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Ingolf Sack - One of the best experts on this subject based on the ideXlab platform.
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measurement of in vivo cerebral Volumetric Strain induced by the valsalva maneuver
Journal of Biomechanics, 2014Co-Authors: Seyed Reza Mousavi, Andreas Fehlner, Kasparjosche Streitberger, Jurgen Braun, Abbas Samani, Ingolf SackAbstract:Abstract Compressibility of biological tissues such as brain parenchyma is related to its poroelastic nature characterized by the geometry and pressure of vasculature and interconnected fluid-filled spaces. Thus, cerebral Volumetric Strain may be sensitive to intracranial pressure which can be altered under physiological conditions. So far Volumetric Strain has attained little attention in studies of the mechanical behavior of the brain. This paper reports a study of measuring the in vivo cerebral Volumetric Strain induced by the Valsalva maneuver (VM) where forced expiration against a closed glottis leads to a transient increase in the intracranial pressure. For this purpose we applied three-dimensional magnetic resonance imaging equipped with a patient-controlled acquisition system to five healthy volunteers. With each volunteer, three experiments were performed: one with VM and two in resting state. i.e. normal ventilation, which were conducted before and after VM. The VM data were registered to reference data by morphology based non-rigid deformation, yielding 3D maps of total displacements and Volumetric Strain. On average, VM induced Volumetric Strain correlated to whole-brain dilatation of −3.14±0.87% and −2.80±0.71% compared to the reference states before and after VM, respectively. These values were well reproduced by repetitive experiments during the same scan as well as by repeated measurements in one volunteer on different days. Combined with literature data of intracranial pressure changes, our Volumetric Strain values can be used to elucidate the static compression modulus of the in vivo human brain. These results add knowledge to the understanding of the brain׳s biomechanical properties under physiological conditions.
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towards compression sensitive magnetic resonance elastography of the liver sensitivity of harmonic Volumetric Strain to portal hypertension
Journal of Magnetic Resonance Imaging, 2014Co-Authors: Sebastian Hirsch, Jurgen Braun, Ingolf Sack, Jing Guo, Rolf Reiter, E Schott, Carsten Buning, R Somasundaram, Thomas J KroenckeAbstract:Purpose To assess induced oscillating Volumetric Strain as a biomarker for intrahepatic blood pressure abnormalities. Materials and Methods Harmonic vibrations of 25 and 50 Hz frequency were induced in the liver and measured by fast 3D vector field magnetic resonance elastography (MRE), followed by processing of the decomposed curl (shear) and divergence (compression) fields. After an initial study on an excised sheep liver, a group of 13 patients with hepatic hypertension were examined before and after implantation of a transjugular intrahepatic portosystemic shunt (TIPS). Results In the sheep liver specimen, Volumetric Strain decreased with excess portal pressure, whereas shear Strain was not sensitive to portal pressure. In the patient cohort, Volumetric Strain was significantly higher after TIPS placement (P = 1.38·10−5), while neither shear Strain nor the shear modulus were affected. Normalized changes in Volumetric Strain were significantly correlated with the hepatic venous pressure gradient (R2 = 0.7258, P = 6.95·10−5) and portal venous pressure (R2 = 0.5028, P = 0.0016). Conclusion These results indicate for the first time the sensitivity of Volumetric Strain to symptomatically high values of tissue pressure and motivate further developments in compression-sensitive MRE and poroelastography towards image-based and noninvasive markers of tissue pressure. J. Magn. Reson. Imaging 2014;39:298–306. © 2013 Wiley Periodicals, Inc.
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in vivo measurement of Volumetric Strain in the human brain induced by arterial pulsation and harmonic waves
Magnetic Resonance in Medicine, 2013Co-Authors: Sebastia Hirsch, Diete Kla, Florian Baptis Freima, Michael Scheel, Ingolf SackAbstract:Motion-sensitive phase contrast magnetic resonance imaging and magnetic resonance elastography are applied for the measurement of Volumetric Strain and tissue compressibility in human brain. Volumetric Strain calculated by the divergence operator using a biphasic effective-medium model is related to dilatation and compression of fluid spaces during harmonic stimulation of the head or during intracranial passage of the arterial pulse wave. In six volunteers, phase contrast magnetic resonance imaging showed that the central cerebrum expands at arterial pulse wave to Strain values of (2.8 ± 1.9)·10−4. The evolution of Volumetric Strain agrees well with the magnitude of the harmonic divergence measured in eight volunteers by magnetic resonance elastography using external activation of 25 Hz vibration frequency. Intracranial Volumetric Strain was proven sensitive to venous pressure altered by abdominal muscle contraction. In eight volunteers, an increase in Volumetric Strain due to abdominal muscle contraction of approximately 45% was observed (P = 0.0001). The corresponding compression modulus in the range of 9.5–13.5 kPa demonstrated that the compressibility of brain tissue at 25 Hz stimulation is much higher than that of water. This pilot study provides the background for compression-sensitive magnetic resonance imaging with or without external head stimulation. Volumetric Strain may be sensitive to fluid flow abnormalities or pressure imbalances between vasculature and parenchyma as seen in hydrocephalus. Magn Reson Med 70:671–683, 2013. © 2012 Wiley Periodicals, Inc.
