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tensile stress

R W Millar, D C S Dumas, K F Gallacher, P Jahandar, C MacGregor, M Myronov, D J Paul
GeSn alloys with Sn contents of 8.4 % and 10.7 % are grown pseudomorphically on Ge buffers on Si (001) substrates. The alloys as-grown are compressively strained, and therefore indirect bandgap. Undercut GeSn on Ge microdisk structures are fabricated and strained by silicon nitride stressor layers, which leads to tensile strain in the alloys, and direct bandgap photoluminescence in the 3-5 µm gas sensing window of the electromagnetic spectrum. The use of pseudomorphic layers and external stress mitigates the need for plastic deformation to obtain direct bandgap alloys...
October 16, 2017: Optics Express
Charles Paillard, Gregory Geneste, Laurent Bellaiche, Brahim Dkhil
Domain Walls (DWs) in ferroic materials exhibit a plethora of unexpected properties that are different from the adjacent ferroic domains. Still, the intrinsic/extrinsic origin of these properties remains an open question. Here, density functional theory calculations are used to investigate the interaction between vacancies and 180º DWs in the prototypical ferroelectric PbTiO3, with a special emphasis on cationic vacancies and released holes. All vacancies are more easily formed within the DW than in the domains...
October 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Arun Kumar Sagotra, Claudio Cazorla
Finding solid-state electrolytes with high ionic conductivity near room temperature is an important prerequisite for developing all-solid-state electrochemical batteries. Here, we investigate the effects of point defects (vacancies) and biaxial stress on the superionic properties of fast-ion conductors (represented by the archetypal compounds CaF$_{2}$, Li-rich anti-perovskite Li$_{3}$OCl, and AgI) by using classical molecular dynamics and first-principles simulation methods. We find that the critical superionic temperature of all analysed families of fast-ion conductors can be reduced by several hundreds of degrees through the application of relatively small biaxial stresses ($|\sigma| \le 1$~GPa) on slightly defective samples ($c_{v} \sim 1$\%)...
October 16, 2017: ACS Applied Materials & Interfaces
Cornelius O Horgan, Jeremiah G Murphy
Fiber-reinforcement is a common feature of many soft biological tissues. Continuum mechanics modeling of the mechanical response of such tissues using transversely isotropic hyperelasticity is now well developed. The fundamental deformation of simple shear within this framework is examined here. It is well known that the normal stress effect characteristic of nonlinear elasticity plays a crucial role in maintaining a homogeneous deformation state in the bulk of the specimen. Here we consider the effect of anisotropy and fiber-orientation on the shear and normal stresses...
September 27, 2017: Journal of Biomechanics
Paul de Kok, Gabriel K R Pereira, Sara Fraga, Niek de Jager, Andressa B Venturini, Cornelis J Kleverlaan
OBJECTIVE: To evaluate the effect of internal roughness and bonding on the load to failure and structural reliability (Weibull analysis) of a lithium disilicate-based glass ceramic under different testing scenarios. METHODS: IPS e.max CAD blocks (Ivoclar Vivadent AG) were shaped into cylinders (N=100), crystalized according to the manufacturer's instructions, and randomly assigned into two surface conditions: (1) polished surface (600-grit SiC polish papers), and (2) a roughened surface (air-abrasion with 50μm Al2O3)...
October 9, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
Carlos De la Fuente, Carlos Cruz-Montecinos, Helen L Schimidt, Hugo Henríquez, Sebastián Ruidiaz, Felipe P Carpes
BACKGROUND: The Dresden technique preserves the paratenon during Achilles tendon repair and may improve the plantarflexor mechanism when combined with mobilization during early rehabilitation. However, the surgical repair design for Achilles tendon ruptures can affect rates of re-rupture or lengthening. Therefore, the aim of this study was to determine the biomechanical properties of the Krackow, Double-Kessler, Double-Dresden, and Triple-Dresden techniques used for repairing mid-substance Achilles tendon ruptures during cyclical and maximum traction...
