Journal articles on the topic 'Transverse compression-extension'
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1
Gudmundsson, G. Hilmar, Almut Iken, and Martin Funk. "Measurements of ice deformation at the confluence area of Unteraargletscher Bernese Alps, Switzerland." Journal of Glaciology 43, no. 145 (1997): 548–56. http://dx.doi.org/10.3189/s0022143000035152.
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AbstractAn experimental study of ice deformation at the confluence area of Unteraargletscher, Bernese Alps, Switzerland, has been carried out. Surface velocities were measured by repeatedly surveying stakes and with the use of remote-sensing methods. The variation of the vertical strain rates with depth was measured in boreholes. The confluence center line is subjected to longitudinal horizontal extension, which is exceeded in magnitude by a concomitant transverse compression. Vertical strain rates change from positive (extension) at the surface to negative (compression) in the lowest layers of the glacier.
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Gudmundsson, G. Hilmar, Almut Iken, and Martin Funk. "Measurements of ice deformation at the confluence area of Unteraargletscher Bernese Alps, Switzerland." Journal of Glaciology 43, no. 145 (1997): 548–56. http://dx.doi.org/10.1017/s0022143000035152.
Full textAbstract:
AbstractAn experimental study of ice deformation at the confluence area of Unteraargletscher, Bernese Alps, Switzerland, has been carried out. Surface velocities were measured by repeatedly surveying stakes and with the use of remote-sensing methods. The variation of the vertical strain rates with depth was measured in boreholes. The confluence center line is subjected to longitudinal horizontal extension, which is exceeded in magnitude by a concomitant transverse compression. Vertical strain rates change from positive (extension) at the surface to negative (compression) in the lowest layers of the glacier.
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Zhang, Bingbing, Shuangqi Hu, and Zhiqiang Fan. "Anisotropic Compressive Behavior of Functionally Density Graded Aluminum Foam Prepared by Controlled Melt Foaming Process." Materials 11, no. 12 (December 5, 2018): 2470. http://dx.doi.org/10.3390/ma11122470.
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Aluminum foams with a functionally graded density have exhibited better impact resistance and a better energy absorbing performance than aluminum foams with a uniform density. Nevertheless, the anisotropic compression behavior caused by the graded density has scarcely been studied. In this paper, a density graded aluminum foam (FG) was prepared by a controlled foaming process. The effect of density anisotropy on the mechanical behavior of FGs was investigated under quasi-static compression and a low-velocity impact. Digital image correlation (DIC) and numerical simulation techniques were used to identify deformation mechanisms at both macro and cell levels. Results show that transverse compression on FGs lead to a higher collapse strength but also to a lower energy absorption, due to the significant decrease in densification strain and plateau stress. The deformation behavior of FGs under longitudinal compression was dominated by the progressive extension of the deformation bands. For FGs under transverse compression, the failure mode of specimens was characterized by multiple randomly distributed deformation bands. Moreover, the transverse compression caused more deformation on cells, through tearing and lateral stretching, because of the high lateral strain level in the specimens. It was concluded that the transverse compression of FGs lead to a lower plateau stress and a lower cell usage, thus resulting in a poorer energy absorption efficient; this constitutes a key factor which should be taken into consideration in structural design.
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Vorontsov, A. P. "Longitudinal bending of compound rod with symmetric tightening." Izvestiya MGTU MAMI 8, no. 4-4 (August 20, 2014): 22–25. http://dx.doi.org/10.17816/2074-0530-67340.
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The paper discusses the problem of longitudinal bending of a compound two-branch rod, with two symmetrical tightening, stressed with longitudinal compressive and transverse loads, which branches are affected by pre-plastic deformation as extension and compression. Calculations were carried out on the basis of equations of longitudinal bending process, taking into account the influence of the efforts of prior rod compression and plastic training of rod branches elements.
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Gennaro, V. De, J. Canou, J. C. Dupla, and N. Benahmed. "Influence of loading path on the undrained behaviour of a medium loose sand." Canadian Geotechnical Journal 41, no. 1 (February 1, 2004): 166–80. http://dx.doi.org/10.1139/t03-082.
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The results of an experimental programme aimed at studying the undrained behaviour of Hostun sand are presented in this paper. Specific conditions concerning the initial relative density (medium loose arrangements) and the loading paths (compression and extension under monotonic and cyclic loadings) were considered in the test programme. Monotonic tests carried out in both drained and undrained conditions show a significant difference in behaviour between compression and extension. It is observed that, in undrained conditions, Hostun sand is weaker in extension than in compression. In compression, the material is stable (dilatant) and the phase-transformation state controls the mechanical behaviour. In extension, the experimental results show an unstable behaviour (contractant), with monotonic, liquefaction-induced instability in undrained conditions. The results of cyclic tests, carried out with one- and two-way stress reversals, show a good correlation with the results of monotonic tests. The loading path strongly influences the undrained mechanical behaviour of the sand, mainly by inducing liquefaction in extension. This situation suggests that differences in soil fabric, caused by the sample preparation technique (air pluviation), can influence the sand behaviour by inducing a significant contraction in extension. By further analysing the cyclic results, it is shown that, during unloading, the stress paths reflect the transverse isotropy (orthotropy) of the sand, with stiffer elastic characteristics in the vertical direction than in the horizontal direction.Key words: liquefaction, cyclic mobility, sands, triaxial test, anisotropy, loading path.
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Rhead, A. T., R. Butler, W. Liu, and N. Baker. "The influence of surface ply fibre angle on the compressive strength of composite laminates containing delamination." Aeronautical Journal 116, no. 1186 (December 2012): 1315–30. http://dx.doi.org/10.1017/s000192400000765x.
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AbstractA combination of uniaxial compression tests and Strip Model and Finite Element analyses of laminates artificially delaminated to create circular (±θ) sublaminates is used to assess the influence of fibre angle on the compressive strength of composite laminates.Sublaminates with 0° < θ < 40° are found to fail by sublaminate-buckling-driven delamination propagation and provide poor tolerance of delamination. This is a consequence of their relatively high axial stiffnesses, low sublaminate buckling strains, Poisson’s ratio induced compressive transverse strains and extension-twist coupling which produces unexpected sublaminate buckling mode shapes. Sublaminates with 40° < θ < 60° are most tolerant to delamination; axial and transverse stiffnesses are minimal, formation of sublaminate buckles is resisted, high laminate buckling strains reduce interaction between laminate and sublaminate buckling mode shapes and extension-twist coupling is minimal. Sublaminates with 60° < θ < 90° are shown to produce varied tolerance of delamination. Sublaminate buckling is generally prevented owing to transverse tensile strains induced by mismatches between laminate and sublaminate Poisson’s ratios but may occur in laminates with low Poisson’s ratios.
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Meyer, Carolin, Jan Bredow, Elisa Heising, Peer Eysel, Lars Peter Müller, and Gregor Stein. "Rheumatoid Arthritis Affecting the Upper Cervical Spine: Biomechanical Assessment of the Stabilizing Ligaments." BioMed Research International 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/6131703.
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Diameters of anterior and posterior atlantodental intervals (AADI and PADI) are diagnostically conclusive regarding ongoing neurological disorders in rheumatoid arthritis. MRI and X-ray are mostly used for patients’ follow-up. This investigation aimed at analyzing these intervals during motion of cervical spine, when transverse and alar ligaments are damaged. AADI and PADI of 10 native, human cervical spines were measured using lateral fluoroscopy, while the spines were assessed in neutral position first, in maximal inclination second, and in maximal extension at last. First, specimens were evaluated under intact conditions, followed by analysis after transverse and alar ligaments were destroyed. Damage of the transverse ligament leads to an increase of the AADI’s diameter about 0.65 mm in flexion and damage of alar ligaments results in significant enhancement of 3.59 mm at mean. In extension, the AADI rises 0.60 mm after the transverse ligament was cut and 0.90 mm when the alar ligaments are damaged. After all ligaments are destroyed, AADI assessed in extension closely resembles AADI at neutral position. Ligamentous damage showed an average significant decrease of the PADI of 1.37 mm in the first step and of 3.57 mm in the second step in flexion, while it is reduced about 1.61 mm and 0.41 mm in the extended and similarly in the neutrally positioned spine. Alar and transverse ligaments are both of obvious importance in order to prevent AAS and movement-related spinal cord compression. Functional imaging is necessary at follow-up in order to identify patients having an advanced risk of neurological disorders.
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Gudmundsson, G. Hilmar. "Ice deformation at the confluence of two glaciers investigated with conceptual map-plane and flowline models." Journal of Glaciology 43, no. 145 (1997): 537–47. http://dx.doi.org/10.3189/s0022143000035140.
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AbstractUsing analytical and numerical techniques, a two-dimensional (2-D) map-plane model and a 2-D flowline model are utilized to elucidate the horizontal and vertical ice deformation at the confluence of two glaciers. For a perfectly symmetrical confluence, the junction point of the two tributaries can be modeled as a no-slip/free-slip transition. A strongly localized surface depression develops around the junction point, accompanied by two broadly elevated zones positioned close to the margins of the tributaries facing the junction point. The confluence center line is subjected to horizontal longitudinal extension and a transverse compression. The compression generally exceeds the concomitant longitudinal extension in magnitude. Depth-integrated vertical strain rates along the center line are positive (extension), but the strain-rate variation with depth depends critically on the type of basal boundary conditions at the glacier bed. For a no-slip boundary condition, vertical strain rates change from positive at the surface to negative close to the base, whereas for a free-slip boundary condition (perfect sliding) vertical strain rates are positive throughout the depth. These theoretical results are compared with field measurements from Unteraargletscher, Bernese Alps, Switzerland.
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Gudmundsson, G. Hilmar. "Ice deformation at the confluence of two glaciers investigated with conceptual map-plane and flowline models." Journal of Glaciology 43, no. 145 (1997): 537–47. http://dx.doi.org/10.1017/s0022143000035140.
