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Finite growth models

S Samaneh Lashkarinia, Senol Piskin, Tijen A Bozkaya, Ece Salihoglu, Can Yerebakan, Kerem Pekkan
Surgical treatment of congenital heart disease (CHD) involves complex vascular reconstructions utilizing artificial and native surgical materials. A successful surgical reconstruction achieves an optimal hemodynamic profile through the graft in spite of the complex post-operative vessel growth pattern and the altered pressure loading. This paper proposes a new in silico patient-specific pre-surgical planning framework for patch reconstruction and investigates its computational feasibility. The proposed protocol is applied to the patch repair of main pulmonary artery (MPA) stenosis in the Tetralogy of Fallot CHD template...
May 14, 2018: Annals of Biomedical Engineering
Dustin Jon Richter, Roger Lyon, Scott Van Valin, Xue-Cheng Liu
The incidence of anterior cruciate ligament (ACL) injuries in the pediatric population has risen in recent years. These injuries have historically presented a management dilemma in skeletally immature patients with open physes and significant growth remaining at time of injury. While those nearing skeletal maturity may be treated with traditional, transphyseal adult techniques, these same procedures risk iatrogenic damage to the growth plates and resultant growth disturbances in younger patients with open physes...
2018: Frontiers in Surgery
Yehuda A Ganan, David A Kessler
In this work, we study the problem of front propagation and pattern formation in the stochastic nonlocal Fisher equation. We find a crossover between two regimes: a steadily propagating regime for not too large interaction range and a stochastic punctuated spreading regime for larger ranges. We show that the former regime is well described by the heuristic approximation of the system by a deterministic system where the linear growth term is cut off below some critical density. This deterministic system is seen not only to give the right front velocity, but also predicts the onset of clustering for interaction kernels which give rise to stable uniform states, such as the Gaussian kernel, for sufficiently large cutoff...
April 2018: Physical Review. E
Yuxuan Jiang, Xudong Liang, Ming Guo, Yanping Cao, Shengqiang Cai
Most bacteria cells divide by binary fission which is part of a bacteria cell cycle and requires tight regulations and precise coordination. Fast separation of Staphylococcus Aureus (S. Aureus) daughter cells, named as popping event, has been observed in recent experiments. The popping event was proposed to be driven by mechanical crack propagation in the peripheral ring which connected two daughter cells before their separation. It has also been shown that after the fast separation, a small portion of the peripheral ring was left as a hinge...
May 10, 2018: Biomechanics and Modeling in Mechanobiology
Behzad Vafaeian, Samer Adeeb, Marwan El-Rich, Dornoosh Zonoobi, Abhilash R Hareendranathan, Jacob L Jaremko
Developmental dysplasia of the hip (DDH) in infants under 6 months of age is typically treated by the Pavlik harness (PH). During successful PH treatment, a subluxed/dislocated hip is spontaneously reduced into the acetabulum, and DDH undergoes self-correction. PH treatment may fail due to avascular necrosis (AVN) of the femoral head. An improved understanding of mechanical factors accounting for the success/failure of PH treatment may arise from investigating articular cartilage contact pressure (CCP) within a hip during treatment...
July 1, 2018: Journal of Biomechanical Engineering
Junkai Fan, Huitao Chen, Wu Zhao, Liang Yan
A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent studies, the hydrogen leads to the decline of the mechanical properties of steel, which is known as hydrogen embrittlement, is another reason for flake formation. In addition, the phenomenon of stress induced hydrogen uphill diffusion should not be neglected...
April 27, 2018: Materials
Yung-Shin Sun
Tumor Treating Fields (TTFields) in combination with chemotherapy and/or radiotherapy have been clinically reported to provide prolonged overall survival in glioblastoma patients. Alternating electric fields with frequencies of 100~300 kHz and magnitudes of 1~3 V/cm are shown to suppress the growth of cancer cells via interactions with polar molecules within dividing cells. Since it is difficult to directly measure the electric fields inside the brain, simulation models of the human head provide a useful tool for predicting the electric field distribution...
