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Mechanical compression

Sebastian Povlsen, Bo Povlsen
The diagnosis of thoracic outlet syndrome (TOS) has long been a controversial and challenging one. Despite common presentations with pain in the neck and upper extremity, there are a host of presenting patterns that can vary within and between the subdivisions of neurogenic, venous, and arterial TOS. Furthermore, there is a plethora of differential diagnoses, from peripheral compressive neuropathies, to intrinsic shoulder pathologies, to pathologies at the cervical spine. Depending on the subdivision of TOS suspected, diagnostic investigations are currently of varying importance, necessitating high dependence on good history taking and clinical examination...
March 20, 2018: Diagnostics
Jong-Min Chae, Keun-Oh Lee, Auezhan Amanov
Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, which depends on the UNSM treatment temperature, via the surface severe plastic deformation (S²PD) method. The cross-sectional microstructure of the specimens was observed by electron backscattered diffraction (EBSD) in order to confirm the microstructural alteration in terms of effective depth and refined grain size...
March 20, 2018: Materials
Hui Ye
Bone cells sense mechanical load, which is essential for bone growth and remodeling. In a fracture, this mechanism is compromised. Electromagnetic stimulation has been widely used to assist in bone healing, but the underlying mechanisms are largely unknown. A recent hypothesis suggests that electromagnetic stimulation could influence tissue biomechanics; however, a detailed quantitative understanding of EM-induced biomechanical changes in the bone is unavailable. This paper used a muscle/bone model to study the biomechanics of the bone under EM exposure...
March 19, 2018: Medical & Biological Engineering & Computing
Wei Jiang, Leilei Yan, Hua Ma, Ya Fan, Jiafu Wang, Mingde Feng, Shaobo Qu
Lightweight structures with multi-functions such as electromagnetic wave absorption and excellent mechanical properties are required in spacecraft. A three-dimensional metamaterial absorber consisting of honeycomb and resistive films was proposed and fabricated through 3D printing and silk-screen printing technology. According to simulation and experiment results, the present three-dimensional metamaterial absorber can realize an absorptivity of more than 90% in a wide band of 3.53-24.00 GHz, and improve absorbing efficiency for transverse magnetic (TM) waves of oblique incidence angle from 0° to 70°...
March 19, 2018: Scientific Reports
Karthika Suresh, Dharmendar Kumar Sharma, Ramya Chulliyil, Ketan Dinkar Sarode, V Ravi Kumar, Arindam Chowdhury, Guruswamy Kumaraswamy
We use single particle tracking to investigate colloidal dynamics in hybrid assemblies comprising colloids enmeshed in a crosslinked polymer network. These assemblies are prepared using ice templating and are macroporous monolithic structures. We investigate microstructure-property relations in assemblies that appear chemically identical, but show qualitatively different mechanical response. Specifically, we contrast elastic assemblies that can recover from large compressive deformations with plastic assemblies that fail on being compressed...
March 20, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Agnes Beckmann, Yousef Heider, Marcus Stoffel, Bernd Markert
The underlying research work introduces a study of the mechanical properties of polycarbonate urethane (PCU), used in the construction of various medical devices. This comprises the discussion of a suitable material model, the application of elemental experiments to identify the related parameters and the numerical simulation of the applied experiments in order to calibrate and validate the mathematical model. In particular, the model of choice for the simulation of PCU response is the non-linear viscoelastic Bergström-Boyce material model, applied in the finite-element (FE) package Abaqus®...
March 9, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Xi Chen, Steven D Schwartz
In this article we study how directed evolution in the Kemp Eliminase family of artificial enzymes makes differential use of rapid rate promoting vibrations as a component of their chemical mechanism. Even though this family was initially created by placing the expected active site in a fixed protein matrix, we find a shift from largely static to more dynamic active sites that make use of donor acceptor compression as the evolutionary process proceeds. We see this introduction of dynamics significantly shifts the order of processes in the reaction...
