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https://www.readbyqxmd.com/read/28336837/pnma-bn-another-boron-nitride-polymorph-with-interesting-physical-properties
#1
Zhenyang Ma, Zheng Han, Xuhong Liu, Xinhai Yu, Dayun Wang, Yi Tian
Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew-Burke-Ernzerhof. This BN, called Pnma-BN, contains four boron atoms and four nitrogen atoms buckled through sp³-hybridized bonds in an orthorhombic symmetry unit cell with Space group of Pnma...
December 28, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28335998/point-shear-wave-elastography-to-evaluate-and-monitor-changing-portal-venous-pressure-in-patients-with-decompensated-cirrhosis
#2
Hao Han, Jian Yang, Yu-Zheng Zhuge, Ming Zhang, Min Wu
This study evaluated whether the stiffness of the liver and spleen, measured using the point shear wave elastography (pSWE) technique, correlates with portal venous pressure (PVP) and whether the result extends to estimate the diminishing change in PVP (ΔPVP) in patients with decompensated cirrhosis. We evaluated the data of 67 prospectively enrolled patients who underwent both transjugular intrahepatic portosystemic shunt (TIPS) and pSWE. The stiffness of liver and spleen were evaluated by measuring shear wave velocity (SWV) to determine the statistical correlation with PVP...
March 20, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28335252/stress-waves-and-characteristics-of-zigzag-and-armchair-silicene-nanoribbons
#3
Yu-Cheng Fan, Te-Hua Fang, Tao-Hsing Chen
The mechanical properties of silicene nanostructures subject to tensile loading were studied via a molecular dynamics (MD) simulation. The effects of temperature on Young's modulus and the fracture strain of silicene with armchair and zigzag types were examined. The maximum in-plane stress and the corresponding critical strain of the armchair and the zigzag silicene sheets at 300 K were 8.85 and 10.62, and 0.187 and 0.244 N/m, respectively. The in-plane stresses of the silicene sheet in the armchair direction at the temperatures of 300, 400, 500, and 600 K were 8...
June 24, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28324974/altered-viscoelastic-properties-of-stroke-affected-muscles-estimated-using-ultrasound-shear-waves-preliminary-data
#4
Ghulam Rasool, Allison B Wang, William Z Rymer, Sabrina S M Lee
As a result of a brain injury such as stroke, the skeletal muscles may undergo numerous structural and functional alterations. These abnormal changes are linked to muscle weakness, joint contracture, and abnormal muscle tone and eventually, result in motor impairment. A subset of these alterations affects passive muscle stiffness, i.e., viscoelastic properties. However, in vivo estimation of changes in viscoelastic properties is a challenging task. Here, we used the shear wave velocity, estimated through ultrasound SuperSonic imaging (SSI), as a surrogate for viscoelastic properties...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28303271/a-computational-method-for-analyzing-the-biomechanics-of-heart-murmurs
#5
Chi Zhu, Jung-Hee Seo, Hani Bakhshaee, Rajat Mittal
A computational framework consisting of a one-way coupled hemodynamic-acoustic method and a wave-decomposition based post-processing approach is developed to investigate the biomechanics of arterial bruits. This framework is then applied to studying the effect of the shear wave on the generation and propagation of bruits from a modeled stenosed artery. The blood flow in the artery is solved by an immersed boundary method (IBM) based incompressible flow solver. The sound generation and propagation in the blood volume is modeled by the linearized perturbed compressible equations, while the sound propagation through the surrounding tissue is modeled by the linear elastic wave equation...
