• MeSH
• lidé MeSH
• pohyby očí * MeSH
• vnímání pohybu fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• Coturnix fyziologie   MeSH
• gravitace MeSH
• křepelky a křepelovití fyziologie   MeSH
• svalové proteiny analýza   fyziologie   MeSH
• svaly analýza   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• svalové proteiny MeSH

We present, using three-dimensional particle-in-cell simulations, an observation that orbital angular momentum (OAM) is transferred to resonant electrons proportionally to longitudinal momentum when Laguerre-Gaussian plasma waves are subjected to Landau damping. A higher azimuthal mode number leads to a larger net orbital angular momentum transfer to particles traveling close to the phase velocity of the plasma wave, implying a population of electrons that are orbiting the same center of rotation as the plasma wave. This observation has implications on magnetic field excitation as a result of the formation and damping of OAM plasma waves. The energy distributions of electrons in damping Laguerre-Gaussian plasma waves are significantly changed as a function of azimuthal mode number. This leads to larger numbers of lower energy particles tending towards a significant narrowing of the energy distribution of accelerated particles.

• Publikační typ
• časopisecké články MeSH

Three-dimensional "particle in cell" simulations show that a quasistatic magnetic field can be generated in a plasma irradiated by a linearly polarized Laguerre-Gauss beam with a nonzero orbital angular momentum (OAM). Perturbative analysis of the electron dynamics in the low intensity limit and detailed numerical analysis predict a laser to electrons OAM transfer. Plasma electrons gain angular velocity thanks to the dephasing process induced by the combined action of the ponderomotive force and the laser induced-radial oscillation. Similar to the "direct laser acceleration," where Gaussian laser beams transmit part of its axial momentum to electrons, Laguerre-Gaussian beams transfer a part of their orbital angular momentum to electrons through the dephasing process.

• Publikační typ
• časopisecké články MeSH

The research and development of modern metallic materials goes hand in hand with increasing their lifetime via optimized deformation processing. The presented work deals with preparation of an Al/Cu clad composite with implemented reinforcing Cu wires by the method of twist channel angular pressing (TCAP). Single and double pass extrusion of the clad composite was simulated numerically and carried out experimentally. This work is unique as no such study has been presented so far. Detailed monitoring of the deformation behavior during both the passes was enabled by superimposed grids and sensors. Both the sets of results revealed that already the single pass imparted significant effective strain (higher than e.g., conventional equal channel angular pressing (ECAP)), especially to the Al matrix, and resulted in notable deformation strengthening of both the Al and Cu composite components, which was confirmed by the increased punch load and decreased plastic flow velocity (second pass compared to first pass). Processing via the second pass also resulted in homogenization of the imposed strain and residual stress across the composite cross-section. However, the investigated parameters featured slight variations in dependence on the monitored location across the cross-section.

• Klíčová slova
• clad composite, effective strain, finite element analysis, residual stress, rotary swaging,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The Timed Up and Go test is a well-known clinical test for assessing of mobility and fall risk. It has been shown that the IMU which use an accelerometer and gyroscope are capable of analysing the quantitative parameters of the sit-to-stand transition. RESEARCH QUESTION: Which signals obtained by the inertial sensors are suitable for continuous Timed Up & Go test sit-to-stand transition analysis? METHODS: In the study we included 29 older adult volunteers and 31 de-novo Parkinson disease (PD) patients. All subjects performed an instrumented extended TUG wearing a gyro-accelerometer. The sit-to-stand transition was detected from an angular velocity signal. The sit-to-stand signal pattern within the subject group was analyzed via an intra-class correlation between curves. Inter-subjects' variability was visualized using prediction bands. RESULTS: The angular velocity about the pitch axis exhibited the best signal match across subjects in both groups (0.50 < ICC < 0.75). When analysing acceleration, the acceleration along the antero-posterior axis showed moderate inter-subjects signal pattern match (0.50 < ICC < 0.75) in the reference group. The analysis of other signals revealed a poor signal pattern in both subject groups. SIGNIFICANCE: For optimal interpretation of the analysis of continuous curves, the signal pattern must be considered. Also, the inter-subject variability along this pattern can be informative and useful.

• Klíčová slova
• Acceleration, Angular velocity, Prediction bands, Repeatability,
• MeSH
• lidé MeSH
• posturální rovnováha fyziologie   MeSH
• pozice sedu MeSH
• stoj MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Bond-breaking in CCl4via dissociative electron attachment (DEA) has been studied using a velocity map imaging (VMI) spectrometer. A number of effects related to the dissociation dynamics have been revealed. The near-zero eV s-wave electron attachment, which leads to the production of Cl- anions, is accompanied by a very efficient intramolecular vibrational redistribution. This is manifested by a small fraction of the excess energy being released in the form of the fragments' translation energy. A similar effect is observed for higher-lying electronic resonances with one exception: the resonance centered around 6.2 eV leads to the production of fast Cl2- fragments and their angular distribution is forward peaking. This behavior could not be explained with a single-electronic-state model in the axial recoil approximation and is most probably caused by bending dynamics initiated by a Jahn-Teller distortion of the transient anion. The CCl2- fragment has a reverse backward-peaking angular distribution, suggesting the presence of a long-distance electron hopping mechanism between the fragments.

