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1
Khan, Mahbub H., and G. Charles Clifton. "Proposed development of a damage-resisting Eccentrically Braced Frame with rotational active links." Bulletin of the New Zealand Society for Earthquake Engineering 44, no. 2 (June 30, 2011): 99–107. http://dx.doi.org/10.5459/bnzsee.44.2.99-107.
Анотація:
Eccentrically Braced Frames (EBFs) are widely used seismic-resisting systems, as they allow both strength and stiffness to be optimised while providing good ductility capacity. However, in theory they have a low damage threshold in severe earthquakes and post-earthquake repair of conventional EBFs will be difficult and expensive.
This paper presents the Numerical Integration Time-History (NITH) analysis of two ten storey EBF buildings; one with a conventional active link and the other with a new form of low damage active link based on rotational sliding bolted plates. The low damage active link can be designed to allow rotation only, or to allow both rotation and axial extension. The conventional active link response in terms of displacement, rotation and inelastic demand was well within the range of the rotational active links under the records considered. The analysis shows that average maximum displacement of the building and rotation of the link for both the rotational and the rotational+extension active links was almost identical. The extension of the rotational active link permitting axial extension was less than 1.5 mm. Axial load demands on the collector beams and braces were similar in the case all three active links.
It can be concluded from the analysis that the rotational active link with extension is not required, as the lateral extensions can be accommodated within the rotational plates with nominal clearances in the bolt holes to accommodate the lateral extension.
2
Ghosh, Shantanu, Debabrata Das, Rahul Varshney, and Sumit Nandy. "Orbital extension of trigeminal schwannoma." Journal of Neurosciences in Rural Practice 6, no. 01 (January 2015): 102–4. http://dx.doi.org/10.4103/0976-3147.143214.
Анотація:
ABSTRACTSchwannomas, also known as neurilemmomas, are benign peripheral nerve sheath tumors. Trigeminal schwannomas are rare intracranial tumors. Here, we report a 35-year-old female presenting with an axial proptosis of right eyeball with right-sided III, IV and VI cranial nerve palsy. Her best corrected visual acuity in the right eye was perception of light absent and in the left eye was 20/20. MRI scan revealed a large right-sided heterogeneous, extra-axial middle cranial fossa mass that extended to the intraconal space of right orbit. A diagnosis of intracranial trigeminal nerve schwannoma with right orbital extension was made. Successful surgical excision of the mass with preservation of the surrounding tissues and orbital exenteration was done. Post-operative period was uneventful.
3
Brinkhorst, Michelle, Geert Streekstra, Joost van Rosmalen, Simon Strackee, and Steven Hovius. "Effects of axial load on in vivo scaphoid and lunate kinematics using four-dimensional computed tomography." Journal of Hand Surgery (European Volume) 45, no. 9 (August 3, 2020): 974–80. http://dx.doi.org/10.1177/1753193420943400.
Анотація:
This in vivo study investigated the effect of axial load on lunate and scaphoid kinematics during flexion–extension and radial–ulnar deviation of the uninjured wrist using four-dimensional computed tomography. We found that applying axial load to the wrist results in a more flexed, radially deviated and pronated position of the lunate and scaphoid during flexion–extension of the wrist compared with when no load is applied. A larger pronation and supination range of the lunate and scaphoid was seen when the wrist was flexed and extended under axial load, whereas a larger flexion and extension range of the lunate and scaphoid occurred during radial–ulnar deviation of the wrist when axial load was applied.
4
AMORIM, R., J. BARCELOS-NETO, and A. DE SOUZA DUTRA. "AXIAL-SCHWINGER MODEL." International Journal of Modern Physics A 11, no. 16 (June 30, 1996): 2931–39. http://dx.doi.org/10.1142/s0217751x96001425.
Анотація:
We consider an extension of the axial model where local gauge symmetries are taken into account. The result is a mixing of the axial and Schwinger models. The anomaly of the axial current is calculated by means of the Fujikawa path integral technique and the model is also solved. Besides the well-known features of the particular models (axial and Schwinger) an effective interaction of scalar and gauge fields via a topological current is obtained. This term is responsible for the appearance of massive poles in the propagators that are different from those of both models.
5
Roche, P. H., S. Malca, D. Gambarelli, and W. Pellet. "Giant central neurocytoma with tetraventricular and extra-axial extension." Acta Neurochirurgica 133, no. 1-2 (March 1995): 95–100. http://dx.doi.org/10.1007/bf01404957.
6
Paredes, Manuel, Thomas Stephan, and Hervé Orcière. "Enhanced formulae for determining the axial behavior of cylindrical extension springs." Mechanics & Industry 20, no. 6 (2019): 625. http://dx.doi.org/10.1051/meca/2019067.
Анотація:
Cylindrical extension springs have been commonly exploited in mechanical systems for years and their behavior could be considered as well identified. Nevertheless, it appears that the influence of the loops on the global stiffness is not yet taken into account properly. Moreover, it would be of key interest to analyze how initial tension in extension springs influences the beginning of the load-length curve. The paper investigates these topics using analytical, simulation and experimental approaches in order to help engineers design extension springs with greater accuracy. As a result, the stiffness of the loops has been analytically defined. It enables to calculate the global stiffness of extension springs with more accuracy and it is now possible to determine the effective beginning of the linear load-length relation of extension springs and thus to enlarge the operating range commonly defined by standards. Moreover, until now manufacturers had to define by a try and error process the axial pitch of the body of extension springs in order to obtain the required initial tension. Our study enables for the first time to calculate quickly this key parameter saving time on the manufacturing process of extension springs.
7
Phuntsok, Rinchen, Marcus D. Mazur, Benjamin J. Ellis, Vijay M. Ravindra, and Douglas L. Brockmeyer. "Development and initial evaluation of a finite element model of the pediatric craniocervical junction." Journal of Neurosurgery: Pediatrics 17, no. 4 (April 2016): 497–503. http://dx.doi.org/10.3171/2015.8.peds15334.
Анотація:
OBJECT There is a significant deficiency in understanding the biomechanics of the pediatric craniocervical junction (CCJ) (occiput–C2), primarily because of a lack of human pediatric cadaveric tissue and the relatively small number of treated patients. To overcome this deficiency, a finite element model (FEM) of the pediatric CCJ was created using pediatric geometry and parameterized adult material properties. The model was evaluated under the physiological range of motion (ROM) for flexion-extension, axial rotation, and lateral bending and under tensile loading. METHODS This research utilizes the FEM method, which is a numerical solution technique for discretizing and analyzing systems. The FEM method has been widely used in the field of biomechanics. A CT scan of a 13-month-old female patient was used to create the 3D geometry and surfaces of the FEM model, and an open-source FEM software suite was used to apply the material properties and boundary and loading conditions and analyze the model. The published adult ligament properties were reduced to 50%, 25%, and 10% of the original stiffness in various iterations of the model, and the resulting ROMs for flexion-extension, axial rotation, and lateral bending were compared. The flexion-extension ROMs and tensile stiffness that were predicted by the model were evaluated using previously published experimental measurements from pediatric cadaveric tissues. RESULTS The model predicted a ROM within 1 standard deviation of the published pediatric ROM data for flexion-extension at 10% of adult ligament stiffness. The model's response in terms of axial tension also coincided well with published experimental tension characterization data. The model behaved relatively stiffer in extension than in flexion. The axial rotation and lateral bending results showed symmetric ROM, but there are currently no published pediatric experimental data available for comparison. The model predicts a relatively stiffer ROM in both axial rotation and lateral bending in comparison with flexion-extension. As expected, the flexion-extension, axial rotation, and lateral bending ROMs increased with the decrease in ligament stiffness. CONCLUSIONS An FEM of the pediatric CCJ was created that accurately predicts flexion-extension ROM and axial force displacement of occiput–C2 when the ligament material properties are reduced to 10% of the published adult ligament properties. This model gives a reasonable prediction of pediatric cervical spine ligament stiffness, the relationship between flexion-extension ROM, and ligament stiffness at the CCJ. The creation of this model using open-source software means that other researchers will be able to use the model as a starting point for research.
