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Search Results: 1 - 10 of 571 matches for " Sotaro Shimada "
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Socially Anxious Tendencies Affect Autonomic Responses during Eye Gaze Perception  [PDF]
Yuki Tsuji, Sotaro Shimada
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.613160
Abstract: Social anxiety disorder is a common psychiatric disorder. The gaze of others is known to frequently induce social anxiety. We conducted a gaze detection experiment to examine the effects of social anxiety on autonomic response, namely heart rate (HR) response. We used the maximum HR deceleration between 0 s and 3 s after stimulus onset as an indicator of emotional stress. Participants were assigned to a high social anxiety (HSA) or low social anxiety (LSA) group on the basis of cut-off scores indicative of clinical levels of stress as per the Japanese version of the Liebowitz Social Anxiety Scale (LSAS-J). Our results showed that HR deceleration was greater for the HSA compared with the LSA group. Moreover, the higher the LSAS-J score was, the greater the increase was in HR deceleration (correlation coefficient rs = 0.52, p < 0.01). Our results suggest that the eye gaze of others can be processed as a threat in individuals with a high tendency towards social anxiety.
Modulation of Motor Area Activity by the Outcome for a Player during Observation of a Baseball Game
Sotaro Shimada
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008034
Abstract: Observing competitive games such as sports is a pervasive entertainment among humans. The inclination to watch others play may be based on our social-cognitive ability to understand the internal states of others. The mirror neuron system, which is activated when a subject observes the actions of others, as well as when they perform the same action themselves, seems to play a crucial role in this process. Our previous study showed that activity of the mirror neuron system was modulated by the outcome of the subject's favored player during observation of a simple competitive game (rock-paper-scissors). However, whether the mirror neuron system responds similarly in a more complex and naturalistic sports game has not yet been fully investigated.
The Effects of Trajectory and Endpoint Errors in a Reaching Movement on the Sense of Agency  [PDF]
Takuro Zama, Yoshiyuki Takahashi, Sotaro Shimada
Psychology (PSYCH) , 2017, DOI: 10.4236/psych.2017.814146
Abstract: The sense of agency (SoA) refers to the subjective feeling that an individual can control their own action with their own will. However, it is still unclear which aspects of the motor control process precisely affect the sense of agency. In this study, we investigated how the SoA is modulated by the online motor performance (trajectory error) and the outcome of the reaching movement (endpoint error). The results showed that the invalid priming and the visual feedback delay significantly increased both the trajectory and endpoint errors and that these errors significantly attenuated the SoA. The further correlation analyses showed that the decrease in SoA was significantly correlated with the trajectory error, but not with the endpoint error, when the error was explicitly noticed. We suggest that the deterioration in online motor performance, at least in a reaching movement, is the main cause of the attenuation in the SoA.
Inferior Parietal Lobe Activity in Visuo-Motor Integration during the Robot Hand Illusion  [PDF]
Mohamad Arif Fahmi Bin Ismail, Sotaro Shimada
Psychology (PSYCH) , 2018, DOI: 10.4236/psych.2018.915174
Abstract: The robot hand illusion (RoHI) is the participant’s illusion of the self-ownership and the self-agency of a robot hand that appears to be moving consistently with their own hand, and feel as if the robot hand belongs to them. Mismatching between motor and visual information disrupt the effect of RoHI respect to the robot hand. In our previous study, we found that participants felt that the virtual hand was their own when the visual feedback was delayed by less than 200 ms. Moreover, although they did not feel that the virtual hand was their own, the participants felt that they could control the virtual hand even with a visual delay of 300 - 500 ms. Here, we used near-infrared spectroscopy (NIRS) to investigate brain activity associated with the RoHI under different delayed visual feedback conditions (100 ms, 400 ms, and 700 ms). We found significant activation in the supramarginal gyrus and superior temporal gyrus in the 100 ms feedback delay condition. An ANOVA indicated that this activation was significantly different from that in other conditions (p < 0.01). These results demonstrate that activity in the inferior parietal cortex was modulated by the delay between the motor command and the visual feedback regarding the movement of the robot hand. We propose that the inferior parietal lobe is essential for integrating motor and visual information that enables one to distinguish their own body from those of others.