2018: Computational and Mathematical Methods in Medicine
William M S Yamashita, Shyam S Das, Grigori Chapiro
BACKGROUND: The global incidences of dengue virus have increased the interest in studying and understanding the mosquito population dynamics. It is predominantly spread by Aedes aegypti in the tropical and sub-tropical countries in the world. Understanding these dynamics is important for public health in countries where climatic and environmental conditions are favorable for the propagation of these diseases. For this reason, a new model has been proposed to investigate the population dynamics of mosquitoes in a city...
April 16, 2018: Parasites & Vectors
Chunlei Ruan
“Skin-core-skin” structure is a typical crystal morphology in injection products. Previous numerical works have rarely focused on crystal evolution; rather, they have mostly been based on the prediction of temperature distribution or crystallization kinetics. The aim of this work was to achieve the “skin-core-skin” structure and investigate the role of external flow and temperature fields on crystal morphology. Therefore, the multiscale algorithm was extended to the simulation of polymer crystallization in a pipe flow...
April 16, 2018: Materials
Kalenia M Márquez-Flórez, James R Monaghan, Sandra J Shefelbine, Angélica Ramirez-Martínez, Diego A Garzón-Alvarado
Joints connect the skeletal components and enable movement. The appearance and development of articulations is due to different genetic, biochemical, and mechanical factors. In the embryonic stage, controlled biochemical processes are critical for organized growth. We developed a computational model, which predicts the appearance, location, and development of joints in the embryonic stage. Biochemical events are modeled with reaction diffusion equations with generic molecules representing molecules that 1) determine the site where the articulation will appear, 2) promote proliferation, and matrix synthesis, and 3) define articular cartilage...
April 10, 2018: Journal of Theoretical Biology
Gonzalo D Maso Talou, Pablo J Blanco, Gonzalo D Ares, Cristiano Guedes Bezerra, Pedro A Lemos, Raúl A Feijóo
Atherosclerotic plaque rupture and erosion are the most important mechanisms underlying the sudden plaque growth, responsible for acute coronary syndromes and even fatal cardiac events. Advances in the understanding of the culprit plaque structure and composition are already reported in the literature, however, there is still much work to be done toward in-vivo plaque visualization and mechanical characterization to assess plaque stability, patient risk, diagnosis and treatment prognosis. In this work, a methodology for the mechanical characterization of the vessel wall plaque and tissues is proposed based on the combination of intravascular ultrasound (IVUS) imaging processing, data assimilation and continuum mechanics models within a high performance computing (HPC) environment...
2018: Frontiers in Physiology
M A Murphy, Sungkwang Mun, M F Horstemeyer, M I Baskes, A Bakhtiary, Michelle C LaPlaca, Steven R Gwaltney, Lakiesha N Williams, R K Prabhu
Continuum finite element material models used for traumatic brain injury lack local injury parameters necessitating nanoscale mechanical injury mechanisms be incorporated. One such mechanism is membrane mechanoporation, which can occur during physical insults and can be devastating to cells, depending on the level of disruption. The current study investigates the strain state dependence of phospholipid bilayer mechanoporation and failure. Using molecular dynamics, a simplified membrane, consisting of 72 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) phospholipids, was subjected to equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial tensile deformations at a von Mises strain rate of 5...
April 9, 2018: Journal of Biomolecular Structure & Dynamics
Taeksang Lee, Elbert E Vaca, Joanna K Ledwon, Hanah Bae, Jolanta M Topczewska, Sergey Y Turin, Ellen Kuhl, Arun K Gosain, Adrian Buganza Tepole
Tissue expansion is a common technique in reconstructive surgery used to grow skin in vivo for correction of large defects. Despite its popularity, there is a lack of quantitative understanding of how stretch leads to growth of new skin. This has resulted in several arbitrary expansion protocols that rely on the surgeon's personal training and experience rather than on accurate predictive models. For example, choosing between slow or rapid expansion, or small or large inflation volumes remains controversial...
March 29, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Mesfin Haile Mamme, Christoph Köhn, Johan Deconinck, Jon Ustarroz
Fundamental understanding of the early stages of electrodeposition at the nanoscale is key to address the challenges in a wide range of applications. Despite having been studied for decades, a comprehensive understanding of the whole process is still out of reach. In this work, we introduce a novel modelling approach that couples a finite element method (FEM) with a random walk algorithm, to study the early stages of nanocluster formation, aggregation and growth, during electrochemical deposition. This approach takes into account not only electrochemical kinetics and transport of active species, but also the surface diffusion and aggregation of adatoms and small nanoclusters...