October 9, 2017: Clinical Biomechanics
Bishnu P Khanal, Moritz Knoche
Cuticles envelope primary surfaces of the above-ground portion of plants. They function as barriers to water movement and to gas exchange, and in pathogen defense. To serve as a barrier on growing organs, cuticles must remain intact but at the same time must accommodate ongoing growth. Minimizing cuticle failure has stimulated significant research on the cuticle's mechanical properties. The objective here is to review the literature on the mechanical properties of isolated fruit and leaf cuticles. Cuticles are viscoelastic polymers...
September 13, 2017: Journal of Experimental Botany
Janani Sampath, Lisa M Hall
Using coarse-grained molecular dynamics simulations, we study ionomers in equilibrium and under uniaxial tensile deformation. The spacing of ions along the chain is varied, allowing us to consider how different ionic aggregate morphologies, from percolated to discrete aggregates, impact the mechanical properties. From the equilibrium simulations, we calculate the stress-stress auto correlation function, showing a distinct deviation from the Rouse relaxation due to ionic associations that depends on ion content...
October 7, 2017: Journal of Chemical Physics
Yancong Feng, Wei-Bing Liao, Jiaxin Zheng, Lin-Wang Wang, Yong Zhang, Jianfei Sun, Feng Pan
Revealing the mechanism of phase selectivity can provide guidance for controlling crystals with certain phases for special properties. In the present work, nanocrystals of about 2-4 nm diameters with a B2 structure (thermodynamic metastable phase) are generated from CuZr glassy fiber by applying tensile stress at ambient temperature. By combining the ab initio calculations with the molecular dynamics simulations, the stabilities of B2 austenite and B19' martensitic phases under applied tensile stress are compared, and the phase transformation mechanism is revealed...
October 6, 2017: Nanoscale
Yoto Oh, Koji Fujita, Yoshiaki Wakabayashi, Yoshiro Kurosa, Atsushi Okawa
INTRODUCTION: Loading stress due to individual variations in femoral morphology is thought to be strongly associated with the pathogenesis of atypical femoral fracture (AFF). In Japan, studies on AFF regarding pathogenesis in the mid-shaft are well-documented and a key factor in the injury is thought to be femoral shaft bowing deformity. Thus, we developed a CT-based finite element analysis (CT/FEA) model to assess distribution of loading stress in the femoral shaft. PATIENTS AND METHODS: A multicenter prospective study was performed at 12 hospitals in Japan from August 2015 to February 2017...
September 27, 2017: Injury
James W Reinhardt, Keith Gooch
We developed an agent-based model that incorporates repetitively applied traction force within a discrete fiber network to understand how microstructural properties of the network influence mechanical properties and traction force-induced remodeling. An important difference between our model and similar finite-element models is that by implementing more biologically-realistic dynamic traction, we can explore a greater range of matrix remodeling. Here, we validated our model by reproducing qualitative trends observed in three sets of experimental data reported by others: tensile and shear testing of cell-free collagen gels, collagen remodeling around a single isolated cell, and collagen remodeling between pairs of cells...
September 21, 2017: Journal of Biomechanical Engineering
Ekta Yadav, Deepika Singh, Pankajkumar Yadav, Amita Verma
Oxidative stress and inflammation contribute as a key factor for retarding the process of dermal wound healing. Trianthema portulcastrum Linn. (TP) leaves reported to possess antioxidant, antifungal, anti-inflammatory and antibacterial properties, which could make TP a promising wound healing agent. The current study was aimed to estimate the antioxidant potential of the fractionated hydroethanolic extract of TP leaves and evaluate wound healing activity by excision and incision wound models along with the assessment of possible underlying mechanism...
September 28, 2017: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Maximilian Zapf, Robert Röder, Karl Winkler, Lisa Kaden, Johannes Greil, Marcel Wille, Marius Grundmann, Rudiger Schmidt-Grund, Alois Lugstein, Carsten Ronning
Realizing visionary concepts of integrated photonic circuits, nanospectroscopy, and nanosensing will tremendously benefit from dynamically tunable coherent light sources with lateral dimensions on the subwavelength scale. Therefore, we demonstrate an individual nanowire laser based device which can be gradually tuned by reversible length changes of the nanowire such that uniaxial tensile stress is applied to the respective semiconductor gain material. By straining the device, the spontaneous excitonic emission of the nanowire shifts to lower energies caused by the bandgap reduction of the semiconductor...
