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IEEE 37th Annual Northeast Bioengineering Conference (NEBEC)

作者： Dentinger, A. M. Jia, C. GE Global Res Ultrasound Lab Niskayuna NY 12309 USA

ISBN: (纸本)9781612848266

The apparent arterial compliance observed from noninvasive measurements of arterial blood pressure and cross-sectional area does not directly correspond to the static compliance curve or dynamic pressure-area loop. The accuracy of continuous, non-invasive blood pressure estimates based on calibrated arterial compliance models to convert area to pressure is affected by both changes in the viscoelastic properties of the artery and in the pressure waveform. The relationship of the apparent compliance curve to static compliance and to dynamic pressure-area loop is demonstrated using a simulated linear viscoelastic model, and the sensitivity of blood pressure estimates to changes in the viscoelastic parameters and pressure waveform is investigated. Changes in the elastic component of the viscoelastic model had the largest effect with a 25% change in the modulus of elasticity resulting in a 5.5% error in the systolic blood pressure estimate.

关键词： Area measurement Biomedical monitoring Blood pressure Elasticity Pressure measurement Shape Ultrasonic imaging apparent arterial compliance arterial blood pressure artery blood pressure measurement blood vessels calibrated arterial compliance models continuous noninvasive blood pressure monitoring cross-sectional area dynamic pressure-area loop elastic moduli elastic modulus estimation theory noninvasive measurements patient monitoring physiological models pressure waveform static compliance curve systolic blood pressure estimation viscoelastic parameters viscoelastic properties

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Peculiarities of Erythrocytic parameters in Patients with Nonalcoholic Steatohepatitis

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Journal of Analytical Sciences, Methods and Instrumentation 2016年第1期6卷 6-14页

作者： Margarita V. Kruchinina Svetlana А. Kurilovich Аndrey А. Gromov Vladimir М. Generalov Vladimir N. Kruchinin Federal State Budgetary of Scientific Institution “Institution of Internal and Preventive Medicine” Novosibirsk Russia The State Research Center of Virology and Biotechnology VECTOR Koltsovo Russia Rzhanov Institute of Semiconductor Physics SB RAS Novosibirsk Russia

Thirty-seven males with non-alcoholic staatohepatitis (NASH) (aged 39 - 62) were included in the study. Clinical, biochemical and instrumental studies were used to verify the diagnosis. The control group was comprised of thirty-three males of comparable age and without confirmed signs of liver diseases and other pathology of inner organs. Dielectrophoresis was applied to evaluate the structural-and-functional erythrocytic parameters. The patients with NASH erythrocytes tended to differ in their much lower amplitude deformation, polarizability, capacity of erythrocytic membranes, pace of translational motion of cells towards electrodes and much higher levels of overall indices of rigidity, viscosity, electroconductivity, destruction and aggregation as compared to the control group (p < 0.001 - 0.05). We discovered cases of correlation of erythrocytic parameters with biochemical findings reflecting inflammatory and cytolytic syndrome, cholestasis, protein-synthesizing liver function as well as markers of metabolic syndrome (BMI, changes in arterial blood pressure, the degree of disturbances in carbohydrate metabolism, atherogenic dyslipidemia) and microalbuminuria. Aggravation of microcirculatory disturbances leading to an increase of fibrogenes is induced by changes in the properties of erythrocytes under NASH suggests the administration of a number of therapeutic techniques which could improve the status of the parameters of red blood cells. This study aims to evaluate the peculiarities of electric and viscoelastic behavior of erythrocytes in patients with primary NASH in order to determine additional methods of treatment for this disease.

