A REALISTIC 3D COMPUTATIONAL MODEL OF THE CLOSURE OF SKIN WOUND WITH INTERRUPTED SUTURES

2017 ◽  
Vol 17 (01) ◽  
pp. 1750025 ◽  
Author(s):  
ARNAB CHANDA ◽  
VINU UNNIKRISHNAN
Keyword(s):  
Computational Model ◽  
Material Properties ◽  
Computational Models ◽  
Wound Closure ◽  
Three Dimensional ◽  
Skin Wound ◽  
Cross Sectional ◽  
Maximum Value ◽  
Robotic Surgeries ◽  
First Time

Wounds or cuts are the most common form of skin injuries. While a shallow wound may heal over time, deep wounds often require clinical interventions such as suturing to ensure the wound closure and timely healing. To date, suturing practices are based on a surgeon's experience and there is no benchmark to what is right or wrong. In the literature, there have been few attempts to characterize wound closure and suture mechanics using simple 2D computational models. In our current work, for the first time, a realistic three-dimensional (3D) computational model of the skin with the two layers, namely the epidermis and dermis, have been developed. A 3D diamond shaped wound with a varying cross-section has been modeled, and interrupted sutures have been placed numerically in multiple steps to close the wound. Nonlinear hyperelastic material properties have been adopted for the skin and a skin pre-stress was applied bi-axially. The force requirements for each suture were estimated numerically using a novel suture pulling technique. The suture forces were found to lie in the range of 0–5 N with a maximum value at the center. Also, the center suture was observed to require an approximately four times pull force compared to the first end suture. All these findings provide important guidelines for suturing. Additionally, the suture force can be approximated as a polynomial function of the displacement. Given a wound geometry, wound depth, skin material properties, skin pre-stress, suture wire material and cross-sectional area, using our computational model, such a relationship can be used to estimate and characterize the suture force requirements accurately. To our knowledge, such a 3D computational model of skin wound closure with interrupted sutures have not been developed till date, and would be indispensable for planning robotic surgeries and improving clinical suturing practices in the future.

Noninvasive In Vivo Characterization of Pediatric Human Spine: 3-D Finite Element Study

2011 ◽  
Author(s):  
Elizabeth S. Doughty ◽  
Nesrin Sarigul-Klijn
Keyword(s):  
Finite Element ◽  
Computational Model ◽  
Muscle Activation ◽  
Computational Models ◽  
Three Dimensional ◽  
Pediatric Spine ◽  
Element Analysis ◽  
Spine Stabilization ◽  
Surgical Tool

There are no full three-dimensional computational models of the pediatric spine to study the many diseases and disorders that afflict the immature spine using finite element analysis. To fully characterize the pediatric spine, we created a pediatric specific computational model of C1-L5 using noninvasive in vivo techniques to incorporate the differences between the adult and pediatric spines: un-fused vertebrae, lax ligaments, and higher water content in the intervertebral discs. Muscle follower loads were included in the model to simulate muscle activation for five muscles involved in spine stabilization. This paper is the first pediatric three-dimensional model developed to date. Due to a lack of experimental pediatric spinal studies, this 3-D computational model has the potential to become a surgical tool to ensure that the most appropriate technique is chosen for treating pediatric spinal dysfunctions such as congenital abnormalities, idiopathic scoliosis, and vertebral fractures.

scholarly journals Propagation Mechanism Modeling in the Near-Region of Arbitrary Cross-Sectional Tunnels

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Ke Guan ◽  
Zhangdui Zhong ◽  
Bo Ai ◽  
Ruisi He ◽  
Yuanxuan Li ◽  
...  
Keyword(s):  
Communication Systems ◽  
Three Dimensional ◽  
Propagation Mechanism ◽  
Multimode Waveguide ◽  
Radio Communication ◽  
Cross Sectional ◽  
Solid Geometry ◽  
Mechanism Modeling ◽  
First Time ◽  
Insight Into

