Second Type Of Motion Research Articles

Getting the nod: Pediatric head motion in a transdiagnostic sample during movie- and resting-state fMRI.

Head motion continues to be a major problem in fMRI research, particularly in developmental studies where an inverse relationship exists between head motion and age. Despite multifaceted and costly efforts to mitigate motion and motion-related signal artifact, few studies have characterized in-scanner head motion itself. This study leverages a large transdiagnostic public dataset (N = 1388, age 5-21y, The Healthy Brain Network Biobank) to characterize pediatric head motion in space, frequency, and time. We focus on practical aspects of head motion that could impact future study design, including comparing motion across groups (low, medium, and high movers), across conditions (movie-watching and rest), and between males and females. Analyses showed that in all conditions, high movers exhibited a different pattern of motion than low and medium movers that was dominated by x-rotation, and z- and y-translation. High motion spikes (>0.3mm) from all participants also showed this pitch-z-y pattern. Problematic head motion is thus composed of a single type of biomechanical motion, which we infer to be a nodding movement, providing a focused target for motion reduction strategies. A second type of motion was evident via spectral analysis of raw displacement data. This was observed in low and medium movers and was consistent with respiration rates. We consider this to be a baseline of motion best targeted in data preprocessing. Further, we found that males moved more than, but not differently from, females. Significant cross-condition differences in head motion were found. Movies had lower mean motion, and especially in high movers, movie-watching reduced within-run linear increases in head motion (i.e., temporal drift). Finally, we used intersubject correlations of framewise displacement (FD-ISCs) to assess for stimulus-correlated motion trends. Subject motion was more correlated in movie than rest, and 8 out of top 10 FD-ISC windows had FD below the mean. Possible reasons and future implications of these findings are discussed.

Editing Domain Motions Preorganize the Synthetic Active Site of Prolyl-tRNA Synthetase.

Prolyl-tRNA synthetases (ProRSs) catalyze the covalent attachment of proline onto cognate tRNAs, an indispensable step for protein synthesis in all living organisms. ProRSs are modular enzymes and the "prokaryotic-like" ProRSs are distinguished from "eukaryotic-like" ProRSs by the presence of an editing domain (INS) inserted between motifs 2 and 3 of the main catalytic domain. Earlier studies suggested the presence of coupled-domain dynamics could contribute to catalysis; however, the role that the distal, highly mobile INS domain plays in catalysis at the synthetic active site is not completely understood. In the present study, a combination of theoretical and experimental approaches has been used to elucidate the precise role of INS domain dynamics. Quantum mechanical/molecular mechanical simulations were carried out to model catalytic Pro-AMP formation by Enterococcus faecalis ProRS. The energetics of the adenylate formation by the wild-type enzyme was computed and contrasted with variants containing active site mutations, as well as a deletion mutant lacking the INS domain. The combined results revealed that two distinct types of dynamics contribute to the enzyme's catalytic power. One set of motions is intrinsic to the INS domain and leads to conformational preorganization that is essential for catalysis. A second type of motion, stemming from the electrostatic reorganization of active site residues, impacts the height and width of the energy profile and has a critical role in fine tuning the substrate orientation to facilitate reactive collisions. Thus, motions in a distal domain can preorganize the active site of an enzyme to optimize catalysis.

Reorientational Motion of BH4 Ions in Alkali Borohydrides MBH4 (M = Li, Na, K) as Studied by Solid-State NMR

Ion dynamics in alkali borohydrides, LiBH4, NaBH4, and KBH4, was studied by solid-state NMR. NMR spectra and spin–lattice relaxation times, T1, of 1H and 11B were measured and analyzed. The T1 results of 1H and 11B indicated that two types of motions take place in the low-temperature (LT) phase of LiBH4. The second moments of 1H and 11B NMR spectra suggested that the sum of the two types of motions resembles isotropic reorientation of the BH4 unit. The T1 minimum values of 1H and 11B supported that the C3 rotation takes place at first. The second type of motion might be either C3 rotation or C2 rotation. The second moments of NMR spectra and the T1 minimum values of 1H and 11B supported that the BH4 unit reorients isotropically in NaBH4 and KBH4.

