scholarly journals Biomechanical Evaluations of Ocular Injury Risk for Blast Loading

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Bahram Notghi ◽  
Rajneesh Bhardwaj ◽  
Shantanu Bailoor ◽  
Kimberly A. Thompson ◽  
Ashley A. Weaver ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Injury Risk ◽  
Animal Studies ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Blast Loading ◽  
Ocular Injury ◽  
Tissue Properties ◽  
Primary Blast ◽  
Combat Injuries

Ocular trauma is one of the most common types of combat injuries resulting from the exposure of military personnel with improvised explosive devices. The injury mechanism associated with the primary blast wave is poorly understood. We employed a three-dimensional computational model, which included the main internal ocular structures of the eye, spatially varying thickness of the cornea-scleral shell, and nonlinear tissue properties, to calculate the intraocular pressure and stress state of the eye wall and internal ocular structure caused by the blast. The intraocular pressure and stress magnitudes were applied to estimate the injury risk using existing models for blunt impact and blast loading. The simulation results demonstrated that blast loading can induce significant stresses in the different components of the eyes that correlate with observed primary blast injuries in animal studies. Different injury models produced widely different injury risk predictions, which highlights the need for experimental studies evaluating mechanical and functional damage to the ocular structures caused by the blast loading.

The Influence of Primary Blast Wave on the Posterior Part of the Eyeball

2018 ◽  
Author(s):  
Junfei Tong ◽  
Linxia Gu
Keyword(s):  
Optic Nerve ◽  
Blast Wave ◽  
Military Service ◽  
Vision Loss ◽  
Life Experience ◽  
Three Dimensional ◽  
Posterior Part ◽  
Ocular Injury ◽  
Primary Blast ◽  
Globe Rupture

With the increasing application of improvised explosive devices, the ratio of traumatic ocular injury significantly increased in the past decades, which has become the fourth most happened injury to military deployment. The ocular injury treatment is costly and has been less effective, which influences the military service and life experience of the soldiers. With years of research on the traumatic ocular injury through experiment or computational simulations, the primary blast wave related overpressure was found to induce macular damage, globe rupture. While the influence of the primary blast wave on the posterior part of the eyeball was poorly understood, such as the optic nerve. In this work, we developed a three-dimensional computation model, which included lamina cribrosa (LC), optic nerve and cerebrospinal fluid (CSF). The strain evaluated in optic nerve was found to exceed neural tissue’s physiological loading range, which might explain the vision loss after the blast.

Computational Simulations of Ocular Blast Loading and Prediction of Eye Injury Risk

2012 ◽  
Author(s):  
Joel D. Stitzel ◽  
Ashley A. Weaver
Keyword(s):  
Injury Risk ◽  
Blast Loading ◽  
Ocular Injury ◽  
Eye Injury ◽  
Computational Simulations ◽  
Improvised Explosive Devices ◽  
War Injuries ◽  
Ocular Morbidity ◽  
Improvised Explosive ◽  
Explosive Devices

Ocular injury from blast loading is associated with severe ocular morbidity and visual impairment [1]. Improvised explosive devices are a common cause of ocular injury and were responsible for 51% of ocular war injuries in a study by Mader et al [2].

scholarly journals Targeting hepatocyte growth factor in epithelial–stromal interactions in an in vitro experimental model of human periodontitis

Odontology ◽  
2021 ◽  
Author(s):  
Yoko Yamaguchi ◽  
Akira Saito ◽  
Masafumi Horie ◽  
Akira Aoki ◽  
Patrick Micke ◽  
...  
Keyword(s):  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Collagen Gel ◽  
Neutralizing Antibody ◽  
Chronic Inflammatory Disease ◽  
Collagen Degradation ◽  
Hepatocyte Growth