关键词： Nonalcoholic Steatohepatitis Electric viscoelastic parameters Erythrocytes Dielectrophoresis

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Dependence of viscoelastic parameters of nematic liquid crystals on pretilt angle and temperature

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CURRENT APPLIED PHYSICS 2010年第2期10卷 561-564页

作者： Huang, Yao-Xiong Tu, Mei Jinan Univ Inst Biomed Engn Guangzhou 510632 Guangdong Peoples R China

The viscoelastic parameters of nematic liquid crystal (LC) E7 in both splay and twist relaxation modes are investigated as functions of pretilt angle and temperature by the technique of dynamic laser light scattering. The results show that the elastic constants of the liquid crystal in the two modes not only depend on temperature, but also depend on pretilt angle. There is a critical pretilt angle (beta(C)) at which nematic LC begins exhibiting elastic property, and beyond which the elastic constants increase with pretilt angle, then keep constant after exceeding another angle (beta(S), with beta(S) > beta(C)). This phenomenon is observed to be universal for different nematic LC's, and significant not only in the understanding of the molecular mechanism of exhibiting viscoelastic properties in nematic LC, but also for their practical purpose. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Nematic liquid crystal Relaxation mode viscoelastic parameters Pretilt angle

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A computational model for dynamic analysis of the human gait

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COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING 2015年第7期18卷 799-804页

作者： Vimieiro, Claysson Andrada, Emanuel Witte, Hartmut Pinotti, Marcos Univ Fed Minas Gerais Dept Mech Engn Bioengn Lab LABBIO Belo Horizonte MG Brazil Pontificia Univ Catolica Minas Gerais Dept Mech Engn Dynam Lab Belo Horizonte MG Brazil Tech Univ Ilmenau Dept Mech Engn Biomech Lab Ilmenau Germany

Biomechanical models are important tools in the study of human motion. This work proposes a computational model to analyse the dynamics of lower limb motion using a kinematic chain to represent the body segments and rotational joints linked by viscoelastic elements. The model uses anthropometric parameters, ground reaction forces and joint Cardan angles from subjects to analyse lower limb motion during the gait. The model allows evaluating these data in each body plane. Six healthy subjects walked on a treadmill to record the kinematic and kinetic data. In addition, anthropometric parameters were recorded to construct the model. The viscoelastic parameter values were fitted for the model joints (hip, knee and ankle). The proposed model demonstrated that manipulating the viscoelastic parameters between the body segments could fit the amplitudes and frequencies of motion. The data collected in this work have viscoelastic parameter values that follow a normal distribution, indicating that these values are directly related to the gait pattern. To validate the model, we used the values of the joint angles to perform a comparison between the model results and previously published data. The model results show a same pattern and range of values found in the literature for the human gait motion.

关键词： lower limbs dynamic analysis computational model viscoelastic parameters human gait

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InSAR measurement of the deformation around Siling Co Lake: Inferences on the lower crust viscosity in central Tibet

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JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 2015年第7期120卷 5290-5310页

作者： Doin, Marie-Pierre Twardzik, Cedric Ducret, Gabriel Lasserre, Cecile Guillaso, Stephane Sun Jianbao Univ Grenoble Alpes CNRS ISTerre Grenoble France Univ Calif Santa Barbara Dept Earth Sci Santa Barbara CA 93106 USA Ecole Normale Super Geol Lab F-75231 Paris France Tech Univ Berlin Comp Vis & Remote Sensing Berlin Germany China Earthquake Adm Inst Geol Beijing Peoples R China

The Siling Co Lake is the largest endorheic lake in Central Tibet. Altimetric measures, combined with lake contours, show that in 1972-1999 its water level remained stable, while it increased by about 1.0m/yr in the period 2000-2006. The increased rate gradually stepped down to 0.2m/yr in 2007-2011. The ground motion associated with the water load increase is studied by interferometric synthetic aperture radar (InSAR) using 107 ERS and Envisat SAR images during the period 1992-2011. The deformation amplitude closely follows the lake level temporal evolution, except that subsidence continues in 2008-2011, while the lake level stagnated. This temporal evolution suggests a non elastic relaxation process taking place at a decade timescale. Phase delay maps are used to constrain possible layered viscoelastic rheological models. An elastic model could partly explain the observed subsidence rate if elastic moduli are about twice lower than those extracted from V-P/V-S profiles. The surface deformation pattern is also extracted by projecting the phase delay maps against the best fit model temporal behavior. It shows that deep relaxation in the asthenosphere is negligible at the decade timescale and favors the existence of a ductile channel in the deep crust above a more rigid mantle. Overall, the best fit model includes a ductile lower crust, with a viscosity of 1-3 x 10(18)Pas between 25 and 35km and the Moho (at 65km), overlying a rigid mantle.