• Publikační typ
• časopisecké články MeSH

INTRODUCTION: The use of motor imagery (MI) has been shown to offer significant improvements in movement performance in sports, and is now receiving a lot of attention as a relatively new therapeutic approach which can be applied in rehabilitation. However, the effects of MI on the quality of movement is still unclear. This study explored the immediate effect of MI on reaching tasks in healthy subjects. METHODS: 17 healthy individuals (33 ± 8.2 years) participated in the study. Surface electromyography (sEMG) and inertial measurement units (IMU) were used to identify muscle activity and angular velocity in both upper limbs. Participants performed a reach task using their dominant and non-dominant arms at their most comfortable speed, they were then asked to imagine themselves performing the same reaching task, and finally they were asked to repeat the reaching task. RESULTS: Significant decreases were seen in the muscle activity between pre and post MI for Biceps Brachii, Anterior Deltoid and Triceps Brachii. In addition, a significant increase was seen in extension angular velocity post MI. DISCUSSION: The results indicate that the use of MI just after physical practice appears to have an immediate effect on the muscle activity and kinematics during a reaching task, which may suggest an improved quality of movement. CONCLUSION: This proof of concept study shows the potential for MI to improve the quality of performing reaching task and offers a possible therapeutic option for Stroke survivors and other neuromuscular disorders.

• Klíčová slova
• Angular velocity, Motor imagery, Reaching task, Surface electromyography,
• MeSH
• elektromyografie MeSH
• horní končetina MeSH
• lidé MeSH
• paže * MeSH
• pohyb * fyziologie   MeSH
• zdraví dobrovolníci pro lékařské studie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

This study investigated the whole-body coordination patterning in successful and faulty spikes using self-organising map-based cluster analysis. Ten young, elite volleyball players (aged 15.5 ± 0.7 years) performed 60 volleyball spikes in a real-game environment. Adopting the cluster analysis, based on a self-organising map, whole-body coordination patterning was explored between successful and faulty spikes of individual players. The self-organising maps (SOMs) portrayed whole body, lower and upper limb coordination dissimilarities during the jump phase and the ball impact phases between the successful and faulty spikes. The cluster analysis illustrated that the whole body, upper limb and lower limb coordination patterning of each individual's successful spikes were similar to their faulty spikes. Range of motion patterning also demonstrated no differences in kinematics between spike outcomes. Further, the upper limb angular velocity patterning of the players' successful/faulty spikes were similar. The SPM analysis portrayed significant differences between the normalized upper limb angular velocities from 35% to 45% and from 76% to 100% of the spike movement. Although the lower limb angular velocities are vital for achieving higher jumps in volleyball spikes, the results of this study portrayed that the upper limb angular velocities distinguish the differences between successful and faulty spikes among the attackers. This confirms the fact that volleyball coaches should shift their focus toward the upper limb velocity and coordination training for higher success rates in spiking for volleyball attackers.

• Klíčová slova
• SOM, angular velocity, coordination, unsupervised machine learning, volleyball spike,
• MeSH
• biomechanika MeSH
• dolní končetina MeSH
• lidé MeSH
• mladiství MeSH
• pohyb MeSH
• rozsah kloubních pohybů MeSH
• shluková analýza MeSH
• sportovní výkon * MeSH
• volejbal * MeSH
• Check Tag
• lidé MeSH
• mladiství MeSH
• Publikační typ
• časopisecké články MeSH

Motor imagery (MI) is a mental simulation of a movement without its actual execution. Our study aimed to assess how MI of two modalities of gait (normal gait and much more posturally challenging slackline gait) affects muscle activity and lower body kinematics. Electromyography (biceps femoris, gastrocnemius medialis, rectus femoris and tibialis anterior muscles) as well as acceleration and angular velocity (shank, thigh and pelvis segments) data were collected in three tasks for both MI modalities of gait (rest, gait imagery before and after the real execution of gait) in quiet bipedal stance in 26 healthy young adults. No significant change was observed in electromyography activity and lower body kinematics when comparing MI tasks of normal gait. A significantly higher acceleration for the lower limb segments in the vertical direction and for the pelvis in the mediolateral and anteroposterior direction and angular velocity for pelvis in the frontal plane were found during MI of slackline gait after its real execution compared to rest. The results show that MI of normal gait does not lead to any significant changes, while MI of slackline gait affects lower body kinematics parameters.

• Klíčová slova
• Acceleration, Angular velocity, Electromyography, Gait, Motor imagery, Muscle activity,
• MeSH
• biomechanika MeSH
• chůze (způsob) * fyziologie   MeSH
• dolní končetina fyziologie   MeSH
• dospělí MeSH
• elektromyografie * MeSH
• imaginace fyziologie   MeSH
• kosterní svaly * fyziologie   MeSH
• lidé MeSH
• mladý dospělý MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH