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Contact force

M Boudissa, H Oliveri, M Chabanas, J Tonetti
Preoperative planning for the management of acetabular fracture is founded on geometric models allowing virtual repositioning of the bone fragments, but not taking account of soft tissue and the realities of the surgical procedure. The present technical note reports results using the first simulator to be based on a patient-specific biomechanical model, simulating the action of forces on the fragments and also the interactions between soft issue and bone: muscles, capsules, ligaments, and bone contacts. In all 14 cases, biomechanical simulation faithfully reproduced the intraoperative behavior of the various bone fragments and reduction quality...
February 16, 2018: Orthopaedics & Traumatology, Surgery & Research: OTSR
Shyam Sunder Salavadhi, Srikanth Chintalapani, Radhika Ramachandran, Kirankumar Nagubandi, Arpita Ramisetti, Ramanarayana Boyapati
Aim: This study aims to ascertain the advantages of Atomic Force Microscopy (AFM) in the morphologic study of microorganisms and their interactions within the subgingival biofilm in patients with gingivitis and periodontitis. Settings and Design: Conducted a study on twenty patients, ten patients with severe periodontitis with probing the pocket depth of ≥8 mm, with a clinical attachment loss (CAL) of ≥6 mm CAL and ten patients with gingivitis: ≥5 mm pocket depth, and no attachment loss, was selected for the study...
July 2017: Journal of Indian Society of Periodontology
Xuegang Xing, Hefeng Wang, Gesheng Xiao, Shangyu Yang, Xuefeng Shu
Surface titanium (Ti) metallization was conducted on alumina (Al 2 O 3 ) through chemical vapor deposition (CVD) method derived from non-contact pack cementation. The effects of different deposition temperature (1000 °C, 1050 °C, and 1100 °C) were examined in this scenario. The morphology, phase composition, and interfacial defects of the resulting films were systematically investigated through scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The nanomechanical characterization of the proposed thin films was evaluated by conducting nano-indentation tests at different depths...
February 1, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Hong Gi Yoon, Hyun Keun Oh, Dong-Yul Lee, Joo-Hee Shin
Objective The purpose of this study was to evaluate, by using finite element analysis, the influence of post location and occlusal loading location on the stress distribution pattern inside the root canals of the mandibular 1st molar. Material and Methods Three different 3-D models of the mandibular 1st molar were established: no post (NP) - a model of endodontic and prosthodontic treatments; mesiobuccal post (MP) - a model of endodontic and prosthodontic treatments with a post in the mesiobuccal canal; and distal post (DP) - a model of endodontic and prosthodontic treatments with a post in the distal canal...
2018: Journal of Applied Oral Science: Revista FOB
Myung-Ku Kim, Jung-Ro Yoon, Se-Hyun Yang, Young-Soo Shin
PURPOSE: Gait analysis is a valuable instrument for measuring function objectively after unicompartmental knee arthroplasty (UKA). However, most gait analysis studies have reported conflicting results for functional assessment after UKA. This meta-analysis compared the gait patterns of UKA patients and healthy controls during level walking. METHODS: Studies were included in the meta-analysis if they recorded vertical ground reaction force (GRF), flexion at initial contact, flexion at loading response, extension at mid-stance, flexion at swing, walking speed, cadence, and stride length in UKA patients or healthy controls...
February 15, 2018: Knee Surgery, Sports Traumatology, Arthroscopy: Official Journal of the ESSKA
Diego Camargo, J A de la Torre, D Duque-Zumajo, Pep Español, Rafael Delgado-Buscalioni, Farid Chejne
Density Functional Theory (DFT) is a successful and well-established theory for the study of the structure of simple and complex fluids at equilibrium. The theory has been generalized to dynamical situations when the underlying dynamics is diffusive as in, for example, colloidal systems. However, there is no such a clear foundation for Dynamic DFT (DDFT) for the case of simple fluids in contact with solid walls. In this work, we derive DDFT for simple fluids by including not only the mass density field but also the momentum density field of the fluid...