Small-Angle Orientational Motions of Spin-Labeled Lipids in Cholesterol-Containing Bilayers Studied at Low Temperatures by Electron Spin Echo Spectroscopy

Electron spin echo (ESE) study was performed for a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer containing an admixture of lipids (of 1:100 molar ratio) spin-labeled at the polar head or at different positions along the acyl chain and optionally containing additionally cholesterol that substituted POPC lipids in a 50:50 molar ratio. ESE signal was observed below 150-115 K, depending on the label position. Three-pulse stimulated ESE is sensitive to two types of orientational motion of spin labels at these temperatures. The first type of motion (which is also seen in a two-pulse primary ESE experiment) is fast stochastic librations, with a correlation time in the nanosecond scale. The second type of motion is slow millisecond rotations, which in the accessible microsecond time scale are seen as small-angle reorientations. (Restricted rotations also refer to this type of motion.) We found that in presence of cholesterol, fast librations are enhanced at all label positions. This effect may be related to the cholesterol ordering effect. Rotational motions in the presence of cholesterol are remarkably suppressed near the bilayer surface, which may be readily explained by the cholesterol condensing effect. In contrast to that, in the bilayer center rotations in the presence of cholesterol are remarkably enhanced. This effect may be attributed to topological properties of a cholesterol-containing membrane system in which beyond the steroid core, more freedom appears for small-angle motions, as compared with the cholesterol-free case. The found property may be important for physiological temperatures, as well. In particular, it may imply that cholesterol weakens interaction between two leaflets in the bilayer.

Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy

Abstract Electron spin echo (ESE) spectroscopy as applied to nitroxide spin probes in glasses is sensitive to molecular motions of two types. The first type of motion is fast stochastic librations, with correlation times on the scale of nanoseconds. In this work, these librations were found in glassy glycerol above ∼190 K and in glassy o-terphenyl above ∼250 K (glass transition temperatures for these two solvents are Tg = 185 K and Tg = 243 K, respectively). Most likely, these librations are of the same origin as anharmonic atomic vibrations, as seen in glasses by neutron scattering above a so-called dynamical transition temperature. The second type of motion is slow millisecond inertial rotations, which are observed in the experimentally accessible microsecond time scale as developing within an angular range of ∼0.1–2°. Over the temperature range studied, the square of the characteristic rotation rate was found to be proportional to the dielectric α-relaxation rate that is known for glycerol and o-terphenyl from literature. This empirical fact probably means that small-angle inertial rotations of spin probes and dielectric α-relaxation in the solvent are interrelated phenomena.

Particle Simulation Study of Dust Particle Dynamics in Sheaths

AbstractDynamics of dust particles in a divertor plasma is simulated using numerical solutions of dust momentum and charging equations in an electrostatic sheath and an ionizing presheath, where an electrostatic force and a drag force due to absorption of plasma ions are taken into account. Spatial distributions of plasma parameters in a divertor are obtained with particle simulations including ionization by electron‐impact. We found that the critical dust radius exists. Dust particles with a larger radius than this critical one are incapable to come off a divertor plate because the ion drag force is stronger compared to the electrostatic force. Control of the plate potential can suppress the dust motion from the plate. The radii of heavy dust particles are classified with respect to equilibrium positions. Considering dust particles started at the plate with radii smaller than the critical one, two types of dust motion were found. Dust particles with the first type of motion come back to the plate before approaching their equilibrium positions. The second type of motion is presented by smaller dust particles which oscillate around their equilibrium positions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Human Versus Robotic Shoulder Motion

In this paper, we studied the maximum inclination angles in the human shoulder girdle and compared them with the motion abilities of the humanoid robotic shoulder proposed in 1,2) We found that the extreme inclination angles of the human shoulder girdle are different when the arm is constantly stretched downward or when the arm executes an inclination co-planar to the girdle's motion. The humanoid robotic shoulder fulfills the range of the maximum inclination angles in the second type of motion but its workspace is obviously too small for the first type of motion. We also measured the working cone of the human arm and found that central axis of the human arm working cone is about 60° inclined in the horizontal plane.

Uncontrollable Rotational Motion of the Mir Orbital Station

The results of determining the rotational motion of the Mir orbital station are presented for four long segments of its unmanned uncontrolled flight in 1999–2000. The determination was carried out using the data of onboard measurements of the Earth's magnetic field intensity. These data, taken for a time interval of several hours, were jointly processed by the least squares method with the help of integration of the equations of station motion relative to its center of mass. As a result of this processing, the initial conditions of motion and the parameters of the mathematical model used were evaluated. The technique of processing is verified using the telemetry data on angular velocity of the station and its attitude parameters. Two types of motion were applied on the investigated segments. One of them (three segments) presents a rotation around the axis of the minimum moment of inertia. This axis executes small oscillations with respect to a normal to the orbit plane. Such a motion was used for the first time on domestic manned orbital complexes. The second type of motion begins with a biaxial rotation which, in a few weeks, goes over into a motion very similar to the rotation around the normal to the orbit plane, but around the axis of the maximum moment of inertia.