关键词： Siling Co Lake Tibet InSAR surface loading lithosphere viscoelastic parameters

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High-resolution mechanical imaging of the human brain by three-dimensional multifrequency magnetic resonance elastography at 7T

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NEUROIMAGE 2014年第0期90卷 308-314页

作者： Braun, Juergen Guo, Jing Luetzkendorf, Ralf Stadler, Joerg Papazoglou, Sebastian Hirsch, Sebastian Sack, Ingolf Bernarding, Johannes Charite Inst Med Informat D-12200 Berlin Germany Charite Dept Radiol D-12200 Berlin Germany Leibniz Inst Neurobiol Magdeburg Germany Otto von Guericke Univ Inst Biometry & Med Informat Magdeburg Germany

Magnetic resonance elastography (MRE) is capable of measuring the viscoelastic properties of brain tissue in vivo. However, MRE is still limited in providing high-resolution maps of mechanical constants. We therefore introduce 3D multifrequency MRE (3DMMRE) at 7T magnetic field strength combined with enhanced multifrequency dual elasto-visco (MDEV) inversion in order to achieve high-resolution elastographic maps of in vivo brain tissue with 1 mm(3) resolution. As demonstrated by phantom data, the new MDEV-inversion method provides two high resolution parameter maps of the magnitude (vertical bar G*vertical bar) and the phase angle (phi) of the complex shear modulus. MDEV inversion applied to cerebral 7T-3DMMRE data of five healthy volunteers revealed structures of brain tissue in greater anatomical details than previous work. The viscoelastic properties of cortical gray matter (GM) and white matter (WM) could be differentiated by significantly lower values of vertical bar G*vertical bar and phi in GM (21% [P < 0.01];8%, [P < 0.01], respectively) suggesting that GM is significantly softer and less viscous than WM. In conclusion, 3DMMRE at ultrahigh magnetic fields and MDEV inversion open a new window into characterizing the mechanical structure of in vivo brain tissue and may aid the detection of various neurological disorders based on their effects to mechanical tissue properties. (C) 2013 Elsevier Inc. All rights reserved.

关键词： Ultrahigh magnetic field MRI High resolution Elastography Multifrequency MRE viscoelastic parameters Brain tissue

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Design and fabrication of cell adhesion measuring device 21

Design and fabrication of cell adhesion measuring device

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21th Iranian Conference on Biomedical Engineering

作者： Salehipour, Saeed Abolfathi, Nabiollah Hashemi, Ataallah Amirkabir Univ Technol Dept Biomed Engn Tehran Iran

ISBN: (纸本)9781479974184

Cell adhesion phenomena has an important role on different behavior of cell. Therefore qualitative and quantitative understanding of cell adhesion force is necessary. A low cost micro device has been developed that can demonstrate cell adhesion force against a specific mechanical stimuli. The device that we developed here allows the measuring cell adhesion. This device is made based on poly methyl methacrylate (PMMA). Finally, to test the system functions, we obtained viscoelastic parameters of cell by applying 10 micron displacement that had a good agreement with literature.

关键词： cell adhesion force microdevice in vitro mechanical stimuli PMMA viscoelastic parameters

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Damping of gravity-capillary waves in the presence of oil slicks according to data from laboratory and numerical experiments

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IZVESTIYA ATMOSPHERIC AND OCEANIC PHYSICS 2012年第5期48卷 565-572页

作者： Ermakov, S. A. Sergievskaya, I. A. Gushchin, L. A. Russian Acad Sci Inst Appl Phys Nizhnii Novgorod 603950 Russia Nizhnii Novgorod State Univ Nizhnii Novgorod 603950 Russia Russian State Hydrometeorol Univ St Petersburg 195196 Russia