8
Gao, Bao Kui, Wei Wang, and Xing Qin. "Feasibility Analysis of Reverse Sealed Testing String in HPHT Wells." Applied Mechanics and Materials 556-562 (May 2014): 2761–64. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.2761.
Анотація:
To solve problems met in an offshore High-Pressure High-Temperature (HPHT) well testing, a new technology is put forward—placing seal bore extension above permanent packer, and the upper landing tools being connected with seal bore extension through shear pins. This method gives a reverse position of seal bore extension compared with conventional way in which seal bore extension is below permanent packer. So, the feasibility must be considered. Two technological procedures, testing before cutting pins and testing after cutting pins, are discussed, and the highlight is on axial force and deformation of testing string at crucial moments. Results indicate that this new technology is feasible. Of the two technological procedures, axial force is the key factor when testing before cutting pins and axial deformation is the key factor when testing after cutting pins. Conclusions have been used in an offshore HPHT well testing design.
9
Yang, W., T. C. Fung, K. S. Chian, and C. K. Chong. "3D Mechanical Properties of the Layered Esophagus: Experiment and Constitutive Model." Journal of Biomechanical Engineering 128, no. 6 (May 11, 2006): 899–908. http://dx.doi.org/10.1115/1.2354206.
Анотація:
The identification of a three dimensional constitutive model is useful for describing the complex mechanical behavior of a nonlinear and anisotropic biological tissue such as the esophagus. The inflation tests at the fixed axial extension of 1, 1.125, and 1.25 were conducted on the muscle and mucosa layer of a porcine esophagus separately and the pressure-radius-axial force was recorded. The experimental data were fitted with the constitutive model to obtain the structure-related parameters, including the collagen amount and fiber orientation. Results showed that a bilinear strain energy function (SEF) with four parameters could fit the inflation data at an individual extension very well while a six-parameter model had to be used to capture the inflation behaviors at all three extensions simultaneously. It was found that the collagen distribution was axial preferred in both layers and the mucosa contained more collagen, which were in agreement with the findings through a pair of uniaxial tensile test in our previous study. The model was expected to be used for the prediction of stress distribution within the esophageal wall under the physiological state and provide some useful information in the clinical studies of the esophageal diseases.
10
Schoeftner, Juergen. "Extension of Castigliano’s method for isotropic beams." Acta Mechanica 231, no. 11 (August 19, 2020): 4621–40. http://dx.doi.org/10.1007/s00707-020-02762-z.
Анотація:
Abstract In the present contribution Castigliano’s theorem is extended to find more accurate results for the deflection curves of beam-type structures. The notion extension in the context of the second Castigliano’s theorem means that all stress components are included for the computation of the complementary strain energy, and not only the dominant axial stress and the shear stress. The derivation shows that the partial derivative of the complementary strain energy with respect to a scalar dummy parameter is equal to the displacement field multiplied by the normalized traction vector caused by the dummy load distribution. Knowing the Airy stress function of an isotropic beam as a function of the bending moment, the normal force, the shear force and the axial and vertical load distributions, higher-order formulae for the deflection curves and the cross section rotation are obtained. The analytical results for statically determinate and indeterminate beams for various load cases are validated by analytical and finite element results. Furthermore, the results of the extended Castigliano theory (ECT) are compared to Bernoulli–Euler and Timoshenko results, which are special cases of ECT, if only the energies caused by the bending moment and the shear force are considered. It is shown that lower-order terms for the vertical deflection exist that yield more accurate results than the Timoshenko theory. Additionally, it is shown that a distributed load is responsible for shrinking or elongation in the axial direction.
11
Cano-de-la-Cuerda, Roberto, Lydia Vela-Desojo, Marcos Moreno-Verdú, María del Rosario Ferreira-Sánchez, Yolanda Macías-Macías, and Juan Carlos Miangolarra-Page. "Trunk Range of Motion Is Related to Axial Rigidity, Functional Mobility and Quality of Life in Parkinson’s Disease: An Exploratory Study." Sensors 20, no. 9 (April 27, 2020): 2482. http://dx.doi.org/10.3390/s20092482.
Анотація:
Background: People with Parkinson’s disease (PD) present deficits of the active range of motion (ROM), prominently in their trunk. However, if these deficits are associated with axial rigidity, the functional mobility or health related quality of life (HRQoL), remains unknown. The aim of this paper is to study the relationship between axial ROM and axial rigidity, the functional mobility and HRQoL in patients with mild to moderate PD. Methods: An exploratory study was conducted. Non-probabilistic sampling of consecutive cases was used. Active trunk ROM was assessed by a universal goniometer. A Biodex System isokinetic dynamometer was used to measure the rigidity of the trunk. Functional mobility was determined by the Get Up and Go (GUG) test, and HRQoL was assessed with the PDQ-39 and EuroQol-5D questionnaires. Results: Thirty-six mild to moderate patients with PD were evaluated. Significant correlations were observed between trunk extensors rigidity and trunk flexion and extension ROM. Significant correlations were observed between trunk flexion, extension and rotation ROM and GUG. Moreover, significant correlations were observed between trunk ROM for flexion, extension and rotations (both sides) and PDQ-39 total score. However, these correlations were considered poor. Conclusions: Trunk ROM for flexion and extension movements, measured by a universal goniometer, were correlated with axial extensors rigidity, evaluated by a technological device at 30°/s and 45°/s, and functional mobility. Moreover, trunk ROM for trunk flexion, extension and rotations were correlated with HRQoL in patients with mild to moderate PD.
12
Gonzalez-Blohm, Sabrina A., James J. Doulgeris, Kamran Aghayev, William E. Lee, Andrey Volkov, and Frank D. Vrionis. "Biomechanical analysis of an interspinous fusion device as a stand-alone and as supplemental fixation to posterior expandable interbody cages in the lumbar spine." Journal of Neurosurgery: Spine 20, no. 2 (February 2014): 209–19. http://dx.doi.org/10.3171/2013.10.spine13612.
Анотація:
Object In this paper the authors evaluate through in vitro biomechanical testing the performance of an interspinous fusion device as a stand-alone device, after lumbar decompression surgery, and as supplemental fixation to expandable cages in a posterior lumbar interbody fusion (PLIF) construct. Methods Nine L3–4 human cadaveric spines were biomechanically tested under the following conditions: 1) intact/control; 2) L3–4 left hemilaminotomy with partial discectomy (injury); 3) interspinous spacer (ISS); 4) bilateral pedicle screw system (BPSS); 5) bilateral hemilaminectomy, discectomy, and expandable posterior interbody cages with ISS (PLIF-ISS); and 6) PLIF-BPSS. Each test consisted of 100 N of axial preload with ± 7.5 Nm of torque in flexion-extension, right/left lateral bending, and right/left axial rotation. Significant changes in range of motion (ROM), neutral zone stiffness (NZS), elastic zone stiffness (EZS), and energy loss (EL) were explored among conditions using nonparametric Friedman test and Wilcoxon signed-rank comparisons (p ≤ 0.05). Results The injury increased ROM in flexion (p = 0.01), left bending (p = 0.03), and right/left rotation (p < 0.01) and also decreased NZS in flexion (p = 0.01) and extension (p < 0.01). Both the ISS and BPSS reduced flexion-extension ROM and increased flexion-extension stiffness (NZS and EZS) with respect to the injury and intact conditions (p < 0.05), but the ISS condition provided greater resistance than BPSS in extension for ROM, NZS, and EZS (p < 0.01). The BPSS increased the rigidity (ROM, NZS, and EZS) of the intact model in lateral bending and axial rotation (p ≤ 0.01), except in EZS for left rotation (p = 0.23, Friedman test). The incorporation of posterior cages marginally increased (p = 0.05) the EZS of the BPSS construct in flexion but these interbody devices provided significant stability to the ISS construct in lateral bending and axial rotation for ROM (p = 0.02), in lateral bending for NZS (p = 0.02), and in flexion/axial rotation for EZS (p ≤ 0.03); however, both PLIF constructs demonstrated equivalent ROM and stiffness (p ≥ 0.16), except in lateral bending where the PLIF-BPSS was more stable (p = 0.02). In terms of EL, the injury increased EL in flexion-extension (p = 0.02), the ISS increased EL for lateral bending and axial rotation (p ≤ 0.03), and the BPSS decreased EL in lateral bending (p = 0.02), with respect to the intact condition. The PLIF-ISS decreased lateral bending EL with respect to the ISS condition (p = 0.02), but not enough to be smaller or, at least, equivalent, to that of the PLIF-BPSS construct (p = 0.02). Conclusions The ISS may be a suitable device to provide immediate flexion-extension balance after a unilateral laminotomy, but the BPSS provides greater immediate stability in lateral bending and axial rotation motions. Both PLIF constructs performed equivalently in flexion-extension and axial rotation, but the PLIF-BPSS construct is more resistant to lateral bending motions. Further biomechanical and clinical evidence is required to strongly support the recommendation of a stand-alone interspinous fusion device or as supplemental fixation to expandable posterior interbody cages.
13
Sopon, Mircea, Valentin Oleksik, Mihai Roman, Nicolae Cofaru, Mihaela Oleksik, Cosmin Mohor, Adrian Boicean, and Radu Fleaca. "Biomechanical Study of the Osteoporotic Spine Fracture: Optical Approach." Journal of Personalized Medicine 11, no. 9 (September 11, 2021): 907. http://dx.doi.org/10.3390/jpm11090907.
Анотація:
Background and objectives: Osteoporotic spine fractures represent a significant factor for decreasing quality of life in the elderly female population. Understanding the mechanisms involved in producing these fractures can improve their prevention and treatment. This study presents a biomechanical method to produce a vertebral fracture, conducted on a human spine segment, observing the displacements and strains in the intervertebral disc, endplate, and vertebral body. Materials and Methods: We performed two tests, one corresponding to an extension loading, and the second to an axial loading. Results: The maximum displacement in the target vertebral body presented higher values in the case of the extension as compared to the axial strain where it mainly occurred after the fracture was produced. The strains occurred simultaneously on both discs. In the case of the axial strain, due to the occurrence of the fracture, the maximum value was recorded in the spine body, while in the case of the extensions, it occurred in the neural part of the upper disc. The advantage of this method was that the entire study was an experiment, using optical methods, increasing the precision of the material data input. Conclusions: The research method allowed recording in real time of a larger amount of data from the different components of the spine segment. If there was an extension component of the compression force at the moment of the initial loading, part of this load was absorbed by the posterior column with higher mechanical resistance. After the maximum capacity of the absorption was reached, in both situations the behavior was similar.
14
Schneider, Susanne A., Anthony E. Lang, Elena Moro, Benedikt Bader, Adrian Danek, and Kailash P. Bhatia. "Characteristic head drops and axial extension in advanced chorea-acanthocytosis." Movement Disorders 25, no. 10 (June 11, 2010): 1487–91. http://dx.doi.org/10.1002/mds.23052.
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Kastanos, K., and I. Jakim. "A combined flexion—extension injury of the atlanto-axial complex." Injury 22, no. 6 (November 1991): 488–89. http://dx.doi.org/10.1016/0020-1383(91)90138-5.
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Valentín, Arturo, and Jay D. Humphrey. "Modeling effects of axial extension on arterial growth and remodeling." Medical & Biological Engineering & Computing 47, no. 9 (August 1, 2009): 979–87. http://dx.doi.org/10.1007/s11517-009-0513-5.
17
Shirazi-Adl, A., and G. Drouin. "Nonlinear Gross Response Analysis of a Lumbar Motion Segment in Combined Sagittal Loadings." Journal of Biomechanical Engineering 110, no. 3 (August 1, 1988): 216–22. http://dx.doi.org/10.1115/1.3108434.
Анотація:
A 3-D nonlinear mathematical model is used to analyze the mechanical response of a lumbar L2–3 motion segment including the posterior elements when subjected to combined sagittal plane loads. The loadings consist of axial compression force, anterior and posterior shear forces, and flexion and extension moments. The facet articulation is modelled as a general moving contact problem and the ligaments as a collection of uniaxial elements. The disk nucleus is considered as an inviscid fluid and the annulus as a composite of collagenous fibers embedded in a matrix of ground substance. The presence of axial compression force reduces the segmental stiffness in flexion whereas a reverse trend is predicted in extension. In the presence of axial compression with and without sagittal shear force, flexion considerably increases the intradiscal pressure while extension reduces it. In other words, under an identical compression force, disk pressure is predicted to be noticeably larger in flexion than in extension. The segmental mechanical response in extension loadings is markedly influenced by the changes in the relative geometry of the articular surfaces at the lower regions. Finally, the deformation of the bony structures plays a significant role in the segmental mechanics under relatively large loads.
18
Godzik, Jakub, Bernardo de Andrada Pereira, Anna G. U. Sawa, Jennifer N. Lehrman, Randall J. Hlubek, Brian P. Kelly, and Jay D. Turner. "Impact of dual-headed pedicle screws on the biomechanics of lumbosacral junction multirod constructs." Journal of Neurosurgery: Spine 34, no. 5 (May 2021): 691–99. http://dx.doi.org/10.3171/2020.8.spine191545.
Анотація:
OBJECTIVE The objective of this study was to evaluate a novel connector design and compare it with traditional side connectors, such as a fixed-angle connector (FAC) and a variable-angle connector (VAC), with respect to lumbosacral stability and instrumentation strain. METHODS Standard nondestructive flexibility tests (7.5 Nm) and compression tests (400 N) were performed using 7 human cadaveric specimens (L1–ilium) to compare range of motion (ROM) stability, posterior rod strain (RS), and sacral screw bending moment (SM). Directions of motion included flexion, extension, left and right lateral bending, left and right axial rotation, and compression. Conditions included 1) the standard 2-rod construct (2R); 2) the dual-tulip head (DTH) with 4-rod construct (4R); 3) FACs with 4R; and 4) VACs with 4R. Data were analyzed using repeated-measures ANOVA. RESULTS Overall, there were no statistically significant differences in ROM across the lumbosacral junction among conditions (p > 0.07). Compared with 2R, DTH and FAC significantly reduced RS in extension, left axial rotation, and compression (p ≤ 0.03). VAC significantly decreased RS compared with 2R in flexion, extension, left axial rotation, right axial rotation, and compression (p ≤ 0.03), and significantly decreased RS compared with DTH in extension (p = 0.02). DTH was associated with increased SM in left and right axial rotation compared with 2R (p ≤ 0.003) and in left and right lateral bending and left and right axial rotation compared with FAC and VAC (p ≤ 0.02). FAC and VAC were associated with decreased SM compared with 2R in right and left lateral bending (p ≤ 0.03). CONCLUSIONS RS across the lumbosacral junction can be high. Supplemental rod fixation with DTH is an effective strategy for reducing RS across the lumbosacral junction. However, the greatest reduction in RS and SM was achieved with a VAC that allowed for straight (uncontoured) accessory rod placement.
19
Perez-Guagnelli, Eduardo, Joanna Jones, and Dana D. Damian. "Hyperelastic Membrane Actuators: Analysis of Toroidal and Helical Multifunctional Configurations." Cyborg and Bionic Systems 2022 (February 2, 2022): 1–12. http://dx.doi.org/10.34133/2022/9786864.
Анотація:
Technologies that provide mechanical assistance are required in the medical field, such as implants that regenerate tissue through elongation and stimulation. One of the challenges is to develop actuators that combine the benefits of high axial extension at low pressures, modularity, multifunction, and load-bearing capabilities into one design while maintaining their shape and softness. Overcoming such a challenge will provide implants with enhanced capacity for mechanical assistance to induce tissue regeneration. We introduce two novel actuators (M2H) built of stacked Hyperelastic Ballooning Membrane Actuators (HBMAs) that can be realized using helical and toroidal configurations. By restraining the HBMA expansion deterministically using a semisoft exoskeleton, the actuators are endowed with axial extension and radial expansion capabilities. These actuators are thus built of modules that can be configured to different therapeutical needs and multifunctionality, to provide anatomically congruent stimulation. We present the design, fabrication, testing, and numerical and experimental validation of the M2H-HBMAs. They can axially extend up to 41% and 32% in their helical and toroidal configurations at input pressures as low as 26 and 24 kPa, respectively. If the axial extension module is used separately, its extension capacity reaches >170%. The M2H-HBMAs can perform independent and simultaneous expansion and extension motions with negligible intraluminal deformation as well as stand at least 1 kg of axial force without collapsing. The M2H-HBMAs overcome the limitations of hyperexpanding machines that show low resistance to load. We envisage M2H-HBMAs as promising tools to perform tissue regeneration procedures.
20
Levy, A. J. "The Fiber Composite With Nonlinear Interface—Part I: Axial Tension." Journal of Applied Mechanics 67, no. 4 (June 25, 2000): 727–32. http://dx.doi.org/10.1115/1.1329319.
Анотація:
This paper treats the effective axial tension response of a composite consisting of fibers that debond from the matrix according to nonlinear Needleman-type cohesive zones. A second, related paper (Part II) treats effective antiplane shear response. The composite cylinders representation of a representative volume element (RVE) is employed throughout. For axial tension loading a simple rotationally symmetric boundary value problem for a single composite cylinder is solved. Bounds on the total potential energy and the total complementary energy are shown to coincide and an exact solution for axial extension and Poisson contraction of an RVE of the composite is obtained. Nonlinear interfacial debonding, however, is shown to have a negligible effect on extensional response and only a small, though potentially destabilizing, effect on Poisson contraction response. [S0021-8936(00)02004-3]
21
Finley, Sean M., J. Harley Astin, Evan Joyce, Andrew T. Dailey, Douglas L. Brockmeyer, and Benjamin J. Ellis. "FEBio finite element model of a pediatric cervical spine." Journal of Neurosurgery: Pediatrics 29, no. 2 (February 1, 2022): 218–24. http://dx.doi.org/10.3171/2021.7.peds21276.
Анотація:
OBJECTIVE The underlying biomechanical differences between the pediatric and adult cervical spine are incompletely understood. Computational spine modeling can address that knowledge gap. Using a computational method known as finite element modeling, the authors describe the creation and evaluation of a complete pediatric cervical spine model. METHODS Using a thin-slice CT scan of the cervical spine from a 5-year-old boy, a 3D model was created for finite element analysis. The material properties and boundary and loading conditions were created and model analysis performed using open-source software. Because the precise material properties of the pediatric cervical spine are not known, a published parametric approach of scaling adult properties by 50%, 25%, and 10% was used. Each scaled finite element model (FEM) underwent two types of simulations for pediatric cadaver testing (axial tension and cardinal ranges of motion [ROMs]) to assess axial stiffness, ROM, and facet joint force (FJF). The authors evaluated the axial stiffness and flexion-extension ROM predicted by the model using previously published experimental measurements obtained from pediatric cadaveric tissues. RESULTS In the axial tension simulation, the model with 50% adult ligamentous and annulus material properties predicted an axial stiffness of 49 N/mm, which corresponded with previously published data from similarly aged cadavers (46.1 ± 9.6 N/mm). In the flexion-extension simulation, the same 50% model predicted an ROM that was within the range of the similarly aged cohort of cadavers. The subaxial FJFs predicted by the model in extension, lateral bending, and axial rotation were in the range of 1–4 N and, as expected, tended to increase as the ligament and disc material properties decreased. CONCLUSIONS A pediatric cervical spine FEM was created that accurately predicts axial tension and flexion-extension ROM when ligamentous and annulus material properties are reduced to 50% of published adult properties. This model shows promise for use in surgical simulation procedures and as a normal comparison for disease-specific FEMs.
22
Reis, Marco T., Phillip M. Reyes, Idris Altun, Anna G. U. S. Newcomb, Vaneet Singh, Steve W. Chang, Brian P. Kelly, and Neil R. Crawford. "Biomechanical evaluation of lateral lumbar interbody fusion with secondary augmentation." Journal of Neurosurgery: Spine 25, no. 6 (December 2016): 720–26. http://dx.doi.org/10.3171/2016.4.spine151386.
Анотація:
OBJECTIVE Lateral lumbar interbody fusion (LLIF) has emerged as a popular method for lumbar fusion. In this study the authors aimed to quantify the biomechanical stability of an interbody implant inserted using the LLIF approach with and without various supplemental fixation methods, including an interspinous plate (IP). METHODS Seven human cadaveric L2–5 specimens were tested intact and in 6 instrumented conditions. The interbody implant was intended to be used with supplemental fixation. In this study, however, the interbody was also tested without supplemental fixation for a relative comparison of these conditions. The instrumented conditions were as follows: 1) interbody implant without supplemental fixation (LLIF construct); and interbody implant with supplemental fixation performed using 2) unilateral pedicle screws (UPS) and rod (LLIF + UPS construct); 3) bilateral pedicle screws (BPS) and rods (LLIF + BPS construct); 4) lateral screws and lateral plate (LP) (LLIF + LP construct); 5) interbody LP and IP (LLIF + LP + IP construct); and 6) IP (LLIF + IP construct). Nondestructive, nonconstraining torque (7.5 Nm maximum) induced flexion, extension, lateral bending, and axial rotation, whereas 3D specimen range of motion (ROM) was determined optoelectronically. RESULTS The LLIF construct reduced ROM by 67% in flexion, 52% in extension, 51% in lateral bending, and 44% in axial rotation relative to intact specimens (p < 0.001). Adding BPS to the LLIF construct caused ROM to decrease by 91% in flexion, 82% in extension and lateral bending, and 74% in axial rotation compared with intact specimens (p < 0.001), providing the greatest stability among the constructs. Adding UPS to the LLIF construct imparted approximately one-half the stability provided by LLIF + BPS constructs, demonstrating significantly smaller ROM than the LLIF construct in all directions (flexion, p = 0.037; extension, p < 0.001; lateral bending, p = 0.012) except axial rotation (p = 0.07). Compared with the LLIF construct, the LLIF + LP had a significant reduction in lateral bending (p = 0.012), a moderate reduction in axial rotation (p = 0.18), and almost no benefit to stability in flexion-extension (p = 0.86). The LLIF + LP + IP construct provided stability comparable to that of the LLIF + BPS. The LLIF + IP construct provided a significant decrease in ROM compared with that of the LLIF construct alone in flexion and extension (p = 0.002), but not in lateral bending (p = 0.80) and axial rotation (p = 0.24). No significant difference was seen in flexion, extension, or axial rotation between LLIF + BPS and LLIF + IP constructs. CONCLUSIONS The LLIF construct that was tested significantly decreased ROM in all directions of loading, which indicated a measure of inherent stability. The LP significantly improved the stability of the LLIF construct in lateral bending only. Adding an IP device to the LLIF construct significantly improves stability in sagittal plane rotation. The LLIF + LP + IP construct demonstrated stability comparable to that of the gold standard 360° fixation (LLIF + BPS).
23
Qiu, Tian-Xia, Ee-Chon Teo, and Qing-Hang Zhang. "VALIDATION OF FINITE ELEMENT MODELS OF THORACOLUMBAR T11-T12 AND T12-L1 AND COMPARISON OF THEIR BIOMECHANICAL RESPONSES." Journal of Musculoskeletal Research 09, no. 03 (September 2005): 133–43. http://dx.doi.org/10.1142/s0218957705001576.
Анотація:
The objective of this study was to build and validate the FE models of thoracolumbar junctional T11-T12 and T12-L1 functional spinal units (FSUs) and compare the biomechanical responses of the two FSUs under physiological loading modes: flexion, extension, lateral bending and axial rotation. Anatomically accurate FE models of thoracolumbar T11-T12 and T12-L1 FSUs were developed and validated against published experimental results in terms of load displacement responses and range of motion (ROM) under flexion and extension pure moments of 7.5 Nm, left and right lateral bending pure moments of 7.5 Nm and left and right axial torque of 7.5 Nm. The overall responses predicted by the T11-T12 and T12-L1 FE models showed differences in stiffness under different load configurations. Amongst all loading configurations, the motions at T11-T12 and T12-L1 were the stiffest under axial torque. The lateral bending motions of T11-T12 and T12-L1 were relatively flexible. Under sagittal moments, the motion in extension was greater than in flexion at level T11-T12, while the rotation in flexion was greater than in extension at level T12-L1.
24
Reis, Marco T., Phillip M. Reyes, and Neil R. Crawford. "Biomechanical Assessment of Anchored Cervical Interbody Cages: Comparison of 2-Screw and 4-Screw Designs." Operative Neurosurgery 10, no. 3 (September 1, 2014): 412–17. http://dx.doi.org/10.1227/neu.0000000000000351.
Анотація:
Abstract BACKGROUND: A new anchored cervical interbody polyetheretherketone spacer was devised that uses only 2 integrated variable-angle screws diagonally into the adjacent vertebral bodies instead of the established device that uses 4 diagonal fixed-angle screws. OBJECTIVE: To compare in vitro the stability provided by the new 2-screw interbody spacer with that of the 4-screw spacer and a 4-screw anterior plate plus independent polyetheretherketone spacer. METHODS: Three groups of cadaveric specimens were tested with 2-screw anchored cage (n = 8), 4-screw anchored cage (n = 8), and standard plate/cage (n = 16). Pure moments (1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while measuring 3-D motion optoelectronically. RESULTS: In all 3 groups, the mean range of motion (ROM) and lax zone were significantly reduced relative to the intact spine after discectomy and fixation. The 2-screw anchored cage allowed significantly greater ROM (P < .05) than the standard plate during flexion, extension, and axial rotation and allowed significantly greater ROM than the 4-screw cage during extension and axial rotation. The 4-screw anchored cage did not allow significantly different ROM or lax zone than the standard plate during any loading mode. CONCLUSION: The 2-screw variable-angle anchored cage significantly reduces ROM relative to the intact spine. Greater stability can be achieved, especially during extension and axial rotation, by using the 4-screw cage or standard plate plus cage.
25
Doğan, Şeref, Seungwon Baek, Volker K. H. Sonntag, and Neil R. Crawford. "Biomechanical Consequences of Cervical Spondylectomy Versus Corpectomy." Operative Neurosurgery 63, suppl_4 (October 1, 2008): ONS303—ONS308. http://dx.doi.org/10.1227/01.neu.0000327569.03654.96.
Анотація:
Abstract Objective: To evaluate the differences in spinal stability and stabilizing potential of instrumentation after cervical corpectomy and spondylectomy. Methods: Seven human cadaveric specimens were tested: 1) intact; 2) after grafted C5 corpectomy and anterior C4–C6 plate; 3) after adding posterior C4–C6 screws/rods; 4) after extending posteriorly to C3–C7; 5) after grafted C5 spondylectomy, anterior C4–C6 plate, and posterior C4–C6 screws/rods; and 6) after extending posteriorly to C3–C7. Pure moments induced flexion, extension, lateral bending, and axial rotation; angular motion was recorded optically. Results: After corpectomy, anterior plating alone reduced the angular range of motion to a mean of 30% of normal, whereas added posterior short- or long-segment hardware reduced range of motion significantly more (P < 0.003), to less than 5% of normal. Constructs with posterior rods spanning C3–C7 were stiffer than constructs with posterior rods spanning C4–C6 during flexion, extension, and lateral bending (P < 0.05), but not during axial rotation (P > 0.07). Combined anterior and C4–C6 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during lateral bending (P = 0.019) and axial rotation (P = 0.001). Combined anterior and C3–C7 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during extension (P = 0.030) and axial rotation (P = 0.0001). Conclusion: Circumferential fixation provides more stability than anterior instrumentation alone after cervical corpectomy. After corpectomy or spondylectomy, long circumferential instrumentation provides better stability than short circumferential fixation except during axial rotation. Circumferential fixation more effectively prevents axial rotation after corpectomy than after spondylectomy.
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Мокряков, Вячеслав Викторович. "Localization of maximal stresses in axisymmetric waves in elastic rods for positive Poisson’s ratio." Вестник Чувашского государственного педагогического университета им. И.Я. Яковлева. Серия: Механика предельного состояния, no. 2(44) (December 14, 2020): 95–100. http://dx.doi.org/10.37972/chgpu.2020.44.2.010.
Анотація:
Рассмотрены максимальные напряжения в осесимметричных волнах в упругих стержнях для положительных значений коэффициента Пуассона. Обнаружена особая длина волны, для которой имеет место наибольшее значение максимального растяжения на оси по отношению к максимальному растяжению на поверхности. Показано, что и особая длина волна, и наибольшее значение отношений растяжений не зависят от коэффициента Пуассона. The maximum stresses in axisymmetric waves in elastic rods for positive values of the Poisson’s ratio are considered. A special wavelength has been found for which the ratio of axial maximal extension to surface maximal extension has the largest value. It is shown that both the special wavelength and the largest value of the extensions ratio are independent of the Poisson’s ratio.
27
Vishteh, A. Giancarlo, Neil R. Crawford, M. Stephen Melton, Robert F. Spetzler, Volker K. H. Sonntag, and Curtis A. Dickman. "Stability of the craniovertebral junction after unilateral occipital condyle resection: a biomechanical study." Journal of Neurosurgery: Spine 90, no. 1 (January 1999): 91–98. http://dx.doi.org/10.3171/spi.1999.90.1.0091.
Анотація:
Object. The authors sought to determine the biomechanics of the occipitoatlantal (occiput [Oc]—C1) and atlantoaxial (C1–2) motion segments after unilateral gradient condylectomy. Methods. Six human cadaveric specimens (skull with attached upper cervical spine) underwent nondestructive biomechanical testing (physiological loads) during flexion—extension, lateral bending, and axial rotation. Axial translation from tension to compression was also studied across Oc—C2. Each specimen served as its own control and underwent baseline testing in the intact state. The specimens were then tested after progressive unilateral condylectomy (25% resection until completion), which was performed using frameless stereotactic guidance. At Oc—C1 for all motions that were tested, mobility increased significantly compared to baseline after a 50% condylectomy. Flexion—extension, lateral bending, and axial rotation increased 15.3%, 40.8%, and 28.1%, respectively. At C1–2, hypermobility during flexion—extension occurred after a 25% condylectomy, during axial rotation after 75% condylectomy, and during lateral bending after a 100% condylectomy. Conclusions. Resection of 50% or more of the occipital condyle produces statistically significant hypermobility at Oc—C1. After a 75% resection, the biomechanics of the Oc—C1 and C1–2 motion segments change considerably. Performing fusion of the craniovertebral junction should therefore be considered if half or more of one occipital condyle is resected.
28
Tronnolone, Hayden, Yvonne M. Stokes, Herbert Tze Cheung Foo, and Heike Ebendorff-Heidepriem. "Gravitational extension of a fluid cylinder with internal structure." Journal of Fluid Mechanics 790 (February 3, 2016): 308–38. http://dx.doi.org/10.1017/jfm.2016.11.
Анотація:
Motivated by the fabrication of microstructured optical fibres, a model is presented for the extension under gravity of a slender fluid cylinder with internal structure. It is shown that the general problem decouples into a two-dimensional surface-tension-driven Stokes flow that governs the transverse shape and an axial problem that depends upon the transverse flow. The problem and its solution differ from those obtained for fibre drawing, because the problem is unsteady and the fibre tension depends on axial position. Solutions both with and without surface tension are developed and compared, which show that the relative importance of surface tension depends upon both the parameter values and the geometry under consideration. The model is compared with experimental data and is shown to be in good agreement. These results also show that surface-tension effects are essential to accurately describing the cross-sectional shape.
