Root Mean Square Displacement Research Articles

CONCENTRATION DEPENDENCE OF ATOMIC MEAN SQUARE DISPLACEMENT IN TITANIUM CARBONITRIDE TiCxNy

The work is dedicated to study of crystal lattice dynamics by means of the neutron diffraction method. The neutron diffraction method studies the dependence of the averaged root-mean-square displacement of atoms in titanium carbonitrides TiCxNy at various concentrations of nonmetals – carbon and nitrogen. Anomalous dependence of the averaged root-mean-square displacement of atoms in titanium carbonitrides TiCxNy on the relative total concentration of nonmetals (C + N) / Ti is established. With decrease of the general contents of nonmetals, that is, with the deviation of the alloy composition from stoichiometry, values of the thermal factor on the neutron diffraction pattern and the averaged root-mean-square atomic displacement at first decreases to the general concentration of nonmetals (C + N) / Ti ≈ 0.80. It increases with further deviation of the composition from stoichiometry. The nonmonotonic change of the root-mean-square atomic displacement with deviation from stoichiometry allows assuming that the dynamic distortion (thermal vibrations amplitude of atoms) in the lattice predominates over the static distortion, since otherwise the overall SCS should be only increase. This, apparently, testifies to difficult concentration dependence of the interatomic interaction in titanium carbonitrides, which has a heterodesmic character characterized by the presence ionic, covalent and metallic chemical bonds. In addition, the work determines the averaged root-mean-square displacements and the individual root-meansquare displacement of atoms and the Debye temperature in stoichiometric titanium carbonitrides TiCxNy at different nonmetallic concentrations (C and N). They are practically equal at different ratios of the carbon and nitrogen atoms concentrations. The results can be useful for materials scientists and designers engaged in instrumentation and production free tungsten structural refractory materials to predict dynamic characteristics of titanium carbonitrides and manage these characteristics.

Motion compensated cine CMR of the fetal heart using radial undersampling and compressed sensing

BackgroundTo develop and evaluate a reconstruction framework for high resolution time-resolved CMR of the fetal heart in the presence of motion.MethodsData were acquired using a golden angle radial trajectory in seven fetal subjects and reconstructed as real-time images to detect fetal movement. Data acquired during through-plane motion were discarded whereas in-plane motion was corrected. A fetal cardiac gating signal was extracted to sort the corrected data by cardiac phase, allowing reconstruction of cine images. The quality of motion corrected images and the effect of data undersampling were quantified using separate expressions for spatial blur and image error.ResultsMotion corrected reordered cine reconstructions (127 slices) showed improved image quality relative to both uncorrected cines and corresponding real-time images across a range of root-mean-squared (RMS) displacements (0.3–3.7 mm) and fetal heart rates (119–176 bpm). The relative spatial blur between cines with and without motion correction increased with in-plane RMS displacement leading to an effective decrease in the effective spatial resolution for images without motion correction. Image error between undersampled and reference images was less than 10% for reconstructions using 750 or more spokes, yielding a minimum acceptable scan time of approximately 4 s/slice during quiescent through plane motion.ConclusionsBy rejecting data corrupted by through-plane motion, and correcting data corrupted by in-plane translation, the proposed reconstruction framework accounts for common sources of motion artifact (gross fetal movement, maternal respiration, fetal cardiac contraction) to produce high quality images of the fetal heart.

Local density variation of gold nanoparticles in aquatic environments

Gold (Au) nanoparticles are widely used in diagnosing cancer, imaging, and identification of therapeutic methods due to their particular quantum characteristics. This research presents different types of aqueous models and potentials used in TIP3P, to study the effect of the particle size and density of Au clusters in aquatic environments; so it can be useful to facilitate future investigation of the interaction of proteins with Au nanoparticles. The EAM potential is used to model the structure of gold clusters. It is observed that in the systems with identical gold/water density and different cluster radii, gold particles are distributed in aqueous environment almost identically. Thus, Au particles have identical local densities, and the root mean square displacement (RMSD) increases with a constant slope. However in systems with constant cluster radii and different gold/water densities, Au particle dispersion increases with density; as a result, the local density decreases and the RMSD increases with a larger slope. In such systems, the larger densities result in more blunted second peaks in gold–gold radial distribution functions, owing to more intermixing of the clusters and less FCC crystalline features at longer range, a mechanism that is mediated by the competing effects of gold–water and gold–gold interactions.

