![]() # It can be used for continuous model fit analysis for the predicted value and by input variable # A binary 0/1 target variable is allowed. # - 7: Created function cumplot() used to plot cumulative y vs. # - 2: Created functions: # - safeLogInv(): computes the inverse of the safeLog() function # - logitInv(): computes the inverse of the logit() function available in the car package # - plot.cdf(): plots the CDF of a variable # - 6: Created function: # - plot.bar(), plot.bars(): makes a bar plot of a target variable in terms of categorical variable # where the bar widths are proportional to the number of cases in each category. For updates see the Git history) # - 9: Created function safeLog(x) to compute sign(x)*log10(constant + abs(x)) # - 3: Created function getAxisLimits() to retrieve the correct X and Y limits of the active plot, since # the values returned by par("usr") are NOT correct for the plots done by default, which use xaxs="r" # and yaxs="r" (regular axis) which imply that the actual "usr" limits are extended from the xlim and # ylim extremes by 4% of the limits range!! (Ref: documentation of par() and the 'xaxs' and 'yaxs' # options therein). For static loading up to 8% strain, the linear elastic model may be used for FE modeling of the spinal cord.# startup-functions.r # Created: July 2008 # Modified: 3 # Author: Daniel Mastropietro # Description: Startup settings to be invoked when R starts # R version: R-2.8.0 (used in SPSS 18.0.0 starting 2013) # INDEX # AUXILIARY functions # DATA TRANSFORMATION functions # GRAPHICAL functions # HISTORY: (keep track of created functions, but no updates. Extensive distraction of the spinal cord resulted in May result in more extensive shear strains than burst fracture injuries, which apply onesided contusion to the cord. Results from this study suggest that dislocation injuries This highlights the possibility of a mechanical or biological The compression results reveal the most extensive damage peripherally, which has notīeen found experimentally. Assuming the hyperelastic model best represents the behaviour of spinal cord tissue, the linear elastic model overestimated the range of axial strains and underestimated the dorsal-ventral and transverse shear strains Linear elastic and hyperelastic constitutive models produced similar strain distributions (difference of less than 1% strain between each maximum component strain) for axial loading of the spinal cord up to 8% axial strain. Critical regions of strain were in the dorsolateral and ventral white matter at the level of the contacting lamina and vertebral body. The dislocation injury mechanism seemed to spare the lateral columns of normal strains, however all columns experienced elevated shear strains. Strains for distraction were more uniformly distributed throughout the cord. The highest strains within the compression injury mechanism were in the dorsal, ventral, and central columns with critical regions in the dorsomedial and ventral white matter between the indentor and the opposing vertebral body. Different strain distributions were found for compression, distraction, and dislocation injury mechanisms. NoĮxperimental data was available for validation of the dislocation injury mechanism. The distraction injury model was validated based on relative displacements of the column and cord (Maiman, Coats et al. ![]() 1979 Hung, Li n et al.ġ982 Tencer, Allen et al. The model of spinal cord compression was validated with previous experimental dataīased on the reaction force at the indentor tip (Hung, Lin et al. Xsort function matlab explain manual#The model was transferred to Abaqus (Abaqus User's Manual version 6.3 2002) for the comparison of constitutive models. ![]() Boundary conditions and loading were designed to simulate experimental data in the literature. ![]() Material properties for the tissues were based on experimental data in the literature. Three vertebrae (C4-6) and the spinal cord were modelled with brick elements, dura mater was modelled with shell elements, and ligaments and discs were modelled with cable elements. Geometry of the model was obtained from the Visible Human Project of the National Library of Medicine and developed into a three-dimensional FE model in Ansys (Ansys User's Manual version 7.1). The final goal was to compare linear elastic and hyperelastic constitutive models for the spinal cord in response to distraction loading. (contusion), distraction, and dislocation. Of this research project were to develop and validate a finite element model of the spinalĬord and the surrounding structures and to use this model to compare the strainĭistributions in the spinal cord for three simple injury mechanisms: compression Mechanical relationship between column and cord injuries is not known. Injuries result from a variety of spinal column injury mechanisms however, the ![]() Spinal cord injury is one of the most devastating medical conditions known. ![]()
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