114 results on '"Current direction"'
Search Results
2. Decoupling the nonthermal effect of current by electrically assisted crystal plasticity modeling of Ni-based single crystal superalloys.
- Author
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Gao, Jia, Li, Hongwei, Zhang, Xin, Shao, Guangda, Xiang, Zhiyu, and Sun, Xinxin
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CRYSTAL models ,ELECTRIC currents ,SINGLE crystals ,DISLOCATION density ,HEAT resistant alloys - Abstract
• Evident tension axis direction—[100] axis within single crystal superalloys along different crystallographic axes during EA tension. • Decreased strength anisotropy along the non-tensile axis direction with higher current density. • Increased stress drop and anisotropy under the current direction increasing from 0° to 45°. The electrically assisted (EA) deformation process has received considerable attention in recent years, accompanied by research on current-induced deformation mechanisms. However, there are still challenges in eliminating thermal effects, which have prevented a comprehensive understanding of the underlying current-induced mechanisms. Opting for a single crystal (SC) in research provides advantages in decoupling the nonthermal effect of electric current at smaller scales and eliminating the complex interactions that exist in polycrystalline materials. Therefore, the innovation of this work lies in decoupling the nonthermal effect of electric current and conducting a comprehensive analysis of anisotropic deformation and mechanisms within a Ni-based SC with different crystallographic axes and various current directions during electrically assisted tensile simulation. A significant tension axis direction in the SC during EA tension was induced by the combination of a higher current direction factor (| cos θ |) and a dimensionless factor for the current density (| J α / J 0 α |) along the [100] axis. The stress drop within the SC due to the nonthermal effect of electric current generally increased with increasing current direction. This was attributed to the increased dislocation density differences and decreased temperature. The increased stress anisotropy of the SC at a current direction of 45° was attributed to fewer activated (111) slip systems and the pinning effect of more dislocations within these systems. This study advances our understanding of the thermal and nonthermal effects of electric current and offers valuable insights for the informed application of EA deformations in industrial and aerospace settings with SC superalloys. [Display omitted] [ABSTRACT FROM AUTHOR] more...
- Published
- 2025
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Catalog
3. TMS Pulse Waveform and Direction
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Sommer, Martin, Hannah, Ricci, Peterchev, Angel V., Paulus, Walter, Wassermann, Eric M., book editor, Peterchev, Angel V., book editor, Ziemann, Ulf, book editor, Lisanby, Sarah H., book editor, Siebner, Hartwig R., book editor, and Walsh, Vincent, book editor more...
- Published
- 2024
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4. Dual optimization of the geometric design and inductor parameters of the induction heating tundish based on numerical simulations
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Xiqing Chen, Pu Wang, Hong Xiao, Bing Yi, Haiyan Tang, and Jiaquan Zhang
- Subjects
Channel-type induction heating tundish ,Number of inductors ,Current direction ,Electromagnetic field ,Temperature field ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Based on the application of electromagnetism and hydrodynamics in metallurgy, the selection of the number of inductors as well as the direction of inductor current access is investigated for channel-type induction heating (IH) tundish with dual-channel (D-Ch), three-channel (T-Ch) and four-channel (F-Ch) tundish designs. The results show that when a single inductor is used, the Joule heat power (JHP) and electromagnetic force (EMF) are essentially the same within the two channels of the D-Ch tundish, but in the T-Ch tundish and the F-Ch tundish, the JHP and EMF of channel No.1 (Ch1) is much larger than other channels, which is extremely asymmetric. This will further be reflected in the influence on the flow and temperature consistency of the molten steel in the tundish. When a single inductor is used in the T-Ch or F-Ch tundish, the molten steel flow velocity in Ch1 is 4.2 and 7.4 times higher than that in the symmetric channel, respectively, and the temperature difference at the symmetric strand can be as high as 11 K or more. However, the maximum flow velocity of the molten steel in Ch1 and channel No.2 (Ch2) of the D-Ch tundish is 0.21 and 0.19 m⋅s−1, respectively, and the maximum temperature difference at the symmetrical strand is only 2.3 K. For the tundish with double inductors, the influence of the direction of the access current of the inductors should be taken into account. The inductors of a D-Ch tundish can effectively heat the molten steel only by accessing the same direction current. The physical fields in the intermediate and side channels are significantly different when the same or opposite current is accessed to the dual inductors of T-Ch tundish. The temperature rise rate of the molten steel is 36% higher when the dual inductors of the F-Ch tundish are accessed to the opposite current than when they are accessed to the same current. Therefore, a D-Ch design should be used for the channel-type tundish with a single inductor. And for the channel-type tundish with dual inductors, the same direction current should be accessed under the D-Ch design, and the opposite current should be accessed under the F-Ch design. more...
- Published
- 2023
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5. Development of Electromagnetic Current Meter for Marine Environment.
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Chen, Shizhe, Wu, Yushang, Liu, Shixuan, Yang, Yingdong, Wan, Xiaozheng, Yang, Xianglong, Zhang, Keke, Wang, Bo, and Yan, Xingkui
- Subjects
ACOUSTIC Doppler current profiler ,OCEAN currents ,ELECTROMAGNETIC induction ,ELECTROMAGNETIC measurements - Abstract
Ocean current is one of the most important parameters in ocean observation, and ocean current measurement based on electromagnetic induction is becoming more and more important because of its advantages such as simple structure and high measurement accuracy. However, it is difficult to detect weak current signals in a complex marine environment. In this paper, an electromagnetic induction current measurement scheme based on lock-in amplification technology is proposed. Key technologies such as the evaluation of induced current intensity, overall design, circuit design, and orientation design of the current meter were studied. The prototype of the electromagnetic current meter was developed and tested in the laboratory and at sea. The repeatability of current velocity and current direction was higher than 1.5 cm/s and 1.5°, respectively. A comparison test between the electromagnetic current meter prototype and Nortek ADCP (Acoustic Doppler Current Profiler) installed on a buoy at sea was carried out, and the correlation coefficients of the current velocity and current direction datum were 0.90 and 0.96, respectively. Through continuous on-site and fault-free operations at sea, the experimental data show that the electromagnetic current meter has good adaptability at sea, which provides feasible technical and equipment support for ocean current observation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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6. Effect of Angle between Pulse Current and Load Direction on Flow Stress of Ti-6Al-4V Alloy under Uniaxial Tension.
- Author
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Chen, Chao, Li, Caixia, Li, Chao, Li, Feng, Zhang, Guangdong, and Yu, Guangning
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TENSION loads ,TENSILE tests ,ANGLES ,CRYSTAL grain boundaries ,ALLOY testing ,ALLOYS - Abstract
In the research field of pure electroplastic effect, uniaxial tensile tests of Ti-6Al-4V alloy were carried out. By changing the position of the electrode, the pulse current with different angles was applied to the stretched specimen, to verify whether the angle between the current direction and the load direction affected the flow stress of the metal. The results show that as the angle between the current and the load direction increases, the stress drop of the material decreases, when the angle increases to 90°, the stress drop of the material was almost 0 MPa. Based on the experimental data, a variable describing the current direction was introduced to the JC model, and a constitutive equation considering the current direction for Ti-6Al-4V under the condition of pulsed current and room temperature was constructed. The verification results showed that the prediction accuracy of this constitutive equation was satisfactory. The influence mechanism of current density and direction on material flow stress was further analyzed by means of HRTEM, the smaller the angle between the current and the load direction, the higher the mobility of atoms at the grain boundaries of the material, and the phenomenon of dislocation packing is alleviated. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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7. Multi-crack spatial propagation evolution analysis of 3D-TSV under thermal-electric-mechanical coupling field.
- Author
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Hou, Kaihong, Fan, Zhengwei, Chen, Yonggui, Zhang, Shufeng, Wang, Yashun, and Chen, Xun
- Subjects
- *
CRACK propagation (Fracture mechanics) , *FRACTURE mechanics , *THROUGH-silicon via , *MICROSTRUCTURE , *ELECTRONS - Abstract
As an interconnected microstructure, Through-Silicon Via (TSV) play a vital role in three-dimension (3D) chip. With the improvement of interconnection density, the reliability problems origin from interface crack initiation and propagation become increasingly prominent. In this study, the effects of the crack type, crack propagation direction, current magnitude and direction on the spatial characteristic of crack propagation under thermal-electric-mechanical coupling field is deeply investigated based on 3D J-integral-based fracture mechanics method. Results shows that: 1) Crack J-integral is consistent with the variation of ambient temperature and positively correlated with the current magnitude; 2) When the current direction is same as crack propagation direction, electron holes will gradually accumulate at crack tip, which can accelerate the crack propagation rate; 3) Different cracks will present different morphological characteristics, the shell pattern cracks can be found at RDL-SiO 2 and Si-SiO 2 cracks, and the internal cracks TSV-Cu present irregular trapezoidal shape. Relevant result is hope to provide certain references for the reliability analysis and optimal design of TSV. [ABSTRACT FROM AUTHOR] more...
- Published
- 2025
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8. The role of the TMS parameters for activation of the corticospinal pathway to the diaphragm.