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measurement of vibration induced Volumetric Strain in the human lung
Magnetic Resonance in Medicine, 2013Co-Authors: Sebastian Hirsch, Jurgen Braun, Oleg Posnansky, Sebastian Papazoglou, Thomas Elgeti, Ingolf SackAbstract:Noninvasive image-based measurement of intrinsic tissue pressure is of great interest in the diagnosis and characterization of diseases. Therefore, we propose to exploit the capability of phase-contrast MRI to measure three-dimensional vector fields of tissue motion for deriving Volumetric Strain induced by external vibration. Volumetric Strain as given by the divergence of mechanical displacement fields is related to tissue compressibility and is thus sensitive to the state of tissue pressure. This principle is demonstrated by the measurement of three-dimensional vector fields of 50-Hz oscillations in a compressible agarose phantom and in the lungs of nine healthy volunteers. In the phantom, the magnitude of the oscillating divergence increased by about 400% with 4.8 bar excess air pressure, corresponding to an effective-medium compression modulus of 230 MPa. In lungs, the averaged divergence magnitude increased in all volunteers (N = 9) between 7 and 78% from expiration to inspiration. Measuring Volumetric Strain by MRI provides a compression-sensitive parameter of tissue mechanics, which varies with the respiratory state in the lungs. In future clinical applications for diagnosis and characterization of lung emphysema, fibrosis, or cancer, divergence-sensitive MRI may serve as a noninvasive marker sensitive to disease-related alterations of regional elastic recoil pressure in the lungs.
V. Palchik - One of the best experts on this subject based on the ideXlab platform.
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use of descartes folium equation for deriving a relation between total aperture of fractures after uniaxial compression and Strain parameters of different rocks exhibiting negative total Volumetric Strains
Rock Mechanics and Rock Engineering, 2014Co-Authors: V. PalchikAbstract:The axial, crack and total Volumetric Strains, porosity, elastic constants, crack damage stresses, uniaxial compressive strengths, as well as fracture apertures and number of fracture traces in rock samples surface after compression were defined for different chalk, basalt, dolomite, granite, limestone and sandstone samples exhibiting negative total Volumetric Strain at failure. It is established that the total (summed) aperture of vertical fractures obtained on the lateral surface of rock sample is related to three characteristic Strain parameters: axial Strain at the onset of negative total Volumetric Strain, axial failure Strain and negative total Volumetric Strain at failure. The relation is based on Descartes folium equation, where the length of the loop of folium is equal to axial Strain coordinate at the onset of negative total Volumetric Strain. This relation shows that the total aperture increases according to power law with increasing difference between axial failure Strain and axial Strain at the onset of negative total Volumetric Strain. Simultaneously, an increase in this difference leads to an increase in the value of negative total Volumetric Strain at failure. It is found that a direct correlation between total aperture of fractures and negative total Volumetric Strain at failure is relatively weak. Nevertheless, total aperture of fractures tends to increase with increasing absolute value of negative total Volumetric Strain at failure. It is revealed that there is no connection between the number of fracture traces and negative total Volumetric Strain at failure.
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Is there Link between the Type of the Volumetric Strain Curve and Elastic Constants, Porosity, Stress and Strain Characteristics ?