Laboratory study results on the damping of gravity-capillary waves (GCWs) on water covered with oil slicks are presented. The nonmonotonic behavior (the presence of a local maximum) of the dependence of the damp coefficient on the slick thickness has been ascertained. The dispersion relation for GCWs in the presence of a viscoelastic slick of arbitrary thickness has been numerically calculated;this confirmed the presence of a damp coefficient maximum as a function of slick thickness. The parameters of oil slicks (interfacial elasticity and viscosity) have been estimated in a wide range of their thickness from a comparison of the calculation results with the data from laboratory measurements of wave parameters on water covered with an oil slick.

关键词： oil slick damping surface waves two-layer fluid viscoelastic parameters

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Rheological Investigation of Thermal-Induced Gelation of Polyacrylonitrile Solutions

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INTERNATIONAL JOURNAL OF THERMOPHYSICS 2009年第4期30卷 1411-1422页

作者： Bercea, M. Morariu, S. Brunchi, C. -E. Petru Poni Inst Macromol Chem Iasi 700487 Romania

In this article, thermal-induced gelation of polyacrylonitrile (PAN) solutions in dimethylformamide was studied through rheological measurements. The entangled and non-entangled states were delimited for an overlap parameter of macromolecular coils of 2.7. In temperature sweep experiments, two types of gelation processes were identified for PAN entangled solutions at: (1) a reversible gelation in the region of low temperatures (below 15A degrees C) due to the formation of a crosslinked structure with a small region of order that dissolves completely in an excess of solvent, and (2) an irreversible gelation at high temperatures (above 60A degrees C) and this gel is insoluble in an excess of solvent, due to the formation of a chemical three-dimensional network. Physical PAN gels with good elastic properties were also obtained by the freezing and thawing method. The gel properties depend on the thermal history of the solution (freezing time, aging time, and aging temperature), its composition (concentration and molar mass of the polymer), and gelation conditions (freezing rate). The gelation was attributed to the formation of junction zones via an aggregation process between a certain number of chain segments due to attractive dipole-dipole interactions.

关键词： Entangled solutions Gel Polyacrylonitrile (PAN) viscoelastic parameters

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Surgical instrumentation for the in vivo determination of human lumbar spinal segment stiffness and viscoelasticity

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MEDICAL ENGINEERING & PHYSICS 2009年第9期31卷 1063-1068页

作者： Ambrosetti-Giudici, Sveva Pfenniger, Alois Krenn, Michael H. Piotrowski, Wolfgang P. Ferguson, Stephen J. Burger, Juergen Bern Univ Appl Sci CH-2501 Biel Switzerland Dept Spine Surg PMU Salzburg Austria Univ Bern Inst Surg Technol & Biomech Bern Switzerland

The definition of spinal instability is still controversial. For this reason, it is essential to better understand the difference in biomechanical behaviour between healthy and degenerated human spinal segments in vivo. A novel computer-assisted instrument was developed with the objective to characterize the biomechanical parameters of the spinal segment. Investigation of the viscoelastic properties as well as the dynamic spinal stiffness was performed during a minimally invasive procedure (microdiscectomy) on five patients. Measurements were performed intraoperatively and the protocol consisted of a dynamic part, where spinal stiffness was computed, and a static part, where force relaxation of the segment under constant elongation was studied. The repeatability of the measurement procedure was demonstrated with five replicated tests. The spinal segment tissues were found to have viscoelastic properties. Preliminary tests confirmed a decrease in stiffness after decompression surgery. Patients with non-relaxed muscles showed higher stiffness and relaxation rate compared to patients with relaxed muscles, which can be explained by the contraction and relaxation reflex of muscles under fast and then static elongation. The results show the usefulness of the biomechanical characterization of the human lumbar spinal segment to improve the understanding of the contribution of individual anatomical structures to spinal stability. (C) 2009 IPEM. Published by Elsevier Ltd. All rights reserved.

关键词： Lumbar spinal instability viscoelastic parameters Characterization spinal segment Surgical instrumentation Spinal stiffness

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