Along with the increase of the use of working frequencies in advanced radio communication systems, the near-region inside tunnels lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. This paper analytically models the propagation mechanisms and their dividing point in the near-region of arbitrary cross-sectional tunnels for the first time. To begin with, the propagation losses owing to the free space mechanism and the multimode waveguide mechanism are modeled, respectively. Then, by conjunctively employing the propagation theory and the three-dimensional solid geometry, the paper presents a general model for the dividing point between two propagation mechanisms. It is worthy to mention that this model can be applied in arbitrary cross-sectional tunnels. Furthermore, the general dividing point model is specified in rectangular, circular, and arched tunnels, respectively. Five groups of measurements are used to justify the model in different tunnels at different frequencies. Finally, in order to facilitate the use of the model, simplified analytical solutions for the dividing point in five specific application situations are derived. The results in this paper could help deepen the insight into the propagation mechanisms in tunnels.

Experimental Measurement of the Flexural Spectrum of a Vibrating Beam Above the Critical Frequency

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
J. Calleja-Ángel ◽  
J. C. Torres-Guzmán ◽  
J. Arriaga ◽  
A. Díaz-de-Anda
Keyword(s):  
Critical Frequency ◽  
Cutoff Frequency ◽  
Three Dimensional ◽  
Beam Theory ◽  
Cross Sectional ◽  
Oscillation Modes ◽  
Dimensional Finite Element ◽  
Bending Modes ◽  
Three Dimensional Finite Element ◽  
First Time

Abstract In this paper, we report the bending spectrum measured experimentally on oscillating beams with free extremes in a frequency range below and above the cutoff or critical frequency. The experimental setup used to obtain the bending spectrum consisted of a novel and selective method to excite mainly bending modes, as well as an identification process in which oscillation modes other than bending were discarded. For the first time, we identified bending modes above the cutoff frequency for square and circular cross-sectional beams and a good agreement is obtained when the measured frequencies are compared with the predictions of the Timoshenko beam theory (TBT) and those numerically obtained from the elasticity theory by using a three-dimensional finite element method (FEM) calculation. Higher frequency values at which TBT should cease to be valid were not achieved in the experiments. Instead, our experimental results show that TBT remains valid above the cutoff frequency, with an error smaller than 6%.

scholarly journals Predicting Postsurgery Nasal Physiology with Computational Modeling

2014 ◽  
Vol 151 (5) ◽  
pp. 751-759 ◽  
Author(s):  
Dennis O. Frank-Ito ◽  
Julia S. Kimbell ◽  
Purushottam Laud ◽  
Guilherme J. M. Garcia ◽  
John S. Rhee
Keyword(s):  
Computational Models ◽  
Medical Center ◽  
Academic Medical Center ◽  
Three Dimensional ◽  
Computer Models ◽  
Diagnostic Tools ◽  
Virtual Surgery ◽  
Prediction Errors ◽  
Cross Sectional ◽  
Computed Tomographic

Introduction High failure rates for surgical treatment of nasal airway obstruction (NAO) indicate that better diagnostic tools are needed to improve surgical planning. This study evaluates whether computer models based on a surgeon’s edits of presurgery scans can accurately predict results from computer models based on postoperative scans of the same patient using computational fluid dynamics. Study Design Prospective study. Setting Academic medical center. Methods Three-dimensional nasal models were reconstructed from computed tomographic scans of 10 patients with NAO presurgery and 5 to 8 months postsurgery. To create transcribed-surgery models, the surgeon digitally modified the preoperative reconstruction in each patient to represent physical changes expected from surgery and healing. Steady-state, laminar, inspiratory airflow was simulated in each model under physiologic, pressure-driven conditions. Results Transcribed-surgery and postsurgery model variables were statistically different from presurgery variables at α = 0.05. Unilateral nasal resistance and airflow were not statistically different between transcribed-surgery and postsurgery models, but bilateral resistance was significantly different. Cross-sectional average pressures in transcribed surgery trended with postsurgery. Transcribed-surgery prediction errors of postsurgery bilateral resistance were within 10% to 20% and 20% to 30% in 5 and 4 subjects, respectively. Prediction errors for unilateral resistance were <10%, 10% to 20%, and 20% to 30% in 1, 2, and 4 subjects, respectively. Conclusions Computational models with modifications mimicking actual surgery and healing have the potential to predict postoperative outcomes. However, software to effectively translate virtual surgery steps into computational models is lacking. The ability to account for healing factors and the current limited virtual surgery tools are challenges that need to be overcome for greater accuracy.