Intensity measures for the assessment of the seismic response of buried steel pipelines

To estimate the demand of structures, investigating the correlation between engineering demand parameters and intensity measures (IMs) is of prime importance in performance-based earthquake engineering. In the present paper, the efficiency and sufficiency of some IMs for evaluating the seismic response of buried steel pipelines are investigated. Six buried pipe models with different diameter to thickness and burial depth to diameter ratios, and different soil properties are subjected to an ensemble of 30 far-field earthquake ground motion records. The records are scaled to several intensity levels and a number of incremental dynamic analyses are performed. The approach used in the analyses is finite element modeling. Pipes are modeled using shell elements while equivalent springs and dashpots are used for modeling the soil. Several ground motion intensity measures are used to investigate their efficiency and sufficiency in assessing the seismic demand and capacity of the buried steel pipelines in terms of engineering demand parameter measured by the peak axial compressive strain at the critical section of the pipe. Using the regression analysis, efficient and sufficient IMs are proposed for two groups of buried pipelines separately. The first one is a group of pipes buried in soils with low stiffness and the second one is those buried in soils with higher stiffness. It is concluded that for the first group of pipes, \(\sqrt {{\text{VSI}}[\upomega_{1} ({\text{PGD}} + {\text{RMS}}_{\text{d}} )]}\) followed by root mean square of displacement (RMSd) are the optimal IMs based on both efficiency and sufficiency; and for the second group, the only optimal IM is PGD2/RMSd.

Experiments and Modeling on the Maximum Displacement of a Long Tensioned Mooring Tether Subjected to Vortex-induced Vibration

The maximum root mean square (RMS) of the displacement of a long tensioned mooring tether undergoing vortex-induced vibration (VIV) as the flow velocity varies was experimentally investigated, and an evaluation model was established to predict the maximum RMS value of the displacement by a dimensionless analysis. The results showed that the maximum RMS of the displacement linearly increased with the increasing of the flow velocity if only the low order modes were excited at the corresponding flow velocities. This kind of maximum RMS of displacement was evaluated by the proposed model, which is more reliable when it was used to predict the maximum RMS of the total displacement.

Use of polydispersity index as control parameter to study melting/freezing of Lennard-Jones system: Comparison among predictions of bifurcation theory with Lindemann criterion, inherent structure analysis and Hansen-Verlet rule

Using polydispersity index as an additional order parameter we investigate freezing/melting transition of Lennard-Jones polydisperse systems (with Gaussian polydispersity in size), especially to gain insight into the origin of the terminal polydispersity. The average inherent structure (IS) energy and root mean square displacement (RMSD) of the solid before melting both exhibit quite similar polydispersity dependence including a discontinuity at solid-liquid transition point. Lindemann ratio, obtained from RMSD, is found to be dependent on temperature. At a given number density, there exists a value of polydispersity index (δ P) above which no crystalline solid is stable. This transition value of polydispersity(termed as transition polydispersity, δ P ) is found to depend strongly on temperature, a feature missed in hard sphere model systems. Additionally, for a particular temperature when number density is increased, δ P shifts to higher values. This temperature and number density dependent value of δ P saturates surprisingly to a value which is found to be nearly the same for all temperatures, known as terminal polydispersity (δ TP). This value (δ TP∼ 0.11) is in excellent agreement with the experimental value of 0.12, but differs from hard sphere transition where this limiting value is only 0.048. Terminal polydispersity (δ TP) thus has a quasiuniversal character. Interestingly, the bifurcation diagram obtained from non-linear integral equation theories of freezing seems to provide an explanation of the existence of unique terminal polydispersity in polydisperse systems. Global bond orientational order parameter is calculated to obtain further insights into mechanism for melting.