February 14, 2018: Journal of Chemical Physics
Varun Vyas, Melani Solomon, Gerard G M D'Souza, Bryan D Huey
The nanomechanical properties of various biological and cellular surfaces are increasingly investigated with Scanning Probe Microscopy. Surface stiffness measurements are currently being used to define metastatic properties of various cancerous cell lines and other related biological tissues. Here we present a unique methodology to understand depth dependent nanomechanical variations in stiffness in biopolymers and live cells. In this study we have used A2780 and NIH3T3 cell lines and 0.5% and 1% Agarose to investigate depth dependent stiffness and porosity on nanomechanical properties in different biological systems...
March 1, 2018: Journal of Nanoscience and Nanotechnology
Madhab Bera, Pragya Gupta, Pradip K Maji
Facile one pot synthesis of graphene oxide (GO) by sonication assisted mechanochemical approach has been reported here. The amalgamation of ultrasonication and mechanical stirring has assisted the synthesis of GO in a short time duration of only 4 hours with good reaction yield. The structural characterization of GO was performed by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectroscopy and Raman spectroscopy. Atomic force microscopic (AFM) analysis manifested the flake like morphology of GO with average sheet thickness ~1...
February 1, 2018: Journal of Nanoscience and Nanotechnology
T Putelat, P Recho, L Truskinovsky
The motility of a cell can be triggered or inhibited not only by an applied force but also by a mechanically neutral force couple. This type of loading, represented by an applied stress and commonly interpreted as either squeezing or stretching, can originate from extrinsic interaction of a cell with its neighbors. To quantify the effect of applied stresses on cell motility we use an analytically transparent one-dimensional model accounting for active myosin contraction and induced actin turnover. We show that stretching can polarize static cells and initiate cell motility while squeezing can symmetrize and arrest moving cells...
January 2018: Physical Review. E
S Bharathraj, V Kumaran
Dense granular flows have been well described by the Bagnold rheology, even when the particles are in the multibody contact regime and the coordination number is greater than 1. This is surprising, because the Bagnold law should be applicable only in the instantaneous collision regime, where the time between collisions is much larger than the period of a collision. Here, the effect of particle stiffness on rheology is examined. It is found that there is a rheological threshold between a particle stiffness of 10^{4}-10^{5} for the linear contact model and 10^{5}-10^{6} for the Hertzian contact model above which Bagnold rheology (stress proportional to square of the strain rate) is valid and below which there is a power-law rheology, where all components of the stress and the granular temperature are proportional to a power of the strain rate that is less then 2...
January 2018: Physical Review. E
Kyle VanderWerf, Weiwei Jin, Mark D Shattuck, Corey S O'Hern
We perform computational studies of static packings of a variety of nonspherical particles including circulo-lines, circulo-polygons, ellipses, asymmetric dimers, dumbbells, and others to determine which shapes form packings with fewer contacts than degrees of freedom (hypostatic packings) and which have equal numbers of contacts and degrees of freedom (isostatic packings), and to understand why hypostatic packings of nonspherical particles can be mechanically stable despite having fewer contacts than that predicted from naive constraint counting...
January 2018: Physical Review. E
Tomohiko G Sano, Hirofumi Wada
When a flat elastic strip is compressed along its axis, it is bent in one of two possible directions via spontaneous symmetry breaking, forming a cylindrical arc. This is a phenomenon well known as Euler buckling. When this cylindrical section is pushed in the other direction, the bending direction can suddenly reverse. This instability is called "snap-through buckling" and is one of the elementary shape transitions in a prestressed thin structure. Combining experiments and theory, we study snap-buckling of an elastic strip with one end hinged and the other end clamped...
January 2018: Physical Review. E
Luca Gagliardi, Olivier Pierre-Louis
We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution...
January 2018: Physical Review. E
Yoshihisa Tanaka, Shinichiro Nakamura, Shinichi Kuriyama, Kohei Nishitani, Hiromu Ito, Moritoshi Furu, Mutsumi Watanabe, Shuichi Matsuda
BACKGROUND: Kinematically aligned total knee arthroplasty is based on the concept to represent the premorbid joint alignment with cruciate-retaining implants, characterized by medial tilt and internal rotation. However, kinematic and kinetic effects of kinematically aligned total knee arthroplasty with posterior-stabilized implants is unknown. The purpose of this study was to examine the effect of medial tilting of the joint line with posterior-stabilized implants. METHODS: A mechanical alignment model, and medial tilt 3° and 5° models were constructed...