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Chakalov, Ivan, Antal, Andrea, Eckardt, Simon S., Paulus, Walter, Saager, Leif, Meissner, Konrad, Bähr, Mathias, Moerer, Onnen, and Stephani, Caspar
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DIAPHRAGM (Anatomy) , *EVOKED potentials (Electrophysiology) , *BRAIN mapping , *RESPIRATORY muscles - Abstract
• Biphasic- compared to monophasic-TMS requires significantly less charge and time to induce diaphragmatic motor-evoked potentials. • Neuronavigated cortical mapping revealed similar best stimulation site of the diaphragm for monophasic- and biphasic-TMS. • The TMS-stimulus modality significantly influences the reliability of the diaphragmatic MEPs. The influence of the TMS-parameters on the efficacy and reliability to induce diaphragmatic motor-evoked potentials (diMEPs) has not been studied so far. Therefore, the objective of the present research is to probe the role of TMS- waveform (monophasic- [Mo] vs. biphasic-pulses [Bi]) and current direction (posterior-anterior [Pa] vs. anterior-posterior [Ap]) in the activation of the diaphragm. Four different pulse-configurations (Mo-Ap, Mo-Pa, Bi-Ap, Bi-Pa) were applied by means of neuronavigated-TMS and surface MEP-recordings at relaxed end-expiration in 19 healthy subjects. The parameters resting motor threshold (RMT), diMEP-amplitude and -latency, as well as best stimulation site (motor hotspot) and central motor conduction time were studied. Diaphragm movements were simultaneously recorded via ultrasound. To control for possible signal contamination the MEPs of muscles neighboring the diaphragm were also obtained. The motor hotspots of the diaphragm showed similar spatial distribution for the Mo-Ap, Mo-Pa, Bi-Ap and Bi-Pa. The biphasic-pulses yielded significantly lower RMTs and higher diMEP-amplitudes as the monophasic-pulses. Anterior to posterior oriented Bi- and Mo-pulses evoked significantly shorter diMEP-latencies than the posterior-anterior oriented ones. The present research demonstrates that biphasic- as compared to monophasic-pulses require significantly less charge and time for inducing diMEPs. The biphasic-TMS is best suited for the demanding stimulation of the diaphragm. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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9. Gas Blow Forming of Nanocrystalline Ni Foil Assisted by Two-Dimensional Pulse Current.
- Author
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Yu, Guangning, Li, Chao, Li, Feng, Zhang, Guangdong, and Chen, Chao
- Subjects
BULGING (Metalwork) ,GASES - Abstract
In order to increase the gas blow formability of Ni foil, a two-dimensional pulse current auxiliary gas blow forming is proposed. In this paper, general free bulging tests, one-dimensional current auxiliary bulging tests, and two-dimensional current auxiliary bulging tests are carried out. The result indicates that the gas blow formability is improved by the two-dimensional pulse current. The ratio of height to diameter is up to 43.75% when the peak current density is 30 A/mm
2 . The ratio of height to diameter is 20.27% higher than that under the one-dimensional current, 44.63% higher than that under general free bulging forming. The mechanism of the two-dimensional pulse current on the deformation is studied. The result shows that the formability is improved more when the current direction is parallel to the radial strain direction. The pulse current can enhance the dislocation activity. Therefore, the formability of the Ni foil during gas blow forming can be increased. [ABSTRACT FROM AUTHOR] more...- Published
- 2022
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10. A New Angle on Transcranial Magnetic Stimulation Coil Orientation: A Targeted Narrative Review.
- Author
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Cerins A, Thomas EHX, Barbour T, Taylor JJ, Siddiqi SH, Trapp N, McGirr A, Caulfield KA, Brown JC, and Chen L
- Subjects
- Humans, Motor Cortex physiology, Brain physiology, Transcranial Magnetic Stimulation methods
- Abstract
Transcranial magnetic stimulation (TMS) is used to treat several neuropsychiatric disorders including depression, where it is effective in approximately one half of patients for whom pharmacological approaches have failed. Treatment response is related to stimulation parameters such as the stimulation frequency, pattern, intensity, location, total number of pulses and sessions applied, and target brain network engagement. One critical but underexplored component of the stimulation procedure is the orientation or yaw angle of the commonly used figure-of-eight TMS coil, which is known to impact neuronal response to TMS. However, coil orientation has remained largely unchanged since TMS was first used to treat depression and continues to be based on motor cortex anatomy, which may not be optimal for the dorsolateral prefrontal cortex treatment site. In this targeted narrative review, we evaluate experimental, clinical, and computational evidence indicating that optimizing coil orientation may improve TMS treatment outcomes. The properties of the electric field induced by TMS, the changes to this field caused by the differing conductivities of head tissues, and the interaction between coil orientation and the underlying cortical anatomy are summarized. We describe evidence that the magnitude and site of cortical activation, surrogate markers of TMS dosing and brain network targeting considered central in clinical response to TMS, are influenced by coil orientation. We suggest that coil orientation should be considered when applying therapeutic TMS and propose several approaches to optimizing this potentially important treatment parameter., (Copyright © 2024 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.) more...
- Published
- 2024
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11. Development of Electromagnetic Current Meter for Marine Environment
- Author
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Shizhe Chen, Yushang Wu, Shixuan Liu, Yingdong Yang, Xiaozheng Wan, Xianglong Yang, Keke Zhang, Bo Wang, and Xingkui Yan
- Subjects
electromagnetic induction current meter ,lock-in amplification technology ,ocean current observation ,current velocity ,current direction ,Naval architecture. Shipbuilding. Marine engineering ,VM1-989 ,Oceanography ,GC1-1581 - Abstract
Ocean current is one of the most important parameters in ocean observation, and ocean current measurement based on electromagnetic induction is becoming more and more important because of its advantages such as simple structure and high measurement accuracy. However, it is difficult to detect weak current signals in a complex marine environment. In this paper, an electromagnetic induction current measurement scheme based on lock-in amplification technology is proposed. Key technologies such as the evaluation of induced current intensity, overall design, circuit design, and orientation design of the current meter were studied. The prototype of the electromagnetic current meter was developed and tested in the laboratory and at sea. The repeatability of current velocity and current direction was higher than 1.5 cm/s and 1.5°, respectively. A comparison test between the electromagnetic current meter prototype and Nortek ADCP (Acoustic Doppler Current Profiler) installed on a buoy at sea was carried out, and the correlation coefficients of the current velocity and current direction datum were 0.90 and 0.96, respectively. Through continuous on-site and fault-free operations at sea, the experimental data show that the electromagnetic current meter has good adaptability at sea, which provides feasible technical and equipment support for ocean current observation. more...
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- 2023
- Full Text
- View/download PDF
12. Primary motor cortex function and motor skill acquisition: insights from threshold-hunting TMS.
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Cirillo, John, Semmler, John G., Mooney, Ronan A., and Byblow, Winston D.
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MOTOR cortex , *MOTOR ability , *MOTOR learning , *TRANSCRANIAL magnetic stimulation , *MOTOR imagery (Cognition) , *THRESHOLD (Perception) - Abstract
Modulation of GABA-mediated inhibition in primary motor cortex (M1) is important for the induction of training-induced plasticity. The downregulation of inhibition during acquisition may promote cortical reorganization, whereas an upregulation once performance has plateaued may promote consolidation of the newly acquired skill. GABA-related inhibition in human M1 is routinely assessed using the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI). However, modulation of SICI with motor skill learning is not a consistent finding and may be influenced by TMS parameters. The aim of this study was to compare the modulation of SICI by motor skill learning between conventional and adaptive threshold-hunting techniques with an anterior–posterior and posterior–anterior induced current. Sixteen participants (21–33 years) trained with their dominant (right) hand on a sequential visual isometric pinch task. Electromyographic recordings were obtained from the right first dorsal interosseous muscle. Corticomotor excitability and SICI were examined before and immediately after 12 blocks of training. Skill increased throughout the training, with performance plateauing before completion. Corticomotor excitability increased after motor training for both current directions. The amount of SICI was greater with anterior–posterior stimulation than posterior–anterior for both conventional and adaptive threshold-hunting techniques. SICI increased after motor training, but only for adaptive threshold-hunting with an anterior–posterior-induced current. The increased GABA-mediated inhibition evident after motor skill learning may promote consolidation of the newly acquired skill. The findings also support the notion that adaptive threshold-hunting SICI using an anterior–posterior current provides an effective assessment in interventional studies. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
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13. Effect of structural changes of Pd/WO3 thin films on response direction and rate in hydrogen detection.
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Han, Seung-Ik, Kumar, Mohit, Duy, Le Thai, Yeasmin, Rubaya, Park, Chiwan, Jung, Gwanggyo, Kim, Hyunsup, Khan, Amir Sohail, Dang, Hyunmin, and Seo, Hyungtak
- Subjects
- *
THIN films , *HYDROGEN detectors , *RADIOFREQUENCY sputtering , *HYDROGEN , *WASTE recycling - Abstract
Hydrogen (H 2) has attracted considerable attention as a renewable energy carrier owing to its recyclability and environmental friendliness. However, due to its explosive nature at concentrations above 4 % in air, the detection of H 2 is a critical safety concern. Thereby, this study investigates the impact of the growth forms of the Pd/WO 3 thin film layer on the sensor's ability to detect H 2 , including the response direction and rate of the sensor's resistance change. The chemoresistive sensors were constructed using a nanoporous WO 3 film (formed via RF sputtering on a Si/SiO 2 wafer) and a palladium layer (deposited via e-beam evaporation). Experimental results display the excellent hydrogen detection performance of the sensors at concentrations ranging from 1- 10 % (in air) by the change of chemoresistance and demonstrate that the strategies used in fabricating the sensors are effective for practical use. By gaining a deeper understanding of the hydrogen sensing mechanisms in Pd/WO 3 thin films, this study reveals how to improve the performance of hydrogen sensors and ensure their safe use in various industries. • Observe changes in sensor resistance and hydrogen binding site movement depending on the growth pattern of Pd/WO 3 layers. • The growth pattern of the Pd/WO 3 induces structural changes, leading to the oxidation of Pd through its bonding with oxygen. • Depending on structural changes in the Pd/WO 3 , the direction and speed of response signals vary when detecting hydrogen. • The discontinuity in the Pd rises, causing a shift in the current direction through the WO 3 instead of the Pd. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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14. Effects of Transcranial Static Magnetic Stimulation on Motor Cortex Evaluated by Different TMS Waveforms and Current Directions.