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Little, Andrew S., Luis Perez-Orribo, Nestor G. Rodriguez-Martinez, Phillip M. Reyes, Anna G. U. S. Newcomb, Daniel M. Prevedello, and Neil R. Crawford. "Biomechanical evaluation of the craniovertebral junction after inferior-third clivectomy and intradural exposure of the foramen magnum: implications for endoscopic endonasal approaches to the cranial base." Journal of Neurosurgery: Spine 18, no. 4 (April 2013): 327–32. http://dx.doi.org/10.3171/2013.1.spine12835.
Анотація:
Object Endoscopic endonasal approaches to the craniovertebral junction (CVJ) and clivus are increasingly performed for ventral skull-base pathology, but the biomechanical implications of these approaches have not been studied. The aim of this study was to investigate the spinal biomechanics of the CVJ after an inferior-third clivectomy and anterior intradural exposure of the foramen magnum as would be performed in an endonasal endoscopic surgical strategy. Methods Seven upper-cervical human cadaveric specimens (occiput [Oc]–C2) underwent nondestructive biomechanical flexibility testing during flexion-extension, axial rotation, and lateral bending at Oc–C1 and C1–2. Each specimen was tested intact, after an inferior-third clivectomy, and after ligamentous complex dissection simulating a wide intradural exposure using an anterior approach. Angular range of motion (ROM), lax zone, and stiff zone were determined and compared with the intact state. Results Modest, but statistically significant, hypermobility was observed after inferior-third clivectomy and intradural exposure during flexion-extension and axial rotation at Oc–C1. Angular ROM increased incrementally between 6% and 12% in flexion-extension and axial rotation. These increases were primarily the result of changes in the lax zone. No significant changes were noted at C1–2. Conclusions Inferior-third clivectomy and an intradural exposure to the ventral CVJ and foramen magnum resulted in hypermobility at Oc–C1 during flexion-extension and axial rotation. Although the results were statistically significant, the modest degree of hypermobility observed compared with other well-characterized CVJ injuries suggests that occipitocervical stabilization may be unnecessary for most patients.
30
Francioni, Mirko, Paolo Pace, Milena Vitulli, Nicola Sciarra, and Fernando Calamita. "Distribution of joints in the hinge-line culmination of foreland-verging overturned anticlines: an example from the Montagna dei Fiori structure in the Central Apennines of Italy." Geological Magazine 156, no. 08 (March 5, 2019): 1445–54. http://dx.doi.org/10.1017/s0016756819000050.
Анотація:
AbstractThe distribution of joints, veins and shear fractures in the Montagna dei Fiori overturned anticline is here reported. Two joint sets, longitudinal and transverse to the NNW–SSE anticline axial trend, and a conjugate system of shear fractures, are recognized. The transverse and longitudinal joint sets have a pre-folding development likely related to the foreland/foredeep flexure. The transverse joints were reopened during layer-parallel shortening along with the development of the shear fractures. Then, during syn-folding outer-arc extension and hinge-line culmination fold-axial parallel extension, both the longitudinal and transverse joints were enhanced and reactivated, respectively.
31
Sun, Qian Qian, Yun Zou, and Qiang Wang. "Nonlinear Numerical Analysis of Transfer Column in SRC-RC Hybrid Structure." Applied Mechanics and Materials 578-579 (July 2014): 936–39. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.936.
Анотація:
Nonlinear numerical analysis of the stress performance of SRC-RC transfer columns was carried out in this paper with the finite element software of ABAQUS. Compered with the experimental result , numerical analysis result are found to be reasonable.Then the influence of factors such as extension length of shape steel , area ratio of shape steel and axial-load ratio were contrastively analyzed . The results show that extension length of shape steel and the area ratio of shape steel have a greater influence on the bearing capacity and the hysteretic performance of transfer column ,but axial-load ratio has less influence .
32
Sensusiati, Anggraini Dwi. "Magnetic Resonance Imaging of Extra-axial Tumor." Jurnal Radiologi Indonesia 3, no. 2 (September 9, 2019): 53–57. http://dx.doi.org/10.33748/jradidn.v3i2.67.
Анотація:
The first step in making decision of intra-cranial tumors is the location of tumor, whether intra- or extra-axial. After localized the lesion we make differential diagnosis that relevant to the location. Once we made the decision, we make the characterization of the tumors. With MRI it is easier to make this decision compared to CT.Meningiomas constitute the most common extra-axial tumors of the brain. Contrast-enhanced MRI can easily detect the location of the tumor, the full extension of the tumor, sinus invasion and/or thrombosis, vascularity, intra-cranial edema, and intra-osseous extension. WHO grades meningiomas in 3 types which are typical, atypical, and malignant meningioma. With structural MRI, MR Spectroscopy, MR perfusion and some methods we can grade this type.Tumors of neurogenic origin such as schwannomas, neurofibromas, neuromas may be similar in appearance. MRI can help distinguishing these tumors with meningiomas. Another extra-axial lesion located in bone or arachnoid is metastases. Contrast-enhanced T2-FLAIR can easily detect these lesions, but inflammatory lesions may also simulate dural metastase. Other extra-axial tumors are choroid plexus masses, non-neoplastic masses (epidermoids, dermoids, teratomas, lipomas). The location as well as specific appearances on imaging will guide us to a specific diagnosis.
33
Joo, Jin-Ho, Hye-Jee Kim, In-Ki Park, and Jae-Ho Shin. "A Case of Extra-axial Anaplastic Meningioma with Direct Orbital Extension." Journal of the Korean Ophthalmological Society 57, no. 11 (2016): 1781. http://dx.doi.org/10.3341/jkos.2016.57.11.1781.
34
Ninomiya, Hiromasa, Richard P. Elinson, and Rudolf Winklbauer. "Antero-posterior tissue polarity links mesoderm convergent extension to axial patterning." Nature 430, no. 6997 (July 2004): 364–67. http://dx.doi.org/10.1038/nature02620.
35
Edri, Shlomit, Penny Hayward, Peter Baillie-Johnson, Benjamin J. Steventon, and Alfonso Martinez Arias. "An epiblast stem cell-derived multipotent progenitor population for axial extension." Development 146, no. 10 (April 25, 2019): dev168187. http://dx.doi.org/10.1242/dev.168187.
36
Aron, M. "Combined axial shearing, extension, and straightening of elastic annular cylindrical sectors." IMA Journal of Applied Mathematics 70, no. 1 (December 17, 2004): 53–63. http://dx.doi.org/10.1093/imamat/hxh059.
37
Argenton, A., and A. Maccagni. "Possible axial extension in the Gulf of Suez rift (work hypothesis)." Tectonophysics 153, no. 1-4 (October 1988): 297–306. http://dx.doi.org/10.1016/0040-1951(88)90022-4.
38
Beck, Felix, and Emma J. Stringer. "The role of Cdx genes in the gut and in axial development." Biochemical Society Transactions 38, no. 2 (March 22, 2010): 353–57. http://dx.doi.org/10.1042/bst0380353.
Анотація:
The Cdx (Caudal-type homeobox) group of ParaHox genes (Cdx1, Cdx2 and Cdx4 in the mouse) perform multiple functions in mammalian development. Cdx1 is concerned with axial positional information, and its deletion appears to have no important effect other than a disturbance of axial patterning. In contrast, Cdx2 is required for trophoblast differentiation, axial patterning and extension, as well as for morphological specification (i.e. patterning) of gut endoderm. Cdx4-knockout animals do not present an abnormal phenotype, but, when combined with Cdx2 haploinsufficiency, present a dramatic picture involving abnormal cloacal specification. The latter is probably due in large part to defective paraxial mesodermal development in the caudal region, but may also involve defective endodermal growth. A significant degree of redundancy is apparent between the Cdx genes with respect to caudal extension and possibly also during gut development.
