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https://www.readbyqxmd.com/read/29495775/free-energy-and-entropy-of-a-dipolar-liquid-by-computer-simulations
#1
Ricardo Palomar, Gemma Sesé
Thermodynamic properties for a system composed of dipolar molecules are computed. Free energy is evaluated by means of the thermodynamic integration technique, and it is also estimated by using a perturbation theory approach, in which every molecule is modeled as a hard sphere within a square well, with an electric dipole at its center. The hard sphere diameter, the range and depth of the well, and the dipole moment have been calculated from properties easily obtained in molecular dynamics simulations. Connection between entropy and dynamical properties is explored in the liquid and supercooled states by using instantaneous normal mode calculations...
February 28, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29191633/sensitivity-of-intervertebral-joint-forces-to-center-of-rotation-location-and-trends-along-its-migration-path
#2
Marco Senteler, Ameet Aiyangar, Bernhard Weisse, Mazda Farshad, Jess G Snedeker
Translational vertebral motion during functional tasks manifests itself in dynamic loci for center of rotation (COR). A shift of COR affects moment arms of muscles and ligaments; consequently, muscle and joint forces are altered. Based on posture- and level-specific trends of COR migration revealed by in vivo dynamic radiography during functional activities, it was postulated that the instantaneous COR location for a particular joint is optimized in order to minimize the joint reaction forces. A musculoskeletal multi-body model was employed to investigate the hypotheses that (1) a posterior COR in upright standing and (2) an anterior COR in forward flexed posture leads to optimized lumbar joint loads...
March 21, 2018: Journal of Biomechanics
https://www.readbyqxmd.com/read/29074465/comparison-of-three-dimensional-helical-axes-of-the-cervical-spine-between-in-vitro-and-in-vivo-testing
#3
René Jonas, Robert Demmelmaier, Steffen P Hacker, Hans-Joachim Wilke
BACKGROUND CONTEXT: The range of motion is a well-accepted parameter for the assessment and evaluation of cervical motion. However, more qualitative data of the kinematics of the cervical spine are needed for the development and success of cervical disc arthroplasty. PURPOSE: The aim of this study was to provide basic information about helical axes of human cervical spine under in vitro conditions. Furthermore, it should clarify whether the three-dimensional helical axes of cervical motion gained from in vitro experiments are in agreement with those gained from in vivo experiments, and therefore to prove its reliability...
March 2018: Spine Journal: Official Journal of the North American Spine Society
https://www.readbyqxmd.com/read/28514063/where-are-you-heading-flexible-integration-of-retinal-and-extra-retinal-cues-during-self-motion-perception
#4
Shenbing Kuang, Jinfu Shi, Yang Wang, Tao Zhang
As we move forward in the environment, we experience a radial expansion of the retinal image, wherein the center corresponds to the instantaneous direction of self-motion. Humans can precisely perceive their heading direction even when the retinal motion is distorted by gaze shifts due to eye/body rotations. Previous studies have suggested that both retinal and extra-retinal strategies can compensate for the retinal image distortion. However, the relative contributions of each strategy remain unclear. To address this issue, we devised a two-alternative-headings discrimination task, in which participants had either real or simulated pursuit eye movements...
June 2017: PsyCh Journal
https://www.readbyqxmd.com/read/28368985/prediction-of-cervical-spinal-joint-loading-and-secondary-motion-using-a-musculoskeletal-multibody-dynamics-model-via-force-dependent-kinematics-approach
#5
Hao Diao, Hua Xin, Jun Dong, Xijing He, Dichen Li, Zhongmin Jin
STUDY DESIGN: A cervical spine biomechanical investigation using multibody dynamics. OBJECTIVE: To develop a comprehensive cervical spine multibody dynamics model incorporated with the force-dependent kinematics (FDK) approach, and to study the influence of soft tissue deformation on the joint loading prediction. SUMMARY OF BACKGROUND DATA: Musculoskeletal multibody dynamics models have been widely used to analyze joint loading. Current cervical spine musculoskeletal models, however, neglect the joint internal motion caused by soft tissue deformation...