- Author
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Davila-Pérez, Paula, Pascual-Leone, Alvaro, and Cudeiro, Javier
- Subjects
- *
TRANSCRANIAL magnetic stimulation , *MOTOR cortex , *YOUNG adults - Abstract
Transcranial static magnetic stimulation (tSMS) modulates cortical excitability probably by interacting with the GABA-glutamate intracortical balance. Different transcranial magnetic stimulation (TMS) waveforms probe distinct GABA-mediated cortical inhibition networks. The goal of the present work is to further characterize tSMS-induced changes in motor cortex reactivity and inhibition–excitation (I/E) balance. We hypothesized that tSMS affects particular cortical networks and thus, the effects of tSMS would be different depending on the TMS waveform used to assess its results. 23 healthy young adults completed two sessions of real or sham tSMS. The order of the sessions was randomized across participants. Motor evoked potentials (MEPs), cortical silent period (CSP), short- and long-interval intracortical inhibition (SICI and LICI), and intracortical facilitation (ICF) were assessed with TMS monophasic posterior–anterior (mono PA ; n = 9), monophasic anterior–posterior (mono AP ; n = 7), or biphasic (bi AP-PA ; n = 7) pulses. Repeated measures analyses of variance and appropriate pairwise comparisons were performed for each TMS measure. After 15 min of real tSMS, the MEP amplitudes decreased compared to sham and baseline, SICI and LICI showed greater inhibition, and a tendency towards longer CSPs and less facilitation was found. These results were only observed with mono PA TMS. MEP amplitude increased compared to sham with mono AP TMS, with no clear changes in general intracortical I/E balance. Biphasic TMS was not able to capture any effects of tSMS. The results show that the effects of tSMS on cortical excitability and inhibition involve specific interneuron circuits that are selectively activated by mono PA TMS. • tSMS-induced inhibition was tested with different TMS waveforms. • Inhibition after single- and paired-pulse TMS was only observed with monophasic PA pulses. • Monophasic AP revealed larger motor responses after tSMS with no change in intracortical I/E balance. • Biphasic TMS did not capture any inhibitory cortical changes due to tSMS. • tSMS induces inhibition via specific GABA-mediated cortical networks. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
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15. Observing Without Acting: A Balance of Excitation and Suppression in the Human Corticospinal Pathway?
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Ricci Hannah, Lorenzo Rocchi, and John C. Rothwell
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transcranial magnetic stimulation ,motor cortex ,current direction ,mirror neurons ,motor resonance ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Transcranial magnetic stimulation (TMS) studies of human primary motor cortex (M1) indicate an increase corticospinal excitability during the observation of another's action. This appears to be somewhat at odds with recordings of pyramidal tract neurons in primate M1 showing that there is a balance of increased and decreased activity across the population. TMS is known to recruit a mixed population of cortical neurons, and so one explanation for previous results is that TMS tends to recruit those excitatory output neurons whose activity is increased during action observation. Here we took advantage of the directional sensitivity of TMS to recruit different subsets of M1 neurons and probed whether they responded differentially to action observation in a manner consistent with the balanced change in activity in primates. At the group level we did not observe the expected increase in corticospinal excitability for either TMS current direction during the observation of a precision grip movement. Instead, we observed substantial inter-individual variability ranging from strong facilitation to strong suppression of corticospinal excitability that was similar across both current directions. Thus, we found no evidence of any differential changes in the excitability of distinct M1 neuronal populations during action observation. The most notable change in corticospinal excitability at the group level was a general increase, across muscles and current directions, when participants went from a baseline state outside the task to a baseline state within the actual observation task. We attribute this to arousal- or attention-related processes, which appear to have a similar effect on the different corticospinal pathways targeted by different TMS current directions. Finally, this rather non-specific increase in corticospinal excitability suggests care should be taken when selecting a “baseline” state against which to compare changes during action observation. more...
- Published
- 2018
- Full Text
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16. The Effects of Waveform and Current Direction on the Efficacy and Test–Retest Reliability of Transcranial Magnetic Stimulation.
- Author
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Davila-Pérez, Paula, Jannati, Ali, Fried, Peter J., Cudeiro Mazaira, Javier, and Pascual-Leone, Alvaro
- Subjects
- *
TRANSCRANIAL magnetic stimulation , *STATISTICAL reliability , *CEREBRAL cortex , *EVOKED potentials (Electrophysiology) , *NEURAL stimulation - Abstract
Highlights • Different TMS pulse parameters (waveforms and current directions) interact with specific neural cortical components. • The influence of TMS pulse parameters on the efficacy and reliability of TMS measures has not been sufficiently studied. • The results show that waveform/current direction significantly influences the efficacy and reliability of TMS protocols. • Monophasic pulses induce greater and more reliable inhibition in LICI and SICI. • TMS pulses with an anterior–posterior component induce greater ICF, with biphasic pulses resulting in more reliable ICF. Abstract The pulse waveform and current direction of transcranial magnetic stimulation (TMS) influence its interactions with the neural substrate; however, their role in the efficacy and reliability of single- and paired-pulse TMS measures is not fully understood. We investigated how pulse waveform and current direction affect the efficacy and test–retest reliability of navigated, single- and paired-pulse TMS measures. 23 healthy adults (aged 18–35 years) completed two identical TMS sessions, assessing resting motor threshold (RMT), motor-evoked potentials (MEPs), cortical silent period (cSP), short- and long-interval intra-cortical inhibition (SICI and LICI), and intracortical facilitation (ICF) using either monophasic posterior–anterior (mono PA ; n = 9), monophasic anterior–posterior (mono AP ; n = 7), or biphasic (bi AP-PA ; n = 7) pulses. Averages of each TMS measure were compared across the three groups and intraclass correlation coefficients were calculated to assess test–retest reliability. RMT was the lowest and cSP was the longest with bi AP-PA pulses, whereas MEP latency was the shortest with mono PA pulses. SICI and LICI had the largest effect with mono PA pulses, whereas only mono AP and bi AP-PA pulses resulted in significant ICF. MEP amplitude was more reliable with either mono PA or mono AP than with bi AP-PA pulses. LICI was the most reliable with mono AP pulses, whereas ICF was the most reliable with bi AP-PA pulses. Waveform/current direction influenced RMT, MEP latency, cSP, SICI, LICI, and ICF, as well as the reliability of MEP amplitude, LICI, and ICF. These results show the importance of considering TMS pulse parameters for optimizing the efficacy and reliability of TMS neurophysiologic measures. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
- Full Text
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17. Conventional or threshold-hunting TMS? A tale of two SICIs.
- Author
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Cirillo, John, Semmler, John G., Mooney, Ronan A., and Byblow, Winston D.
- Abstract
Abstract Background In human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. Objective To examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. Methods In 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. Results Inhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P < 0.001) and posterior-anterior stimulation at both ISIs (2 ms 8.6 ± 8.7%, 3 ms 5.9 ± 4.8%; P < 0.001). There was an association between inhibition obtained with conventional and adaptive threshold-hunting for posterior-anterior but not anterior-posterior stimulation (2 ms only, r = 0.68, P = 0.03). Conclusions More inhibition was evident with anterior-posterior than posterior-anterior current for both adaptive threshold-hunting and conventional paired-pulse TMS. Assessment of SICI with anterior-posterior stimulation was not directly comparable between the two approaches. However, the amount of inhibition was dependent on conditioning stimulus intensity and ISI for both SICI techniques. Highlights • Greater intracortical inhibition can be obtained using anterior-posterior induced current in the brain compared with posterior-anterior for both conventional and adaptive threshold-hunting paired-pulse transcranial magnetic stimulation. • With both techniques, the amount of inhibition assessed with anterior-posterior induced current was dependent on the conditioning stimulus intensity and interstimulus interval. • Assessment of primary motor cortex short-latency inhibition using equivalent stimulation intensities may not be directly comparable between conventional and adaptive threshold-hunting techniques. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
- Full Text
- View/download PDF
18. Adaptive threshold hunting reveals differences in interhemispheric inhibition between young and older adults.
- Author
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Mooney, Ronan A., Cirillo, John, and Byblow, Winston D.
- Subjects
- *
CORPUS callosum , *NEURAL stimulation , *BRAIN stimulation , *TELENCEPHALON , *OLDER people , *NEURAL inhibition , *YOUNG adults - Abstract
Abstract: Interhemispheric inhibition between bilateral motor cortices is important for the performance of unimanual activities and may be compromised with advancing age. Conventionally, interhemispheric inhibition is assessed using paired‐pulse transcranial magnetic stimulation (TMS) with constant conditioning and test stimulation parameters. Adaptive threshold hunting TMS, whereby a target motor‐evoked potential amplitude is maintained in the presence of the conditioning, may provide an alternative means of assessment. Furthermore, interhemispheric inhibition may suppress late indirect‐waves more so than early indirect‐waves which can be preferentially elicited using anterior–posterior (AP) and posterior–anterior (PA) induced currents, respectively. The aim of this study was to assess age‐related effects on interhemispheric inhibition using both conventional and threshold hunting techniques with PA‐ and AP‐induced current. In 15 young and 15 older adults, short (10 ms) and long (40 ms) interval interhemispheric inhibition was examined in the nondominant extensor carpi radialis muscle at rest and during voluntary extension of the contralateral wrist. With the conventional technique, there were no age‐related differences in short‐interval interhemispheric inhibition. With threshold hunting and AP‐induced current, young adults exhibited greater short‐interval interhemispheric inhibition during contralateral activation compared with rest and compared with older adults. Furthermore, long‐interval interhemispheric inhibition was greater in older adults compared with young for both conventional and threshold hunting techniques. Age‐related differences in interhemispheric inhibition are evident with threshold hunting using PA‐ and AP‐induced current. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
- Full Text
- View/download PDF
19. Adaptive threshold hunting for the effects of transcranial direct current stimulation on primary motor cortex inhibition.