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AbstractUsing analytical and numerical techniques, a two-dimensional (2-D) map-plane model and a 2-D flowline model are utilized to elucidate the horizontal and vertical ice deformation at the confluence of two glaciers. For a perfectly symmetrical confluence, the junction point of the two tributaries can be modeled as a no-slip/free-slip transition. A strongly localized surface depression develops around the junction point, accompanied by two broadly elevated zones positioned close to the margins of the tributaries facing the junction point. The confluence center line is subjected to horizontal longitudinal extension and a transverse compression. The compression generally exceeds the concomitant longitudinal extension in magnitude. Depth-integrated vertical strain rates along the center line are positive (extension), but the strain-rate variation with depth depends critically on the type of basal boundary conditions at the glacier bed. For a no-slip boundary condition, vertical strain rates change from positive at the surface to negative close to the base, whereas for a free-slip boundary condition (perfect sliding) vertical strain rates are positive throughout the depth. These theoretical results are compared with field measurements from Unteraargletscher, Bernese Alps, Switzerland.
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Niu, Ran, Meera Ramaswamy, Christopher Ness, Abhishek Shetty, and Itai Cohen. "Tunable solidification of cornstarch under impact: How to make someone walking on cornstarch sink." Science Advances 6, no. 19 (May 2020): eaay6661. http://dx.doi.org/10.1126/sciadv.aay6661.
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Hundreds of YouTube videos show people running on cornstarch suspensions demonstrating that dense shear thickening suspensions solidify under impact. Such processes are mimicked by impacting and pulling out a plate from the surface of a thickening cornstarch suspension. Here, using both experiments and simulations, we show that applying fast oscillatory shear transverse to the primary impact or extension directions tunes the degree of solidification. The forces acting on the impacting surface are modified by varying the dimensionless ratio of the orthogonal shear to the compression and extension flow rate. Simulations show varying this parameter changes the number of particle contacts governing solidification. To demonstrate this strategy in an untethered context, we show the sinking speed of a cylinder dropped onto the suspension varies markedly by changing this dimensionless ratio. These results suggest applying orthogonal shear while people are running on cornstarch would de-solidify the suspension and cause them to sink.
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Gien Pooke, Tamara. "The effectiveness of seated combined extension-compression and transverse load traction in increasing cervical lordosis- challenging the underlying framework." International e-Journal of Science, Medicine & Education 10, no. 3 (2016): 24–33. http://dx.doi.org/10.56026/imu.10.3.24.
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Barone, M. R., and D. A. Caulk. "A Model for the Flow of a Chopped Fiber Reinforced Polymer Compound in Compression Molding." Journal of Applied Mechanics 53, no. 2 (June 1, 1986): 361–71. http://dx.doi.org/10.1115/1.3171765.
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The flow of a chopped fiber reinforced polymer compound in compression molding is modelled as a two-dimensional membrane-like sheet which extends uniformly through the cavity thickness with slip at the mold surface. The model is consistent with both the kinematic mechanisms observed in actual flow and the three-dimensional anisotropy caused by the arrangement of fibers in the sheet. The material resistance to extension is expressed in a constitutive equation for the two-dimensional stress resultant formed by integrating the planar stress components through the thickness of the cavity. This stress resultant is assumed to be a linear function of the corresponding planar rate of deformation in the molding compound. Through a mechanism of fiber-resin interaction, the material resistance to extension can be characterized by a single scalar function of the transverse temperature distribution. Three alternatives are considered for the friction response at the cavity surface: (i) constant magnitude, (ii) proportional to the relative velocity (hydrodynamic), and (iii) proportional to the normal component of the stress vector (Coulomb). These three assumptions are compared by considering their general implications on the flow-front progression. The latter two are examined in some detail for thin charges in which the material resistance to extension is negligible compared to the effect of friction. Analytical solutions for an elliptical charge are obtained for both hydrodynamic and Coulomb friction. By comparing these solutions with experimental results, we conclude that the hydrodynamic model for the friction response is the best of the three proposed alternatives.
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Louis, Robert G., Chun Po Yen, Carrie A. Mohila, James W. Mandell, and Jason Sheehan. "A rare intraosseous arteriovenous malformation of the spine." Journal of Neurosurgery: Spine 15, no. 3 (September 2011): 336–39. http://dx.doi.org/10.3171/2011.5.spine10872.
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The authors report the case of a patient with an intraosseous spinal arteriovenous malformation (AVM) presenting as an epidural mass lesion that was causing spinal cord compression. The 59-year-old woman had bilateral numbness, weakness, and hyperreflexia of both legs. Magnetic resonance imaging revealed intermediate T1 signal and hyperintense T2 signal involving the right transverse process, bilateral pedicles, and T-5 spinous process; the lesion's epidural extension was causing severe canal compromise and cord displacement. Coil embolization was performed, and the patient underwent resection, after which preoperative symptoms improved. Histopathological analysis revealed a benign vascular proliferation consistent with an intraosseous spinal AVM. On review of the literature, the authors found this case to be the second intraosseous spinal AVM, and the first in a patient whose clinical presentation was consistent with that of a mass lesion of the bone.
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Butler, Richard, Andrew T. Rhead, Wenli Liu, and Nikolaos Kontis. "Compressive strength of delaminated aerospace composites." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1965 (April 28, 2012): 1759–79. http://dx.doi.org/10.1098/rsta.2011.0339.
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An efficient analytical model is described which predicts the value of compressive strain below which buckle-driven propagation of delaminations in aerospace composites will not occur. An extension of this efficient strip model which accounts for propagation transverse to the direction of applied compression is derived. In order to provide validation for the strip model a number of laminates were artificially delaminated producing a range of thin anisotropic sub-laminates made up of 0°, ±45° and 90° plies that displayed varied buckling and delamination propagation phenomena. These laminates were subsequently subject to experimental compression testing and nonlinear finite element analysis (FEA) using cohesive elements. Comparison of strip model results with those from experiments indicates that the model can conservatively predict the strain at which propagation occurs to within 10 per cent of experimental values provided (i) the thin-film assumption made in the modelling methodology holds and (ii) full elastic coupling effects do not play a significant role in the post-buckling of the sub-laminate. With such provision, the model was more accurate and produced fewer non-conservative results than FEA. The accuracy and efficiency of the model make it well suited to application in optimum ply-stacking algorithms to maximize laminate strength.
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Harrison, Deed E., Donald D. Harrison, Joeseph J. Betz, Tadeusz J. Janik, Burt Holland, Christopher J. Colloca, and Jason W. Haas. "Increasing the cervical lordosis with chiropractic biophysics seated combined extension-compression and transverse load cervical traction with cervical manipulation: nonrandomized clinical control trial." Journal of Manipulative and Physiological Therapeutics 26, no. 3 (March 2003): 139–51. http://dx.doi.org/10.1016/s0161-4754(02)54106-3.
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Schile, Richard. "Engineering a Better Guitar." Mechanical Engineering 133, no. 02 (February 1, 2011): 38–41. http://dx.doi.org/10.1115/1.2011-feb-5.
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This article discusses applying engineering principles to build a superior guitar. In one prototype created, the transverse underbrace, located directly opposite the bridge, is proportioned so that the neutral plane at this location lies within the soundboard. The underbrace is notched to allow the king brace, made of fir, to pass through. Four spruce diagonal braces are also present in the compression zone between the bridge and the lower edge of the sound hole. To support the soundboard, two short, stiff cantilever beams are bonded to the upper neck extension using spacer blocks to allow the beams to pass outside of the sound hole. The free ends are connected with a short bar to provide a reactive member supporting the compressive forces in the soundboard. In the first six months or so after construction, the acoustic performance of the first prototype was good but unexceptional. After a year, however, both the acoustic power and quality of sound were found to be outstanding.
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Takao, Hanabusa, Ayumi Shiro, and Tatsuya Okada. "Residual Stress Measurement around the Interface of Copper Bicrystal Deformed by Uniaxial Extension." Advances in Science and Technology 64 (October 2010): 125–34. http://dx.doi.org/10.4028/www.scientific.net/ast.64.125.
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Residual stresses of a copper bicrystal were measured by X-ray diffraction and synchrotron radiation. A copper bicrystal specimen with a 90-degree tilt boundary was fabricated by the Brigdman technique. After the plastic extension of 30%, kink bands developed in a deformed matrix along the grain boundary. In this study, we focused on the residual stress distribution along the transverse direction of the specimen surface and the residual stresses in deformed matrix and kink band near the grain boundary. Residual stresses were evaluated by the X-ray single crystal measurement method. Stereographic projections were used to determine crystal orientations of deformed regions. It was found that crystal orientations were different between the deformed matrix and the kink band. Residual stresses in the direction along the grain boundary were compressive in the vicinity of the boundary and tensile in the region apart from the boundary. Residual stresses in the kink band were large in compression in compared with those in the deformation matrix. The difference in the results between X-rays and synchrotron radiation suggests that there is a depth variation in the deformation and therefore the residual stress development.
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Trikhunkov, Ya I., D. М. Bachmanov, О. V. Gaydalenok, А. V. Marinin, and S. А. Sokolov. "Recent mountain-building at the boundary juction of the North-Western Caucasus and intermediate Kerch-Taman Region, Russia." Геотектоника, no. 4 (August 13, 2019): 78–96. http://dx.doi.org/10.31857/s0016-853x2019378-96.
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In this paper the recent evolution of marginal segment of the North-Western Caucasus orogen in its junction to Kerch-Taman periclinal trough was studied. Geomorphological analysis included geological, tectonophysics data and digital elevation models was carried out. The North-Western Caucasus torn-folded morphostructures that had their extension in intermediate Kerch-Taman region westward to North-Western Caucasus mountain structure are both established to be developed in uniform regional compression settings. The prevailing horizontal compression direction changed from N–E in the North-Western Caucasus to the meridional one in Taman region, which was expressed in the reorientation of the axes of the folded morphostructures and geophysical anomalies from N–W to the latitudinal direction. The separation of the compressional vectors occurred in Pliocene-Quaternary period. Pre-Pliocene fault structures of N–E strike in this area were replaced with meridional Anapa-Dzhiginka and Abrau active fault zones.We compared Abrau zone with Anapa-Dzhiginka zone and established the faulting in Abrau zone became more dynamic in Pliocene-Quaternary stage, we revealed clear signs of vertical amplitude droppable-sliding kinematics of 500–600 m of normal fault deformation in Abrau zone during this stage. Abrau zone is the Greater Caucasus western boundary zone.The possible reasons for the restructuring of regional structural geometry and lateral transition activity of the faults transverse to the Northern-Western Caucasus orogen, are considered.
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Benzel, Edward C., and Nevan G. Baldwin. "Crossed-screw fixation of the unstable thoracic and lumbar spine." Journal of Neurosurgery 82, no. 1 (January 1995): 11–16. http://dx.doi.org/10.3171/jns.1995.82.1.0011.