Rock Mechanics and Rock Engineering, 2012Co-Authors: V. PalchikAbstract:The stress [crack damage stress (σcd) and uniaxial compressive strength (σc)] and Strain characteristics [maximum total Volumetric Strain (ecd), axial failure Strain (eaf)], porosity (n) and elastic constants [elastic modulus (E) and Poisson’s ratio (ν)] and their ratios were coordinated with the existence of two different types (type 1 and type 2) of Volumetric Strain curve. Type 1 Volumetric Strain curve has a reversal point and, therefore, σcd is less than the uniaxial compressive strength (σc). Type 2 has no reversal point, and the bulk volume of rock decreases until its failure occurs (i.e., σcd = σc). It is confirmed that the ratio between the elastic modulus (E) and the parameter λ = n/ecd strongly affects the crack damage stress (σcd) for both type 1 and type 2 Volumetric Strain curves. It is revealed that heterogeneous carbonate rock samples exhibit different types of the Volumetric Strain curve even within the same rock formation, and the range of σcd/σc = 0.54–1 for carbonate rocks is wider than the range (0.71 < σcd/σc < 0.84) obtained by other researchers for granites, sandstones and quartzite. It is established that there is no connection between the type of the Volumetric Strain curve and values of n, E, σcd, ν, E/(1 − 2ν), MR = E/σc and E/λ. On the other hand, the type of Volumetric Strain curve is connected with the values of λ and the ratio between the axial failure Strain (eaf) and the maximum total Volumetric Strain (ecd). It is argued that in case of small eaf/ecd–small λ, Volumetric Strain curve follows the type 2.
Naoji Koizumi - One of the best experts on this subject based on the ideXlab platform.
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frequency characteristics of the response of water pressure in a closed well to Volumetric Strain in the high frequency domain
Journal of Geophysical Research, 2011Co-Authors: Yuichi Kitagawa, Norio Matsumoto, Satoshi Itaba, Naoji KoizumiAbstract:[1] Oscillations of water pressures and crustal Strains due to the seismic waves of the 2010 Chile earthquake were observed in Japan. The oscillations of water pressures observed over the frequency range of 0.002 to 0.1 Hz were negative proportional to the oscillations of Volumetric Strains. The responses of water pressures in closed wells are frequency-dependent. The expression for the response of water pressure in a closed well to crustal Strain is developed based on the poroelastic theory. The expression developed in the present paper describes the frequency characteristics of the responses. The response is useful for the estimation of rock properties. In addition, the responses of water pressure due to tidal Volumetric Strain are estimated and compared with the responses due to the seismic waves.
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Evaluation of the effects of ground shaking and static Volumetric Strain change on earthquake-related groundwater level changes in Taiwan
Earth Planets and Space, 2010Co-Authors: Wen-chi Lai, Naoji Koizumi, Kuo-chin Hsu, Chjeng-lun Shieh, Youe-ping Lee, Kuo-chang Chung, Norio MatsumotoAbstract:Between 2001 and 2005, the Disaster Prevention Research Center of National Cheng-Kung University established a groundwater observation network consisting of 16 wells. Most of these were located along active faults for research on earthquake-related groundwater changes. They were selected mainly from among the 550 groundwater observation wells of the Water Resources Agency (WRA), which monitors and manages groundwater resources in Taiwan. The groundwater level was observed at a resolution of 0.2 mm at the wells. The depths of the well screens ranged between 80 and 252 m. Groundwater level data at six of the 16 wells were analyzed between 2003 and 2006 in an evaluation of such data for use in detecting earthquake-related groundwater level changes. The Strain sensitivities of the groundwater level at these six wells ranged between 0.1 and 0.5 mm/10^−9, indicating that an analysis of groundwater level data at these six wells can detect Volumetric Strain changes on the order of 10^−9. Coseismic and/or postseismic groundwater level changes associated with 17 earthquakes in and around Taiwan whose magnitudes were ≥6 were also analyzed. Our analysis shows that ground shaking seems the main reason for earthquake-related changes but that the acceleration of ground shaking cannot always explain the observed groundwater level changes.
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preseismic changes in groundwater level and Volumetric Strain associated with earthquake swarms off the east coast of the izu peninsula japan
Geophysical Research Letters, 1999Co-Authors: Naoji Koizumi, Eikichi Tsukuda, Osamu Kamigaichi, Norio Matsumoto, Makoto Takahashi, Tsutomu SatoAbstract:We have observed the groundwater level at Omuroyama-kita (OMR) well on the Izu Peninsula, Japan since October 1994. During the observation period, there were four earthquake swarms. We detected one or two preseismic groundwater level changes together with preseismic crustal deformation recorded at the other nearby stations. Therefore those preseismic groundwater level changes are considered to be caused by crustal deformation or Volumetric Strain changes. The crustal deformations are inferred to be caused by the magmatic dike intrusion, which is a possible source of the earthquake swarms off the east coast of the Izu Peninsula.