- Author
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Mooney, Ronan A., Cirillo, John, and Byblow, Winston D.
- Subjects
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MOTOR cortex , *TRANSCRANIAL direct current stimulation , *GABA , *POSTERIOR segment (Eye) , *ANTERIOR eye segment - Abstract
Primary motor cortex excitability can be modulated by anodal and cathodal transcranial direct current stimulation (tDCS). These neuromodulatory effects may, in part, be dependent on modulation within gamma-aminobutyric acid (GABA)-mediated inhibitory networks. GABAergic function can be quantified non-invasively using adaptive threshold hunting paired-pulse transcranial magnetic stimulation (TMS). The previous studies have used TMS with posterior-anterior (PA) induced current to assess tDCS effects on inhibition. However, TMS with anterior-posterior (AP) induced current in the brain provides a more robust measure of GABA-mediated inhibition. The aim of the present study was to assess the modulation of corticomotor excitability and inhibition after anodal and cathodal tDCS using TMS with PA- and AP-induced current. In 16 young adults (26 ± 1 years), we investigated the response to anodal, cathodal, and sham tDCS in a repeated-measures double-blinded crossover design. Adaptive threshold hunting paired-pulse TMS with PA- and AP-induced current was used to examine separate interneuronal populations within M1 and their influence on corticomotor excitability and short- and long-interval inhibition (SICI and LICI) for up to 60 min after tDCS. Unexpectedly, cathodal tDCS increased corticomotor excitability assessed with AP (P = 0.047) but not PA stimulation (P = 0.74). SICIAP was reduced after anodal tDCS compared with sham (P = 0.040). Pearson’s correlations indicated that SICIAP and LICIAP modulation was associated with corticomotor excitability after anodal (P = 0.027) and cathodal tDCS (P = 0.042). The after-effects of tDCS on corticomotor excitability may depend on the direction of the TMS-induced current used to make assessments, and on modulation within GABA-mediated inhibitory circuits. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
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20. Differences in coastal and oceanic SST trends north of Yucatan Peninsula.
- Author
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Varela, R., Costoya, X., Enriquez, C., Santos, F., and Gómez-Gesteira, M.
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OCEAN temperature , *GLOBAL warming , *UPWELLING (Oceanography) , *COOLING , *CONTINENTAL shelf - Abstract
The coastal area north of Yucatan has experienced a cooling SST trend from 1982 to 2015 during the upwelling season (May–September) that contrasts with the warming observed at the adjacent ocean area. Different drivers were analyzed to identify the possible causes of that unusual coastal cooling. Changes in coastal upwelling and in sea-atmosphere heat fluxes are not consistent with the observed coastal cooling. The eastward shift of the Yucatan Current observed over the last decades is hypothesized as the most probable cause of coastal cooling. This shift enhances the vertical transport of cold deeper water to the continental shelf from where it is pumped to the surface by upwelling favorable westerly winds. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
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21. Observing Without Acting: A Balance of Excitation and Suppression in the Human Corticospinal Pathway?
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Hannah, Ricci, Rocchi, Lorenzo, and Rothwell, John C.
- Subjects
PYRAMIDAL tract ,TRANSCRANIAL magnetic stimulation ,MOTOR cortex physiology - Abstract
Transcranial magnetic stimulation (TMS) studies of human primary motor cortex (M1) indicate an increase corticospinal excitability during the observation of another's action. This appears to be somewhat at odds with recordings of pyramidal tract neurons in primate M1 showing that there is a balance of increased and decreased activity across the population. TMS is known to recruit a mixed population of cortical neurons, and so one explanation for previous results is that TMS tends to recruit those excitatory output neurons whose activity is increased during action observation. Here we took advantage of the directional sensitivity of TMS to recruit different subsets of M1 neurons and probed whether they responded differentially to action observation in a manner consistent with the balanced change in activity in primates. At the group level we did not observe the expected increase in corticospinal excitability for either TMS current direction during the observation of a precision grip movement. Instead, we observed substantial inter-individual variability ranging from strong facilitation to strong suppression of corticospinal excitability that was similar across both current directions. Thus, we found no evidence of any differential changes in the excitability of distinct M1 neuronal populations during action observation. The most notable change in corticospinal excitability at the group level was a general increase, across muscles and current directions, when participants went from a baseline state outside the task to a baseline state within the actual observation task. We attribute this to arousal- or attention-related processes, which appear to have a similar effect on the different corticospinal pathways targeted by different TMS current directions. Finally, this rather non-specific increase in corticospinal excitability suggests care should be taken when selecting a "baseline" state against which to compare changes during action observation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
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22. Current Directions In Exchange Theory
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Graeber, David and Graeber, David
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- 2001
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23. Attention modulates specific motor cortical circuits recruited by transcranial magnetic stimulation.
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Mirdamadi, J.L., Suzuki, L.Y., and Meehan, S.K.
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ATTENTION , *MOTOR cortex , *TRANSCRANIAL magnetic stimulation , *NEURAL circuitry , *AFFERENT pathways - Abstract
Skilled performance and acquisition is dependent upon afferent input to motor cortex. The present study used short-latency afferent inhibition (SAI) to probe how manipulation of sensory afference by attention affects different circuits projecting to pyramidal tract neurons in motor cortex. SAI was assessed in the first dorsal interosseous muscle while participants performed a low or high attention-demanding visual detection task. SAI was evoked by preceding a suprathreshold transcranial magnetic stimulus with electrical stimulation of the median nerve at the wrist. To isolate different afferent intracortical circuits in motor cortex SAI was evoked using either posterior–anterior (PA) or anterior–posterior (PA) monophasic current. In an independent sample, somatosensory processing during the same attention-demanding visual detection tasks was assessed using somatosensory-evoked potentials (SEP) elicited by median nerve stimulation. SAI elicited by AP TMS was reduced under high compared to low visual attention demands. SAI elicited by PA TMS was not affected by visual attention demands. SEPs revealed that the high visual attention load reduced the fronto-central P20-N30 but not the contralateral parietal N20-P25 SEP component. P20-N30 reduction confirmed that the visual attention task altered sensory afference. The current results offer further support that PA and AP TMS recruit different neuronal circuits. AP circuits may be one substrate by which cognitive strategies shape sensorimotor processing during skilled movement by altering sensory processing in premotor areas. [ABSTRACT FROM AUTHOR] more...
- Published
- 2017
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24. Particulate waste outflow from fish-farming cages. How much is uneaten feed?
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Ballester-Moltó, M, Sanchez-Jerez, P, Cerezo-Valverde, J, and Aguado-Giménez, F
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PARTICULATE matter ,FISH farming ,FISH culturists ,FISH waste ,PASSIVE sampling devices (Environmental sampling) - Abstract
Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability. [ABSTRACT FROM AUTHOR] more...
- Published
- 2017
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25. Analysis and Control of Electromagnetic Coupling Effect of Levitation and Guidance Systems for Semi-High-Speed Maglev Train Considering Current Direction.
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Jeong, Jae-Hoon, Ha, Chang-Wan, Lim, Jaewon, and Choi, Jang-Young
- Subjects
- *
ELECTROMAGNETIC coupling , *ELECTROMAGNETISM , *MAGNETIC suspension , *MAGNETIC field effects , *MAGNETIC levitation vehicles - Abstract
A semi-high-speed magnetic levitation (maglev) train with a maximum speed of 200 km/h is being developed in Korea. It utilizes linear induction motors for propulsion and adopts electromagnetic suspension for levitation. For high-speed operation, guidance systems should be adopted to stabilize the train especially on curved tracks. For compatibility of the rail with previously developed urban maglev trains, the installation of the guidance electromagnet has to be restricted to be placed near the levitation electromagnet. Owing to the spatial closeness, mutual magnetic flux by the levitation and guidance electromagnets is produced at an overlapping portion of the rail. For stable control of the two systems, the coupling effects must be analyzed, because the levitation and guidance electromagnets are not operated independently. This paper aims to analyze the coupling effects by considering the magnetic field and a magnetic equivalent circuit. This paper suggests levitation and guidance systems for the semi-high-speed maglev train by considering each electromagnetic characteristic depending on the current direction. [ABSTRACT FROM AUTHOR] more...
- Published
- 2017
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26. Current direction-dependent modulation of human hand motor function by intermittent theta burst stimulation (iTBS).
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Shirota, Yuichiro, Dhaka, Suman, Paulus, Walter, and Sommer, Martin
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- *
HAND physiology , *MOTOR ability , *TRANSCRANIAL magnetic stimulation , *MOTOR cortex , *PERFORMANCE evaluation - Abstract
Background Transcranial magnetic stimulation (TMS) with different current directions can activate different sets of neurons. Current direction can also affect the results of repetitive TMS. Objective : To test the influence of uni-directional intermittent theta burst stimulation (iTBS) using different current directions, namely posteroanterior (PA) and anteroposterior (AP), on motor behaviour. Methods In a cross-over design, PA- and AP-iTBS was applied over the left primary motor cortex in 19 healthy, right-handed volunteers. Performance of a finger-tapping task was recorded before and 0, 10, 20, and 30 min after the iTBS. The task was conducted with the right and left hands separately at each time point. As a control, AP-iTBS with reduced intensity was applied to 14 participants in a separate session (AP weak condition). Results The finger-tapping count with the left hand was decreased after PA-iTBS. Neither AP- nor AP weak -iTBS altered the performance. Conclusions Current direction had a significant impact on the after-effects of iTBS. [ABSTRACT FROM AUTHOR] more...