AbstractPeriodontitis is a chronic inflammatory disease leading to progressive connective tissue degradation and loss of the tooth-supporting bone. Clinical and experimental studies suggest that hepatocyte growth factor (HGF) is involved in the dysregulated fibroblast–epithelial cell interactions in periodontitis. The aim of this study was to explore effects of HGF to impact fibroblast-induced collagen degradation. A patient-derived experimental cell culture model of periodontitis was applied. Primary human epithelial cells and fibroblasts isolated from periodontitis-affected gingiva were co-cultured in a three-dimensional collagen gel. The effects of HGF neutralizing antibody on collagen gel degradation were tested and transcriptome analyses were performed. HGF neutralizing antibody attenuated collagen degradation and elicited expression changes of genes related to extracellular matrix (ECM) and cell adhesion, indicating that HGF signaling inhibition leads to extensive impact on cell–cell and cell–ECM interactions. Our study highlights a potential role of HGF in periodontitis. Antagonizing HGF signaling by a neutralizing antibody may represent a novel approach for periodontitis treatment.

scholarly journals Numerical and Experimental Studies on a Three-Dimensional Numerical Wave Tank

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 6585-6593 ◽  
Author(s):  
Xiaojie Tian ◽  
Qingyang Wang ◽  
Guijie Liu ◽  
Wei Deng ◽  
Zhiming Gao
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Numerical Wave

Numerical Modeling of Tube Hydropiercing Using Phenomenological and Micro-Mechanical Damage Criteria

2013 ◽  
Vol 549 ◽  
pp. 172-179 ◽  
Author(s):  
Amir Hassannejadasl ◽  
Daniel E. Green
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Equivalent Plastic Strain ◽  
Mechanical Damage ◽  
High Strength ◽  
Dimensional Finite Element ◽  
Steel Dp600 ◽  
Three Dimensional Finite Element ◽  
Jc Model ◽  
Damage Criteria

Hydropiercing is an efficient way of piercing holes in mass produced hydroformed parts with complex geometries. By driving piercing punches radially into a hydroformed and fully pressurized tube, holes will be pierced and extruded into the tube-wall. Recent experimental studies have shown that the formability of advanced high strength steel (AHSS) tubes can be increased with the application of internal pressure. In this study, three-dimensional finite element simulations of a tube hydropiercing process of a dual phase steel (DP600) were performed in LS-DYNA, using phenomenological, micromechanical and combined damage criteria. Damage was included in the numerical analysis by applying constant equivalent plastic strain (CEPS), the Gurson-Tvergaard-Needleman (GTN), and the Extended GTN (GTN+JC) model. In order to calibrate the parameters in each model, a specialized hole-piercing fixture was designed and piercing tests were carried out on non-pressurized tube specimens. Of the various ductile fracture criteria, the results predicted with the GTN+JC model, such as the punch load-displacement, the roll-over depth, and the quality of the clearance zone correlated the best with the experimental data.

Fracture Mechanics of Thin Plates and Shells Under Combined Membrane, Bending, and Twisting Loads

2005 ◽  
Vol 58 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Alan T. Zehnder ◽  
Mark J. Viz
Keyword(s):  
Fracture Mechanics ◽  
Plate Theory ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Crack Tip ◽  
Thin Plates ◽  
Element Analysis ◽  
Crack Tip Fields ◽  
Plates And Shells ◽  
Membrane Bending

The fracture mechanics of plates and shells under membrane, bending, twisting, and shearing loads are reviewed, starting with the crack tip fields for plane stress, Kirchhoff, and Reissner theories. The energy release rate for each of these theories is calculated and is used to determine the relation between the Kirchhoff and Reissner theories for thin plates. For thicker plates, this relationship is explored using three-dimensional finite element analysis. The validity of the application of two-dimensional (plate theory) solutions to actual three-dimensional objects is analyzed and discussed. Crack tip fields in plates undergoing large deflection are analyzed using von Ka´rma´n theory. Solutions for cracked shells are discussed as well. A number of computational methods for determining stress intensity factors in plates and shells are discussed. Applications of these computational approaches to aircraft structures are examined. The relatively few experimental studies of fracture in plates under bending and twisting loads are also reviewed. There are 101 references cited in this article.

