Viscohyperelastic Material Modeling of Liver Tissue

2007 ◽  
Author(s):  
Kumar Vemaganti ◽  
Esra Roan
Keyword(s):  
Soft Tissue ◽  
Liver Tissue ◽  
Critical Role ◽  
Experimental Studies ◽  
Strain Energy Function ◽  
Bovine Liver ◽  
Disease Diagnosis ◽  
Strain Rates ◽  
The Continuum

Mechanical characterization of soft tissue plays a critical role in applications such as automated surgery, disease diagnosis and tissue engineering. Soft tissue is often modeled as an isotropic incompressible and hyperelastic material. However, it is well known that viscoelasticity plays an important role in determining the response of soft tissue to mechanical loads [1]. This work is concerned with the development of hyperviscoelastic models of soft tissue in general and liver tissue in particular. Experimental studies in uniaxial compression are conducted on bovine liver tissue at strain rates between 0.001 s−1 and 0.04 s−1. The response of liver tissue is modeled using the continuum mechanics framework using an exponential form of the strain energy function.

The Nonlinear Material Properties of Liver Tissue Determined From No-Slip Uniaxial Compression Experiments

2006 ◽  
Vol 129 (3) ◽  
pp. 450-456 ◽  
Author(s):  
Esra Roan ◽  
Kumar Vemaganti
Keyword(s):  
Soft Tissue ◽  
Uniaxial Compression ◽  
Material Properties ◽  
Liver Tissue ◽  
Mechanical Response ◽  
Strain Energy Function ◽  
Bovine Liver ◽  
Hyperelastic Material ◽  
Nonlinear Material ◽  
Material Parameters

The mechanical response of soft tissue is commonly characterized from unconfined uniaxial compression experiments on cylindrical samples. However, friction between the sample and the compression platens is inevitable and hard to quantify. One alternative is to adhere the sample to the platens, which leads to a known no-slip boundary condition, but the resulting nonuniform state of stress in the sample makes it difficult to determine its material parameters. This paper presents an approach to extract the nonlinear material properties of soft tissue (such as liver) directly from no-slip experiments using a set of computationally determined correction factors. We assume that liver tissue is an isotropic, incompressible hyperelastic material characterized by the exponential form of strain energy function. The proposed approach is applied to data from experiments on bovine liver tissue. Results show that the apparent material properties, i.e., those determined from no-slip experiments ignoring the no-slip conditions, can differ from the true material properties by as much as 50% for the exponential material model. The proposed correction approach allows one to determine the true material parameters directly from no-slip experiments and can be easily extended to other forms of hyperelastic material models.

scholarly journals Nonlinear viscoelastic constitutive model for bovine liver tissue

2020 ◽  
Vol 19 (5) ◽  
pp. 1641-1662 ◽  
Author(s):  
Adela Capilnasiu ◽  
Lynne Bilston ◽  
Ralph Sinkus ◽  
David Nordsletten
Keyword(s):  
Constitutive Equation ◽  
Liver Tissue ◽  
Motor Vehicle ◽  
Bovine Liver ◽  
Disease Diagnosis ◽  
Tissue Response ◽  
Viscoelastic Behaviour ◽  
Biomechanical Models ◽  
Nonlinear Viscoelastic ◽  
Viscoelastic Constitutive Model

Abstract Soft tissue mechanical characterisation is important in many areas of medical research. Examples span from surgery training, device design and testing, sudden injury and disease diagnosis. The liver is of particular interest, as it is the most commonly injured organ in frontal and side motor vehicle crashes, and also assessed for inflammation and fibrosis in chronic liver diseases. Hence, an extensive rheological characterisation of liver tissue would contribute to advancements in these areas, which are dependent upon underlying biomechanical models. The aim of this paper is to define a liver constitutive equation that is able to characterise the nonlinear viscoelastic behaviour of liver tissue under a range of deformations and frequencies. The tissue response to large amplitude oscillatory shear (1–50%) under varying preloads (1–20%) and frequencies (0.5–2 Hz) is modelled using viscoelastic-adapted forms of the Mooney–Rivlin, Ogden and exponential models. These models are fit to the data using classical or modified objective norms. The results show that all three models are suitable for capturing the initial nonlinear regime, with the latter two being capable of capturing, simultaneously, the whole deformation range tested. The work presented here provides a comprehensive analysis across several material models and norms, leading to an identifiable constitutive equation that describes the nonlinear viscoelastic behaviour of the liver.

scholarly journals ADI 1050-6 Mechanical Behavior at Different Strain Rates and Temperatures