- Published
- 2017
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27. Current Directions in Hyper-Programming
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Morrison, Ronald, Connor, Richard C. H., Cutts, Quintin I., Dearle, Alan, Farkas, Alex, Kirby, Graham N. C., McGettrick, Robert, Zirintsis, Evangelos, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Bjøner, Dines, editor, Broy, Manfred, editor, and Zamulin, Alexandre V., editor more...
- Published
- 2000
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28. Current Directions in Mathematical Learning Theory
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Suppes, Patrick, Hintikka, Jaakko, editor, Davidson, Donald, editor, Nuchelmans, Gabriël, editor, Salmon, Wesley C., editor, and Suppes, Patrick
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- 1993
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29. Pulse Duration as Well as Current Direction Determines the Specificity of Transcranial Magnetic Stimulation of Motor Cortex during Contraction.
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Hannah, Ricci and Rothwell, John C.
- Abstract
Background Previous research suggested that anterior–posterior (AP) directed currents induced by TMS in motor cortex (M1) activate interneuron circuits different from those activated by posterior–anterior currents (PA). The present experiments provide evidence that pulse duration also determines the activation of specific interneuron circuits. Objective To use single motor unit (SMU) recordings to confirm the difference in onset latencies of motor-evoked potentials (MEPs) evoked by different current directions and pulse durations: AP 30 , AP 120 , PA 30 and PA 120 . To test whether the amplitude of the MEPs is differentially influenced by somatosensory inputs from the hand (short-latency afferent inhibition, SAI), and examine the sensitivity of SAI to changes in cerebellar excitability produced by direct current stimulation (tDCS Cb ). Methods Surface electromyograms and SMUs were recorded from the first dorsal interosseous muscle. SAI was tested with an electrical stimulus to median or digital nerves ~20–25 ms prior to TMS delivered over the M1 hand area via a controllable pulse parameter TMS (cTMS) device. SAI was also tested during the application of anodal or sham tDCS Cb . Because TMS pulse specificity is greatest at low stimulus intensities, most experiments were conducted with weak voluntary contraction to reduce stimulus threshold. Results AP 30 currents recruited the longest latency SMU and surface MEP responses. During contraction SAI was greater for AP 30 responses versus all other pulses. Online anodal tDCS Cb reduced SAI for the AP 30 currents only. Conclusions AP 30 currents activate an interneuron circuit with functional properties different from those activated by other pulse types. Pulse duration and current direction determine what is activated in M1 with TMS. [ABSTRACT FROM AUTHOR] more...
- Published
- 2017
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30. Threshold tracking primary motor cortex inhibition: the influence of current direction.
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Cirillo, John, Byblow, Winston D., and Thut, Gregor
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- *
MOTOR cortex physiology , *ELECTROMYOGRAPHY , *TRANSCRANIAL magnetic stimulation , *EVOKED potentials (Electrophysiology) , *STIMULUS & response (Psychology) - Abstract
Paired-pulse transcranial magnetic stimulation ( TMS) can be used to probe inhibitory activity in primary motor cortex (M1). Recruitment of descending volleys with TMS depends on the induced current direction in M1. Anterior-posterior ( AP) stimulation preferentially activates late indirect- (I-) waves that are most susceptible to paired-pulse TMS. Threshold tracking TMS can assess intracortical inhibition; however, previous studies have only used a current direction that preferentially recruits early I-waves [posterior-anterior ( PA)]. Our objective was to examine intracortical inhibition with threshold tracking TMS designed to preferentially recruit early vs. late I-waves with PA and AP stimulation respectively. Electromyographic recordings were obtained from the right first dorsal interosseous muscle of 15 participants (21-50 years). Motor evoked potentials elicited by TMS over left M1 were recorded for PA, AP and lateromedial ( LM) induced currents, with I-wave recruitment calculated as the onset latency difference between PA- LM and AP- LM. Short- and long-interval intracortical inhibition ( SICI and LICI) were examined across a range of conditioning stimulus intensities and interstimulus intervals (3 and 100-260 ms) with threshold tracking TMS for PA and AP stimulation. SICI and LICI were greater for AP compared with PA current direction using threshold tracking. In addition, the efficacy of late I-wave recruitment was associated with the extent of SICI for AP but not PA stimulation, and was not associated with LICI. These findings indicate that threshold tracking with an AP-induced current provides a more robust and sensitive measure of M1 intracortical inhibition than PA. [ABSTRACT FROM AUTHOR] more...
- Published
- 2016
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31. Enhanced motor learning with bilateral transcranial direct current stimulation: Impact of polarity or current flow direction?
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Naros, Georgios, Geyer, Marc, Koch, Susanne, Mayr, Lena, Ellinger, Tabea, Grimm, Florian, and Gharabaghi, Alireza
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- *
MOTOR ability , *BRAIN stimulation , *DIRECT currents , *MOTOR learning , *ROBOTIC exoskeletons , *ELECTRODES - Abstract
Objective Bilateral transcranial direct current stimulation (TDCS) is superior to unilateral TDCS when targeting motor learning. This effect could be related to either the current flow direction or additive polarity-specific effects on each hemisphere. Methods This sham-controlled randomized study included fifty right-handed healthy subjects in a parallel-group design who performed an exoskeleton-based motor task of the proximal left arm on three consecutive days. Prior to training, we applied either sham, right anodal (a-TDCS), left cathodal (c-TDCS), concurrent a-TDCS and c-TDCS with two independent current sources and return electrodes (double source (ds)-TDCS) or classical bilateral stimulation (bi-TDCS). Results Motor performance improved over time for both unilateral (a-TDCS, c-TDCS) and bilateral (bi-TDCS, ds-TDCS) TDCS montages. However, only the two bilateral paradigms led to an improvement of the final motor performance at the end of the training period as compared to the sham condition. There was no difference between the two bilateral stimulation conditions (bi-TDCS, ds-TDCS). Conclusion Bilateral TDCS is more effective than unilateral stimulation due to its polarity-specific effects on each hemisphere rather than due to its current flow direction. Significance This study is the first systematic evaluation of stimulation polarity and current flow direction of bi-hemispheric motor cortex TDCS on motor learning of proximal upper limb muscles. [ABSTRACT FROM AUTHOR] more...
- Published
- 2016
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32. Involvement of different neuronal components in the induction of cortical plasticity with associative stimulation.
- Author
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Ni, Zhen, Cash, Robin F.H., Gunraj, Carolyn, Bercovici, Eduard, Hallett, Mark, and Chen, Robert
- Abstract
Abstract Background Paired associative stimulation (PAS), with stimulus interval of 21.5 or 25 ms, using transcranial magnetic stimulation in the posterior-anterior (PA) current direction, produces a long-term-potentiation-like effect. Stimulation with PA directed current generates both early and late indirect (I)-waves while that in anterior-posterior (AP) current predominantly elicits late I-waves. Short interval intracortical inhibition (SICI) inhibits late I-waves but not early I-waves. Objective To investigate how cortical inhibition modulates the effects of PAS. Methods PAS at stimulus interval of 21.5 ms conditioned by SICI (SICI-PAS) was compared to PAS alone with both PA and AP directed currents. Results PAS with both current directions increased cortical excitability. SICI-PAS increased cortical excitability in the PA but not the AP current direction. Conclusions Both early and late I-waves circuits can mediate cortical PAS plasticity under different conditions. Plasticity induction with the late but not the early I-wave circuits is blocked by SICI. Highlights • Cortical circuits mediating early and late I-waves can produce associative plasticity. • The circuits involved depend on current direction and stimulus interval. • Plasticity induction can be blocked by cortical inhibition. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
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33. Experimental study of soil responses around a pipeline in a sandy seabed under wave-current load.
- Author
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Chen, Hao, Zhang, Jisheng, Tong, Linlong, Sun, Ke, Guo, Yakun, and Wei, Chao
- Subjects
- *
OCEAN bottom , *SOIL liquefaction , *CURRENT distribution , *SURFACE pressure - Abstract
• 1,First comprehensive experimental data for the wave-current-induced pore pressure along the surface of the pipeline and beneath the pipeline. • 2,Effect of both the wave and the current characteristics on the distribution of the pore pressure around the pipeline are discussed in detail. • 3,Liquefaction risk around the pipeline is tested and investigated for both the exposed and completely embedded pipelines. Wave and current coexist widely in the oceans. Ever-changing wave characteristics, such as height and length, have a significant influence on the dynamic response within the seabed soil due to the presence of currents. Some aspects of wave, seabed and pipeline interactions have been widely investigated over past years, incorporating both experimental and numerical approaches. However, previous studies on seabed dynamic response around pipelines have mainly focused on cases with wave loading. In this experimental laboratory study, the current loading and diverse backfill conditions which commonly occur far offshore are discussed in depth. It is found that when subjected to the combined wave and current loads, the response of the seabed around a pipeline is more complex than that subjected to pure wave loading as current velocity and propagation direction would significantly change the wave characteristics as well as seabed response. Most notably when comparing with the pure wave loading, the pore pressure amplitude and its attenuation rate within the seabed increases when current and wave travel in the same direction. This could increase the possibility of liquefaction around the pipeline. When current travels in opposing direction to the wave, the effect of current on the decrease of pore pressure and its attenuation rate is more significant than that of the co-current actions. This means that the counter-current will reduce the probability of soil liquefaction. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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34. Effect of coil orientation on strength-duration time constant and I-wave activation with controllable pulse parameter transcranial magnetic stimulation.