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✓ An ideal spinal construct should immobilize only the unstable spinal segments, and thus only the segments fused. Pedicle fixation techniques have provided operative stabilization with the instrumentation of a minimal number of spinal segments; however, some failures have been observed with pedicle instrumentation. These failures are primarily related to excessive preload forces and limitations caused by the size and orientation of the pedicles. To circumvent these problems, a new technique, the crossed-screw fixation method, was developed and is described in this report. This technique facilitates short-segment spinal fixation and uses a lateral extracavitary approach, which provides generous exposure for spinal decompression and interbody fusion. The technique employs two large transverse vertebral body screws (6.5 to 8.5 mm in diameter) to bear axial loads, and two unilateral pedicle screws (placed on the side of the exposure) to restrict flexion and extension deformation around the transverse screws and to provide three-dimensional deformity correction. The horizontal vertebral body and the pedicle screws are connected to rods and then to each other via rigid crosslinking. The transverse vertebral body screws are unloaded during insertion by placing the construct in a compression mode after the interbody bone graft is placed, thus optimizing the advantage gained by the significant “toe-in” configuration provided and further decreasing the chance for instrumentation failure. The initial results of this technique are reported in a series of 10 consecutively treated patients, in whom correction of the deformity was facilitated. Follow-up examination (average 10.1 months after surgery) demonstrated negligible angulation. Chronic pain was minimal. The crossed-screw fixation technique is biomechanically sound and offers a rapid and safe form of short-segment three-dimensional deformity correction and solid fixation when utilized in conjunction with the lateral extracavitary approach to the unstable thoracic and lumbar spine. This approach also facilitates the secure placement of an interbody bone graft.
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Pooke, Tamara G., Rozi Mahmud, Poh Sin Yap, Suraini Binti Mohamad Saini, Roohi Syed Ahmad, and Harwant Singh. "THE RELATIONSHIP BETWEEN STRUCTURAL AND CLINICAL CHANGES IN SEATED COMBINED EXTENSION-COMPRESSION AND TRANSVERSE LOAD (ECTL) TRACTION IN INCREASING CERVICAL LORDOSIS: A RANDOMISED CONTROLLED TRIAL." Journal of Musculoskeletal Research 22, no. 03n04 (September 2019): 1950006. http://dx.doi.org/10.1142/s0218957719500064.
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Purpose: The aim was to assess for any relationships in changes between improved cervical lordosis and clinical outcomes of neck pain and disability. Methods: Single center, randomized controlled trial in Malaysia, to compare seated combined extension-compression and transverse load (ECTL) traction combined with exercises, to the same exercises. Participants with a reduced lordosis of less than [Formula: see text] were randomly assigned into groups, and underwent 40 treatments over 14 weeks. Pre and post lateral radiographs were reviewed by a blinded musculoskeletal radiologist for changes in cervical lordosis. VAS and Neck Disability Index (NDI) scores were used to assess clinical outcomes. Correlations between changes in curve and changes in pain and disability were assessed. Non-parametric analyses were performed on all who completed ([Formula: see text]). Results: No significant correlations between changes in lordosis and pain and disability were seen, with rho less than 0.33 and 0.24, respectively. Pain scores improved significantly in both treatment and control groups ([Formula: see text]). Disability scores also showed significant decrease in both treatment ([Formula: see text]) and control ([Formula: see text]) groups, despite a non-significant reduction in lordosis. Conclusions: Improvement in neck pain and disability did not require an improvement in lordosis. Abnormal sagittal cervical alignment therefore, is perhaps not the sole underlying cause for clinical outcomes, and a number of other psychosocial factors when considering management options.
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Bartaschuk, Оleksii, and Vasyl Suyarko. "GEODYNAMICS." GEODYNAMICS 1(30)2021, no. 1(30) (June 29, 2021): 25–35. http://dx.doi.org/10.23939/jgd2021.01.025.
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The second part of the article studies the tectonic conditions and natural mechanisms of tectonic inversion of the Dnieper-Donets Basin and the Western Donets Graben. Method. The research uses the original method of reconstruction of fields of tectonic stresses and deformations. It also makes tectonophysical analysis of geostructures was used. The analytical base of the research consisted of the latest materials of geo-mapping, numerical modeling of deformations of the southern edge of the Eastern European platform and comparison of model and reconstructed stress fields. Results. In the geodynamic environment of the interference of the intraplate submeridional collision compression with the regional strike-slip stress field, the inversion deformations of the rift-like geostructure took place in the uplift-thrust and strike-slip modes. This led to significant horizontal movements of geomass of sedimentary rocks, deformation folding with the formation of three inversion floors - Late Hercynian (Saal-Pfalz), Early Alpine (Laramian) and Late Alpine (Attic). They formed structural ensembles of scaly tectonic covers of transverse displacement of geomass a from axial to onboard zones, folded covers of longitudinal approach from the Donbas Foldbelt and long linear anti- and synforms, the axes of which are oriented orthogonally to the direction of geomass advancement. Together they form the body of the Segment of Tectonic Wedging of geomass, which is distinguished as part of the Cover-Folded System of Tectonic Thrusting of regional scale. A feature of the tectonic framework of the Segment is the curvature of the planes of the main thrusts, which limit it, and smaller plumage thrusts, which control the folded covers of the thrust. It is associated with a change in the extension of the thrusts from the north-west in the territory of the Western Donets Graben to the western direction in the extreme south-east of the Basin. This causes the corresponding bending of the axes of the fracture anti- and synforms. Structural patterns of folding with a tendency to adapt the axes of folds to the extension of thrusts indicate significant horizontal displacements of geomas of the sedimentary stratum, which in conditions of limited geological space cause secondary deformations of linear folded forms. Due to the displacement of geomas from the zones of maximum compression in the axial part of the Graben to the zones of geodynamic shadow - in the direction of the Oryl depression and Graben boards, the West Donets Cover-Folded Tectonic Region was formed within the transition zone. Scientific novelty. The study completed an original kinematic model of tectonic inversion of the Western Donets Graben was completed. The mechanism of inversion, due to which the riftogenic structure is completely destroyed by folded deformations of platform orogeneses, is caused by the pressure of the "tectonic stamp" of the Donbas Foldbelt. Under its influence, a segment of tectonic wedge was formed in the Graben, which was diagnosed with oroclin of transverse extension of the sliding type. The body of the Oroclin is formed by echeloned, rock-articulated ensembles of anticlinal uplift -folds, synclines and scaly plates-covers of pushing. A geodynamic injection band was formed in the foreland of the Tectonic Orocline extension, where folded zones of geomas displacement were formed, which consist of coulisse articulated uplift-anticlines. At the top of the Orocline, at the ends of dynamically conjugate main thrusts, an advanced tectonic compression fan is formed. In the rear of the Oroclin – hinterland are tectonic sutures – the roots of the folding covers of the approach. Practical significance. Development of a structural-kinematic model of tectonic inversion of the Western Donets Graben will allow to improve the geodynamic model of tectonic inversion of the Dnieper-Donets paleorift, on the basis of which regional schemes of tectonic and oil-gas-geological zoning will be adjusted.
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Rippin, David, Ian Willis, and Neil Arnold. "Seasonal patterns of velocity and strain across the tongue of the polythermal glacier midre Lovénbreen, Svalbard." Annals of Glaciology 42 (2005): 445–53. http://dx.doi.org/10.3189/172756405781812781.
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AbstractTerrestrial surveys to 17 markers distributed across the tongue of the polythermal glacier midre Lovénbreen, Svalbard, are used to calculate annual and seasonal (summer 1998, autumn/winter/ spring 1998/99, summer 1999) patterns of surface velocity and strain. The annual period and the three seasonal periods have similar velocity azimuths and patterns, with fastest velocities along the centre line and in the upper tongue. Velocities in both summers are of similar magnitude, and greater than those in the autumn/winter/spring period. In all periods, longitudinal compression (increasing towards the snout) and transverse and vertical extension dominate the surface strain field. However, an area of longitudinal extension develops in the middle tongue during the 1998 summer. Surface strain patterns are used to estimate the components of the force balance. Basal drag is the dominant force resisting flow, but patterns are rather different between the three seasons. In summer 1998, a slippery spot in the upper-middle tongue is confined to the central part of the glacier. In autumn/winter/spring, this slippery spot has expanded towards the western glacier margin. In summer 1999, it has disappeared, and a slight sticky spot now covers virtually the entire upper and middle tongue. The location and extent of the slippery spot are explained in terms of the distribution of warm and cold ice, and the location and morphology of the subglacial drainage system, which control the patterns of water pressure beneath the glacier tongue.
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Rolstad, Cecilie, Jostein Amlien, Jon-Ove Hagen, and Bengt Lundén. "Visible and near-infrared digital images for determination of ice velocities and surface elevation during a surge on Osbornebreen, a tidewater glacier in Svalbard." Annals of Glaciology 24 (1997): 255–61. http://dx.doi.org/10.3189/s026030550001226x.
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A field of vectors showing the average velocity of the surging glacier Osbornebreen, Svalbard, was determined by comparing sequential SPOT (Système pour l’Observation de la Terre) and Landsat thematic mapper images. Crevasses which developed during the initial phase of the surge in the winter of 1986–87 were tracked using a fast Fourier chip cross-correlation technique. A digital elevation model (DEM) was developed using digital photogrammetry on aerial photographs from 1990. This new DEM was compared with a map drawn in 1966. The velocity field could be almost entirely determined with 1 month separation of the images, but only partly determined with images 1 year apart, due to changes of the crevasse pattern. The velocity field is similar to that found for Kronebreen, a continuously fast-moving tidewater glacier. No distinct zones of compressive flow were present and the data gave no evidence of a compression zone/surge front traveling downstream. The velocity field, the rapid advance of the terminus and the development of transverse crevasses in the upper accumulation area within a 6 month period may indicate that the surge developed as a zone of extension starting near the terminus and propagating quickly upstream. The crevasse pattern in the images is therefore interpreted to be the result of the extension zone traveling upstream, and, as the whole glacier starts to slide, the crevasse pattern alters according to the bedrock topography.