39
Bishop, Frank S., Mical M. Samuelson, Michael A. Finn, Kent N. Bachus, Darrel S. Brodke, and Meic H. Schmidt. "The biomechanical contribution of varying posterior constructs following anterior thoracolumbar corpectomy and reconstruction." Journal of Neurosurgery: Spine 13, no. 2 (August 2010): 234–39. http://dx.doi.org/10.3171/2010.3.spine09267.
Анотація:
Object Thoracolumbar corpectomy is a procedure commonly required for the treatment of various pathologies involving the vertebral body. Although the biomechanical stability of anterior reconstruction with plating has been studied, the biomechanical contribution of posterior instrumentation to anterior constructs remains unknown. The purpose of this study was to evaluate biomechanical stability after anterior thoracolumbar corpectomy and reconstruction with varying posterior constructs by measuring bending stiffness for the axes of flexion/extension, lateral bending, and axial rotation. Methods Seven fresh human cadaveric thoracolumbar spine specimens were tested intact and after L-1 corpectomy and strut grafting with 4 different fixation techniques: anterior plating with bilateral, ipsilateral, contralateral, or no posterior pedicle screw fixation. Bending stiffness was measured under pure moments of ± 5 Nm in flexion/extension, lateral bending, and axial rotation, while maintaining an axial preload of 100 N with a follower load. Results for each configuration were normalized to the intact condition and were compared using ANOVA. Results Spinal constructs with anterior-posterior spinal reconstruction and bilateral posterior pedicle screws were significantly stiffer in flexion/extension than intact spines or spines with anterior plating alone. Anterior plating without pedicle screw fixation was no different from the intact spine in flexion/extension and lateral bending. All constructs had reduced stiffness in axial rotation compared with intact spines. Conclusions The addition of bilateral posterior instrumentation provided significantly greater stability at the thoracolumbar junction after total corpectomy than anterior plating and should be considered in cases in which anterior column reconstruction alone may be insufficient. In cases precluding bilateral posterior fixation, unilateral posterior instrumentation may provide some additional stability.
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Urbonas, Kestutis, and Alfonsas Daniūnas. "COMPONENT METHOD EXTENSION TO STEEL BEAM‐TO‐BEAM AND BEAM‐TO‐COLUMN KNEE JOINTS UNDER BENDING AND AXIAL FORCES." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 11, no. 3 (September 30, 2005): 217–24. http://dx.doi.org/10.3846/13923730.2005.9636353.
Анотація:
This paper presents an analysis of semi‐rigid beam‐to‐beam end‐plate bolted and beam‐to‐column end‐plate bolted knee joints that are subjected to bending and tension or compression axial force. Usually the influence of axial force on joint rigidity is neglected. According to EC3, the axial load, which is less than 10 % of plastic resistance of the connected member under axial force, may be disregarded in the design of joint. Actually the level of axial forces in joints of structures may be significant and has a significant influence on joint rigidity. One of the most popular practical method permitting the determination of rigidity and strength of joint is the so‐called component method. The extension of the component method for evaluating the influence of bending moment and axial force on the rigidity and strength of the joint are presented in the paper. The numerical results of calculations of rigidity and strength of beam-to-beam and beam-to-column knee joints are presented in this paper as well.
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Saxena, Shashank, Darius Diogo Barreto, and Ajeet Kumar. "Extension–torsion–inflation coupling in compressible electroelastomeric thin tubes." Mathematics and Mechanics of Solids 25, no. 3 (November 28, 2019): 644–63. http://dx.doi.org/10.1177/1081286519886901.
Анотація:
We present an axisymmetric and axially homogeneous variational formulation to obtain coupled extension–torsion–inflation deformation in compressible electroelastomeric tubes in the presence of axial and radial electric fields. We show that such deformations occur under the following two conditions: (1) only the axial electric field is imposed, with the electric poling direction in the tube (if present) lying in the radial plane; and (2) only the radial electric field is imposed within the tube, with the electric poling direction (if present) also along the radial direction. The poling direction in condition (1) generates helical anisotropy in the tube. We then obtain the governing differential equations necessary to solve the above deformation problem for thick tubes. We further apply the thin tube limit to obtain simplified algebraic equations to solve the same deformation problem. The effect of applied electric field parameters on the extension–inflation coupling and induced internal pressure vs. imposed inflation behavior is finally presented through numerical solution of the above obtained algebraic equations. The study will be useful in designing soft electroelastic tubular actuators.
42
Yin Wei, Chris Chan, Sem Sei Haw, Elrofai Suliman Bashir, Saw Lim Beng, Rukmanikanthan Shanmugam, and Kwan Mun Keong. "Biomechanical comparison between cortical screw–rod construct versus pedicle screw–rod construct in transforaminal lumbar interbody fusion." Journal of Orthopaedic Surgery 25, no. 1 (January 1, 2017): 230949901769065. http://dx.doi.org/10.1177/2309499017690656.
Анотація:
Objective: To compare construct stiffness of cortical screw (CS)-rod transforaminal lumbar interbody fusion (TLIF) construct (G2) versus pedicle screw (PS)-rod TLIF construct (G1) in the standardized porcine lumbar spine. Methods: Six porcine lumbar spines (L2–L5) were separated into 12 functional spine units. Bilateral total facetectomies and interlaminar decompression were performed for all specimens. Non-destructive loading to assess stiffness in lateral bending, flexion and extension as well as axial rotation was performed using a universal material testing machine. Results: PS and CS constructs were significantly stiffer than the intact spine except in axial rotation. Using the normalized ratio to the intact spine, there is no significant difference between the stiffness of PS and CS: flexion (1.41 ± 0.27, 1.55 ± 0.32), extension (1.98 ± 0.49, 2.25 ± 0.44), right lateral flexion (1.93 ± 0.57, 1.55 ± 0.30), left lateral flexion (2.00 ± 0.73, 2.16 ± 0.20), right axial rotation (0.99 ± 0.21, 0.83 ± 0.26) and left axial rotation (0.96 ± 0.22, 0.92 ± 0.25). Conclusion: The CS-rod TLIF construct provided comparable construct stiffness to a traditional PS-rod TLIF construct in a ‘standardized’ porcine lumbar spine model.
43
Fuschi, P., and C. Polizzotto. "Interaction Diagram of a Circular Bar in Torsion and Extension." Journal of Applied Mechanics 62, no. 1 (March 1, 1995): 233–35. http://dx.doi.org/10.1115/1.2895910.
Анотація:
For a circular bar of perfectly plastic material and subjected to a cyclically variable torque and a constant axial force, the interaction (or generalized Bree) diagram is derived by a direct method in which Melan’s theorem is used to locate the nonratchetting load boundary.
44
Bin-Shuwaish, M., J. B. Dennison, P. Yaman, and G. Neiva. "Estimation of Clinical Axial Extension of Class II Caries Lesions with Ultraspeed and Digital Radiographs: An In-vivo Study." Operative Dentistry 33, no. 6 (January 1, 2008): 613–21. http://dx.doi.org/10.2341/07-167.
Анотація:
Clinical Relevance Both Ultraspeed and RVG-6000 radiographs underestimated the true clinical extension of Class II caries lesions; however, the RVG-6000 was more accurate in estimating the axial extension of a lesion than Ultraspeed films. Placement of Ultraspeed film was more pleasant for the patient than the RVG-6000 size 2 sensor.
45
Hursin, Mathieu, and Tatjana Jevremovic. "Agent code: Neutron transport benchmark example and extension to 3D lattice geometry." Nuclear Technology and Radiation Protection 20, no. 2 (2005): 10–16. http://dx.doi.org/10.2298/ntrp0502010h.