Новi результати в теорiї колективної самодифузiї в рiдинах

Results of new researches concerning the collective nature of transfer phenomena in liquids are reported. Attention is concentrated on the consistent analysis of a nontrivial time dependence of the root-mean-square displacement (RMSD) of molecules. The account of the contribution associated with the collective component of the molecular motion is shown to result in a more adequate description of the RMSD of molecules at short time intervals. A new method for the determination of the Maxwell relaxation time, which is one of the most important dynamic parameters of molecular systems, is expounded. Mechanisms of one-particle diffusion in water and argon are proposed. The correlation between the results obtained and the results of molecular dynamics studies in computer experiments by G.G.Malenkov, Yu.I.Naberukhin, and V.P.Voloshin aimed at determining the dimensions of Lagrange particles are discussed. A brief historical review of the problem of self-diffusion in liquids is made.

SU‐E‐T‐396: Evaluation of Novel Open Face Intracranial Immobilization Devices

Purpose:Focal intracranial treatments, such as stereotactic radiosurgery, require that motion be minimized during treatment. This level of immobilization is typically achieved with custom thermoplastic masks that cover the patient's face. These masks they do not allow active monitoring of patient position during treatment, and in many cases they induce claustrophobia and anxiety. This work evaluates potential motion using a newly developed faceless mask system designed to reduce anxiety and allow intrafraction monitoring.Methods:Custom masks were created for five healthy volunteers using both the standard mask and the mask with integrated bite system (IBS). Each volunteer was monitored with surface imaging system for 15 minutes to evaluate physiological motion. They were then asked to move as much as possible to evaluate forced motion. The real time surface imaging information was recorded and analyzed off‐line.Results:The mean root‐mean‐square (RMS) of the linear displacements over the 15 minute monitoring periods ranged from 0.3 mm – 0.7 mm with the standard mask and 0.3 mm – 0.5 mm for the mask with IBS. The maximum individual variance was 0.4 mm (2 standard deviations) both with and without IBS. The maximum RMS displacement during forced movements was 9.2 mm without IBS and 4.9 mm with IBS. The mean RMS difference in position before and after forced motion over all patients and movements (with and without IBS) was 0.5 mm +/−0.5 mm (2 SD), i.e. the volunteers were returning to within 0.5 mm of their initial position after forced movements.Conclusion:The intracranial mask system is able to provide sub‐millimeter immobilization for resting volunteers, and the system can limit motion to < 5 mm under the adverse conditions, providing adequate immobilization for any type of intracranial treatment while potentially improving patient comfort and reducing anxiety and claustrophobic episodesThis work was partially supported by Qfix.

Effect of a buried ion pair in the hydrophobic core of a protein: An insight from constant pH molecular dynamics study.

Constant pH molecular dynamics (CpHMD) is a commonly used sampling method, which incorporates the coupling of conformational flexibility and protonation state of a protein during the simulation by using pH as an external parameter. The effects on the structure and stability of a hyperstable variant of staphylococcal nuclease (Δ+PHS) protein of an artificial charge pair buried in its hydrophobic core are investigated by applying both CpHMD and accelerated molecular dynamics coupled with constant pH (CpHaMD) methods. Generalized Born electrostatics is used to model the solvent water. Two sets of starting coordinates of V23E/L36K variant of Δ+PHS, namely, Maestro generated coordinates from Δ+PHS and crystal structure coordinates of the same are considered for detail investigations. On the basis of root mean square displacement (RMSD) and root mean square fluctuations (RMSF) calculations, it is observed that this variant is stable over a wide range of pH. The calculated pKa values for aspartate and glutamate residues based on both CpHMD and CpHaMD simulations are consistent with the reported experimental values (within ± 0.5 to ± 1.5 pH unit), which clearly indicates that the local chemical environment of the carboxylic acids in V23E/L36K variant are comparable to the parent form. The strong salt bridge interaction between the mutated pair, E23/K36 and additional hydrogen bonds formed in the V23E/L36K variant, may help to compensate for the unfavorable self-energy experienced by the burial of these residues in the hydrophobic core. However, from RMSD, RMSF, and pKa analysis, no significant change in the global conformation of V23E/L36K variant with respect to the parent form, Δ+PHS is noticed.