December 15, 2017: Spine
https://www.readbyqxmd.com/read/28364336/reduced-instantaneous-center-of-rotation-movement-in-patients-with-low-back-pain
#6
Peemongkon Wattananon, Nattaporn Intawachirarat, Marco Cannella, Won Sung, Sheri P Silfies
PURPOSE: The instantaneous center of rotation (ICR) can be used to investigate movement coordination and control in patients with low back pain (LBP). Tracking of the ICR in LBP patients has not been systematically investigated. This study aimed to (1) determine the within-session measurement error of ICR parameters, and (2) characterize the change in ICR among three groups of participants (no history of LBP = HC; history of LBP = HLBP; and current LBP = LBP). METHODS: Ninety-three participants (HC = 31; HLBP = 33; and LBP = 29) were recruited...
January 2018: European Spine Journal
https://www.readbyqxmd.com/read/28062121/instantaneous-centers-of-rotation-for-lumbar-segmental-extension-in-vivo
#7
Ameet Aiyangar, Liying Zheng, William Anderst, Xudong Zhang
The study aimed to map instantaneous centers of rotation (ICRs) of lumbar motion segments during a functional lifting task and examine differences across segments and variations caused by magnitude of weight lifted. Eleven healthy participants lifted loads of three different magnitudes (4.5, 9, and 13.5kg) from a trunk-flexed (~75°) to an upright position, while being imaged by a dynamic stereo X-ray (DSX) system. Tracked lumbar vertebral (L2-S1) motion data were processed into highly accurate 6DOF intervertebral (L2L3, L3L4, L4L5, L5S1) kinematics...
February 8, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/27441174/finite-element-analysis-of-sacroiliac-joint-fixation-under-compression-loads
#8
Claire Bruna-Rosso, Pierre-Jean Arnoux, Rohan-Jean Bianco, Yves Godio-Raboutet, Léo Fradet, Carl-Éric Aubin
BACKGROUND: Sacroiliac joint (SIJ) is a known chronic pain-generator. The last resort of treatment is the arthrodesis. Different implants allow fixation of the joint, but to date there is no tool to analyze their influence on the SIJ biomechanics under physiological loads. The objective was to develop a computational model to biomechanically analyze different parameters of the stable SIJ fixation instrumentation. METHODS: A comprehensive finite element model (FEM) of the pelvis was built with detailed SIJ representation...
2016: International Journal of Spine Surgery
https://www.readbyqxmd.com/read/26127284/su-e-p-45-an-analytical-formula-for-deriving-mechanical-iso-center-of-rotational-gantry-treatment-unit-rotational-gantry-treatment-unit
#9
X Ding, M Bues
PURPOSE: To present an analytical formula for deriving mechanical isocenter (MIC) of a rotational gantry treatment unit. The input data to the formula is obtained by a custom-made device. The formula has been implemented and used in an operational proton therapy facility since 2005. METHODS: The custom made device consisted of 3 mutually perpendicular dial indicators and 5 clinometers, to obtain displacement data and gantry angle data simultaneously. During measurement, a steel sphere was affixed to the patient couch, and the device was attached to the snout rotating with the gantry...
June 2015: Medical Physics
https://www.readbyqxmd.com/read/25919370/analysis-and-experimental-kinematics-of-a-skid-steering-wheeled-robot-based-on-a-laser-scanner-sensor
#10
Tianmiao Wang, Yao Wu, Jianhong Liang, Chenhao Han, Jiao Chen, Qiteng Zhao
Skid-steering mobile robots are widely used because of their simple mechanism and robustness. However, due to the complex wheel-ground interactions and the kinematic constraints, it is a challenge to understand the kinematics and dynamics of such a robotic platform. In this paper, we develop an analysis and experimental kinematic scheme for a skid-steering wheeled vehicle based-on a laser scanner sensor. The kinematics model is established based on the boundedness of the instantaneous centers of rotation (ICR) of treads on the 2D motion plane...
