'actuation électromouillante est caractérisé pour la majorité des paramètres de procédé, tels que le voltage d'actuation, la dimension des canaux, la taille des électrodes et la vitesse résultante. [source] | ||||||||||