Noninvasive three-dimensional electrocardiographic imaging of ventricular activation sequence

2005 ◽  
Vol 289 (6) ◽  
pp. H2724-H2732 ◽  
Author(s):  
Xin Zhang ◽  
Indiresha Ramachandra ◽  
Zhongming Liu ◽  
Basharat Muneer ◽  
Steven M. Pogwizd ◽  
...  
Keyword(s):  
Surface Potential ◽  
Body Surface ◽  
Cardiac Arrhythmias ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Electrocardiographic Imaging ◽  
Ventricular Activation ◽  
Body Surface Potential ◽  
Life Threatening ◽  
Activation Sequence

Imaging the myocardial activation sequence is critical for improved diagnosis and treatment of life-threatening cardiac arrhythmias. It is desirable to reveal the underlying cardiac electrical activity throughout the three-dimensional (3-D) myocardium (rather than just the endocardial or epicardial surface) from noninvasive body surface potential measurements. A new 3-D electrocardiographic imaging technique (3-DEIT) based on the boundary element method (BEM) and multiobjective nonlinear optimization has been applied to reconstruct the cardiac activation sequences from body surface potential maps. Ultrafast computerized tomography scanning was performed for subsequent construction of the torso and heart models. Experimental studies were then conducted, during left and right ventricular pacing, in which noninvasive assessment of ventricular activation sequence by means of 3-DEIT was performed simultaneously with 3-D intracardiac mapping (up to 200 intramural sites) using specially designed plunge-needle electrodes in closed-chest rabbits. Estimated activation sequences from 3-DEIT were in good agreement with those constructed from simultaneously recorded intracardiac electrograms in the same animals. Averaged over 100 paced beats (from a total of 10 pacing sites), total activation times were comparable (53.3 ± 8.1 vs. 49.8 ± 5.2 ms), the localization error of site of initiation of activation was 5.73 ± 1.77 mm, and the relative error between the estimated and measured activation sequences was 0.32 ± 0.06. The present experimental results demonstrate that the 3-D paced ventricular activation sequence can be reconstructed by using noninvasive multisite body surface electrocardiographic measurements and imaging of heart-torso geometry. This new 3-D electrocardiographic imaging modality has the potential to guide catheter-based ablative interventions for the treatment of life-threatening cardiac arrhythmias.

Experimental Studies of Leading Edge Contouring Influence on Secondary Losses in Transonic Turbines

2012 ◽  
Author(s):  
Ranjan Saha ◽  
Jens Fridh ◽  
Torsten Fransson ◽  
Boris I. Mamaev ◽  
Mats Annerfeldt
Keyword(s):  
Gas Turbine ◽  
Guide Vane ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Leading Edge ◽  
Secondary Flows ◽  
Noticeable Effect ◽  
Flow Angle ◽  
Wide Range ◽  
Contour Plots

An experimental study of the hub leading edge contouring using fillets is performed in an annular sector cascade to observe the influence of secondary flows and aerodynamic losses. The investigated vane is a three dimensional gas turbine guide vane (geometrically similar) with a mid-span aspect ratio of 0.46. The measurements are carried out on the leading edge fillet and baseline cases using pneumatic probes. Significant precautions have been taken to increase the accuracy of the measurements. The investigations are performed for a wide range of operating exit Mach numbers from 0.5 to 0.9 at a design inlet flow angle of 90°. Data presented include the loading, fields of total pressures, exit flow angles, radial flow angles, as well as profile and secondary losses. The vane has a small profile loss of approximately 2.5% and secondary loss of about 1.1%. Contour plots of vorticity distributions and velocity vectors indicate there is a small influence of the vortex-structure in endwall regions when the leading edge fillet is used. Compared to the baseline case the loss for the filleted case is lower up to 13% of span and higher from 13% to 20% of the span for a reference condition with Mach no. of 0.9. For the filleted case, there is a small increase of turning up to 15% of the span and then a small decrease up to 35% of the span. Hence, there are no significant influences on the losses and turning for the filleted case. Results lead to the conclusion that one cannot expect a noticeable effect of leading edge contouring on the aerodynamic efficiency for the investigated 1st stage vane of a modern gas turbine.

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