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Tajima, Naoya, Etsuo Chosa, Koji Totoribe, Shinichiro Kubo, and Hiroshi Kuroki. "Posterolateral Lumbar Fusion — Biomechanical Study and Clinical Results." Journal of Musculoskeletal Research 02, no. 02 (June 1998): 101–7. http://dx.doi.org/10.1142/s0218957798000123.
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This paper discusses the biomechanics and long-term results of posterolateral (PL) lumber fusion for degenerative lumbar spinal diseases. In the biomechanical study, the geometry of the finite element model is based on the L4-5 motion segment. The disc degeneration model was simulated by changing the interbody material properties. The behavior of the PL fusion model and the effects of the anterior elements on PL lumber fusion were studied in compression, flexion, and extension. In the clinical study, 40 patients with a mean age of 39 years (19 to 63) were treated with PL fusion and the mean follow-up period was 14 years. Clinical evaluation was made by the Japanese Orthopaedic Association (J.O.A.) score. Fusion success was determined by X-ray radiographs. Stress distribution results indicate that there were high stresses in the upper part of the grafted bone for PL fusion. The axial displacement of the L4 vertebral body and the stress of the grafted bone for PL fusion increased in the disc degeneration model. In flexion, the extension load stress concentrated on the L4 side of PL fusion model between transverse processes. Clinically, the J.O.A. score improved by 24 points postoperatively. Radiographically, the success rate of the fusion was 93%. The long-term results were so good that this technique can be recommended. It is suggested that the instability including the degree of disc degeneration is one of the important factors in PL lumbar fusion.
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Rolstad, Cecilie, Jostein Amlien, Jon-Ove Hagen, and Bengt Lundén. "Visible and near-infrared digital images for determination of ice velocities and surface elevation during a surge on Osbornebreen, a tidewater glacier in Svalbard." Annals of Glaciology 24 (1997): 255–61. http://dx.doi.org/10.1017/s026030550001226x.
Full textAbstract:
A field of vectors showing the average velocity of the surging glacier Osbornebreen, Svalbard, was determined by comparing sequential SPOT (Système pour l’Observation de la Terre) and Landsat thematic mapper images. Crevasses which developed during the initial phase of the surge in the winter of 1986–87 were tracked using a fast Fourier chip cross-correlation technique. A digital elevation model (DEM) was developed using digital photogrammetry on aerial photographs from 1990. This new DEM was compared with a map drawn in 1966. The velocity field could be almost entirely determined with 1 month separation of the images, but only partly determined with images 1 year apart, due to changes of the crevasse pattern. The velocity field is similar to that found for Kronebreen, a continuously fast-moving tidewater glacier. No distinct zones of compressive flow were present and the data gave no evidence of a compression zone/surge front traveling downstream. The velocity field, the rapid advance of the terminus and the development of transverse crevasses in the upper accumulation area within a 6 month period may indicate that the surge developed as a zone of extension starting near the terminus and propagating quickly upstream. The crevasse pattern in the images is therefore interpreted to be the result of the extension zone traveling upstream, and, as the whole glacier starts to slide, the crevasse pattern alters according to the bedrock topography.
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BARTASHCHUK, Оleksiy. "Сollision deformations of the Dnieper-Donets Depression. Article 2. Kinematic mechanisms of tectonic inversion." Geology and Geochemistry of Combustible Minerals 4, no. 181 (December 27, 2019): 32–44. http://dx.doi.org/10.15407/ggcm2019.04.032.
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The second article is devoted to the investigation of the natural mechanisms of tectonic inversion of the Dnieper-Donets depression. Using the materials of geological mapping of the territory of the West-Donetsk graben, structural proofs of the destruction of the riftogenic structure by collision tectonic movements of Hercinian and Alpic tectogenesis were obtained. The consequence of the inversion deformations is the formation of the West Donets cover-folding tectonic region within the Lugansk-Komyshuvasky tectonic area of the uplift-folding and the Kalmius-Toretsky region of the scalloped thrust covers, which are divided by the Main anticline. For the diagnosis of kinematic mechanisms of tectonic inversion, the data of reconstruction of tectonic stress fields and quantitative modeling of deformations of the southern outskirts of the Eastern European Platform were used. It is assumed that the tectonic inversion of the Dnieper-Donets basin began in the Zaal and Pfalz phases of orogenesis due to the collision motions of the compression orogen at the outskirts of Paleotetis. The formation of linear folding occurred in the uplifting-thrust mode in the field of stresses of the oblique left-hand compression of the sub-meridional directions. The kinematic mechanism of the folded deformations determined the longitudinal bending of the layers due to the extrusion of sedimentary geomas from the zone of maximum compression in the axial part to the zones of “geodynamic shadow” – in the direction of the sides of the depression. In the late Mesozoic and Cenozoic, uplifting-thrust and strike-slip stresses formed echeloned cover-thrust and coulisse-jointed uplift-folded structural paragenesis. According to the results of tectonophysical diagnostics of deformation structures, it was found that under geodynamic conditions of clustering of compression axes in the central part of the West-Donets graben against the reduction of the geological space horizontally and extension of the section due to the formation of the cover-folded allochthon, there were flexural deformations of the primary linear Hercinian folded forms. Such data can be considered as a kinematic mechanism of tectonic inversion of the invasion of the “tectonic stamp” by the Donets folded structure. Under its influence, the wedge-shaped segment of the tectonic thrust, which was diagnosed by the orcline of the transverse extension of the shallow type, was formed by the repeatedly deposited folds of sedimentary geomas in the articulation zone between the depression and the folded structure. In the front of the thrusted were formed folded zones of extrusion of geomas, which consist of coulisse-jointed uplift-anticlines and folded plates-coverings of tectonic thrusted. At the apex of the orocline, at the end of the dynamically coupled main thrusts, an advanced tectonic fan of compression is formed. In the rearward of the oraclline formed sutures – the roots of folded cover.
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Waqar, Mueez, Calvin Soh, John Ealing, Susan Huson, Gareth Evans, Konstantina Karabatsou, and Joshi George. "353 C2 Segmental Neurofibromas in Patients with Neurofibromatosis Type 1: A Particularly Aggressive Phenotype." Neurosurgery 64, CN_suppl_1 (August 24, 2017): 280–81. http://dx.doi.org/10.1093/neuros/nyx417.353.
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Abstract INTRODUCTION Segmental neurofibromas affecting the C2 nerve roots in patients with neurofibromatosis type 1 (NF1) can be particularly aggressive, though their clinical course and imaging characteristics are unexplored. The aim of this study was to present clinical and radiological outcomes of C2 neurofibromas in patients referred to a supra-regional NF1 centre. METHODS Imaging review of regional NF1 referrals 2009–2016. Inclusion criteria: (1) diagnosis of NF1; (2) at least one C2 root neurofibroma; (3) magnetic resonance imaging of the C-spine or whole spine. Multivariate logistic regression analysis was used to identify factors associated with need for surgery. RESULTS >54 patients with 106 neurofibromas were included. The median age was 32.5 years (range 15–61 years) and there was a slight male excess (M: F, 33:21). 32% had myelopathy. Neurofibromas were distributed in all spine regions (65%) or the cervical spine alone (22%). Intradural invasion and cord compression in the cervical spine included the C2 level in 95% and 80% of patients, respectively. Compared to all other cervical spine neurofibromas, C2 neurofibromas had higher rates of intraspinal extension (75% vs. 33%; OR = 6.03, 95% CI 3.75 - 9.71; P < 0.001), intradural invasion (53% vs. 26%; OR = 3.13, 95% CI 2.04 - 4.82; P < 0.001) and cord compression (25% vs. 13%; OR = 2.20, 95% CI 1.32 - 3.69; P = 0.003). However, C2 neurofibromas had lower rates of extraforaminal growth beyond the transverse process (12% vs. 63%; OR = 0.08, 95% CI 0.04 - 0.15; P < 0.001). 13% of patients underwent surgery to decompress the C2 level. Factors associated with surgery included myelopathy (P = 0.03) but not radiological cord compression (p > 0.99). CONCLUSION C2 neurofibromas are particularly aggressive tumours due to preferential intraspinal growth.
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Macki, Mohamed, Rafael De la Garza-Ramos, Ashley A. Murgatroyd, Kenneth P. Mullinix, Xiaolei Sun, Bryan W. Cunningham, Brandon A. McCutcheon, Mohamad Bydon, and Ziya L. Gokaslan. "Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model." Journal of Neurosurgery: Spine 27, no. 5 (November 2017): 570–77. http://dx.doi.org/10.3171/2017.2.spine161128.
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OBJECTIVEAggressive sacral tumors often require en bloc resection and lumbopelvic reconstruction. Instrumentation failure and pseudarthrosis remain a clinical concern to be addressed. The objective in this study was to compare the biomechanical stability of 3 distinct techniques for sacral reconstruction in vitro.METHODSIn a human cadaveric model study, 8 intact human lumbopelvic specimens (L2–pelvis) were tested for flexion-extension range of motion (ROM), lateral bending, and axial rotation with a custom-designed 6-df spine simulator as well as axial compression stiffness with the MTS 858 Bionix Test System. Biomechanical testing followed this sequence: 1) intact spine; 2) sacrectomy (no testing); 3) Model 1 (L3–5 transpedicular instrumentation plus spinal rods anchored to iliac screws); 4) Model 2 (addition of transiliac rod); and 5) Model 3 (removal of transiliac rod; addition of 2 spinal rods and 2 S-2 screws). Range of motion was measured at L4–5, L5–S1/cross-link, L5–right ilium, and L5–left ilium.RESULTSFlexion-extension ROM of the intact specimen at L4–5 (6.34° ± 2.57°) was significantly greater than in Model 1 (1.54° ± 0.94°), Model 2 (1.51° ± 1.01°), and Model 3 (0.72° ± 0.62°) (p < 0.001). Flexion-extension at both the L5–right ilium (2.95° ± 1.27°) and the L5–left ilium (2.87° ± 1.40°) for Model 3 was significantly less than the other 3 cohorts at the same level (p = 0.005 and p = 0.012, respectively). Compared with the intact condition, all 3 reconstruction groups statistically significantly decreased lateral bending ROM at all measured points. Axial rotation ROM at L4–5 for Model 1 (2.01° ± 1.39°), Model 2 (2.00° ± 1.52°), and Model 3 (1.15° ± 0.80°) was significantly lower than the intact condition (5.02° ± 2.90°) (p < 0.001). Moreover, axial rotation for the intact condition and Model 3 at L5–right ilium (2.64° ± 1.36° and 2.93° ± 1.68°, respectively) and L5–left ilium (2.58° ± 1.43° and 2.93° ± 1.71°, respectively) was significantly lower than for Model 1 and Model 2 at L5–right ilium (5.14° ± 2.48° and 4.95° ± 2.45°, respectively) (p = 0.036) and L5–left ilium (5.19° ± 2.34° and 4.99° ± 2.31°) (p = 0.022). Last, results of the axial compression testing at all measured points were not statistically different among reconstructions.CONCLUSIONSThe addition of a transverse bar in Model 2 offered no biomechanical advantage. Although the implementation of 4 iliac screws and 4 rods conferred a definitive kinematic advantage in Model 3, that model was associated with significantly restricted lumbopelvic ROM.