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D'Ostilio, Kevin, Goetz, Stefan M., Hannah, Ricci, Ciocca, Matteo, Chieffo, Raffaella, Chen, Jui-Cheng A., Peterchev, Angel V., and Rothwell, John C.
- Subjects
- *
TRANSCRANIAL magnetic stimulation , *MOTOR cortex physiology , *EVOKED potentials (Electrophysiology) , *ULNAR nerve , *STIMULUS & response (Psychology) , *AXONS , *NEURAL physiology , *PHYSIOLOGY - Abstract
Objective: To compare the strength-duration (S-D) time constants of motor cortex structures activated by current pulses oriented posterior-anterior (PA) or anterior-posterior (AP) across the central sulcus. Methods: Motor threshold and input-output curve, along with motor evoked potential (MEP) latencies, of first dorsal interosseus were determined at pulse widths of 30, 60, and 120 μs using a controllable pulse parameter (cTMS) device, with the coil oriented PA or AP. These were used to estimate the S-D time constant and we compared with data for responses evoked by cTMS of the ulnar nerve at the elbow. Results: The S-D time constant with PA was shorter than for AP stimulation (230.9 ± 97.2 vs. 294.2 ± 90.9 μs; p < 0.001). These values were similar to those calculated after stimulation of ulnar nerve (197 ± 47 μs). MEP latencies to AP, but not PA stimulation were affected by pulse width, showing longer latencies following short duration stimuli. Conclusion: PA and AP stimuli appear to activate the axons of neurons with different time constants. Short duration AP pulses are more selective than longer pulses in recruiting longer latency corticospinal output. Significance: More selective stimulation of neural elements may be achieved by manipulating pulse width and orientation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2016
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35. Effect of electric current direction on the microstructural evolution and mechanical properties of a cold-rolled Cu–Zn alloy during the phase transformation induced by electric current pulses.
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Wang, Xinli, Liu, Meishuai, Dai, Wenbin, Wu, Nan, and Zhao, Xiang
- Subjects
COPPER-zinc alloys ,ELECTRIC currents ,PHASE transitions ,MECHANICAL properties of solids - Abstract
The effect of current direction (CD) on the microstructural evolution and mechanical properties of a Cu–Zn binary phase (α + β) alloy during the primary process of phase transformation induced by electric current pulses (ECP) treatment was investigated. To clarify the effect of CD, the samples were prepared with different angles between the CD and rolling direction (RD) from 0° to 90°. Results showed that not only the microstructural evolution but also the corresponding mechanical properties all had a saddle point in the sample with the angle 45°. Analyzed from the mechanical properties, it could be found that the anisotropic of the materials becomes stronger due to the application of ECP. An important finding is that by changing the angles between the CD and the RD, a novel and effective approach to control the phase transformation process could be provided. [ABSTRACT FROM PUBLISHER] more...
- Published
- 2015
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36. Superconducting Ultra-Wideband (UWB) Bandpass Filter Design Based on Quintuple/Quadruple/ Triple-Mode Resonator.
- Author
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Lu, Xilong, Wei, Bin, Xu, Zhan, Cao, Bisong, Guo, Xubo, Zhang, Xiaoping, Wang, Ruixia, and Song, Fei
- Subjects
- *
HIGH-temperature superconducting filters , *BANDPASS filters , *MULTIMODE waveguides , *ULTRA-wideband communication , *CRITICAL current density (Superconductivity) , *EIGENVECTORS - Abstract
This paper analyzes the coupling modes when multiple hairpin resonators are coupled. Three kinds of current distribution and direction states exist in the coupled hairpin resonators: the current along the clockwise direction, the current along the counterclockwise direction, and no current density distribution. Different combinations of these current states lead to different coupling modes. In order to distinguish these modes, auxiliary lines are introduced between each two coupled resonators to denote each coupling mode, and this method is theoretically based on the analysis of the eigenvector of the coupling matrix. A simple and effective technique to construct multi-mode resonators (MMRs) is then proposed. An n-mode resonator can be constructed by connecting n hairpins with small patches. Resonant modes of this class of MMRs were analyzed in detail using the proposed auxiliary lines method. Single stage and four stages of quintuple-mode resonators were used to design high-temperature superconducting ultra-wideband (UWB) filters by properly allocating the first five resonant peaks. Two UWB filters based on quadruple-mode and triple-mode resonators are also given. Parallel-coupled three lines were used to provide tight external couplings, which also generated two transmission poles. Measured results are in good agreement with the simulated ones without any tuning. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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37. Synthetic polymer membranes as a proxy of skins in permeation studies of biologically active compounds.
- Author
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Hwang, Yoon, Choi, Jang, Hwang, Cheng, Park, Wooram, Park, Ki-Dong, Suh, Kyung-Do, and Kim, Jin
- Abstract
This study provides a practical approach that can afford evaluation of drug compound permeability through the skin in which synthetic polymer membranes are used as a proxy. For this, permeation behaviors of a variety of drug molecules through the synthetic membranes were characterized under the iontophoresis condition as well as passive delivery. As a proof of concept, the permeability of caffeine and Triamiondil™, both of which are model drug compounds, through the membranes correlated with conventional use of porcine skin. The synthetic polymer membranes showed similar drug permeation patterns to that of the porcine skin, which allowed us to apply them to an alternate to the animal skin. Moreover, the application of iontophoresis to the device system enabled the drug molecules to pass through both the polymer membranes and porcine skin. Our study also verified that drug permeation is substantially influenced by the current direction that likely drives either electrorepulsion or electroosmosis under iontophoretic conditions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR] more...
- Published
- 2012
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38. Transcranial magnetic stimulation with a half-sine wave pulse elicits direction-specific effects in human motor cortex.
- Author
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Jung, Nikolai H, Delvendahl, Igor, Pechmann, Astrid, Gleich, Bemhard, Gattinger, Norbert, Siebner, Hartwig R, and Maill, Volker
- Subjects
- *
MOTOR cortex , *FRONTAL lobe , *NERVOUS system , *NEURONS , *CELLS - Abstract
Background: Transcranial magnetic stimulation (TMS) commonly uses so-called monophasic pulses where the initial rapidly changing current flow is followed by a critically dampened return current. It has been shown that a monophasic TMS pulse preferentially excites different cortical circuits in the human motor hand area (M1-HAND), if the induced tissue current has a posterior-to-anterior (PA) or anterior-to-posterior (AP) direction. Here we tested whether similar direction-specific effects could be elicited in M1-HAND using TMS pulses with a half-sine wave configuration. Results: In 10 young participants, we applied half-sine pulses to the right M1-HAND which elicited PA or AP currents with respect to the orientation of the central sulcus. Measurements of the motor evoked potential (MEP) revealed that PA half-sine stimulation resulted in lower resting motor threshold (RMT) than AP stimulation. When stimulus intensity (SI) was gradually increased as percentage of maximal stimulator output, the stimulus-response curve (SRC) of MEP amplitude showed a leftward shift for PA as opposed to AP half-sine stimulation. Further, MEP latencies were approximately 1 ms shorter for PA relative to AP half-sine stimulation across the entire SI range tested. When adjusting SI to the respective RMT of PA and AP stimulation, the direction-specific differences in MEP latencies persisted, while the gain function of MEP amplitudes was comparable for PA and AP stimulation. Conclusions: Using half-sine pulse configuration, single-pulse TMS elicits consistent direction-specific effects inM1-HAND that are similar to TMS with monophasic pulses. The longer MEP latency for AP half-sine stimulation suggests that PA and AP half-sine stimulation preferentially activates different sets of cortical neurons that are involved in the generation of different corticospinal descending volleys. [ABSTRACT FROM AUTHOR] more...
- Published
- 2012
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39. Breaks during 5Hz rTMS are essential for facilitatory after effects
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Rothkegel, H., Sommer, M., and Paulus, W.
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- *
TRANSCRANIAL magnetic stimulation , *DEVELOPMENTAL neurophysiology , *EXPERIMENTAL design , *MEDICAL protocols , *HELPLESSNESS (Psychology) , *PULSE measurement , *PYRAMIDAL tract , *NEUROPLASTICITY - Abstract
Abstract: Objective: Stimulation frequency has been considered the most important factor in conventional repetitive transcranial magnetic stimulation (rTMS) for determining the direction of after effects on corticospinal excitability. Here, we examined the functional relevance of breaks during high-frequency subthreshold rTMS for the induction of facilitatory after effects. Methods: The after effects on corticospinal excitability of a standard 5Hz rTMS protocol in a block design were compared to a continuous rTMS protocol using the same number of pulses. In addition the effect of current direction both for rTMS and single pulse TMS was included in the study design. Results: While 5Hz rTMS in a standard block design induces facilitatory after effects on corticospinal excitability, the continuous protocol does not induce facilitation but rather inhibition. In our study only rTMS using an initially posterior–anterior current direction in the brain leads to significant neuroplastic effects at all. Conclusions: Breaks during conventional high-frequency rTMS are a crucial factor determining the direction of induced neuroplastic changes. Significance: These results contribute to the understanding of rTMS-induced neuroplasticity and are important for the design of rTMS protocols both for experimental and clinical studies. [Copyright &y& Elsevier] more...
- Published
- 2010
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40. The Influence of Current Direction on the Cu-Ni Cross-Interaction in Cu/Sn/Ni Diffusion Couples.
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Wu, W. H., Chung, H. L., Chen, C. N., and Ho, C. E.