Adsorption of humic acid by amine-modified nanocellulose: an experimental and simulation study

The purpose of this study was to evaluate the adsorption of humic acid (HA) by amine-modified nanocellulose. At first, nanocellulose was synthesized by acid hydrolysis, and then was modified by N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. In the next step, HA and amine-modified nanocellulose were incubated at different conditions (pH, incubation time, temperature, and concentration). Furthermore, we used molecular dynamic (MD) simulation for observation of adsorption at molecular scale. For this purpose, HA and amine-modified nanocellulose were prepared by HyperChem software (Hypercube, Inc., USA), and inserted in Ascalaph Designer 1.8.69 software. Once equilibrium was reached, interactions were simulated for 1,000 ps. Finally, different parameters such as interaction energy, potential energy, and root-mean-square displacement (RMSD) were measured. This study demonstrated that the adsorption of HA was pH-, temperature-, dose-, and time-dependent. Based on simulation results, the interaction energy was reduced, but potential energy and RMSD were increased at the final stage of simulation, which indicated the adsorption of HA. The authors suggest amine-modified nanocellulose for removal of HA in wastewater.

Multiple sclerosis: Benefits of q-space imaging in evaluation of normal-appearing and periplaque white matter

IntroductionDiffusion tensor imaging (DTI) reveals white matter pathology in patients with multiple sclerosis (MS). A recent non-Gaussian diffusion imaging technique, q-space imaging (QSI), may provide several advantages over conventional MRI techniques in regard to in vivo evaluation of the disease process in patients with MS. The purpose of this study is to investigate the use of root mean square displacement (RMSD) derived from QSI data to characterize plaques, periplaque white matter (PWM), and normal-appearing white matter (NAWM) in patients with MS. MethodsWe generated apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps by using conventional DTI data from 21 MS patients; we generated RMSD maps by using QSI data from these patients. We used the Steel–Dwass test to compare the diffusion metrics of regions of interest in plaques, PWM, and NAWM. ResultsADC differed (P<0.05) between plaques and PWM and between plaques and NAWM. FA differed (P<0.05) between plaques and NAWM. RMSD differed (P<0.05) between plaques and PWM, plaques and NAWM, and PWM and NAWM. ConclusionRMSD values from QSI may reflect microstructural changes and white-matter damage in patients with MS with higher sensitivity than do conventional ADC and FA values.

Galvanic Vestibular Stimulation and the Ability to Maintain Arm-Hand Posture

Vestibular illusions are the most common illusions that can cause spatial disorientation in flight. This study aims to find out whether and how the ability of keeping arm-hand posture is affected by the vestibular illusions induced by galvanic vestibular stimulation (GVS). With their heads and trunks firmly fixed, 16 subjects maintained arm-hand posture under three GVS conditions (no stimulation, anode right, and anode left) for 10 s. Range of sway (RS), root mean square of displacement (RMS), and mean deviation (D) of the hand, as well as the rotation angle of the wrist, elbow, and shoulder in the horizontal plane, were measured. One-way ANOVA was used to analyze the effects of GVS on keeping arm-hand posture. With GVS, the hand deviated to the anode side continuously in the lateral direction, but moved at random in the sagittal direction. RS and RMS in the lateral direction were significantly increased by 89.0% and 104.7%, respectively. D was significantly increased about 6 mm to the anode. The shoulder joint and elbow joint always turned toward the anode, but the wrist joint turned at random. Furthermore, GVS polarity had no significant effect on the amplitude of each parameter. GVS can decrease both the accuracy and precision of hand position, especially in the lateral direction. The continuous hand deviation to the anode side is mainly induced by the rotation of elbow and shoulder. Extra attention needs to be paid to these findings in future spatial disorientation studies.