February 9, 2018: Clinical Biomechanics
Cheolwoong Ko, Mikyung Yang, Taemin Byun, Sang-Wook Lee
This study proposed a way to design femur fracture fixation plates made of shape memory alloy based on CT (Computed Tomography) images of Korean cadaveric femurs. To this end, 3 major design factors of femur fracture fixation plates (circumference angle, thickness, and inner diameter) were selected based on the contact pressure when a femur fracture fixation plate was applied to a cylinder model using the Taguchi Method. Then the effects of the design factors were analyzed. It was shown that the design factors were statistically significant at a level of p=0...
February 15, 2018: International Journal for Numerical Methods in Biomedical Engineering
Piotr Luczkiewicz, Karol Daszkiewicz, Wojciech Witkowski, Jacek Chróścielewski, Tomasz Ferenc, Boguslaw Baczkowski
OBJECTIVE: The purpose of this study was to evaluate the influence of a change in the meniscus cross sectional shape on its position and on the biomechanics of a knee joint. METHODS: One main finite element model of a left knee joint was created on the basis of MRI images. The model consisted of bones, articular cartilages, menisci and ligaments. Eight variants of this model with an increased or decreased meniscus height were then prepared. Nonlinear static analyses with a fixed flexion/extension movement for a compressive load of 1000 N were performed...
2018: PloS One
Kazutoshi Nakamura, Ichiro Minami, Junichiro Wada, Yasuha Ikawa, Noriyuki Wakabayashi
BACKGROUND: Despite numerous reports describing the relationship between head position and mandibular movement in human subjects, the direction and magnitude of force at the occlusal contacts have not been investigated in relation to head position. OBJECTIVE: To investigate the effect of head position on the direction of occlusal force while subjects performed a tapping movement. METHODS: Twenty-three healthy adult subjects were asked to sit on a chair with their back upright and to perform 15 tapping movements in five different head positions: natural head position (control); forward; backward; and right and left rolled...
February 15, 2018: Journal of Oral Rehabilitation
Zhiqiang Shen, Huilin Ye, Ying Li
For nanoparticle (NP)-based drug delivery platforms, the elasticity of the NPs has a significant influence on their blood circulation time and cellular uptake efficiency. However, due to the complexity of the endocytosis process and the inconsistency in the definition of elasticity for NPs in experiments, the understanding about the receptor-mediated endocytosis process of elastic NPs is still limited. In this work, we developed a coarse-grained molecular dynamics (CGMD) model for elastic NPs. The energy change of the elastic NPs can be precisely controlled by the bond, area, volume and bending potentials of this CGMD model...
February 15, 2018: Physical Chemistry Chemical Physics: PCCP
Umberto Celano, Feng-Chun Hsia, Danielle Vanhaeren, Kristof Paredis, Torbjörn E M Nordling, Josephus G Buijnsters, Thomas Hantschel, Wilfried Vandervorst
Wear mechanisms including fracture and plastic deformation at the nanoscale are central to understand sliding contacts. Recently, the combination of tip-induced material erosion with the sensing capability of secondary imaging modes of AFM, has enabled a slice-and-view tomographic technique named AFM tomography or Scalpel SPM. However, the elusive laws governing nanoscale wear and the large quantity of atoms involved in the tip-sample contact, require a dedicated mesoscale description to understand and model the tip-induced material removal...
February 14, 2018: Scientific Reports
Yao Li, Jingran Bi, Siqi Wang, Tan Zhang, Xiaomeng Xu, Haitao Wang, Shasha Cheng, Bei-Wei Zhu, Mingqian Tan
Significant wastage of residual liquid food, such as milk, yogurt, and honey, in food container has attracted great attention. In this work, a bio-inspired edible super-hydrophobic interface was fabricated using the FDA-approved and edible honeycomb wax, arabic gum, and gelatin by a simple and low-cost method. The bio-inspired edible super-hydrophobic interface showed multiscale structures, which were similar to that of lotus leaf surface. This bio-inspired edible super-hydrophobic interface displayed high contact angles for a variety of liquid foods and the residue of liquid foods could be effectively reduced using the bio-inspired interface...
February 14, 2018: Journal of Agricultural and Food Chemistry
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