March 19, 2018: Biochemistry
Yuling Xu, Juntao Zhang, Haibo Wang, Dong Xie
Several new urethane-based dimethacrylates were synthesized, characterized and used to formulate the resin composites. Compressive strength (CS) was used as a screen tool to evaluate the mechanical property of the formed composites. Flexural strength, diametral tensile strength, water sorption, degree of conversion and shrinkage of the composites were also evaluated. The results show that most of the synthesized urethane-based dimethacrylates were solid, which are not suitable to dental filling restorations...
March 17, 2018: Dental Materials Journal
Qiaomu Tian, Jose Antonio Mendez, Laura Rivera-Castaneda, Omar Mahmood, Adam Showalter, Elizabeth Ang, Sarah Kazmi, Huinan Liu
Medical implants play a key role in treating bone fractures. Permanent implants are currently used for immobilization of fractures and bearing physiological loads during bone healing. After bone has healed, these implants, if not removed, often cause complications in the long run; and secondary surgeries for removing them pose additional discomfort and expenses for patients. Magnesium (Mg)-based bioresorbable implants, can potentially eliminate the need for additional surgeries by degrading safely over time in the human body...
April 15, 2018: Materials Letters
Keitaro Kubo, Takashi Koike, Takayuki Ueda, Kaoru Sakurai
STATEMENT OF PROBLEM: Information is lacking about the selection criteria for silicone resilient denture liners applied as a matrix material for attachments on overdentures. PURPOSE: The purpose of this in vitro study was to investigate the mechanical properties of silicone resilient denture liners and their influence on the initial retention force of overdenture attachments and the reduction in retention force over time. MATERIAL AND METHODS: Nine types of silicone resilient denture liner were injected and fixed to the matrix section of an experimental denture base...
March 15, 2018: Journal of Prosthetic Dentistry
Jody L Clements, Daranee Tantbirojn, Antheunis Versluis, David R Cagna
STATEMENT OF PROBLEM: Denture tooth fracture may limit the longevity of dental prostheses. Whether the strength of the denture tooth material is affected by the denture processing technique is unclear. PURPOSE: The purpose of this in vitro study was to investigate whether the denture processing technique affects the mechanical properties of denture tooth materials. MATERIAL AND METHODS: Two denture processing techniques, injection and compression molding, were tested for 3 types of denture teeth: nanohybrid composite (NHC), interpenetrating network (IPN), and microfiller-reinforced polyacrylic (MRP)...
March 15, 2018: Journal of Prosthetic Dentistry
Muhammad Naveed, Lei Han, Ghulam Jilany Khan, Sufia Yasmeen, Reyaj Mikrani, Muhammad Abbas, Li Cunyu, Zhou Xiaohui
Congestive heart failure (CHF) is a complicated pathophysiological syndrome, leading cause of hospitalization as well as mortalities in developed countries wherein an irregular function of the heart leads to the insufficient blood supply to the body organs. It is an accumulative slackening of various complications including myocardial infarction (MI), coronary heart disease (CAD), hypertension, valvular heart disease (VHD) and cardiomyopathy; its hallmarks include hypertrophy, increased interstitial fibrosis and loss of myocytes...
March 14, 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Akira Furukawa
A model for describing growing length scale accompanying the vitrification is introduced, in which we assume that in a subsystem whose density is above a certain threshold value, ρ_{c}, due to steric constraints, particle rearrangements are highly suppressed for a sufficiently long time period (∼structural relaxation time). We regard such a subsystem as a glassy cluster. With this assumption and without introducing any complicated thermodynamic arguments, we predict that with compression (increasing average density ρ) at a fixed temperature T in supercooled states, the characteristic length of the clusters, ξ, diverges as ξ∼(ρ_{c}-ρ)^{-2/d}, where d is the spatial dimensionality...
February 2018: Physical Review. E
Thorsten Tjardes, Markus Luecking
Introduction: To achieve the aim of zero preventable deaths on the battlefield a deeper understanding of uncontrolled hemorrhage from junctional or proximal extremity sources is mandatory. While tourniquet application to the extremities has drastically reduced morbidity and mortality, there is still room for improvement regarding the timing of tourniquet placement as the available evidence clearly points out a tight correlation between timing of tourniquet application and outcome. To save as many lives as possible the "point of no return" regarding the circulatory breakdown due to hemorrhage, colloquially addressed as platinum 5 min, needs to be determined...