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Bartaschuk, Оleksii, and Vasyl Suyarko. "GEODYNAMICS." GEODYNAMICS 2(31)2021, no. 2(31) (December 29, 2021): 53–65. http://dx.doi.org/10.23939/jgd2021.02.053.
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The article studies the system organization of inversion tectonic deformations of the Dnieper-Donetsk Basin which covered the territory of the Western Donetsk Graben. The research uses the kinematic and structural-paragenetic analysis of inversion structural transformation of the folded floors of the sedimentary cover of the Graben. The original model of tectonic inversion of the Dnieper-Donets Basin was completed from the previous models. The tectonic inversion of the Dnieper-Donets Paleorift rift-like structures began at the late Hercynian stage in the geodynamic environment of the territory of the Eastern European Platform general collision. Tectonophysical analysis shows that the inversion folding was formed by the mechanism of sedimentary horizons longitudinal bending in the environment of the interference of the intraplate submeridional collision compression and the regional strike-slip stress field. At the Mesozoic-Cenozoic stage, tectonic inversion continued in the field of right-hand strike-slip deformations with a variable compressive component. This caused the formation of folded covers of tectonic plates and scales in the uplift-thrust mode. They, Hercynian neo-autochthonous formations and further the weakly located syneclise autochthon of the South-east of the Basin. The pressure of the "tectonic stamp" geoblock of the Donetsk Foldbelt contributed to the formationof the Segment body of geomass Tectonic Wedging. It was diagnosed with a structural orocline of transverse extension of the sliding type. Large linear throw-folded zones were formed within geodynamic bands of injection and displacement of geomass along the front of the orocline. The tectonic compression fan, characteristic of geodynamic compression zones, was formed in the foreland of the orocline, on the ends of the main thrusts. They served as “tectonic rails”of the allochthon invasion within the rift-like structure. There are the transverse zones of tectonic sutures formed on the roots of the folding covers of the Hercynian neo-autochthon thrusting, which are located in the hinterland of the orocline in the Foldbelt Western slope. The study completed an original kinematic model of tectonic inversion of the transition zone between the Dnieper-Donets Basin and Donets Foldbelt. According to the model, the pressure of the “tectonic stamp” geoblock initiated the invasion of the Segment of Tectonic Wedging which consists of the intensively dislocated allochthonous geomass. The Segment destroyed the rift-like structure and formed the Western Donetsk Cover-Folded Region in the South-eastern part of the Basin. The system organization model of inversion complications of the rift-like structure in the territory of the Western Donetsk Graben will allow to improve the regional geological schemes of tectonic oil and gas zoning.
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Özsayin, Erman, and Kadir Dirik. "The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extension." Geologica Carpathica 62, no. 4 (August 1, 2011): 345–59. http://dx.doi.org/10.2478/v10096-011-0026-7.
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The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extensionThe NW-SE striking extensional Inönü-Eskişehir Fault System is one of the most important active shear zones in Central Anatolia. This shear zone is comprised of semi-independent fault segments that constitute an integral array of crustal-scale faults that transverse the interior of the Anatolian plateau region. The WNW striking Eskişehir Fault Zone constitutes the western to central part of the system. Toward the southeast, this system splays into three fault zones. The NW striking Ilıca Fault Zone defines the northern branch of this splay. The middle and southern branches are the Yeniceoba and Cihanbeyli Fault Zones, which also constitute the western boundary of the tectonically active extensional Tuzgölü Basin. The Sultanhanı Fault Zone is the southeastern part of the system and also controls the southewestern margin of the Tuzgölü Basin. Structural observations and kinematic analysis of mesoscale faults in the Yeniceoba and Cihanbeyli Fault Zones clearly indicate a two-stage deformation history and kinematic changeover from contraction to extension. N-S compression was responsible for the development of the dextral Yeniceoba Fault Zone. Activity along this structure was superseded by normal faulting driven by NNE-SSW oriented tension that was accompanied by the reactivation of the Yeniceoba Fault Zone and the formation of the Cihanbeyli Fault Zone. The branching of the Inönü-Eskişehir Fault System into three fault zones (aligned with the apex of the Isparta Angle) and the formation of graben and halfgraben in the southeastern part of this system suggest ongoing asymmetric extension in the Anatolian Plateau. This extension is compatible with a clockwise rotation of the area, which may be associated with the eastern sector of the Isparta Angle, an oroclinal structure in the western central part of the plateau. As the initiation of extension in the central to southeastern part of the Inönü-Eskişehir Fault System has similarities with structures associated with the Isparta Angle, there may be a possible relationship between the active deformation and bending of the orocline and adjacent areas.
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Weijermars, Ruud, and Jihoon Wang. "Stress Reversals near Hydraulically Fractured Wells Explained with Linear Superposition Method (LSM)." Energies 14, no. 11 (June 2, 2021): 3256. http://dx.doi.org/10.3390/en14113256.
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Prior studies have noted that the principal stress orientations near the hydraulic fractures of well systems used for energy extraction may wander over time. Typically, the minimum and maximum principal stresses—in the horizontal map view—swap their respective initial directions, due to (1) fracture treatment interventions, and (2) pressure depletion resulting from production. The present analysis shows with stress trajectory visualizations, using a recently developed linear superposition method (LSM), that at least two generations of stress reversals around hydraulic fractures occur. The first generation occurs during the fracture treatment; the second occurs immediately after the onset of so-called flow-back. During each of these stress swaps in the vicinity of the hydraulic fractures, reservoir directions that were previously in compression subsequently exhibit extension, and directions previously stretching subsequently exhibit shortening. The pressure change in the hydraulic fractures—from over-pressured to under-pressured (only held open by proppant packs)—caused the neutral points that separate domains with different stress states to migrate from locations transverse to the fracture to locations beyond the fracture tips. Understanding such detailed geo-mechanical dynamics, related to the pressure evolution in energy reservoirs, is extremely important for improving both the fracture treatment and the well operation, as future hydrocarbon and geothermal energy extraction projects emerge.
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Benn, Douglas, Jason Gulley, Adrian Luckman, Artur Adamek, and Piotr S. Glowacki. "Englacial drainage systems formed by hydrologically driven crevasse propagation." Journal of Glaciology 55, no. 191 (2009): 513–23. http://dx.doi.org/10.3189/002214309788816669.
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AbstractRecent work has shown that surface-to-bed drainage systems re-form annually on parts of the Greenland ice sheet and some High Arctic glaciers, leading to speed-up events soon after the onset of summer melt. Surface observations and geophysical data indicate that such systems form by hydrologically driven fracture propagation (herein referred to as ‘hydrofracturing’), although little is known about their characteristics. Using speleological techniques, we have explored and surveyed englacial drainage systems formed by hydrofracturing in glaciers in Svalbard, Nepal and Alaska. In Hansbreen, Svalbard, vertical shafts were followed through ∼60 m of cold ice and ∼10 m of temperate basal ice to a subglacial conduit. Deep hydrofracturing occurred at this site due to a combination of extensional ice flow and abundant surface meltwater at a glacier confluence. The englacial drainage systems in Khumbu Glacier, Nepal, and Matanuska Glacier, Alaska, USA, formed in areas of longitudinal compression and transverse extension and consist of vertical slots that plunge down-glacier at angles of 55° or less. The occurrence of englacial drainages initiated by hydrofracturing in diverse glaciological regimes suggests that it is a very widespread process, and that surface-to-bed drainage can occur wherever high meltwater supply coincides with ice subjected to sufficiently large tensile stresses.
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Kehrl, Laura M., Huw J. Horgan, Brian M. Anderson, Ruzica Dadic, and Andrew N. Mackintosh. "Glacier velocity and water input variability in a maritime environment: Franz Josef Glacier, New Zealand." Journal of Glaciology 61, no. 228 (2015): 663–74. http://dx.doi.org/10.3189/2015jog14j228.
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AbstractShort-term glacier velocity variations typically occur when a water input is accommodated by an increase in the subglacial water pressure. Although these velocity variations have been well documented on many glaciers, few studies have considered them on glaciers where heavy rain and glacier melt occur year-round. This study investigates the relationship between water inputs and glacier velocity on Franz Josef Glacier, New Zealand. We installed six GNSS stations across the lower glacier during austral summer 2010/11 and one station during summer 2012/13. Glacier velocity remained elevated at all stations for ∼7 days following large rain events. During diurnal melt events, we find velocity variations in the early afternoon (12:00–16:00) at 600 m a.s.l. and in the late evening (20:00–01:00) at 400 m a.s.l. We hypothesize that the late-evening velocity variations occurred as an upstream region of high subglacial water pressures and accelerated ice motion propagated downstream. This mechanism may also explain the increased longitudinal compression and transverse extension across the lower glacier during speed-up events. Our results indicate that the subglacial drainage system likely decreases in efficiency upstream and that the water input variability can still cause short-term velocity variations despite the large year-round water inputs.
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Charmetant, Adrien, Emmanuelle Vidal-Sallé, and Philippe Boisse. "3D Hyperelastic Constitutive Model for Yarn Behaviour Description." Key Engineering Materials 504-506 (February 2012): 267–72. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.267.