New diffusion metrics for spondylotic myelopathy at an early clinical stage

ObjectivesTo investigate the use of root mean square displacement (RMSD) and mean diffusional kurtosis (DK) metrics of q-space imaging data to estimate spinal cord compression in patients with early cervical spondylosis.MethodsWe studied 50 consecutive patients at our institution (22 male, 28 female; mean age 58 years; age range 20–86 years) who had clinical signs and symptoms suggestive of early clinical stage cervical myelopathy. After conventional magnetic resonance (MR) imaging, diffusion tensor and q-space image data were acquired using 3-T MR imaging. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), RMSD and mean DK values were calculated and compared between compressed and uncompressed spinal cords.ResultsFA and mean DK values were significantly lower and RMSD was significantly higher (P = 0.0060, 0.0020 and 0.0062, respectively; Mann–Whitney U test with the Bonferroni correction) in compressed spinal cords than in uncompressed cords. ADC was also higher in compressed cords, but this difference was not statistically significant.ConclusionsIn the evaluation of spinal cord damage in early cervical spondylosis, mean DK and RMSD values in the spinal cord may be highly sensitive indicators of microstructural change and damage.Key Points• Absolute surgical indications for cervical spondylosis with myelopathy remain to be established.• Diffusion tensor MRI shows abnormalities in normal-appearing but compressed spinal cord.• Non-Gaussian diffusion analysis is highly sensitive in revealing spinal cord damage.

Quantitative assessment of pivot-shift using inertial sensors

The pivot-shift phenomenon has been identified to be one of the essential signs of functional anterior cruciate ligament (ACL) insufficiency. However, the pivot-shift test remains a surgeon-subjective examination, lacking a general recognized quantitative measurement. The goal of the present study was to validate the use of an inertial sensor for quantifying the pivot-shift test, using a commercial navigation system. An expert surgeon intra-operatively performed the pivot-shift test on 15 consecutive patients before ACL reconstruction. A single accelerometer and a commercial navigation system simultaneously acquired limb kinematics. An additional optical tracker mounted on the accelerometer allowed following sensor movements. Anteroposterior (a-p) tibial acceleration obtained with the navigation system was compared with three-dimensional (3D) acceleration acquired by the accelerometer. The effect of skin artifacts and test-retest positioning were estimated. Repeatability of the acceleration parameter and waveform was analyzed. Correlation between the two measurements was also assessed. Average root mean square (RMS) error in test-retest positioning reported a good value of 5.5±2.9mm. Mean RMS displacement due to soft tissue artifacts was 4.9±2.6mm. The analysis of acceleration range repetitions reported a good intra-tester repeatability (Cronbach's alpha=0.86). Inter-patients similarity analysis showed a mean acceleration waveform correlation of 0.88±0.14. The acceleration ranges demonstrated a good positive correlation between the two measurements (rs=0.72, P<0.05). This study showed good reliability of the new device and good correlation with the navigation system results. Therefore, the accelerometer is a valid method to assess dynamic joint laxity. II.

Limit Wind Loads of a Concrete Filled Steel-Tube Transmission Tower

Limit wind loads of a Concrete Filled Steel-Tube (CFST) transmission tower in a long-span tower-line system is computed. Firstly, fine Finite Element Method (FEM) model of the tower and its Multiple-Degrees-Of-Freedom (MDOF) model are built and the material nonlinear models including steel-tube and CFST are also modeled. Secondly, based on MDOF model, mean displacements under mean wind force are evaluated and the Root Mean Square Displacement (RMSD) under fluctuating wind force is also evaluated by random vibration theory. Then, Equivalent Static Wind Loads (ESWL) are computed considering the first three order modes. Finally, based on FEM model, the nodes are loaded by the ESWL and the nodal loads increase step by step in order to impel materials into plastic status until calculation can not converge. Plastic analysis shows the tower’s failure is caused by steel-tube element failure and the CFST elements have enough strength reserve. The tower’s three kinds of limit wind loads are computed based on different references and it is suggested to select the limit wind loads, whose corresponding wind velocity is 69.7m/s, as the design limit wind loads of the tower.

Time-averaged quadratic functionals of a Gaussian process

The characterization of a stochastic process from its single random realization is a challenging problem for most single-particle tracking techniques which survey an individual trajectory of a tracer in a complex or viscoelastic medium. We consider two quadratic functionals of the trajectory: the time-averaged mean-square displacement (MSD) and the time-averaged squared root mean-square displacement (SRMS). For a large class of stochastic processes governed by the generalized Langevin equation with arbitrary frictional memory kernel and harmonic potential, the exact formulas for the mean and covariance of these functionals are derived. The formula for the mean value can be directly used for fitting experimental data, e.g., in optical tweezers microrheology. The formula for the variance (and covariance) allows one to estimate the intrinsic fluctuations of measured (or simulated) time-averaged MSD or SRMS for choosing the experimental setup appropriately. We show that the time-averaged SRMS has smaller fluctuations than the time-averaged MSD, in spite of much broader applications of the latter one. The theoretical results are successfully confirmed by Monte Carlo simulations of the Langevin dynamics. We conclude that the use of the time-averaged SRMS would result in a more accurate statistical analysis of individual trajectories and more reliable interpretation of experimental data.