Swimming performance, resonance and shape evolution in heaving flexible panels

2018 ◽  
Vol 847 ◽  
pp. 386-416 ◽  
Author(s):  
Alexander P. Hoover ◽  
Ricardo Cortez ◽  
Eric D. Tytell ◽  
Lisa J. Fauci
Keyword(s):  
Computational Model ◽  
Swimming Speed ◽  
Material Properties ◽  
Computational Study ◽  
Swimming Performance ◽  
Three Dimensional ◽  
Leading Edge ◽  
Trailing Edge ◽  
Propulsive Performance ◽  
Flexible Panels

Many animals that swim or fly use their body to accelerate the fluid around them, transferring momentum from their flexible bodies and appendages to the surrounding fluid. The kinematics that emerge from this transfer result from the coupling between the fluid and the active and passive material properties of the flexible body or appendages. To elucidate the fundamental features of the elastohydrodynamics of flexible appendages, recent physical experiments have quantified the propulsive performance of flexible panels that are actuated on their leading edge. Here we present a complementary computational study of a three-dimensional flexible panel that is heaved sinusoidally at its leading edge in an incompressible, viscous fluid. These high-fidelity numerical simulations enable us to examine how propulsive performance depends on mechanical resonance, fluid forces, and the emergent panel deformations. Moreover, the computational model does not require the tethering of the panel. We therefore compare the thrust production of tethered panels to the forward swimming speed of the same panels that can move forward freely. Varying both the passive material properties and the heaving frequency of the panel, we find that local peaks in trailing edge amplitude and forward swimming speed coincide and that they are determined by a non-dimensional quantity, the effective flexibility, that arises naturally in the Euler–Bernoulli beam equation. Modal decompositions of panel deflections reveal that the amplitude of each mode is related to the effective flexibility. Panels of different material properties that are actuated so that their effective flexibilities are closely matched have modal contributions that evolve similarly over the phase of the heaving cycle, leading to similar vortex structures in their wakes and comparable thrust forces and swimming speeds. Moreover, local peaks in the swimming speed and trailing edge amplitude correspond to peaks in the contributions of the different modes. This computational study of freely swimming flexible panels gives further insight into the role of resonance in swimming performance that is important in the engineering and design of robotic propulsors. Moreover, we view this reduced model and its comparison to laboratory experiments as a building block and validation for a more comprehensive three-dimensional computational model of an undulatory swimmer that will couple neural activation, muscle mechanics and body elasticity with the surrounding viscous, incompressible fluid.

Cross-Sectional Design and Analysis of Multiscale Carbon Nanotubes-Reinforced Composite Beams and Blades

2018 ◽  
Vol 10 (03) ◽  
pp. 1850032 ◽  
Author(s):  
M. Rafiee ◽  
F. Nitzsche ◽  
M. R. Labrosse
Keyword(s):  
Carbon Nanotubes ◽  
Polymer Matrix ◽  
Material Properties ◽  
Three Dimensional ◽  
Composite Beams ◽  
Cross Sectional ◽  
Weight Percentage ◽  
Stiffness Properties ◽  
Multiscale Composite ◽  
Cross Sectional Design