March 17, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/28299813/improvement-of-liver-stiffness-in-patients-with-hepatitis-c-virus-infection-who-received-direct-acting-antiviral-therapy-and-achieved-sustained-virological-response
#6
Toshifumi Tada, Takashi Kumada, Hidenori Toyoda, Kazuyuki Mizuno, Yasuhiro Sone, Saki Kataoka, Shinichi Hashinokuchi
BACKGROUND AND AIM: There is insufficient research on whether direct-acting antiviral (DAA) therapy can improve liver fibrosis in patients with chronic hepatitis C virus (HCV). We evaluated sequential changes in liver stiffness using shear wave elastography (SWE) in patients with HCV who received DAA therapy. METHODS: A total of 210 patients with HCV who received daclatasvir and asunaprevir therapy and achieved sustained virological response (SVR) were analyzed...
March 15, 2017: Journal of Gastroenterology and Hepatology
https://www.readbyqxmd.com/read/28295027/improved-shear-wave-motion-detection-using-coded-excitation-for-transient-elastography
#7
Xiao-Nian He, Xian-Fen Diao, Hao-Ming Lin, Xin-Yu Zhang, Yuan-Yuan Shen, Si-Ping Chen, Zheng-Di Qin, Xin Chen
Transient elastography (TE) is well adapted for use in studying liver elasticity. However, because the shear wave motion signal is extracted from the ultrasound signal, the weak ultrasound signal can significantly deteriorate the shear wave motion tracking process and make it challenging to detect the shear wave motion in a severe noise environment, such as within deep tissues and within obese patients. This paper, therefore, investigated the feasibility of implementing coded excitation in TE for shear wave detection, with the hypothesis that coded ultrasound signals can provide robustness to weak ultrasound signals compared with traditional short pulse...
March 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28294580/effect-of-cerebrospinal-fluid-modelling-on-spherically-convergent-shear-waves-during-blunt-head-trauma
#8
Amit Madhukar, Ying Chen, Martin Ostoja-Starzewski
The MRI-based computational model, previously validated by tagged MRI and HARP imaging analysis technique on in vivo human brain deformation, is employed to study transient wave dynamics during blunt head trauma. Three different constitutive models are used for the cerebrospinal fluid (CSF): incompressible solid elastic, viscoelastic and fluid-like elastic using an equation of state model. Three impact cases are simulated which indicate that the blunt impacts give rise not only to a fast pressure wave but also to a slow, and potentially much more damaging, shear (distortional) wave that converges spherically towards the brain center...
March 14, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28292005/current-status-of-musculoskeletal-application-of-shear-wave-elastography
#9
JeongAh Ryu, Woo Kyoung Jeong
Ultrasonography (US) is a very powerful diagnostic modality for the musculoskeletal system due to the ability to perform real-time dynamic high-resolution examinations with the Doppler technique. In addition to acquiring morphologic data, we can now obtain biomechanical information by quantifying the elasticity of the musculoskeletal structures with US elastography. The earlier diagnosis of degeneration and the ability to perform follow-up evaluations of healing and the effects of treatment are possible. US elastography enables a transition from US-based inspection to US-based palpation in order to diagnose the characteristics of tissue...
February 4, 2017: Ultrasonography
https://www.readbyqxmd.com/read/28286981/shear-wave-ultrasound-elastography-of-the-liver-in-normal-weight-and-obese-children
#10
Smita Sane Bailey, Mostafa Youssfi, Mittun Patel, Houchun H Hu, Gabriel Q Shaibi, Richard B Towbin
Background The identification and subsequent management of liver diseases in children is challenging due to the lack of non-invasive imaging biomarkers. Ultrasound shear-wave elastography (US-SWE) is an emerging imaging technique which can quantitatively assess liver stiffness and may be useful as a tool in the management of liver disease in overweight and obese children. Purpose To evaluate US-SWE velocities of the liver in normal-weight and obese children, to correlate US-SWE findings with age and body-mass-index (BMI), and to compare US-SWE values with qualitative assessment (i...