Investigation of Brownian Motion of Micro- and Nano-Bubble

In this paper, nanobubble shrunk from microbubble generated by electrolysis was observed by optical microscope in order to distinguish a bubble from impurities or contamination in the water. To keep microbubbles in focus, it is necessary to generate microbubble whose diameter is less than 5μm in focal position directly since its rising velocity is negligibly small and shrink rapidly. Therefore, diameter distribution of bubble generated by electrolysis was firstly investigated under the different configurations of electrode diameter, concentration of solution and voltage. In the result, when diameter of electrode was less than 1μm, distribution of bubble diameter was decreased to generate smaller bubble. Observation of Brownian motion of nanobubble was succeeded. Root mean square of displacement and diameter of nanobubble were simultaneously measured and compared with a behavior of the ZnO solid particle. As a consequence, root mean square of displacement of bubble is smaller than that of ZnO particle due to different structure of interface.

Surface Melting and Sintering of Metallic Nanoparticles

The melting and sintering of two different-sized metallic nanoparticles are simulated by a molecular dynamics method in this work. The particles are partitioned into different regimes where tracing atoms are arranged to investigate the melting and sintering kinetics. The melting of individual particles is firstly investigated and compared with established studies, where the size-dependent melting depression and surface melting phenomenon are revealed. The detailed sintering process of two nickel nanoparticles, 3.52 and 1.76 nanometers in diameter respectively, is subsequently examined by the gyration radius, mean square displacement (MSD), root mean square displacement (RMSD), sintering diffusivity and activation energy. A three-stage sintering scenario is illustrated, and the layered structure shows the regime dependent behavior of diffusivity during the sintering process. Beside the surface diffusion, sintering of different-sized nanoparticles is found to be affected by a few other mechanisms.

High temperature unfolding of Bacillus anthracis amidase-03 by molecular dynamics simulations.

The stability of amidase-03 structure (a cell wall hydrolase protein) from Bacillus anthracis was studied using classical molecular dynamics (MD) simulation. This protein (GenBank accession number: NP_844822) contains an amidase-03 domain which is known to exhibit the catalytic activity of N-acetylmuramoyl-L-alanine amidase (digesting MurNAc-Lalanine linkage of bacterial cell wall). The amidase-03 enzyme has stability at high temperature due to the core formed by the combination of several secondary structure elements made of beta-sheets. We used root-mean-square-displacement (RMSD) of the simulated structure from its initial state to demonstrate the unfolding of the enzyme using its secondary structural elements. Results show that amidase-03 unfolds in transition state ensemble (TSE). The data suggests that alpha-helices unfold before beta-sheets from the core during simulation.

Olfactory stimuli and enhanced postural stability in older adults

Ameliorating postural instability is an important component of geriatric health care. The effect of olfactory stimuli (lavender and black pepper oils) on postural control in 17 older adults (78 ± 6 years old) who had no apparent neurological deficits was studied. Measurements of center of pressure (CoP) trajectories were done with subjects standing quietly on a force plate. Control measurements were compared with olfactory interventions: brief exposure to sham (distilled water), lavender oil, and black pepper oil; experiments were repeated with eyes open and eyes closed. From the CoP data, the root mean square (RMS) displacement and velocity in mediolateral (ML) and antero-posterior (AP) directions, and the total trajectory length were computed. This study found that with eyes closed, olfactory stimulation with either lavender or black pepper oil significantly decreased both ML and AP RMS velocities and trajectory lengths compared with baseline. In contrast, little effect was observed under the eyes-open condition. Decreases in RMS displacements were small and mostly insignificant. The study suggests that olfactory stimulation may improve posture stability in older adults through decreasing the velocities of postural adjustments during normal sway.