2015: Sensors
https://www.readbyqxmd.com/read/25853772/comparison-of-hybrid-constructs-with-2-level-artificial-disc-replacement-and-2-level-anterior-cervical-discectomy-and-fusion-for-surgical-reconstruction-of-the-cervical-spine-a-kinematic-study-in-whole-cadavers
#11
COMPARATIVE STUDY
Baoge Liu, Zheng Zeng, Tom Van Hoof, Jean Pierre Kalala, Zhenyu Liu, Bingxuan Wu
BACKGROUND: Multi-level cervical degeneration of the spine is a common clinical pathology that is often repaired by anterior cervical discectomy and fusion (ACDF). The aim of this study was to investigate the kinematics of the cervical spine after hybrid surgery compared with 2-level ACDF. MATERIAL AND METHODS: Five freshly frozen, unembalmed whole human cadavers were used including 3 males and 2 females with a mean age of 51 ± 8 years. After evaluating the intact spine for range of motion (ROM), sagittal alignment and instantaneous center of rotation (ICR), each cadaver underwent 4 consecutive surgeries: 2-level artificial disc replacement (ADR) from C4 to C6 (ADR surgery); 2-level ACDF from C4 to C6 (ACDF surgery); hybrid C4-5 ACDF and C5-6 ADR (ACDF+ADR surgery); and hybrid C4-5 ADR and C5-6 ACDF (ADR+ACDF surgery)...
April 8, 2015: Medical Science Monitor: International Medical Journal of Experimental and Clinical Research
https://www.readbyqxmd.com/read/25675463/design-and-evaluation-of-a-prosthetic-knee-joint-using-the-geared-five-bar-mechanism
#12
Yuanxi Sun, Wenjie Ge, Jia Zheng, Dianbiao Dong
This paper presents the mechanical design, dynamics analysis and ankle trajectory analysis of a prosthetic knee joint using the geared five-bar mechanism. Compared with traditional four-bar or six-bar mechanisms, the geared five-bar mechanism is better at performing diverse movements and is easy to control. This prosthetic knee joint with the geared five-bar mechanism is capable of fine-tuning its relative instantaneous center of rotation and ankle trajectory. The centrode of this prosthetic knee joint, which is mechanically optimized according to the centrode of human knee joint, is better in the bionic performance than that of a prosthetic knee joint using the four-bar mechanism...
November 2015: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/25597813/analyzing-center-of-rotation-during-opening-and-closing-movements-of-the-mandible-using-computer-simulations
#13
COMPARATIVE STUDY
Sug-Joon Ahn, Ling Tsou, C Antonio Sánchez, Sidney Fels, Ho-Beom Kwon
The traditional hinge axis theory for guiding clinical procedures in dentistry and dental articulators has been challenged by the concept of an instantaneous center of rotation (ICR), which is becoming more prevalent in modern explanations of mandibular movement. The purpose of this study was to analyze traditional hinge axis theory using three-dimensional computer simulations and to compare it with ICR. Three-dimensional computational models that reproduced the traditional pantograph tracing method were created to simulate the opening and closing movements of the jaw...
February 26, 2015: Journal of Biomechanics
https://www.readbyqxmd.com/read/25201441/the-effect-of-supraspinatus-tears-on-glenohumeral-translations-in-passive-pitching-motion
#14
Andreas M Mueller, Claudio Rosso, Vahid Entezari, Brett McKenzie, Andrew Hasebroock, Andrea Cereatti, Ugo Della Croce, Ara Nazarian, Arun J Ramappa, Joseph P DeAngelis
BACKGROUND: Supraspinatus tears are common in pitchers. However, the effect of these tears on glenohumeral (GH) mechanics is incompletely understood. PURPOSE/HYPOTHESIS: To describe the effect of supraspinatus tears and repairs on GH kinematics during an abbreviated throwing motion using the intact shoulder girdle. The hypothesis was that supraspinatus tears would lead to an increase of GH translation in the coronal plane and supraspinatus repairs would restore GH kinematics...
October 2014: American Journal of Sports Medicine
https://www.readbyqxmd.com/read/25146896/kinematic-effect-of-chinese-herbal-fomentation-on-patients-with-chronic-neck-pain
#15
RANDOMIZED CONTROLLED TRIAL
Zhen-Yu Liu, Bao-Ge Liu, Xin Lin
OBJECTIVE: To clarify the effectiveness of Chinese herbal fomentation in treating chronic neck pain by means of changes in cervical kinematics. METHODS: Seventy-six patients with chronic neck pain were included in the study and were randomized into two groups based on the random number generator of the SPSS software: fomentation combined with Chinese herbal (Group 1) and fomentation without any medicine (Group 2). In both groups, the fomentation lasted for 60 min and heated to 35 °C, once a day for 28 consecutive days...