January 1, 2017: Acta Radiologica
https://www.readbyqxmd.com/read/28285729/evaluation-of-post-stroke-spastic-muscle-stiffness-using-shear-wave-ultrasound-elastography
#11
Chueh-Hung Wu, Yu-Chun Ho, Ming-Yen Hsiao, Wen-Shiang Chen, Tyng-Guey Wang
Current clinical evaluations of post-stroke upper limb spasticity are subjective and qualitative. We proposed a quantitative measurement of post-stroke spastic muscle stiffness by using shear-wave ultrasound elastography and tested its reliability. Acoustic radiation force impulse with shear wave velocity (SWV) detection was used to evaluate stiffness of the biceps brachii muscles at 90° and 0° elbow flexion. In 21 control subjects, SWV did not significantly differ between dominant and non-dominant sides at either flexion angle (0°: p = 0...
March 9, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28284571/dynamic-mechanical-analysis-to-assess-viscoelasticity-of-liver-tissue-in-a-rat-model-of-nonalcoholic-fatty-liver-disease
#12
Xinyu Zhang, Xuehua Gao, Pengpeng Zhang, Yanrong Guo, Haoming Lin, Xianfen Diao, Yingxia Liu, Changfeng Dong, Yaxin Hu, Siping Chen, Xin Chen
Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder in both developed and developing countries. A noninvasive method of detecting early stage NAFLD and distinguishing non-alcoholic steatohepatitis (NASH) from simple steatosis (SS) would be useful. The over-accumulation of fat in hepatocytes alters the physical microstructure and chemical contents of the liver tissue. This study included dynamic mechanical analysis (DMA) testing on liver samples from a rat model of NAFLD to determine whether the tissue shows any significant changes in viscoelasticity due to the histological changes...
March 8, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28282165/instability-of-the-abrikosov-lattice-due-to-nonanalytic-core-reconstruction-of-vortices-in-bosonic-superfluids
#13
Avraham Klein, Oded Agam, Igor L Aleiner
We study the impact of the nonanalytic reconstruction of vortex cores on static vortex structures in weakly coupled superfluids. We show that, in rotating two-dimensional systems, the Abrikosov vortex lattice is unstable to vortex core deformation: Each zero of the wave function becomes a cut of finite length. The directors characterizing the orientations of the cuts are themselves ordered in superstructures due either to surface effects or to interaction with shear deformations of the lattice (spiral structure)...
February 24, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28279881/acoustomicrofluidic-application-of-quasi-shear-surface-waves
#14
A N Darinskii, M Weihnacht, H Schmidt
The paper analyzes the possibility of using predominantly boundary polarized surface acoustic waves for actuating fluidic effects in microchannels fabricated inside containers made of PDMS. The aim is to remove a shortcoming peculiar to conventionally utilized predominantly vertically polarized waves. Such waves strongly attenuate while they propagate under container side walls because of the leakage into them. Due to a specific feature of PDMS - extremely small shear elastic modulus - losses of boundary polarized modes should be far smaller...
February 20, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28279018/correlation-of-ultrasound-shear-wave-elastography-with-pathological-analysis-in-a-xenografic-tumour-model
#15
Eli Elyas, Efthymia Papaevangelou, Erwin J Alles, Janine T Erler, Thomas R Cox, Simon P Robinson, Jeffrey C Bamber
The objective of this study was to evaluate the potential value of ultrasound (US) shear wave elastography (SWE) in assessing the relative change in elastic modulus in colorectal adenocarcinoma xenograft models in vivo and investigate any correlation with histological analysis. We sought to test whether non-invasive evaluation of tissue stiffness is indicative of pathological tumour changes and can be used to monitor therapeutic efficacy. US-SWE was performed in tumour xenografts in 15 NCr nude immunodeficient mice, which were treated with either the cytotoxic drug, Irinotecan, or saline as control...