Анотація:
The general methodology be hind 2D arbitrary geometry neutron transport AGENT code is the theory of R-functions, which al lows for simple modeling of complex geometries, and the method of characteristics, which solves the integral transport equation along characteristic neutron trajectories. This paper focuses on the extension of the methodology to ac count for 3D lattice geometries. Since the direct application of method of characteristics to 3D non-homogenized core con figuration may re quire a tremendous amount of memory and computing time, an alternative approximate solution based on coupling 2D method of characteristics and 1D diffusion solution is developed. The planar 2D method of characteristics and axial 1D diffusion solutions are coupled through the trans verse leak age. The use of a lower order 1D solution in the axial direction is justified by the fact that more heterogeneity in current PWR and BWR reactor cores occurs in the radial direction than in the axial one. In order to demonstrate the versatility and accuracy of the AGENT code, a 2D heterogeneous lattice problem, C5G7 is described in details. A theoretical description of the coupling methodology for 3D method of characteristics solution is followed by preliminary validation in comparison to the DeCART code.
46
Zhu, Q. A., Y. B. Park, S. G. Sjovold, C. A. Niosi, D. C. Wilson, P. A. Cripton, and T. R. Oxland. "Can extra-articular strains be used to measure facet contact forces in the lumbar spine? An in-vitro biomechanical study." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 222, no. 2 (February 1, 2008): 171–84. http://dx.doi.org/10.1243/09544119jeim290.
Анотація:
Experimental measurement of the load-bearing patterns of the facet joints in the lumbar spine remains a challenge, thereby limiting the assessment of facet joint function under various surgical conditions and the validation of computational models. The extra-articular strain (EAS) technique, a non-invasive measurement of the contact load, has been used for unilateral facet joints but does not incorporate strain coupling, i.e. ipsilateral EASs due to forces on the contralateral facet joint. The objectives of the present study were to establish a bilateral model for facet contact force measurement using the EAS technique and to determine its effectiveness in measuring these facet joint contact forces during three-dimensional flexibility tests in the lumbar spine. Specific goals were to assess the accuracy and repeatability of the technique and to assess the effect of soft-tissue artefacts. In the accuracy and repeatability tests, ten uniaxial strain gauges were bonded to the external surface of the inferior facets of L3 of ten fresh lumbar spine specimens. Two pressure-sensitive sensors (Tekscan) were inserted into the joints after the capsules were cut. Facet contact forces were measured with the EAS and Tekscan techniques for each specimen in flexion, extension, axial rotation, and lateral bending under a ±7.5 N m pure moment. Four of the ten specimens were tested five times in axial rotation and extension for repeatability. These same specimens were disarticulated and known forces were applied across the facet joint using a manual probe (direct accuracy) and a materials-testing system (disarticulated accuracy). In soft-tissue artefact tests, a separate set of six lumbar spine specimens was used to document the virtual facet joint contact forces during a flexibility test following removal of the superior facet processes. Linear strain coupling was observed in all specimens. The average peak facet joint contact forces during flexibility testing was greatest in axial rotation (71±25 N), followed by extension (27±35 N) and lateral bending (25±28 N), and they were most repeatable in axial rotation (coefficient of variation, 5 per cent). The EAS accuracy was about 20 per cent in the direct accuracy assessment and about 30 per cent in the disarticulated accuracy test. The latter was very similar to the Tekscan accuracy in the same test. Virtual facet loads (r.m.s.) were small in axial rotation (12 N) and lateral bending (20 N), but relatively large in flexion (34 N) and extension (35 N). The results suggested that the bilateral EAS model could be used to determine the facet joint contact forces in axial rotation but may result in considerable error in flexion, extension, and lateral bending.
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Rana, Masud, Sandipan Roy, Palash Biswas, Shishir Kumar Biswas, and Jayanta Kumar Biswas. "Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study." International Journal of Artificial Organs 43, no. 12 (April 28, 2020): 803–10. http://dx.doi.org/10.1177/0391398820917390.
Анотація:
The aim of this study is to design a novel expanding flexible rod device, for pedicle screw fixation to provide dynamic stability, based on strength and flexibility. Three-dimensional finite-element models of lumbar spine (L1-S) with flexible rod device on L3-L4-L5 levels are developed. The implant material is taken to be Ti-6Al-4V. The models are simulated under different boundary conditions, and the results are compared with intact model. In natural model, total range of motion under 10 Nm moment were found 66.7°, 24.3° and 13.59°, respectively during flexion–extension, lateral bending and axial rotation. The von Mises stress at intact bone was 4 ± 2 MPa and at bone, adjacent to the screw in the implanted bone, was 6 ± 3 MPa. The von Mises stress of disc of intact bone varied from 0.36 to 2.13 MPa while that of the disc between the fixed vertebra of the fixation model reduced by approximately 10% for flexion and 25% for extension compared to intact model. The von Mises stresses of pedicle screw were 120, 135, 110 and 90 MPa during flexion, extension, lateral bending, and axial rotation, respectively. All the stress values were within the safe limit of the material. Using the flexible rod device, flexibility was significantly increased in flexion/extension but not in axial rotation and lateral bending. The results suggest that dynamic stabilization system with respect to fusion is more effective for homogenizing the range of motion of the spine.
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Robinson, A., C. R. P. Lind, R. J. Smith, and V. Kodali. "Atlanto-Axial Infection after Acupuncture." Acupuncture in Medicine 34, no. 2 (April 2016): 149–51. http://dx.doi.org/10.1136/acupmed-2015-212110rep.
Анотація:
A 67-year-old man presented with neck cellulitis following acupuncture for cervical spondylosis. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus. Increased neck pain and bacteraemia prompted MRI, which showed atlanto-axial septic arthritis without signs of infection of the tissues between the superficial cellulitic area and the atlanto-axial joint, thus making direct extension of infection unlikely. It is more likely that haematogenous spread of infection resulted in seeding in the atlanto-axial joint, with the proximity of the arthritis and acupuncture site being coincidental. Acupuncture is a treatment option for some indolent pain conditions. As such, acupuncture services are likely to be more frequently utilised. A history of acupuncture is rarely requested by the admitting doctor and seldom offered voluntarily by the patient, especially where the site of infection due to haematogenous spread is distant from the needling location. Awareness of infectious complications following acupuncture can reduce morbidity through early intervention.
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Staudt, Michael D., Doron Rabin, Ali A. Baaj, Neil R. Crawford, and Neil Duggal. "Biomechanical evaluation of the ProDisc-C stability following graded posterior cervical injury." Journal of Neurosurgery: Spine 29, no. 5 (November 2018): 515–24. http://dx.doi.org/10.3171/2018.3.spine171248.
Анотація:
OBJECTIVEThere are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.METHODSFourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.RESULTSRange of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).CONCLUSIONSForaminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.
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Zeng, Zhi-li, Rui Zhu, Yang-chun Wu, Wei Zuo, Yan Yu, Jian-jie Wang, and Li-ming Cheng. "Effect of Graded Facetectomy on Lumbar Biomechanics." Journal of Healthcare Engineering 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/7981513.
Анотація:
Facetectomy is an important intervention for spinal stenosis but may lead to spinal instability. Biomechanical knowledge for facetectomy can be beneficial when deciding whether fusion is necessary. Therefore, the aim of this study was to investigate the biomechanical effect of different grades of facetectomy. A three-dimensional nonlinear finite element model of L3–L5 was constructed. The mobility of the model and the intradiscal pressure (IDP) of L4-L5 for standing were inside the data from the literature. The effect of graded facetectomy on intervertebral rotation, IDP, facet joint forces, and maximum von Mises equivalent stresses in the annuli was analyzed under flexion, extension, left/right lateral bending, and left/right axial rotation. Compared with the intact model, under extension, unilateral facetectomy increased the range of intervertebral rotation (IVR) by 11.7% and IDP by 10.7%, while the bilateral facetectomy increased IVR by 40.7% and IDP by 23.6%. Under axial rotation, the unilateral facetectomy and the bilateral facetectomy increased the IVR by 101.3% and 354.3%, respectively, when turned to the right and by 1.1% and 265.3%, respectively, when turned to the left. The results conclude that, after unilateral and bilateral facetectomy, care must be taken when placing the spine into extension and axial rotation posture from the biomechanical point of view.