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The preforming stage of the LCM composite manufacturing processes lead to fibrous reinforcement deformations which may be very large especially for double curvature shapes. Those deformations have significant influence on the second stage of the process, i.e. the injection of the resin. A way to predict accurately the spatial distribution of the permeability tensor consists in simulating for various configurations, the deformed shape of the reinforcement at the scale of the yarns. Mesoscopic scale analyses of textile reinforcements generally consider the yarns as a continuous material despite their fibrous nature. In order to have an accurate simulation tool, it is necessary to build up a constitutive law which accounts for the physical specificities linked to the microstructure of the yarns. Several models exist with reasonable accuracy. The present paper proposes a new approach in the hyperelasticity framework. The proposed model is based on the definition of mathematical invariants linked to the four main deformation modes of the yarn material: tension, compaction, longitudinal shear and transverse shear. The strain energy potential build up with those invariants is identified using classical fabric material tests: uni- and bi-axial tension and compression. The model has been validated on laboratory tests such as bias extension tests and gives promising results.
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Waqar, Mueez, Susan Huson, D. Gareth Evans, John Ealing, Konstantina Karabatsou, K. Joshi George, and Calvin Soh. "C2 neurofibromas in neurofibromatosis type 1: genetic and imaging characteristics." Journal of Neurosurgery: Spine 30, no. 1 (January 2019): 126–32. http://dx.doi.org/10.3171/2018.7.spine171340.
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OBJECTIVEC2 nerve root neurofibromas have been reported frequently in patients with neurofibromatosis type 1 (NF1), although their genetic and imaging characteristics are unexplored. The aim of this study was to characterize genetic and spinal imaging findings in a large cohort of NF1 patients with C2 neurofibromas.METHODSThe authors performed a review of national NF1 referrals between 2009 and 2016. Inclusion criteria were at least 1 C2 root neurofibroma and cervical-spine or whole-spine MRI scans available for analysis. Blinded imaging review was performed by a neuroradiologist with an interest in NF1.RESULTSFifty-four patients with 106 C2 neurofibromas were included. The median age was 32.5 years (range 15–61 years), and there were slightly more male patients (33 vs 21 female patients). Splice-site (30%) and missense (20%) variants were frequent. Spinal neurofibromas were distributed in all spine regions (65%) or in the cervical spine alone (22%). Most (93%) C2 neurofibromas were visible on MRI scans of the head. Intradural invasion and cord compression in the cervical spine included the C2 level in 95% and 80% of patients, respectively. Compared with all other cervical spine neurofibromas in these patients, C2 neurofibromas had higher rates of intraspinal extension (75% vs 32%; OR 6.20, 95% CI 3.85–9.97; p < 0.001), intradural invasion (53% vs 26%; OR 3.20, 95% CI 2.08–4.92; p < 0.001), and cord compression (25% vs 13%; OR 2.26, 95% CI 1.35–3.79; p = 0.002). However, C2 neurofibromas had lower rates of extraforaminal growth beyond the transverse process (12% vs 62%; OR 0.09, 95% CI 0.05–0.16; p < 0.001).CONCLUSIONSC2 neurofibromas are associated with an aggressive intraspinal phenotype, limited growth outside the spinal canal, and an uncommon genetic profile. These observations require future study.
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Rabus, B. T., and D. R. Fatland. "Comparison of SAR-interferometric and surveyed velocities on a mountain glacier: Black Rapids Glacier, Alaska, U.S.A." Journal of Glaciology 46, no. 152 (2000): 119–28. http://dx.doi.org/10.3189/172756500781833214.
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AbstractAn interferogram reflecting the motion of Black Rapids Glacier, Alaska, U.S.A., was obtained from two European Remote-sensing Satellite (ERS-1) syntheticaperture radar (SAR) images, acquired on 22 and 25 January 1992. We investigate whether the interferometric data are quantitatively consistent with terrestrial velocity measurements along three transverse profiles. These terrestrial data are from different years (1987, 1990, 1996) and cover different periods (6–28 April, 23 May–7 July and a whole year) than the SAR interferogram. Terrestrial ice velocity at the date of the SAR imagery is obtained via seasonal and annual corrections that are calculated from other terrestrial velocity measurements available at higher time resolution for selected sites on the glacier. Interferometric and terrestrial velocity are in excellent agreement if a (terrestrially measured) surface-normal velocity component (v⊥) is properly accounted for. This suggests that both the interferometric velocities and the conversions of terrestrial data to the winter period are reliable. The terrestrial velocity measurements show that ice flow in the upper ablation area (14–16 km sites) changes from longitudinal compression in mid-winter (v⊥ = + 0.82 cm d−1) to moderate longitudinal extension during summer (v⊥ ≈ –0.25 cm d−1). In the lower ablation area, the seasonal variations of the longitudinal strain rate are much smaller: +1.0 and about +0.85 cm d−1 for the respective mid-winter and summer values of v⊥ at the 20 km site.
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Pokalyuk, V. V., I. E. Lomakin, and V. G. Verkhovtsev. "Baltic-Iranian super lineament — long-lived Trans-Eurasian belt of dislocations and planetary megafractures." Kosmìčna nauka ì tehnologìâ 26, no. 5 (2020): 48–72. http://dx.doi.org/10.15407/knit2020.05.048.
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Information on fault tectonics and the deep structure of the global trans-Eurasian belt of dislocations and planetary megafractures (Baltic-Iranian Super Lineament) is generalized based on the analysis of literary, geological and geophysical, cartographic, cosmographic materials, including the results of tectonic lineaments interpretation of cosmo-images of the Earth’s surface. The features of its distribution and segmentation are clarified. This Super Lineament is the trans-Eurasian structure of a planetary rank — an integral part of the regularly spatially oriented ancient reghmatic fault net of Eurasia, formed at the early stages of the formation of the rigid earth crust under the influence of global stresses associated with the factor of rotation of the Earth. The long-lived nature of the belt (the Upper Proterozoic — Cenozoic) and its quasi-stationary position throughout its formation history, as well as the absence of large-scale, hundreds of kilometers, of shear displacements along it and at intersections with transverse tectolineament belts of a similar rank indicate the low probability of the plate-tectonic convergence model of Afro-Arabia and Eurasia. The destruction model of the once united Afro-Eurasian continent in a potentially shear field of relatively low amplitude (on a planetary scale) dislocations is preferable. The geodynamic mode of formation and development of the belt as a whole cannot be described by any one type — riftogenic, or collisional ones. Regional and supra-regional zones of extension (riftogenic zones) and compression (collision) alternate in it periodically. It shows the global nature of the belt, the union of different geodynamic regimes in it, as well as the wave character and hierarchy of the tectonic process.
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Almefty, Kaith K., and Ossama Al-Mefty. "Petrosal Approach With Preservation of the Superior Petrosal Sinus (the Graceful Petrosal) for Resection of Giant Trigeminal Schwannoma: 2-Dimensional Operative Video." Operative Neurosurgery 20, no. 5 (April 15, 2021): E342—E343. http://dx.doi.org/10.1093/ons/opaa427.
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Abstract Trigeminal schwannomas are benign tumors amendable to curative surgical resection.1 Excellent outcomes, with preservation and improvement of cranial nerve function, including trigeminal nerve function, have been reported with microsurgical resection through skull base approaches.2 Dumbell shaped tumors, involving the middle and posterior fossa, are more challenging.3 They are resected via a middle cranial fossa approach with the expanded Meckel cave providing access to the posterior fossa. However, tumors with a large caudal extension below the internal auditory meatus typically cannot be adequately accessed with this approach and the posterior petrosal approach is utilized.2 Specific venous anatomy might deter from cutting the tentorium. This article describes the surgical resection of a trigeminal schwannoma with a large posterior fossa component through a petrosal approach without cutting the tentorium.4 The patient is a 34-yr-old man who presented with headaches and gait disturbance. Neurological exam revealed hypoesthesia and hypoalgesia in the left V1 and V2 distributions. Magnetic resonance imaging (MRI) revealed a large dumbbell-shaped schwannoma causing brainstem compression. Magnetic resonance venography (MRV) demonstrated temporal lobe venous drainage into the superior petrosal sinus and tentorium proximal to the transverse sigmoid junction. A single temporal-suboccipital bone flap and a retro-labrynthine mastoidectomy were performed. The petrous apex was drilled and Meckle's cave opened. The presigmoid dura was opened and extended toward the petrous apex region beneath the tentorium. This provided access to and safe resection of the tumor. A gross total tumor resection was achieved. The patient remained stable neurologically and was without tumor recurrence at 3 yr postoperatively. The patient had consented to the procedure. Figures in video at 4:06 from Jafez et al, Preservation of the superior petrosal sinus during the petrosal approach, J Neurosurg. 2011;114(5):1294-1298, with permission from JNSPG.
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Bayir, A., U. Kaldirim, S. Ardic, Y. E. Eyi, I. Arziman, and M. Durusu. "(P2-62) An Infrequent Case of Orthopedic Emergencies – Open Dorsal Dislocation of the Proximal Interphalangeal (PIP) Joint Dislocation." Prehospital and Disaster Medicine 26, S1 (May 2011): s155—s156. http://dx.doi.org/10.1017/s1049023x11005061.
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IntroductionReducible open dorsal dislocation of the single finger's PIP joint is an infrequent case of orthopedic emergencies. The severity of this injury may be underestimated. These injuries are associated with long-term complications such as synovitis, stiffness, degenerative arthrosis, septic arthritis, and loss of the digit if suboptimally treated.CaseA 90-year-old male came to the emergency department with an open dorsal PIP dislocation due to a fall on his right hand. There was a transverse skin laceration just proximal to the PIP flexion crease of his small and ring fingers. The condyles of his small finger's proximal phalanx protruded through the wound. X-rays showed a dorsal dislocation of the PIP joint without fracture. There was no neurovascular injury determined. The proximal phalanx was hyperextended slightly with gentle axial traction. After irrigation, the skin wound was closed primarily without repair of damaged structures, and systemic antibiotherapy was performed for a week. The PIP joint was immobilized for three weeks by applying the splint dorsally with the joint in 20 degrees of flexion. Active range of motion exercises were then implemented, and the patient regained full digital flexion with only a 10 degree loss of extension within eight weeks.DiscussionForced hyperextension with axial compression causes a dorsal dislocation of the PIP joint. Dorsal PIP dislocations are more common than volar IP dislocation. Open dorsal dislocation of the PIP joint is an infrequent case of orthopedic emergencies. Such injuries can be treated safely in the emergency department by closed reduction and extensor splinting until a definite treatment plan is made by an orthopedic hand surgeon. The complications must be taken into consideration. Early active motion leads to significantly superior results in the range of motion than static splinting, because prolonged immobilization may result in flexion contracture.