December 2017: Scientific Reports
https://www.readbyqxmd.com/read/28271231/quantitative-assessment-of-muscle-stiffness-with-acoustic-radiation-force-impulse-elastography-after-botulinum-toxin-a-injection-in-children-with-cerebral-palsy
#16
Meltem Ceyhan Bilgici, Tumay Bekci, Yasemin Ulus, Ayhan Bilgici, Leman Tomak, Mustafa Bekir Selcuk
PURPOSE: Our objective in this study was to assess the changes in medial gastrocnemius muscle (GCM) stiffness after botulinum toxin A (BTA) injection in children with cerebral palsy (CP) by using acoustic radiation force impulse (ARFI) elastography and to research the usability of this technique in clinical practice. MATERIALS AND METHODS: Twenty-four spastic lower extremities of 12 children with CP were assessed. BTA injection treatment was applied to the medial GCM...
March 7, 2017: Journal of Medical Ultrasonics
https://www.readbyqxmd.com/read/28268916/tissue-characterization-using-simultaneous-estimation-of-backscatter-coefficient-and-elastic-shear-modulus
#17
Julien Rouyer, Gabriela Torres, Matthew W Urban, Roberto Lavarello
Tissue characterization using quantitative ultrasound (QUS) parameters has received significant attention in recent years due to its potential to improve the detection and diagnosis of diseased states. However, the vast majority of studies in QUS tissue typing have used parameters derived from either longitudinal or shear waves in isolation, thereby discarding potentially useful complementary information these parameters may carry. In this study, the simultaneous estimation of backscatter coefficients (derived from longitudinal waves) and shear modulus (derived from shear waves) was implemented on data from a clinical scanner...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268914/shear-wave-elastography-using-wigner-ville-distribution-a-simulated-multilayer-media-study
#18
Pooya Sobhe Bidari, Javad Alirezaie, Jahan Tavakkoli
Shear Wave Elastography (SWE) is a quantitative ultrasound-based imaging modality for distinguishing normal and abnormal tissue types by estimating the local viscoelastic properties of the tissue. These properties have been estimated in many studies by propagating ultrasound shear wave within the tissue and estimating parameters such as speed of wave. Vast majority of the proposed techniques are based on the cross-correlation of consecutive ultrasound images. In this study, we propose a new method of wave detection based on time-frequency (TF) analysis of the ultrasound signal...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268544/comparison-of-viscoelastic-property-characterization-of-plastisol-phantoms-with-magnetic-resonance-elastography-and-high-frequency-rheometry
#19
P M Lefebvre, K Tse Ve Koon, E Brusseau, S Nicolle, J-F Palieme, S A Lambert, D Grenier
This study aims at evaluating Magnetic Resonance Elastography (MRE) as a reliable technique for the characterization of viscoelastic properties of soft tissues. Three phantoms with different concentrations of plastisol and softener were prepared in order to mechanically mimic a broad panel of healthy and pathological soft tissues. Once placed in a MRI device, each sample was excited by a homemade external driver, inducing shear waves within the medium. The storage (G') and loss (G") moduli of each phantom were then reconstructed from MRE acquisitions over a frequency range from 300 to 1,000 Hz, by applying a 2D Helmholtz inversion algorithm...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28267542/comparison-between-acoustic-radiation-force-impulse-quantification-data-and-perfusion-ct-parameters-in-hepatocellular-carcinoma
#20
Michael Esser, Sven Schneeweiß, Manuel Kolb, Mustafa Kurucay, Christer Ruff, Konstantin Nikolaou, Marius Horger
OBJECTIVE: To find out, if ultrasound elastography of hepatocellular carcinoma (HCC) can predict patterns of tumor perfusion in volume perfusion computed tomography (VPCT). MATERIAL AND METHODS: 25 consecutive patients (mean age, 68.9; range, 51-85 years) with liver cirrhosis suspected of HCC underwent VPCT and acoustic radiation force impulse (ARFI) elastography the same day. Quantitative elasticity values were registered, while blood flow (BF), blood volume (BV) and hepatic perfusion index (HPI) of the HCC lesions were calculated...
April 2017: European Journal of Radiology
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