- Subjects
ELECTRIC currents ,ELECTRODIFFUSION ,CONSTITUTION of matter ,PHYSICAL metallurgy ,APPROXIMATION theory - Abstract
The influence of current direction on the Cu-Ni cross-interaction in the Cu/Sn/Ni joint configuration was investigated in this study. During current stressing, an electric current towards or away from the Ni-side of Cu/Sn/Ni was imposed at 150°C. It was observed that the (Cu,Ni)
6 Sn5 ternary compound was the dominant reaction product at both interfaces, and its growth at the Ni-side strongly depended upon the direction and magnitude of the electron flow. When the electron flow was towards the Ni-side, more Cu was found to be driven to the Ni-side, resulting in an increase in the thickness of (Cu,Ni)6 Sn5 . This is due to the chemical-potential-induced Cu flux ( $$ J_{\rm{chem}}^{\rm{Cu}} $$) that was enhanced by the electromigration ( $$ J_{\rm{em}}^{\rm{Cu}} $$). In the case of electron flow away from the Ni-side, the supply of Cu to the Ni-side was retarded due to the fact that $$ J_{\rm{em}}^{\rm{Cu}} $$ was in the opposite direction to $$ J_{\rm{chem}}^{\rm{Cu}} . $$ The results of this study revealed that the Ni-side (Cu,Ni)6 Sn5 thickness remained almost unchanged under current stressing of 104 A/cm2 at 150°C, which suggests the inward Cu flux is approximately equal to the outward flux, i.e., $$ J_{\rm{chem}}^{\rm{Cu}} \approx J_{\rm{em}}^{\rm{Cu}} . $$ [ABSTRACT FROM AUTHOR] more...- Published
- 2009
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41. Three-dimensional scour hole model and scour effects on the ultimate capacity of lateral loaded rigid piles.
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Chen, Xuguang and Liu, Jinzhong
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DEAD loads (Mechanics) , *LATERAL loads , *WIND turbines , *ENGINEERING models - Abstract
• Scour tests and lateral static load tests were conducted. • A three-dimensional scour hole model under steady current and its analytical expression is proposed. • The scour effect is positively related to the scour depth, and has nothing to do with the load eccentricity. • A formula for evaluating the ultimate lateral capacity of rigid piles after scour is presented. The rigid pile with a large diameter and a small slenderness ratio is the most widely used foundation for offshore wind turbines. Scour around piles seriously threatens the safe operation of offshore wind turbines, so its effects on rigid piles need to be studied urgently. In this paper, scour tests under steady current and static lateral load tests after scour are conducted. According to the results of scour tests, a three-dimensional scour hole model suitable for engineering reality and its analytical expression are proposed. Then, the results of load tests indicate that scour reduces the ultimate lateral capacity of foundations, and the percentage of reduction is related to the current direction, whereas does not change with load eccentricity. Finally, a preliminary formula for evaluating the ultimate lateral capacity of rigid piles after scour is presented, which can easily and quickly determine the upper and lower limits of scour effects. [ABSTRACT FROM AUTHOR] more...
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- 2022
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42. Movement of the Kuroshio axis to the northeast shelf of Taiwan during typhoon events
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Morimoto, Akihiko, Kojima, Shoichiro, Jan, Sen, and Takahashi, Daisuke
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TYPHOONS , *GEOSTROPHIC currents , *SEA surface microlayer , *RADAR , *SEA level , *UPWELLING (Oceanography) , *ARTIFICIAL satellites in oceanography , *REMOTE sensing ,KUROSHIO - Abstract
Abstract: We investigated the movement of the Kuroshio axis on the northeast shelf of Taiwan associated with the passage of typhoons, using sea surface current data observed by the ocean radar system on Yonaguni and Ishigaki islands. First, we examined daily Kuroshio axis variation on the northeast shelf of Taiwan during typhoon events. The ocean radar data showed that the Kuroshio axis moved onto the shelf after passages of typhoons. The Kuroshio moved onto the shelf and stayed there after the passage of Typhoon Hai-Tang; while the Kuroshio maintained this pattern, southerly wind blew continuously for 4 days. The mean current speed northeast of Taiwan after the typhoon''s passage increased by 18cms−1. In addition, the sea level difference between two satellite altimetry tracks east of Taiwan increased by 14.4cm. These results suggest that coastal upwelling east of Taiwan caused by the southerly wind generated an east–west sea level difference that, in turn, generated a northward geostrophic current. This current could have enhanced the Kuroshio east of Taiwan, and pushed it onto the shelf. [Copyright &y& Elsevier] more...
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- 2009
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43. Influence of the conductor’s arrangement and current on the AC loss characteristics of a fault current limiting coil
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Li, Z.Y., Ma, Y.H., Ryu, K., Choi, S., Park, K.B., and Oh, I.S.
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ELECTRIC fields , *ELECTRIC currents , *ELECTRIC circuit breakers , *ELECTROMAGNETIC fields - Abstract
Abstract: Researches and developments on a superconducting fault current limiting (SFCL) system have been done for several decades. The SFCL system, which is using a high temperature superconducting (HTS) conductor such as Bi-2212 bulk and YBCO film, has recently become technically available. In this work, we are developing a 22.9kV/25 MVA SFCL system for a power distribution network. A Bi-2212 bulk SFCL element, which has the merits of large current capacity and high allowable electric field during fault of the power network, becomes a candidate for our resistive SFCL system. AC loss of the HTS conductor has a strong influence on the economic viability of the SFCL system, which offers an attractive means to limit short circuit current in the power network. As an earlier stage of our 22.9kV/25 MVA SFCL system development, we prepared several samples of the fault current limiting elements in a coil shape to reduce AC loss of the SFCL system. The effect of conductor’s arrangement and current direction on AC loss characteristics of the fault current limiting coils has been investigated experimentally. The test result shows that the measured AC loss depends significantly on the conductor’s arrangement and also on the current direction even in the same arrangement. The AC loss of a face-to-face coil in bifilar mode, which is even smaller than the self-field loss of the conductor, is smallest among our fabricated coil samples. Moreover, the measured loss in the face-to-face coil in bifilar mode is invariable regardless of thickness in an insulator which is placed between conductors. [Copyright &y& Elsevier] more...
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- 2008
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44. Wave and Current Regime off the Southwest Coast of India.
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Hameed, T. S. Shahul, Kurian, N. E., Thomas, K. V., Rajith, K., and Prakash, T. N.
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OCEAN currents , *TIDAL currents , *OCEAN circulation , *WATER waves , *MONSOONS , *WIND speed , *WEATHER , *ANTICYCLONES , *COASTAL changes - Abstract
Waves and currents recorded off Chavara, southwest coast of India, over a period of 2 years are used to understand the wave-current regime of this monsoon dominated coast. The waves during monsoon are characterised by higher heights, shorter periods, and are confined to westerly directions. The wave characteristics indicate nearby generation. The premonsoon and postmonsoon waves are characterised by lower heights and higher periods with the direction being more southerly. Waves arrive from a wider range of generating areas during the fair weather periods, particularly during the premonsoon months. The wave heights exhibit yearly variations, but the periods and directions remain relatively constant. Like the waves, the currents also show seasonal changes with stronger currents during monsoon and weaker currents during fair weather. The alongshore components of the currents are mostly much stronger than the cross-shore flows and the pattern is mostly diurnal although a semidiurnal signal is also readily apparent, the latter associated with tidal currents. The diurnal activity is mostly wind-induced. In the monsoon season, the dominant direction is southerly to southwesterly, whereas during the premonsoon and postmonsoon it varies between northwest and southeast. Notable deviations to the generally understood pattern of southerly currents during monsoon and northerly currents during fair weather are observed. This could be attributed to the reported occurrence of a cyclonic eddy during monsoon and anticyclonic eddy during fair weather in the Lakshadweep Sea. [ABSTRACT FROM AUTHOR] more...
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- 2007
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45. Inter-individual variability in optimal current direction for transcranial magnetic stimulation of the motor cortex
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Balslev, Daniela, Braet, Wouter, McAllister, Craig, and Miall, R. Chris
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MOTOR cortex , *TRANSCRANIAL magnetic stimulation , *THORACIC vertebrae , *FRONTAL lobe - Abstract
Abstract: We evaluated inter-individual variability in optimal current direction for biphasic transcranial magnetic stimulation (TMS) of the motor cortex. Motor threshold for first dorsal interosseus was detected visually at eight coil orientations in 45° increments. Each participant (n =13) completed two experimental sessions. One participant with low test–retest correlation (Pearson''s r <0.5) was excluded. In four subjects, visual detection of motor threshold was compared to EMG detection; motor thresholds were very similar and highly correlated (0.94–0.99). Similar with previous studies, stimulation in the majority of participants was most effective when the first current pulse flowed towards postero-lateral in the brain. However, in four participants, the optimal coil orientation deviated from this pattern. A principal component analysis using all eight orientations suggests that in our sample the optimal orientation of current direction was normally distributed around the postero-lateral orientation with a range of 63° (S.D.=13.70°). Whenever the intensity of stimulation at the target site is calculated as a percentage from the motor threshold, in order to minimize intensity and side-effects it may be worthwhile to check whether rotating the coil 45° from the traditional posterior–lateral orientation decreases motor threshold. [Copyright &y& Elsevier] more...