September 29, 2017: Nano Letters
Wen Xi, Xiaoqing Song, Shi Hu, Zheng Chen
In this work, the phase field crystal (PFC) method is used to study the localized solid-state amorphization (SSA) and its dynamic transformation process in polycrystalline materials under the uniaxial tensile deformation with different factors. The impacts of these factors, including strain rates, temperatures and grain sizes, are analyzed. Kinetically, the ultra-high strain rate makes the lattice be serious distorted and the grain gradual collapse, so the dislocation density rises remarkably. Therefore, localized SSA occurs...
September 29, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Bibiane Steinecker-Frohnwieser, Heike Kaltenegger, Lukas Weigl, Anda Mann, Werner Kullich, Andreas Leithner, Birgit Lohberger
BACKGROUND: Osteoarthritis (OA) as the main chronic joint disease arises from a disturbed balance between anabolic and catabolic processes leading to destructions of articular cartilage of the joints. While mechanical stress can be disastrous for the metabolism of chondrocytes, mechanical stimulation at the physiological level is known to improve cell function. The disease modifying OA drug (DMOAD) diacerein functions as a slowly-acting drug in OA by exhibiting anti-inflammatory, anti-catabolic, and pro-anabolic properties on cartilage...
September 2017: Biochemistry and Biophysics Reports
Patrick Lacolley, Véronique Regnault, Patrick Segers, Stéphane Laurent
The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis...
October 1, 2017: Physiological Reviews
D Remache, M Caliez, M Gratton, S Dos Santos
When a living tissue is subjected to cyclic stretching, the stress-strain curves show a shift down with the increase in the number of cycles until stabilization. This phenomenon is referred to in the literature as a preconditioning and is performed to obtain repeatable and predictable measurements. Preconditioning has been routinely performed in skin tissue tests; however, its effects on the mechanical properties of the material such as viscoelastic response, tangent modulus, sensitivity to strain rate, the stress relaxation rate, etc…...
September 11, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Reza Mehrabi, Milad Dorri, Mohammad Elahinia
In this study, an umbrella-shaped device that is used for osteonecrosis treatment is simulated. The femoral head is subjected to various complex loadings as a result of a person's daily movements. Implant devices used in the body are made of shape memory alloy materials because of their remarkable resistance to wear and corrosion, good biocompatibility, and variable mechanical properties. Since this NiTi umbrella-shaped implant is simultaneously under several loadings, a 3-D model of shape memory alloy is utilized to investigate the behavior of the implant under different conditions...
March 12, 2017: Bioengineering
Narges Shayesteh Moghaddam, Ahmadreza Jahadakbar, Amirhesam Amerinatanzi, Roman Skoracki, Michael Miller, David Dean, Mohammad Elahinia
The current gold standard of care for mandibular segmental defeat reconstruction is the use of Ti-6Al-4V immobilization hardware and fibular double barrel graft. This method is often successful immediately at restoring mandible function, however the highly stiff fixation hardware causes stress shielding of the grafted bone and stress concentration in the fixation device over time which can lead to fixation device failure and revision surgery. The purpose of reconstructive surgery could be to create normal stress trajectories in the mandible following engraftment...
January 22, 2017: Bioengineering
Jack Hornsby, Donna M Daly, David Grundy, Fangzhou Cheng, Anne M Robertson, Paul N Watton, Mark S Thompson
Urodynamic tests are the gold standard for the diagnosis of bladder dysfunction, and the mechanical compliance of the bladder is an important parameter in these tests. The bladder wall has a layered structure, differentially affected by pathology, so knowledge of the contribution and role of these layers and their constituents to overall bladder compliance will enhance interpretation of these clinical tests. In this study we document the functional morphology of the detrusor and lamina propria of the murine bladder wall using a custom in-situ tensile loading system under multiphoton microscopy (MPM) observation in unloaded state and under incremental uniaxial stretch...
September 22, 2017: Acta Biomaterialia
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