March 14, 2018: Military Medicine
Min Liu, Qing-Xian Ma, Jian-Bin Luo
20Mn5 steel is widely used in the manufacture of heavy hydro-generator shaft forging due to its strength, toughness, and wear resistance. However, the hot deformation and recrystallization behaviors of 20Mn5 steel compressed under a high temperature were not studied. For this article, hot compression experiments under temperatures of 850-1200 °C and strain rates of 0.01 s-1 -1 s-1 were conducted using a Gleeble-1500D thermo-mechanical simulator. Flow stress-strain curves and microstructure after hot compression were obtained...
March 16, 2018: Materials
Yi Sun, Liping Yan, Chaorong Li, Benyong Chen
Disordered wrinkles are widely observed in stiff film deposited onto a thermally expanded polymer when compressive stress exceeds the critical wrinkling stress of the film. Highly ordered wrinkles can be fabricated by introducing regularly arranged patterns on the polymer before deposition. However, the study on the morphological evolution of localized wrinkling patterns near defects on the stiff film/compliant substrate is neglected. In this paper, we show two morphological transitions of the local wrinkles induced by defects on an Au film/PDMS substrate...
March 19, 2018: European Physical Journal. E, Soft Matter
Daisuke Nakashima, Tsukasa Kanchiku, Norihiro Nishida, Saki Ito, Junji Ohgi, Hidenori Suzuki, Yasuaki Imajo, Masahiro Funaba, Xian Chen, Toshihiko Taguchi
Vertebral fractures commonly occur at the thoracolumbar junction. These fractures can be treated with mild residual deformity in many cases, but are reportedly associated with increased risk of secondary vertebral fractures. In the present study, a three-dimensional (3D) whole spine model was constructed using the finite element method to explore the mechanism of development of compression fractures. The 3D model of the whole spine, from the cervical spine to the pelvis, was constructed from computed tomography (CT) images of an adult male...
April 2018: Experimental and Therapeutic Medicine
Roger W Nightingale, Cameron R Bass, Barry S Myers
BACKGROUND: Cervical bilateral facet dislocations are among the most devastating spine injuries in terms of likelihood of severe neurological sequelae. More than half of patients with tetraparesis had sustained some form of bilateral facet fracture dislocation. They can occur at any level of the sub-axial cervical spine, but predominate between C5 and C7. The mechanism of these injuries has long been thought to be forceful flexion of the chin towards the chest. This "hyperflexion" hypothesis comports well with intuition and it has become dogma in the clinical literature...
March 8, 2018: Clinical Biomechanics
Jiangbin Su, Xianfang Zhu
The nanoinstability of single crystal Si nanowire under electron beam irradiation was in-situ investigated at room temperature by transmission electron microscopy technique. It was observed that the Si nanowire amorphized preferentially from the surface towards the center with the increasing of electron dose. In contrast, in the center of the Si nanowire the amorphization seemed much more difficult accompanying with rotation of crystal grains and compression of d-spacing. Such a preferential amorphization as athermally induced by the electron beam irradiation can be well accounted for by our proposed concepts of nanocurvature effect and energetic beam-induced athermal activation effect, while the classical knock-on mechanism and the electron beam heating effect seem inadequate to explain these processes...
March 15, 2018: Nanotechnology
Angus McMullen, Hendrick W de Haan, Jay X Tang, Derek Stein
Measurements and Langevin dynamics simulations of filamentous viruses driven through solid-state nanopores reveal a superlinear rise in the translocation velocity with driving force. The mobility also scales with the length of the virus in a nontrivial way that depends on the force. These dynamics are consequences of the buckling of the leading portion of a virus as it emerges from the nanopore and is put under compressive stress by the viscous forces it encounters. The leading tip of a buckled virus stalls and this reduces the total viscous drag force...
February 16, 2018: Physical Review Letters
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