Estimation of shear rates inside a ball mill

Grinding slurries are known to be non-Newtonian. For such suspensions, slurry viscosity is not a constant, but is a function of shear rate. This study was aimed at the derivation of an estimate of a typical shear rate range inside a ball mill, in order to determine appropriate values of apparent viscosity for studies of the effects of rheology on grinding. Shear rates were estimated by considering the ball charge motion inside the mill. Two types of ball motion, cascading and cataracting, were taken into account. For the first type of motion, Morrell's power model approach [Morrell, S., 1996. Power draw of wet tumbling mills and its relationship to charge dynamics: Part 1. A continuum approach to mathematical modelling of mill power draw. Trans. I.M.M. 105, C43–C53] was employed. This approach considers the mill charge to be comprised of layers or `shells' which slide against one another. The relative velocity between layers of the charge was calculated. Distance over which this change in velocity occurs was determined from the slurry volume filling the interstices of the charge and from the contact area between the slurry and ball surfaces. Shear rate defined as the velocity gradient between layers of the charge in the cascading motion was hence estimated to be 13 s −1 as a lower limit of the shear rate range for a ball mill of 4.57 m in diameter. For the second type of motion, the velocity of a free-flight ball striking the mill shell was resolved into two components, and a typical shear rate of 730 s −1 was estimated from the tangential velocity of the ball for the same ball mill. It is therefore recommended that a shear rate in the range of 13–730 s −1 be used to characterise the apparent viscosities of slurry in grinding applications.

The dynamics of a spherical pendulum with a vibrating suspension

The motion of a spherical pendulum whose point of suspension performs high-frequency vertical harmonic oscillations of small amplitude is investigated. It is shown that two types of motion of the pendulum exist when it performs high-frequency oscillations close to conical motions, for which the pendulum makes a constant angle with the vertical and rotates around it with constant angular velocity. For the motions of the first and second types the centre of gravity of the pendulum is situated below and above the point of suspension, respectively. A bifurcation curve is obtained, which divides the plane of the parameters of the problem into two regions. In one of these only the first type of motion can exist, while in the other, in addition to the first type of motion, there are two motions of the second type. The problem of the stability of these motion of the pendulum, close to conical, is solved. It is shown that the first type of motion is stable, while of the second type of motion, only the motion with the higher position of the centre of gravity is stable.

A unified theory of the dynamics of linear chain macromolecules: From unentangled to entangled polymer fluids

We present an analytically tractable model of the dynamics of a flexible linear polymer. The polymer is represented by a freely jointed chain that undergoes two types of motion. The first motion is a slithering along its contour that mimics reptation. The second type of motion is a generalization of the Stockmayer ‘‘kink–jump’’ algorithm that includes the effects of a medium that relaxes with a finite time scale. A fixed fraction of the beads are immobilized by obstacles that relax with a rate whose magnitude may be smaller than, larger than, or comparable to the rate at which a bead executes jumps in the absence of obstacles. The calculation of observables such as the autocorrelation function of the end-to-end vector, viscoelastic moduli, and the diffusion coefficient is related to the solution of a set of random walk problems with dynamical disorder. Analytical results based on the dynamical effective medium approximation are presented. Our results recover the behavior of an isolated (Rouse) chain and of a reptating chain in an entangled melt as limiting cases, and describe the crossover regime between these limits.

Molecular motion in supercooled liquids and glasses

Recently obtained data on dielectric and NMR relaxation, pulsed EPR, and other methods indicate the presence in glassy liquids of two types of molecular rotational motion. One type corresponds to macroscopic motion of the molecules and is apparent in measurements of mechanical relaxation, macroviscosity, and dielectric ..cap alpha.. relaxation. A small number of molecules display the second type of motion, which is distinguished from the first type by much higher frequency of motion and is apparent in dielectric ..beta.. relaxation, NMR relaxation, and pulsed EPR of spin probes. It is especially characteristic for impurity molecules. We discuss the connection between molecular motion and the structural features of glasses. We indicate examples of chemical reactions whose kinetics are determined by the second type of motion.

