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Coil Orientations (coil + orientation)
Selected AbstractsIntracortical modulation of cortical-bulbar responses for the masseter muscleTHE JOURNAL OF PHYSIOLOGY, Issue 14 2008Enzo Ortu Short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were evaluated in the masseter muscles of 12 subjects and the cortical silent period (SP) in nine subjects. Motor evoked potentials (MEPs) were recorded from contralateral (cMM) and ipsilateral (iMM) masseters, activated at 10% of maximal voluntary contraction (MVC). Interstimulus intervals (ISIs) were 2 and 3 ms for SICI, 10 and 15 ms for ICF. TMS of the left masseteric cortex induced MEPs that were larger in the cMM than the iMM; stimulation of right masseteric cortex produced a similar asymmetry in response amplitude. SICI was only observed using a CS intensity of 70% AMT and was equal in both cMM and iMM. SICI was stronger at higher TS intensities, was abolished by muscle activation greater than 10% MVC, and was unaffected by coil orientation changes. Control experiments confirmed that SICI was not contaminated by any inhibitory peripheral reflexes. However, ICF could not be obtained because it was masked by bilateral reflex depression of masseter EMG caused by auditory input from the coil discharge. The SP was bilateral and symmetric; its duration ranged from 35 to 70 ms depending on TS intensity and coil orientation. We conclude that SICI is present in the cortical representation of masseter muscles. The similarity of SICI in cMM and iMM suggests either that a single pool of inhibitory interneurons controls ipsi- and contralateral corticotrigeminal projections or that inhibition is directed to bilaterally projecting corticotrigeminal fibres. Finally, the corticotrigeminal projection seems to be weakly influenced by inhibitory interneurons mediating the cortical SP. [source] Detection of resistive features using towed slingram electromagnetic induction instrumentsARCHAEOLOGICAL PROSPECTION, Issue 2 2009Julien Thiesson Abstract Slingram frequency domain electromagnetic (FDEM) instruments allow simultaneous measurement of both magnetic susceptibility and electrical conductivity, which should justify their widespread use in archaeological surveying. However, this is not the case and their application remains quite limited due to: (i) a lack of knowledge about the role of coil orientation and spacing in terms of the detection abilities for archaeological features (especially for resistive bodies); and (ii) a lack of instrumentation specifically designed for shallow targets. We present here a test of a new version of the CS60 instrument (VCP coil configuration and 0.6,m intercoil spacing) for shallow depth resistive feature detection. This experiment was undertaken on the Roman site of Vieil-Evreux where a complete series of control resistivity and radar data was obtained. Detection of buried Roman walls was successful, in accordance with what can be expected from three-dimensional modelling. This confirms that the application of this type of instrument in archaeological surveys merits to be extended significantly. Copyright © 2009 John Wiley & Sons, Ltd. [source] Sensitivity of multi-coil frequency domain electromagnetic induction sensors to map soil magnetic susceptibilityEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2010D. Simpson Magnetic susceptibility is an important indicator of anthropogenic disturbance in the natural soil. This property is often mapped with magnetic gradiometers in archaeological prospection studies. It is also detected with frequency domain electromagnetic induction (FDEM) sensors, which have the advantage that they can simultaneously measure the electrical conductivity. The detection level of FDEM sensors for magnetic structures is very dependent on the coil configuration. Apart from theoretical modelling studies, a thorough investigation with field models has not been conducted until now. Therefore, the goal of this study was to test multiple coil configurations on a test field with naturally enhanced magnetic susceptibility in the topsoil and with different types of structures mimicking real archaeological features. Two FDEM sensors were used with coil separations between 0.5 and 2 m and with three coil orientations. First, a vertical sounding was conducted over the undisturbed soil to test the validity of a theoretical layered model, which can be used to infer the depth sensitivity of the coil configurations. The modelled sounding values corresponded well with the measured data, which means that the theoretical models are applicable to layered soils. Second, magnetic structures were buried in the site and the resulting anomalies measured to a very high resolution. The results showed remarkable differences in amplitude and complexity between the responses of the coil configurations. The 2-m horizontal coplanar and 1.1-m perpendicular coil configurations produced the clearest anomalies and resembled best a gradiometer measurement. [source] Exposure of mouse preosteoblasts to pulsed electromagnetic fields reduces the amount of mature, type I collagen in the extracellular matrixJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2006Yoshitada Sakai Abstract We tested the hypothesis that exposure of a mouse preosteoblast cell line to pulsed electromagnetic fields (PEMF) would affect components of the extracellular matrix. We report that exposure of MC3T3-E1 cells to a single PEMF waveform significantly reduced the amount of mature, ,1(I) collagen in the extracellular matrix (ECM) and the conditioned medium, without affecting the amount of total ECM protein. This decrease was not due to changes in the steady-state level of Col1A1 mRNA or to degradation of mature collagen. We then tested the effect of three distinct PEMF waveforms, two orthogonal coil orientations, and two waveform amplitude levels on the amount of ,1(I) collagen in the conditioned medium. A sequence of factorial ANOVAs and stepwise regression modeling revealed that the period (duration) of the individual pulses accounted for a significant proportion of the variance associated with the amount of ,1(I) collagen in the conditioned medium. The total variance accounted for, however, was small (R2,=,0.155, p,<,0.001 and R2,=,0.172, p,<,0.001, in the horizontal and vertical orientations, respectively). The positive and negative regression coefficients for the coil orientations revealed that the influence of pulse period was significantly different for the orthogonal coil orientations (p,<,0.001). The findings imply that the dominant influence of PEMF on the amount of mature, ,1(I) collagen in the ECM is related to variables other than those expressed in the time-amplitude domain. The results provide objective direction toward identifying waveform characteristics that contribute to the observed between-waveform differences with regard to collagen. Advances in this area may lead toward improving waveforms and waveform delivery protocols. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Evaluating the multiple coil configurations of the EM38DD and DUALEM-21S sensors to detect archaeological anomaliesARCHAEOLOGICAL PROSPECTION, Issue 2 2009David Simpson Abstract The multiple coil configurations of two electromagnetic induction sensors were tested on a field with strong electrical and magnetic contrasts. The first sensor, EM38DD, measures either the apparent electrical conductivity (ECa or ,a) or the apparent magnetic susceptibility (MSa or ,a) of the soil at two coil orientations. The second sensor, DUALEM-21S, measures both ECa and MSa at two coil orientations and two coil separations. The goal was to test if measuring with the multiple coils resulted in a better detection of near-surface artefacts and the natural soil variability. The ECa of all coil configurations was closely related to the depth of a clay substrate beneath the topsoil sandy loam, which was verified by soil augering. Configurations with a shallower theoretical depth of exploration were less influenced by the clay substrate. Combining two coil configurations revealed important ECa anomalies, not visible on individual measurements, associated with a brick wall foundation and a former ditch. The MSa maps showed totally different anomaly patterns, related to anthropogenic disturbances in the soil, such as the filling-in with brick rubble of a former pond. Depending on the depth and thickness of the disturbance and the relative response of the sensor configurations, the MSa anomalies were entirely positive for one configuration but other configurations also had negative anomalies. It was concluded that multiple coil configurations provide a better insight into the build-up of the soil profile and are better able to detect anomalies than single measurements. Copyright © 2009 John Wiley & Sons, Ltd. [source] A Novel Low Temperature Transcutaneous Energy Transfer System Suitable for High Power Implantable Medical Devices: Performance and Validation in SheepARTIFICIAL ORGANS, Issue 5 2010Thushari D. Dissanayake Abstract Transcutaneous energy transfer (TET) systems use magnetic fields to transfer power across the skin without direct electrical connectivity. This offers the prospect of lifetime operation and overcomes risk of infection associated with wires passing through the skin. Previous attempts at this technology have not proved suitable due to poor efficiency, large size, or tissue damage. We have developed a novel approach utilizing frequency control that allows for wide tolerance in the alignment between internal and external coils for coupling variations of 10 to 20 mm, and relatively small size (50 mm diameter, 5 mm thickness). Using a sheep experimental model, the secondary coil was implanted under the skin in six sheep, and the system was operated to deliver a stable power output to a 15 W load continuously over 4 weeks. The maximum surface temperature of the secondary coil increased by a mean value of 3.4 ± 0.4°C (±SEM). The highest absolute mean temperature was 38.3°C. The mean temperature rise 20 mm from the secondary coil was 0.8 ± 0.1°C. The efficiency of the system exceeded 80% across a wide range of coil orientations. Histological analysis revealed no evidence of tissue necrosis or damage after four weeks of operation. We conclude that this technology is able to offer robust transfer of power to implantable devices without excess heating causing tissue damage. [source] | |||||||||||||