Rubber Hand Illusion under Delayed Visual Feedback
Sotaro Shimada,Kensuke Fukuda,Kazuo Hiraki
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0006185
Abstract: Rubber hand illusion (RHI) is a subject's illusion of the self-ownership of a rubber hand that was touched synchronously with their own hand. Although previous studies have confirmed that this illusion disappears when the rubber hand was touched asynchronously with the subject's hand, the minimum temporal discrepancy of these two events for attenuation of RHI has not been examined.
Detailed Mechanism and Engineering Applicability of Electrolytic Polymerization Aided by a Magnetic Field in Natural Rubber by Mechanical Approach for Sensing (Part 1): The Effect of Experimental Conditions on Electrolytic Polymerization  [PDF]
Kunio Shimada, Norihiko Saga
World Journal of Mechanics (WJM) , 2016, DOI: 10.4236/wjm.2016.610026
Abstract: Ordinary electrolytic polymerization has involved plastic-type polymer solutions. Rubber, especially natural rubber, is one such polymer solution. Rubber has not been focused on until recently due to the fact that electrolytic polymerization has only a very small effect on rubber. However, when we focus on the C=C bonds of natural rubber, the same electrolytic polymerization is applicable to be enlarged on the natural rubber if a magnetic field and a filler are added. With the application of a magnetic field and a magnetic responsive fluid such as magnetic compound fluid (MCF), the effect of electrolytic polymerization on NR-latex such as plastic-type polymer solutions is enhanced, and the thickness of the vulcanized MCF rubber grows in a short time. The present new method of vulcanization of MCF rubber is effective enough that it is widely used in haptic sensors in various engineering applications. In the present report, as mechanical approach for the sensing, by measuring the temperature under electrolytic polymerization, by investigating the electric and dynamic characteristics, and by observing the magnified appearance of the MCF rubber, we clarified the extrinsic effects of many experimental conditions, including magnetic field strength, applied voltage, the electrodes gap, mass concentration, and the ingredients of the MCF. This report is Part 1, to be followed by another sequential report, Part 2, in which other intrinsic effects on the characteristics are dealt with. The experimental conditions used and the results obtained in the present report provide valuable data that will be useful in the making of MCF rubber.
Detailed Mechanism and Engineering Applicability of Electrolytic Polymerization Aided by a Magnetic Field in Natural Rubber by Mechanical Approach for Sensing (Part 2): Other and Intrinsic Effects on MCF Rubber Property  [PDF]
Kunio Shimada, Norihiko Saga
World Journal of Mechanics (WJM) , 2016, DOI: 10.4236/wjm.2016.610027
Abstract: The same ordinary electrolytic polymerization of plastic-type polymer solution is applicable to natural rubber, with its C=C bonds, if a magnetic field and a filler are added. With the application of a magnetic field and the magnetic responsive fluid known as magnetic compound fluid (MCF), we have clarified the enhancement of the electrolytic polymerization of NR-latex and the growth of the thickness of vulcanized MCF rubber that results from the addition of a magnetic field. The present new method of MCF rubber vulcanization is effective for use in haptic sensors, which are used widely in various engineering applications. In the previous report, part 1 of this study, we investigated many experimental conditions under mechanical approach for sensing: magnetic field strength; applied voltage; electrodes gap; mass concentration, and the ingredients of the MCF. In the present sequential report, part 2, we investigate many other effects on electrolytic polymerization by the same mechanical approach for sensing as in part 1: the Mullins effect; the Piezo effect; vibration; kind of electrode; atmospheric gas. In particular, we clarify that the voltage generates spontaneously in the MCF rubber and that the MCF rubber becomes a Piezo element. These effects on the electrolytic polymerization as well as the effects of the experimental conditions will be useful in engineering applications. By taking the above-mentioned parameters and effects into account, MCF rubber that is electrolytically polymerized with the aid of a magnetic field, the use of MCF as a filler, and doping, can be useful in haptic sensor applications. In particular, the effectiveness of the Piezo element can be shown.