Flip-flop motion and spin symmetry conversion of methyl groups

It is commonly supposed that hindered methyl groups in solids undergo phonon induced rotations through +or-120. This may be symbolized (1) to (2) or (1) to (3) where (1), (2) and (3) indicate equivalent orientations of the group. The authors show both theoretically and experimentally that a second type of motion may be more important. In this motion a transition to a mixed state occurs: (1) to 2/3((2)+(3)-1/2(1)). The operator which converts (1) to the mixed state converts the latter back to (1) so the motion involves two states only and may be described as flip-flop motion. It may be distinguished experimentally from rotation because it does not modulate matrix elements between pairs of states of E symmetry. Both the rotation and flip-flop rates are measured for the 4-methyl group in 4-methyl-2,6-ditertiarybutylphenol (MDBP) between 10K and 50K. The flip-flop rate is six times greater than the rotation rate. The measurement technique combines proton spin-lattice relaxation measurements with a novel way of determining the rate of conversion between proton spin symmetry species.

Steady Motion of a Dislocation in a Lattice

Athermal motion of a dislocation in a lattice is studied. Using Nabarro force which represents the anharmonicity of the potential in the slip plane, a formula which describes the energy dissipated from a moving dislocation is given. Results of computer simulations of a one-dimensional dislocation are analyzed by the formula. It is shown that there are three types of motion: (i) a dislocation emits lattice waves, (ii) the displacement field around a moving dislocation is almost the same as the static one, (iii) dislocation velocity changes remarkably in the period of the lattice parameter. The boundaries between velocities of these types of motion depend strongly on the shape of the potential and damping of lattice waves. The continuum approximation is justified for the second type of motion which appears if a lattice has large damping and the low Peierls stress.

The swirling vortex

We consider an infinite vortex line in a viscous fluid interacting with a plane boundary surface at right angles to the line. If the boundary surface were absent, the vortex would impart to the fluid a circular motion about the vortex line with speed inversely proportional to the distance to the line. The presence of the boundary surface, however, leads to a secondary flow due to the forced adherence of the fluid at the surface. The purpose of the paper is to describe a family of exact solutions of the Navier-Stokes equations which applies to the above situation. Under quite general hypotheses, it is shown that there can exist only three types of motion compatible with the assumed structure. In the first kind, the radial velocity component (using spherical polar coordinates about the point where the vortex meets the plane surface) is directed inward along the plane surface and upward along the axis of the vortex. In the second type of motion the radial velocity component is directed inward along the plane surface and downward on the axis, with a compensating outflow at an intermediate angle. In the third kind the radial velocity is directed outward near the plane and downward on the central axis. The results can also be used as a basis for numerical calculations of the solutions in question, and several typical flow patterns have been explicitly computed in order to illustrate the theory. The paper concludes with a discussion of the relation between the theoretical solutions and observed phenomena near the point of contact of tornadoes with the ground; this requires that the flows under discussion be considered as mean motions in a turbulent flow with constant eddy viscosity. The present work adds theoretical weight to the argument that central downdrafts can occur in tornadoes. Moreover, the model provides an explanation, other than centrifugal action, for the frequent appearance of a cascade effect at the foot of both tornadoes and water-spouts; finally it offers a unified point of view from which to consider the diversity of flow patterns observed when vortex fields interact with a boundary surface.

Axisymmetric Torsional Wave Propagation in Circular Viscoelastic Rods

A semi-infinite viscoelastic circular cylindrical rod is subjected at its end surface to an arbitrary radial, axially symmetric tangential shear stress distribution, harmonic in time. Expressions are derived for the tangential and radial shear stress distributions, as well as for the tangential displacement. Near the forced end of the rod, the tangential displacement takes on a complicated form which consists of the superposition of a simple rotational oscillation of the undeformed cross section and motions deforming the cross section in its plane. The last type of motion permits infinitely many nodal circles. Owing to the large magnitude of the space attenuation coefficients, this second type of motion dies out rapidly and only the simple rotation, which is less attenuated, remains. Numerical computations were performed for two polymethyl methacrylate rods of 1 and 10 cm diam, subjected to a shear stress distribution varying periodically with time and cubic in the radial distance from the center. The results are presented in graphical form.