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comparison of postseismic groundwater temperature changes with earthquake induced Volumetric Strain release yudani hot spring japan
Geophysical Research Letters, 1996Co-Authors: Yuuichi Kitagawa, Naoji Koizumi, Tameshige TsukudaAbstract:We observed temporal variations of the groundwater temperature during two observation periods (May 1983 - July 1984, September 1991 - August 1995) at Yudani hot spring in Tottori Prefecture, Japan. The groundwater temperature is affected by tides, atmospheric pressure changes and earthquakes. Assuming that Volumetric Strain change is the cause of these temperature changes, we calculated the respective Strain sensitivities of the groundwater temperature. As a result, the sensitivities estimated from theoretical Volumetric Strain changes by earthquake fault models are more than 1,000 times larger than those from tides and atmospheric pressure. We infer that the actual Volumetric Strain changes near Yudani hot spring due to the earthquakes are larger than theoretical Strain changes calculated by earthquake fault models.
Nan Jiang - One of the best experts on this subject based on the ideXlab platform.
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Controllable Preparation of Ordered and Hierarchically Buckled Structures for Inflatable Tumor Ablation, Volumetric Strain Sensor, and Communication via Inflatable Antenna
ACS Applied Materials & Interfaces, 2019Co-Authors: Run Wang, Zhongsheng Liu, Guoyun Wan, Tianjiao Jia, Chao Zhang, Xuemin Wang, Mei Zhang, Dong Qian, Mônica Jung De Andrade, Nan JiangAbstract:Inflatable conducting devices providing improved properties and functionalities are needed for diverse applications. However, the difficult part in making high-performance inflatable devices is the enabling of two-dimensional (2D) buckles with controlled structures on inflatable catheters. Here, we report the fabrication of highly inflatable devices with controllable structures by wrapping the super-aligned carbon nanotube sheet (SACNS) on the pre-inflated catheter. The resulting structure exhibits unique 2D buckled structures including quasi-parallel buckles, crisscrossed buckles, and hierarchically buckled structures, which enables reversible structural changes of 7470% Volumetric Strain. The 2D SACNS buckled structures show stable electrical conductance and surface wettability during large Strain inflation/deflation cycles. Inflatable devices including inflatable tumor ablation, capacitive Volumetric Strain sensor, and communication via inflatable radio frequency antenna based on these structures are d...
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Controllable Preparation of Ordered and Hierarchically Buckled Structures for Inflatable Tumor Ablation, Volumetric Strain Sensor, and Communication via Inflatable Antenna
2019Co-Authors: Run Wang, Zhongsheng Liu, Guoyun Wan, Tianjiao Jia, Chao Zhang, Xuemin Wang, Mei Zhang, Dong Qian, Mônica Jung De Andrade, Nan JiangAbstract:Inflatable conducting devices providing improved properties and functionalities are needed for diverse applications. However, the difficult part in making high-performance inflatable devices is the enabling of two-dimensional (2D) buckles with controlled structures on inflatable catheters. Here, we report the fabrication of highly inflatable devices with controllable structures by wrapping the super-aligned carbon nanotube sheet (SACNS) on the pre-inflated catheter. The resulting structure exhibits unique 2D buckled structures including quasi-parallel buckles, crisscrossed buckles, and hierarchically buckled structures, which enables reversible structural changes of 7470% Volumetric Strain. The 2D SACNS buckled structures show stable electrical conductance and surface wettability during large Strain inflation/deflation cycles. Inflatable devices including inflatable tumor ablation, capacitive Volumetric Strain sensor, and communication via inflatable radio frequency antenna based on these structures are demonstrated
Zhongrong Zhou - One of the best experts on this subject based on the ideXlab platform.
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modeling the initial volume dependent approximate compressibility of porcine liver tissues using a novel Volumetric Strain energy model
Journal of Biomechanics, 2020Co-Authors: Bingrui Wang, Jiantao Liu, Zhongrong ZhouAbstract:Abstract Experimental observations in the open literature indicate that soft tissues are slightly compressible, and this characteristic affects not only their overall elastic response but also their damage evolution and failure mechanism. In this study, we find that the compressibility of liver tissues is also closely related to the initial specimen volume according to the confined compression tests: the samples with smaller initial volume exhibit more compressible behavior compared to the larger ones. To include this initial-volume dependent effect, we developed a novel Volumetric Strain energy model with two variables, i.e., the bulk modulus and the compressibility factor. A detailed scheme was proposed as well to identify these two parameters, and the relationship between the bulk modulus and the initial volume was clarified. Findings from this study will help to deepen the understanding of the biomechanical properties of soft tissues. Statement of significance Liver is a highly vascular organ and traditionally assumed to be an incompressible medium. However, through the confined compression tests, we found that the samples with smaller initial volumes exhibit more compressible behavior. Hence, we developed a novel Strain energy density model to characterize the initial-volume dependent hyperelastic response, and found that the bulk modulus of liver tissues is positively related to the initial volume. Our results suggest that the compressibility of liver tissues should be considered in the future study of liver biomechanics.