December 2014: Chinese Journal of Integrative Medicine
https://www.readbyqxmd.com/read/24979812/pitching-effects-of-buoyancy-during-four-competitive-swimming-strokes
#16
Raymond C Z Cohen, Paul W Cleary, Simon M Harrison, Bruce R Mason, David L Pease
The purpose of this study was to determine the pitching effects of buoyancy during all competitive swimming strokes--freestyle, backstroke, butterfly, and breaststroke. Laser body scans of national-level athletes and synchronized multiangle swimming footage were used in a novel markerless motion capture process to produce three-dimensional biomechanical models of the swimming athletes. The deforming surface meshes were then used to calculate swimmer center-of-mass (CoM) positions, center-of-buoyancy (CoB) positions, pitch buoyancy torques, and sagittal plane moments of inertia (MoI) throughout each stroke cycle...
October 2014: Journal of Applied Biomechanics
https://www.readbyqxmd.com/read/24972979/kinematic-study-of-the-relation-between-the-instantaneous-center-of-rotation-and-degenerative-changes-in-the-cervical-intervertebral-disc
#17
Baoge Liu, Zhenyu Liu, Tom VanHoof, JeanPierre Kalala, Zheng Zeng, Xin Lin
PURPOSE: We located the instantaneous center of rotation (ICR) for the cervical spine at various ages and investigated age-related changes. We evaluated the impact of cervical disc degeneration on the ICR using a scoring system based on plain radiographs. METHODS: Flexion, extension, and neutral lateral radiographs were obtained from 680 asymptomatic subjects (363 men, 317 women; ages 20-79 years) divided into six 10-year-age groups. The ICRs from C3/C4 to C6/C7 were determined from the radiographs using MIMICS software...
November 2014: European Spine Journal
https://www.readbyqxmd.com/read/24922434/frame-frequency-prediction-for-risley-prism-based-imaging-laser-radar
#18
Yafei Lu, Yuan Zhou, Mo Hei, Dapeng Fan
A dual-wedge scanner has potential applications in laser imaging radar. To realize fast scanning imaging without a blind region, the rotation rates of the wedges have to be controlled to perform beam scanning along appropriate track paths. The first-order paraxial approximation method is employed to investigate the 2D scan patterns and path density for different angular frequency ratios of the wedges rotating steadily in the same and opposite directions. The frame rate of no-blind-region scanning imaging is estimated in terms of the imaging coverage requirement...
June 1, 2014: Applied Optics
https://www.readbyqxmd.com/read/24726191/vector-field-statistics-for-objective-center-of-pressure-trajectory-analysis-during-gait-with-evidence-of-scalar-sensitivity-to-small-coordinate-system-rotations
#19
Todd C Pataky, Mark A Robinson, Jos Vanrenterghem, Russell Savage, Karl T Bates, Robin H Crompton
Center of pressure (COP) trajectories summarize the complex mechanical interaction between the foot and a contacted surface. Each trajectory itself is also complex, comprising hundreds of instantaneous vectors over the duration of stance phase. To simplify statistical analysis often a small number of scalars are extracted from each COP trajectory. The purpose of this paper was to demonstrate how a more objective approach to COP analysis can avoid particular sensitivities of scalar extraction analysis. A previously published dataset describing the effects of walking speed on plantar pressure (PP) distributions was re-analyzed...
2014: Gait & Posture
https://www.readbyqxmd.com/read/24650972/point-of-optimal-kinematic-error-improvement-of-the-instantaneous-helical-pivot-method-for-locating-centers-of-rotation
#20
Helios De Rosario, Alvaro Page, Vicente Mata
This paper proposes a variation of the instantaneous helical pivot technique for locating centers of rotation. The point of optimal kinematic error (POKE), which minimizes the velocity at the center of rotation, may be obtained by just adding a weighting factor equal to the square of angular velocity in Woltring׳s equation of the pivot of instantaneous helical axes (PIHA). Calculations are simplified with respect to the original method, since it is not necessary to make explicit calculations of the helical axis, and the effect of accidental errors is reduced...
May 7, 2014: Journal of Biomechanics
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