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Altafulla, Juan, Emre Yilmaz, Stefan Lachkar, Joe Iwanaga, Jacob Peacock, Zachary Litvack, and R. Shane Tubbs. "Neck movement during cervical transforaminal epidural injections and the position of the vertebral artery: an anatomical study." Acta Radiologica Open 8, no. 3 (March 2019): 205846011983468. http://dx.doi.org/10.1177/2058460119834688.
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Background Cervical transforaminal epidural steroid injections (CTFESIs) are sometimes performed in patients with cervical radiculopathy secondary to nerve-root compression. Neck movements for patient positioning may include rotation, flexion, and extension. As physicians performing such procedures do not move the neck for fear of injuring the vertebral artery, we performed fluoroscopy and cadaveric dissection to analyze any movement of the vertebral artery during head movement and its relation to the foramina in the setting of CTFESI. Purpose To determine cervical rotational positioning for optimized vertebral artery location in the setting of cervical transforaminal epidural steroid injections. Material and Methods Four sides from two Caucasian whole cadavers (all fresh-frozen) were used. Using a guide wire and digital subtraction fluoroscopy, we evaluated the vertebral artery mimicking a CTFESI, then we removed the transverse processes and evaluated the vertebral artery by direct observation. Results After performing such maneuvers, no displacement of the vertebral artery was seen throughout its course from the C6 to the C2 intervertebral foramina. To our knowledge, this is the first anatomical observation of its kind that evaluates the position of the vertebral artery inside the foramina during movement of the neck. Conclusion Special caution should be given to the medial border of the intervertebral foramina when adjusting the target site and needle penetration for the injection. This is especially true for C6-C4 levels, whereas for the remaining upper vertebrae, the attention should be focused on the anterior aspect of the foramen. Since our study was centered on the vertebral artery, we do not discard the need for contrast injection and real-time digital subtraction fluoroscopy while performing the transforaminal epidural injection in order to prevent other vascular injuries.
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Rajasekaran, Shanmuganathan, Dilip Chand Raja Soundararajan, Ajoy Prasad Shetty, and Rishi Mugesh Kanna. "Motion-Preserving Navigated Primary Internal Fixation of Unstable C1 Fractures." Asian Spine Journal 14, no. 4 (August 31, 2020): 466–74. http://dx.doi.org/10.31616/asj.2019.0189.
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Study Design: Prospective observational study.Purpose: To assess the safety, efficacy, and benefits of computed tomography (CT)-guided C1 fracture fixation.Overview of Literature: The surgical management of unstable C1 injuries by occipitocervical and atlantoaxial (AA) fusion compromises motion and function. Monosegmental C1 osteosynthesis negates these drawbacks and provides excellent functional outcomes.Methods: The patients were positioned in a prone position, and cranial traction was applied using Mayfield tongs to restore the C0–C2 height and obtain a reduction in the displaced fracture fragments. An intraoperative, CT-based navigation system was used to enable the optimal placement of C1 screws. A transverse rod was then placed connecting the two screws, and controlled compression was applied across the fixation. The patients were prospectively evaluated in terms of their clinical, functional, and radiological outcomes, with a minimal follow-up of 2 years.Results: A total of 10 screws were placed in five patients, with a mean follow-up of 40.8 months. The mean duration of surgery was 77±13.96 minutes, and the average blood loss was 84.4±8.04 mL. The mean combined lateral mass dislocation at presentation was 14.6±1.34 mm and following surgery, it was 5.2±1.64 mm, with a correction of 9.4±2.3 mm (<i>p</i> <0.001). The follow-up CT showed excellent placement of screws and sound healing. There were no complications and instances of AA instability. The clinical range of movement at 2 years in degrees was as follows: rotation to the right (73.6°±9.09°), rotation to the left (71.6°±5.59°), flexion (35.4°±4.5°), extension (43.8°±8.19°), and lateral bending on the right (28.4°±10.45°) and left (24.8°±11.77°). Significant improvement was observed in the functional Neck Disability Index from 78±4.4 to 1.6±1.6. All patients returned to their occupation within 3 months.Conclusions: Successful C1 reduction and fixation allows a motion-preserving option in unstable atlas fractures. CT navigation permits accurate and adequate monosegmental fixation with excellent clinical and radiological outcomes, and all patients in this study returned to their preoperative functional status.
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Minto, Bruno Watanabe, Paloma Do Espírito Santo Silva, Paulo Vinícius Tertuliano Marinho, Carolina Camargo Zani, Pedro Henrique Ferreira Teles, Karin Werther, Tiago Barbolho Lima, and Júlio Carlos Canola. "Lumbar Myelography in a Crab-Eating Raccoon (Procyon cancrivorus)." Acta Scientiae Veterinariae 44, no. 1 (January 16, 2016): 5. http://dx.doi.org/10.22456/1679-9216.84509.
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Background: The Crab-eating raccoon (Procyon cancrivorus) is a nocturnal mammal and lives in savannah, but loss of their natural habitat makes increase cases of traffic accidents on the roads. A growing number of wildlife are treated in veterinary hospitals, but we have some limitation about the correct interpretation of the diagnostic test, specially because, even the tests were not described. Myelography is a radiographic technique indicated for compressive lesions of the spinal cord that are not seen on plain radiographs. The present report aims to describe, for the first time, a lumbar myelogram performed in a paraplegic crab-eating raccoon after it suffer a traffic trauma.Case: A free living adult, 8-kg, female raccoon was presenting acute paraplegia and swelling in the region of the left humerus was referred at veterinary hospital. The patient was alert and aggressive, good body score and no signs of active bleeding. The animal temper did not allow approaching it; therefore, physical and neurological examinations were not feasible. The raccoon was tranquilized (1.6 mL of nilperidol® intramuscular), anesthetized (propofol, dose-effect intravenous) and tracheal intubation to provide oxygen and the patient was monitored continuously, followed by referred for radiology service. The simple radiograph showed a complete transverse fracture in the humerus and compression fracture of the twelfth thoracic vertebra (T12), being then indicated the myelographic examination to assess the extent of spinal cord compression. The lumbar region was surgical antisepsis prepared. After being properly positioned in lateral decubitus with moderate cranial flexion of the trunk, the patient underwent lumbar puncture by inserting a spinal needle between the 5th and 6th intervertebral lumbar spaces. The spinal needle was introduced slightly caudolaterally to the spinous process of the 6th lumbar vertebra and cranioventrally directed at an angle of 45º. Then, the needle was pierced through the ligamentum flavum and the dura mater while, concomitantly, we observed the tail moving and the cerebrospinal fluid (CSF) output while the contrast was injected. The contrast iohexol (300 mg/mL) was used at a dose of 0.25 mL/kg. Immediately after the slow injection of contrast (approximately 3 min), radiographs were taken in the latero-lateral and ventrodorsal projections to identify the location of the spinal cord disorder. The extension degree of the lesion was evidenced by the reduction of the contrast column width at the location of instability. The patient was referred for surgical decompression and stabilization.Discussion: In cases where paraplegia results from trauma, spinal radiography and myelography are important means to confirm the diagnosis, specially the extent of the compression and prognosis. There are certain risks inherent in the myelography procedure as arrhythmias and bradycardia during collection, transient apnea during contrast injection and seizures during recovery. Furthermore, deteriorating neurological signs, emesis, urinary retention and hyperthermia are other possible complications. Most of these complications are seen predominantly during cervical myelography compared to lumbar puncture because in the first exam, the contrast hardly reaches the brain and there is no risk of iatrogenic injury to the medulla oblongata. To minimize the neurotoxic effects, the ideal contrast should be radiopaque, water soluble, miscible with the cerebrospinal fluid (CSF), nontoxic and removed from the CSF by physiological processes. Iohexol contrast was used effectively, without neurotoxicity upon clinical evaluation while the volume used was sufficient to determine the injury site. The reported case demonstrated the possibility of performing lumbar myelography on Procyon cancrivorus effectively without significant complications or difficulties.Keywords: wildlife, neurology, myelographic examination, Procyon cancrivoru.
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Pustovitenko, B., and E. Eredzhepov. "SPECTRAL and SOURCE PARAMETERS of CRIMEAN-BLACK SEA EARTHQUAKES." Earthquakes in Northern Eurasia, no. 23 (December 15, 2020): 250–62. http://dx.doi.org/10.35540/1818-6254.2020.23.25.
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The spectral and dynamic source parameters (М0, r0, , , ησ, , ū, Eu and Mw) of 13 Crimean earthquakes with КП = 7.2–11.2 (Mw=2.6–4.1), restored by 123 amplitude spectra of longitudinal and transverse seismic waves recorded by digital regional seismic stations is shown. Approximation of the spectra and the source dynamic parameters calculation based on their parameters is performed in the framework of the Brune dislocation model. Four to seven station definitions participated in the averaging of focal parameters, which ensured a small standard deviation, the scattering degree index of the individual estimates. The best convergence of the station definitions is obtained for the radius of a circular dislocation. The highest values of dynamic para-meters have been obtained for the perceptible earthquake on March 2 with КП=11.2, and the lowest values have been obtained for its weak aftershock on April 6 with КП = 7.2. Within the total range of energies the value of the stress drop does not exceed = 106Pa(10 bar), and the apparent stress drop does not exceed ησ<3∙105Pa (3 bar). The average values of seismic moments and circular dislocation radius within the errors of their deter-mination match the average long-term correlations of the parameters on the earthquake energy level obtained by the analog recording.For the strongest earthquakes on March 2 with Mwreg=4.1 and October 18 with Mwreg=3.8 solutions of the focal mechanisms were obtained. The March 2 earthquake occurred in the central part of the region near the South Coast of Crimea under the action of horizontal tensile forces oriented near the latitude. The type of movement in the focus is a obligue slip with predominance of a normal component over a strike-slip. The earthquake on October 18 occurred in the central part of the Black Sea basin in condition of sublatitudinal compression and submeridional extension. Type of movement in the source is a pure strike-slip. For the main shock on March 2 and its six aftershocks, energy spectra according to the data of Alushta station and their main parameters are given. The analysis of obtained results is given.
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Alnahas, Zeinab, and Mohamad H. Horani. "RF11 | PSAT274 A Dramatic Response of a Thyroid Lymphoma to R-CHOP Chemotherapy Reversing Mechanical Airway Obstruction and Respiratory failure, A Case Report." Journal of the Endocrine Society 6, Supplement_1 (November 1, 2022): A854. http://dx.doi.org/10.1210/jendso/bvac150.1766.