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- 2007
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46. Involvement of different neuronal components in the induction of cortical plasticity with associative stimulation
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Mark Hallett, Eduard Bercovici, Zhen Ni, Robert Chen, Robin F.H. Cash, and Carolyn Gunraj
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Adult ,Male ,Intracortical circuit ,medicine.medical_treatment ,Primary motor cortex ,Long-Term Potentiation ,Biophysics ,Neural Inhibition ,Stimulation ,Article ,050105 experimental psychology ,lcsh:RC321-571 ,03 medical and health sciences ,Paired associative stimulation ,0302 clinical medicine ,Neuroplasticity ,medicine ,Humans ,0501 psychology and cognitive sciences ,Motor evoked potential ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,Chemistry ,General Neuroscience ,05 social sciences ,Motor Cortex ,Long-term potentiation ,Evoked Potentials, Motor ,Transcranial magnetic stimulation ,medicine.anatomical_structure ,Current direction ,Cortical Excitability ,Female ,Neurology (clinical) ,Neuroscience ,030217 neurology & neurosurgery ,Motor cortex - Abstract
Background Paired associative stimulation (PAS), with stimulus interval of 21.5 or 25 ms, using transcranial magnetic stimulation in the posterior-anterior (PA) current direction, produces a long-term-potentiation-like effect. Stimulation with PA directed current generates both early and late indirect (I)-waves while that in anterior-posterior (AP) current predominantly elicits late I-waves. Short interval intracortical inhibition (SICI) inhibits late I-waves but not early I-waves. Objective To investigate how cortical inhibition modulates the effects of PAS. Methods PAS at stimulus interval of 21.5 ms conditioned by SICI (SICI-PAS) was compared to PAS alone with both PA and AP directed currents. Results PAS with both current directions increased cortical excitability. SICI-PAS increased cortical excitability in the PA but not the AP current direction. Conclusions Both early and late I-waves circuits can mediate cortical PAS plasticity under different conditions. Plasticity induction with the late but not the early I-wave circuits is blocked by SICI. more...
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- 2019
47. Significance of coil orientation for motor evoked potentials from nasalis muscle elicited by transcranial magnetic stimulation
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Dubach, Patrick, Guggisberg, Adrian G., Rösler, Kai M., Hess, Christian W., and Mathis, Johannes
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MOTOR cortex , *FRONTAL lobe , *FACIAL muscles , *EVOKED potentials (Electrophysiology) , *ELECTROPHYSIOLOGY , *ELECTROENCEPHALOGRAPHY - Abstract
Objective: In transcranial magnetic stimulation (TMS) of the motor cortex, the optimal orientation of the coil on the scalp is dependent on the muscle under investigation, but not yet known for facial muscles.Methods: Using a figure-of-eight coil, we compared TMS induced motor evoked potentials (MEPs) from eight different coil orientations when recording from ipsi- and contralateral nasalis muscle.Results: The MEPs from nasalis muscle revealed three components: The major ipsi- and contra-lateral middle latency responses of approximately 10 ms onset latency proved entirely dependent on voluntary pre-innervation. They were most easily obtained from a coil orientation with posterior inducing current direction, and in this respect resembled the intrinsic hand rather than the masseter muscles. Early short duration responses of around 6 ms onset latency were best elicited with an antero-lateral current direction and not pre-innervation dependent, and therefore most probably due to stimulation of the nerve roots. Late responses (>18 ms) could inconsistently be elicited with posterior coil orientations in pre-innervated condition.Conclusions: By using the appropriate coil orientation and both conditions relaxed and pre-innervated, cortically evoked MEP responses from nasalis muscle can reliably be separated from peripheral and reflex components and also from cross talk of masseter muscle activation. [Copyright &y& Elsevier] more...
- Published
- 2004
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48. Effects of Transcranial Static Magnetic Stimulation on Motor Cortex Evaluated by Different TMS Waveforms and Current Directions
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Javier Cudeiro, Alvaro Pascual-Leone, and Paula Davila-Pérez
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0301 basic medicine ,Adult ,Male ,Interneuron ,Adolescent ,Paired-pulse TMS ,Transcranial static magnetic stimulation ,medicine.medical_treatment ,Biphasic ,Stimulation ,Monophasic ,Article ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,medicine ,Humans ,Muscle, Skeletal ,Balance (ability) ,Chemistry ,Electromyography ,General Neuroscience ,Motor Cortex ,Repeated measures design ,Neural Inhibition ,Evoked Potentials, Motor ,Transcranial Magnetic Stimulation ,Transcranial magnetic stimulation ,030104 developmental biology ,medicine.anatomical_structure ,Current direction ,Facilitation ,Silent period ,Female ,Neuroscience ,030217 neurology & neurosurgery ,Motor cortex - Abstract
Transcranial static magnetic stimulation (tSMS) modulates cortical excitability probably by interacting with the GABA-glutamate intracortical balance. Different transcranial magnetic stimulation (TMS) waveforms probe distinct GABA-mediated cortical inhibition networks. The goal of the present work is to further characterize tSMS-induced changes in motor cortex reactivity and inhibition–excitation (I/E) balance. We hypothesized that tSMS affects particular cortical networks and thus, the effects of tSMS would be different depending on the TMS waveform used to assess its results. 23 healthy young adults completed two sessions of real or sham tSMS. The order of the sessions was randomized across participants. Motor evoked potentials (MEPs), cortical silent period (CSP), short- and long-interval intracortical inhibition (SICI and LICI), and intracortical facilitation (ICF) were assessed with TMS monophasic posterior–anterior (monoPA; n = 9), monophasic anterior–posterior (monoAP; n = 7), or biphasic (biAP-PA; n = 7) pulses. Repeated measures analyses of variance and appropriate pairwise comparisons were performed for each TMS measure. After 15 min of real tSMS, the MEP amplitudes decreased compared to sham and baseline, SICI and LICI showed greater inhibition, and a tendency towards longer CSPs and less facilitation was found. These results were only observed with monoPA TMS. MEP amplitude increased compared to sham with monoAP TMS, with no clear changes in general intracortical I/E balance. Biphasic TMS was not able to capture any effects of tSMS. The results show that the effects of tSMS on cortical excitability and inhibition involve specific interneuron circuits that are selectively activated by monoPA TMS. more...
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- 2019
49. The effects of waveform and current direction on the efficacy and test-retest reliability of transcranial magnetic stimulation
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Ali Jannati, Javier Cudeiro Mazaira, Peter J. Fried, Alvaro Pascual-Leone, and Paula Davila-Pérez
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0301 basic medicine ,Adult ,Male ,medicine.medical_specialty ,Adolescent ,Intraclass correlation ,medicine.medical_treatment ,Rest ,Audiology ,Article ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Pulse waveform ,medicine ,Waveform ,Humans ,Muscle, Skeletal ,Reliability (statistics) ,Physics ,Monophasic waveform ,Pulse (signal processing) ,Electromyography ,General Neuroscience ,Motor Cortex ,Reproducibility of Results ,Paired-pulse ,Neural Inhibition ,Reliability ,Evoked Potentials, Motor ,Hand ,Transcranial Magnetic Stimulation ,Transcranial magnetic stimulation ,030104 developmental biology ,Amplitude ,Current direction ,Biphasic waveform ,Silent period ,Female ,030217 neurology & neurosurgery - Abstract
The pulse waveform and current direction of transcranial magnetic stimulation (TMS) influence its interactions with the neural substrate; however, their role in the efficacy and reliability of single- and paired-pulse TMS measures is not fully understood. We investigated how pulse waveform and current direction affect the efficacy and test-retest reliability of navigated, single- and paired-pulse TMS measures. 23 healthy adults (aged 18–35 years) completed two identical TMS sessions, assessing resting motor threshold (RMT), motor evoked potentials (MEPs), cortical silent period (cSP), short- and long-interval intra-cortical inhibition (SICI and LICI), and intracortical facilitation (ICF) using either monophasic posterior-anterior (mono(PA); n=9), monophasic anterior-posterior (mono(AP); n=7), or biphasic (bi(AP-PA); n=7) pulses. Averages of each TMS measure were compared across the three groups and intraclass correlation coefficients were calculated to assess test-retest reliability. RMT was the lowest and cSP was the longest with bi(AP-PA) pulses, whereas MEP latency was the shortest with mono(PA) pulses. SICI and LICI had the largest effect with mono(PA) pulses, whereas only mono(AP) and bi(AP-PA) pulses resulted in significant ICF. MEP amplitude was more reliable with either mono(PA) or mono(AP) than with bi(AP-PA) pulses. LICI was the most reliable with mono(AP) pulses, whereas ICF was the most reliable with bi(AP-PA) pulses. Waveform/current direction influenced RMT, MEP latency, cSP, SICI, LICI, and ICF, as well as the reliability of MEP amplitude, LICI, and ICF. These results show the importance of considering TMS pulse parameters for optimizing the efficacy and reliability of TMS neurophysiologic measures. more...
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- 2018
50. Conventional or threshold-hunting TMS? A tale of two SICIs
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Ronan A. Mooney, Winston D. Byblow, John Cirillo, and John G. Semmler
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Adult ,Male ,medicine.medical_specialty ,Short-interval intracortical inhibition ,genetic structures ,medicine.medical_treatment ,Conditioning, Classical ,Biophysics ,Stimulation ,Audiology ,Stimulus (physiology) ,050105 experimental psychology ,lcsh:RC321-571 ,Adaptive threshold-hunting ,03 medical and health sciences ,0302 clinical medicine ,Interneurons ,Interstimulus interval ,medicine ,Humans ,0501 psychology and cognitive sciences ,Evoked potential ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,Mathematics ,Electromyography ,General Neuroscience ,05 social sciences ,Motor Cortex ,Neural Inhibition ,Evoked Potentials, Motor ,Transcranial Magnetic Stimulation ,Transcranial magnetic stimulation ,Current direction ,Intracortical inhibition ,Conditioning ,Conditioning, Operant ,Female ,Neurology (clinical) ,Primary motor cortex ,030217 neurology & neurosurgery - Abstract
Background: In human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. Objective: To examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. Methods: In 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. Results: Inhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P more...
- Published
- 2018
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