April 5, 2018: Nanoscale
Emiel M J van Disseldorp, Niels J Petterson, Frans N van de Vosse, Marc R H M van Sambeek, Richard G P Lopata
Aims: Using non-invasive 3D ultrasound, peak wall stress (PWS) and aortic stiffness can be evaluated, which may provide additional criteria in abdominal aortic aneurysm (AAA) risk assessment. In this study, these measures were determined in both young and age-matched individuals, and AAA patients while its relation to age, maximum diameter, and growth was assessed statistically. Methods and results: Time-resolved 3D-US data were acquired for 30 volunteers and 65 AAA patients...
March 29, 2018: European Heart Journal Cardiovascular Imaging
Xiao Qian, Yuan Zhang, Desmond S Lun, G Charles Dismukes
Boosting cellular growth rates while redirecting metabolism to make desired products are the preeminent goals sought by gene engineering of photoautotrophs, yet so far has under achieved owing to lack of understanding of the functional pathways and their choke points. Here we apply a 13C mass isotopic method (INST-MFA) to quantify instantaneous fluxes of metabolites during photoautotrophic growth. INST-MFA determines the globally most accurate set of absolute fluxes for each metabolite from a finite set of measured 13C-isotopomer fluxes by minimizing the sum of squared residuals between experimental and predicted mass isotopomers...
April 4, 2018: ACS Synthetic Biology
Ollie Yiru Yu, Irene Shuping Zhao, May Lei Mei, Edward Chin-Man Lo, Chun-Hung Chu
Dental caries form through a complex interaction over time among dental plaque, fermentable carbohydrate, and host factors (including teeth and saliva). As a key factor, dental plaque or biofilm substantially influence the characteristic of the carious lesions. Laboratory microbial culture models are often used because they provide a controllable and constant environment for cariology research. Moreover, they do not have ethical problems associated with clinical studies. The design of the microbial culture model varies from simple to sophisticated according to the purpose of the investigation...
June 19, 2017: Dentistry journal
Hyunhee Ahn, Ravi R Patel, Anthony J Hoyt, Angela S P Lin, F Brennan Torstrick, Robert E Guldberg, Carl P Frick, R Dana Carpenter, Christopher M Yakacki, Nick J Willett
Poly(para-phenylene) (PPP) is a novel aromatic polymer with higher strength and stiffness than polyetheretherketone (PEEK), the gold standard material for polymeric load-bearing orthopaedic implants. The amorphous structure of PPP makes it relatively straightforward to manufacture different architectures, while maintaining mechanical properties. PPP is promising as a potential orthopaedic material; however, the biocompatibility and osseointegration have not been well investigated. The objective of this study was to evaluate biological and mechanical behavior of PPP, with or without porosity, in comparison to PEEK...
March 18, 2018: Acta Biomaterialia
Chanyuan Jiang, Yilue Zheng, Ningbei Yin, Tao Song
The aim of this study was to investigate the anatomical features of the maxillae and vomer in patients with bilateral cleft lip and palate (BCLP). Craniofacial measurements of 24 adult BCLP patients (GB) and 32 normal adult controls (GN) were carried out. We measured the width and length of the maxillae, their relative positions with respect to the coronal plane passing through the basion, and the volume, length, cross-sectional area, and mean width of the vomer. Between-group differences were assessed using independent-sample t tests...
March 16, 2018: Journal of Craniofacial Surgery
Ana L Schaigorodsky, Juan I Perotti, Nahuel Almeira, Orlando V Billoni
In this work we introduce a variant of the Yule-Simon model for preferential growth by incorporating a finite kernel to model the effects of bounded memory. We characterize the properties of the model combining analytical arguments with extensive numerical simulations. In particular, we analyze the lifetime and popularity distributions by mapping the model dynamics to corresponding Markov chains and branching processes, respectively. These distributions follow power laws with well-defined exponents that are within the range of the empirical data reported in ecologies...
February 2018: Physical Review. E
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