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Abstract Introduction Primary thyroid lymphoma is extremely rare and accounts for <5% of all thyroid malignancies, with an estimated incidence of 2 per 1 million each year. It usually occurs in patients with preexisting Hashimoto thyroiditis and commonly presents between 60 to 70 years. Almost all thyroid lymphomas are non-Hodgkin's lymphoma of B-cell origin, with diffuse large B-cell lymphoma being the most common subtype. Chemotherapy and radiotherapy are the primary treatment of thyroid lymphomas. This case report shows a dramatic response to chemotherapy in a patient with mechanical airway obstruction due to large thyroid lymphoma, which facilitated her extubation. Case Presentation An 83-year-old woman with a past medical history significant for type 2 diabetes, coronary heart disease, and hypothyroidism controlled on L-thyroxine replacement therapy was presented with 3 months history of gradually progressive dysphagia. It was associated with left-sided neck pain with swallowing, choking on food, and shortness of breath. She denied fever, chills, or excessive sweats. Local examination of her neck revealed a large firm thyroid mass associated with left cervical lymphadenopathy. Her CT neck scan with intravenous contrast showed an enlarged, probably malignant thyroid gland with marked amount of adjacent pathologic lymph nodes and marked transverse narrowing of the trachea to approximately 8.6 mm with no retrosternal extension. Also, Her CT abdominal scan with intravenous contrast showed a 3.6 cm lesion of the medial right hepatic lobe (segment 8) concerning for metastases. The patient underwent an ultrasound-guided thyroid biopsy, and the results confirmed the diagnosis of diffuse large B cell lymphoma of the neck and thyroid. A few days later, the patient experienced respiratory distress and failure secondary to mechanical airway obstruction that required urgent intubation and mechanical ventilation. The discussion among different specialties, including general surgery, concluded that the patient was not a candidate for surgical intervention or tracheostomy, and recommendations were to proceed to palliative chemotherapy. She started R-CHOP chemotherapy (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone), followed by a marked reduction in the thyroid size and relieving of the tracheal compression on the following CT neck scan. Her condition dramatically improved, and she was extubated after 5 days of receiving the first cycle of R-CHOP chemotherapy. Conclusion Our case report demonstrates dramatic reversal of mechanical airway obstruction caused by a thyroid lymphoma within a few days of initiation of R-CHOP chemotherapy. These cases are usually considered terminal and do not undergo aggressive surgical interventions. R-CHOP chemotherapy needs to be considered in these cases before considering hospice care. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Saturday, June 11, 2022 1:12 p.m. - 1:17 p.m.
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Lazopoulos, K. A., A. K. Lazopoulos, and D. Stamenovic. "A model of cytoskeletal reorientation in response to substrate stretching." Theoretical and Applied Mechanics 35, no. 1-3 (2008): 171–90. http://dx.doi.org/10.2298/tam0803171l.
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Living adherent cells change their orientation in response to substrate stretching such that their cytoskeletal components reorganize in a new direction. To study this phenomenon, we model the cytoskeleton as a planar system of elastic cables and struts both pinned at their endpoints to a flat flexible substrate. Tensed (pre-strained) cables represent acting stress fibers, whereas compression-bearing struts represent microtubules. We assume that in response to uniaxial substrate stretching the model reorients and deforms into a new configuration that minimizes its total potential energy. Using the Maxwell's global stability criterion, we find global minima configurations during static extension and compression of the substrate. Based on these results, we predict reorientation during cyclic stretching of the substrate. We find that in response to cyclic stretching cells either reorient transversely to the direction of stretching, or exhibit multiple configurations symmetrically distributed relative to the direction of stretching. These predictions are consistent with experimental data on living cells from the literature.
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Souza, Maria Verônica de, Carlos Henrique Osório Silva, Micheline Ozana da Silva, Marcela Bueno Martins da Costa, Raul Felipe Dornas, Andréa Pacheco Batista Borges, and Antônio José Natali. "Achilles tendon of wistar rats treated with laser therapy and eccentric exercise." Revista Brasileira de Medicina do Esporte 21, no. 5 (October 2015): 332–37. http://dx.doi.org/10.1590/1517-869220152105144256.
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ABSTRACT Introduction: Both laser therapy and eccentric exercises are used in tendon injuries. However, the association of these physiotherapeutic modalities is yet little investigated. Objective: To evaluate the effect of low-level laser therapy associated to eccentric exercise (downhill walking) on Achilles tendinopathy of Wistar rats. Method: Eighteen Achilles tendon from 15 adult male Wistar rats were used. Tendons were distributed in six groups (laser, eccentric exercise, laser and eccentric exercise, rest, contralateral tendon, and healthy tendon). Unilateral tendinopathy was surgically induced by transversal compression followed by scarification of tendon fibers. The treatments laser therapy (904 nm, 3J/cm²) and/or eccentric exercise (downhill walking; 12 m/min; 50 min/day; 15o inclination treadmill) began 24 hours after surgery and remained for 20 days. Clinical and biomechanical analyzes were conducted. Achilles tendon was macroscopically evaluated and the transversal diameter measured. Euthanasia was performed 21 days after lesion induction. Tendons of both limbs were collected and frozen at -20°C until biomechanical analysis, on which the characteristic of maximum load (N), stress at ultimate (MPa) and maximum extension (mm) were analyzed. Results: Swelling was observed within 72 hours postoperative. No fibrous adhesions were observed nor increase in transversal diameter of tendons. Animals with the exercised tendons, but not treated with laser therapy, presented lower (p=0.0000) locomotor capacity. No difference occurred be-tween groups for the biomechanical characteristics maximum load (p=0.4379), stress at ultimate (p=0.4605) and maximum extension (p=0.3820) evaluated, even considering healthy and contralateral tendons. Conclusion: The concomitant use of low-level laser and the eccentric exercise of downhill walking, starting 24 hours after surgically induced tendinopathy, do not result in a tendon with the same biomechanical resistance or elasticity as a healthy tendon. On the other hand, it also does not influence negatively the structure and function of the Achilles tendon.
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Nomikou, Paraskevi, Dimitris Evangelidis, Dimitrios Papanikolaou, Danai Lampridou, Dimitris Litsas, Yannis Tsaparas, and Ilias Koliopanos. "Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece." Geosciences 11, no. 2 (February 20, 2021): 102. http://dx.doi.org/10.3390/geosciences11020102.
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On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.
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Shiraiwa, Takayuki, Yaroslav D. Murav’yev, Takao Kameda, Fumihiko Nishio, Yoko Toyama, Akiyoshi Takahashi, Alexander A. Ovsyannikov, Andrey N. Salamatin, and Kotaro Yamagata. "Characteristics of a crater glacier at Ushkovsky volcano, Kamchatka, Russia, as revealed by the physical properties of ice cores and borehole thermometry." Journal of Glaciology 47, no. 158 (2001): 423–32. http://dx.doi.org/10.3189/172756501781832061.
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AbstractA glacier at the summit of Ushkovsky volcano, Kamchatka peninsula, Russia, was studied in order to obtain information about the physical characteristics of a glacier that fills a volcanic crater. The glacier has a gentle surface and a concave basal profile with a maximum measured depth of 240 m at site K2. The annual accumulation rate was 0.54 m a−1 w.e., and the 10 m depth temperature was −15.8°C. A 211.70 m long ice core drilled at K2 indicates that (1) the site is categorized as a percolation zone, (2) the stress field in the glacier changes at 180 m depth from vertical and longitudinal compression with transversal extension, which is divergent flow, to a shear-dominated stress field, and (3) the frequent occurrence of ash layers can be a good tool for dating the ice core. The borehole temperature profiles were considered to be non-stationary, but the linear profile made it possible to estimate the basal temperature and the geothermal heat flux at K2. Assuming constant surface and the basal boundary conditions, we constructed two depth–age relationships at K2. These predicted that the bottom ages of the ice core were about 511 or 603 years.
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Rasel, Nur-E.-Alam, Md Sofiqul Alam, Md Mostafizur Rahman Siddique, Narottam Debnath, Md Jahangir Alam, Md Shahi Emran Hossain, and Rumana Afroze Rume. "Homoeopathic Treatment of Pituitary Adenoma: A Case Report." Malaysian Journal of Medical and Biological Research 7, no. 2 (September 3, 2020): 109–28. http://dx.doi.org/10.18034/mjmbr.v7i2.509.
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Most pituitary adenomas are slow-growing and benign, which means they are not cancer and do not spread to other parts of the body. They generally have a slow but severe impact on vision due to compression of the optic nerves, optic chiasm, and cavernous sinus. However, as they grow big they can put pressure on nearby structures, such as the nerves that connect the eyes to the brain and cause symptoms. Pituitary adenomas are the third most common intracranial tumor and arise from the pituitary gland. An individual case is presented in this paper with radiological evidence (MRI) of a large lobulated intrasellar mass (3.0 cm transversely, 3.5 cm craniocaudally and 2 cm anteroposteriorly) with supra-sellar extension is causing elevation of the floor of the 3rd ventricle of the brain. Pituitary macroadenoma and hemorrhagic foei, pituitary apoplexy, and pituitary adenomas were founded by different CT scan and MRI reports in different laboratories. The patient was treated with constitutional homoeopathic medicines – Natrum muriticum-m/1, 16 doses up to Natrum muriticum-m/20, 16 doses each from 26/04/2014 to 07/08/2017. Before treatment imaging was done several times from 6/04/2011 to 12/01/2012showed complete resolution of the pituitary adenoma and during treatment3 follow-up imaging was done on 25/07/2015 and 06/08/2017. This case report reviews the clinical presentation, homoeopathic management, and treatment of the major classification of pituitary adenomas and call attention to the need for repertorization in individualized homoeopathic prescription. It is hoped that if this type of clinical research continues in the future, homeopathy will have a breakthrough result and it’s symptomatic medical treatment will play a beneficial role in the near future from the deadly evils of various types of chemotherapy, radiotherapy, or combined therapy.
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Xin, Meng, and Benny Davidovitch. "Stretching Hookean ribbons part I: relative edge extension underlies transverse compression and buckling instability." European Physical Journal E 44, no. 7 (July 2021). http://dx.doi.org/10.1140/epje/s10189-021-00092-z.
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