Effect of Signal Filtering on Image Quality of Projection-Based Magnetic Particle Imaging  [PDF]
Kazuki Shimada, Kenya Murase
Open Journal of Medical Imaging (OJMI) , 2017, DOI: 10.4236/ojmi.2017.72005
Abstract: Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It is necessary to increase the signal-to-noise ratio to enhance the reliability of MPI. The purpose of this study was to investigate the effect of signal filtering on the image quality and quantitativity in projection-based MPI using phantoms. Materials and Methods: We fabricated two kinds of phantom (cylindrical tube phantom with a diameter of 6 mm and A-shaped phantom) and evaluated the effect of signal filtering in terms of root-mean-square (RMS) granularity and the correlation coefficient between iron concentrations of MNPs and average MPI values for four filter modes (THRU, BPF, BEF, and LPF). In the THRU mode, the signal input was output without passing through the filter. In the BPF mode, only the third-harmonic signal was passed using a band-pass filter (central frequency: 1200 Hz, band width: 1/3 octave). In the BEF mode, the first-harmonic signal was eliminated using a band-elimination filter (central frequency: 400 Hz, band width: 1/3 octave). In the LPF mode, only the signal with a frequency less than the third-harmonic frequency was passed using a low-pass filter (cut-off frequency: 1200 Hz, -24 ± 2 dB/octave). The RMS granularity was obtained by calculating standard deviations of the pixel values in the MPI image without MNPs, whereas average MPI values were obtained by drawing a circular region of interest with a diameter of 6 mm on the MPI image of the cylindrical tube phantom. Results: When using the filtered back-projection (FBP) method with a ramp filter for image reconstruction, the RMS granularity and correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF. In the BPF mode, however, some artifacts were observed. When using the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15, the correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF, whereas the RMS granularity did not largely depend on the filter mode and was significantly (p < 0.05) lower than that for the FBP method for all the filter modes. Conclusion: The BEF mode is adequate for the FBP method in projection-based MPI, whereas THRU is a best option in use of the ML-EM algorithm.
Lock-in-Amplifier Model for Analyzing the Behavior of Signal Harmonics in Magnetic Particle Imaging  [PDF]
Kenya Murase, Kazuki Shimada
Open Journal of Applied Sciences (OJAppS) , 2018, DOI: 10.4236/ojapps.2018.85014
Abstract: The purpose of this study was to present a lock-in-amplifier model for analyzing the behavior of signal harmonics in magnetic particle imaging (MPI) and some simulation results based on this model. In the lock-in-amplifier model, the signal induced by magnetic nanoparticles (MNPs) in a receiving coil was multiplied with a reference signal, and was then fed through a low-pass filter to extract the DC component of the signal (output signal). The MPI signal was defined as the mean of the absolute value of the output signal. The magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively, and the strength of the selection magnetic field (SMF) in MPI was assumed to be given by the product of the gradient strength of the SMF and the distance from the field-free region (x). In addition, Gaussian noise was added to the signal induced by MNPs using normally-distributed random numbers. The relationships between the MPI signal and x were calculated for the odd- and even-numbered harmonics and were investigated for various time constants of the low-pass filter used in the lock-in amplifier and particle sizes and their distributions of MNPs. We found that the behavior of the MPI signal largely depended on the time constant of the low-pass filter and the particle size of MNPs. This lock-in-amplifier model will be useful for better understanding, optimizing, and developing MPI, and for designing MNPs appropriate for MPI.
Perturbation Analysis of Superconductivity in the Trellis-Lattice Hubbard Model
Sotaro Sasaki,Hiroaki Ikeda,Kosaku Yamada
Physics , 2004, DOI: 10.1143/JPSJ.73.2822
Abstract: We investigate pairing symmetry and transition temperature in the trellis-lattice Hubbard model. We solve the \'Eliashberg equation using the third-order perturbation theory with respect to the on-site repulsion $U$. We find that a spin-singlet state is very stable in a wide range of parameters. On the other hand, when the electron number density is shifted from the half-filled state and the band gap between two bands is small, a spin-triplet superconductivity is expected. Finally, we discuss a possibility of unconventional superconductivity and pairing symmetry in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$.
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