The present work addresses with the cross-sectional design and analysis of fiber-reinforced multiscale composite beams of general cross-sectional shape and arbitrary anisotropic material properties and investigates the effect of carbon nanotubes (CNTs) on their stiffness properties. The three-dimensional strain field was formulated in terms of one-dimensional strains and a three-dimensional warping displacement. The bulk material properties of the multiscale composite were predicted using Halpin–Tsai equations and fiber micromechanics. The carbon nanotubes were assumed to be uniformly distributed and randomly oriented throughout the polymer matrix. The variational asymptotic beam section (VABS) was used to numerically evaluate the stiffness and mass matrices of four test cases: strip, circular pipe, box beam and airfoil. The influence of CNTs weight percentage and volume fraction of fibers was investigated through a detailed parametric study. The numerical results indicate that the inclusion of a small weight percentage of carbon nanotubes in the polymer matrix is sufficient to induce a significant improvement in stiffness properties.

scholarly journals A Stochastic Spatiotemporal Model of Rat Ventricular Myocyte Calcium Dynamics Demonstrated Necessary Features for Calcium Wave Propagation

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 989
Author(s):  
Tuan Minh Hoang-Trong ◽  
Aman Ullah ◽  
William Jonathan Lederer ◽  
Mohsin Saleet Jafri
Keyword(s):  
Computational Model ◽  
Cell Biology ◽  
Computational Models ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Three Dimensional ◽  
Ionic Currents ◽  
Cardiac Contraction ◽  
Calcium Dynamics ◽  
Deterministic Models

Calcium (Ca2+) plays a central role in the excitation and contraction of cardiac myocytes. Experiments have indicated that calcium release is stochastic and regulated locally suggesting the possibility of spatially heterogeneous calcium levels in the cells. This spatial heterogeneity might be important in mediating different signaling pathways. During more than 50 years of computational cell biology, the computational models have been advanced to incorporate more ionic currents, going from deterministic models to stochastic models. While periodic increases in cytoplasmic Ca2+ concentration drive cardiac contraction, aberrant Ca2+ release can underly cardiac arrhythmia. However, the study of the spatial role of calcium ions has been limited due to the computational expense of using a three-dimensional stochastic computational model. In this paper, we introduce a three-dimensional stochastic computational model for rat ventricular myocytes at the whole-cell level that incorporate detailed calcium dynamics, with (1) non-uniform release site placement, (2) non-uniform membrane ionic currents and membrane buffers, (3) stochastic calcium-leak dynamics and (4) non-junctional or rogue ryanodine receptors. The model simulates spark-induced spark activation and spark-induced Ca2+ wave initiation and propagation that occur under conditions of calcium overload at the closed-cell condition, but not when Ca2+ levels are normal. This is considered important since the presence of Ca2+ waves contribute to the activation of arrhythmogenic currents.

Psychological Resilience Provides No Independent Protection From Suicidal Risk

Crisis ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 130-139 ◽  
Author(s):  
Danica W. Y. Liu ◽  
A. Kate Fairweather-Schmidt ◽  
Richard Burns ◽  
Rachel M. Roberts ◽  
Kaarin J. Anstey
Keyword(s):  
Risk Factors ◽  
Well Being ◽  
Current Status ◽  
Psychological Resilience ◽  
Cross Sectional ◽  
Life Project ◽  
Resilience Factors ◽  
First Time

Abstract. Background: Little is known about the role of resilience in the likelihood of suicidal ideation (SI) over time. Aims: We examined the association between resilience and SI in a young-adult cohort over 4 years. Our objectives were to determine whether resilience was associated with SI at follow-up or, conversely, whether SI was associated with lowered resilience at follow-up. Method: Participants were selected from the Personality and Total Health (PATH) Through Life Project from Canberra and Queanbeyan, Australia, aged 28–32 years at the first time point and 32–36 at the second. Multinomial, linear, and binary regression analyses explored the association between resilience and SI over two time points. Models were adjusted for suicidality risk factors. Results: While unadjusted analyses identified associations between resilience and SI, these effects were fully explained by the inclusion of other suicidality risk factors. Conclusion: Despite strong cross-sectional associations, resilience and SI appear to be unrelated in a longitudinal context, once risk/resilience factors are controlled for. As independent indicators of psychological well-being, suicidality and resilience are essential if current status is to be captured. However, the addition of other factors (e.g., support, mastery) makes this association tenuous. Consequently, resilience per se may not be protective of SI.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

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