2018 ◽  
Vol 925 ◽  
pp. 196-202 ◽  
Author(s):  
Andrew Ruggiero ◽  
Gianluca Iannitti ◽  
Stefano Masaggia ◽  
Federico Vettore
Keyword(s):  
Strain Rate ◽  
Damage Mechanics ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Continuum Damage Mechanics ◽  
Tensile Tests ◽  
Yield Function ◽  
Strain Rates ◽  
The Continuum

An experimental characterization of the austempered ductile iron ISO 17804/JS/1050-6/S was performed carrying out tensile tests under different strain rates, temperatures and stress triaxiality levels. Then, composing a yield function surface, a hardening relation, and a damage criterion, a constitutive model was developed to describe the salient features of the observed macroscopic response. In particular, the Mohr-Coulomb yield function was selected to account for the pressure effect observed on the yield surface. A new hardening relation was proposed in order to account for both strain rate and temperature effects. The Bonora’s damage model, developed in the framework of the continuum damage mechanics, was adopted to capture the failure condition under different stress triaxiality levels. The damage model was appropriately modified to account for the effect of strain rate and temperature on the failure strain.

scholarly journals Characterization of bacterial DNA identified in abscessed and non-abscessed bovine hepatic tissue at the time of harvest

2021 ◽  
Author(s):  
Miranda K Stotz ◽  
Darren D Henry ◽  
Whitney L Crossland
Keyword(s):  
Liver Tissue ◽  
Bovine Liver ◽  
Fusobacterium Necrophorum ◽  
Laboratory Culture ◽  
Hepatic Tissue ◽  
Rrna Gene ◽  
Pathogenic Potential ◽  
Bacterial Dna ◽  
Cultural Methods

Abstract Bacteriological characterization of bovine liver abscesses has been accomplished by cultural methods but DNA methods are still needed, as many bacteria are not conducive to laboratory culture. In addition to this gap in research, there have been no studies which identify the bacterial presence within healthy, non-abscessed liver tissue. The objective of this study was to compare the bacteriome of both abscessed and non-abscessed bovine livers in an observational case-control study design. Fifty-six livers, obtained from Holstein steers, were scored according to a modified Elanco liver abscess score description where A- was partitioned into active abscesses or scarred where only scars were present. Parenchyma tissue was collected from non-abscessed livers (n=22), and scarred livers (n=7), and purulent material was collected from abscessed livers (n=24), and DNA was extracted for 16s rRNA gene sequence-based bacterial analysis. Across liver samples, 21 total phyla were identified with a mean of 14. Predominant phyla, accounting for > 98% of reads, were Fusobacteria (51.7%), Bacteroidetes (26.9%), Proteobacteria (8.03%), Firmicutes (5.39%), Cyanobacteria (3.85 %) and Actinobacteria (2.21%). Proteobacteria, Cyanobacteria and Firmicutes were greater in non-abscessed and scarred livers, whereas Fusobacteria and Bacteroidetes prevailed in abscessed livers. Non-abscessed livers shared 3,059 operational taxonomic units (OTU) with abscessed livers (total OTU of all livers= 4,167), but non-abscessed livers had greater richness and evenness whereas abscessed livers had greater dominance (P ≤ 0.0014). Liver score affected the relative abundance of OTU (R = 0.463; P = 0.001) but abscessed livers shared ≥ 40% similarity and were not different from each other (P ≥ 0.370). Of the predominant OTU (top 10 as a % of reads), three OTU (Fusobacteria necrophorum, Bacteroides spp., and Trueperella pyogenes) were shared across both abscessed and non-abscessed livers. Fusobacterium necrophorum was the dominant OTU regardless of liver score, and the single most abundant OTU, even among non-abscessed livers. We describe bacterial DNA detected in non-abscessed bovine liver tissue for the first time, which indicates possible presence of viable bacteria with pathogenic potential in apparently healthy liver tissue.

The capacity of short term memory from an evolutionary perspective

2019 ◽  
Author(s):  
Majid Manoochehri
Keyword(s):  
Short Term Memory ◽  
Memory Span ◽  
Critical Role ◽  
Experimental Studies ◽  
Cognitive System ◽  
Evolutionary Approach ◽  
Evolutionary Perspective ◽  
Short Term ◽  
Term Memory

Memory span in humans has been intensely studied for more than a century. In spite of the critical role of memory span in our cognitive system, which intensifies the importance of fundamental determinants of its evolution, few studies have investigated it by taking an evolutionary approach. Overall, we know hardly anything about the evolution of memory components. In the present study, I briefly review the experimental studies of memory span in humans and non-human animals and shortly discuss some of the relevant evolutionary hypotheses.

Imaging of soft tissue tumors

2020 ◽  
Vol 16 ◽  
Author(s):  
Shinji Tsukamoto ◽  
Andreas F. Mavrogenis ◽  
Yasuhito Tanaka ◽  
Costantino Errani
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Soft Tissue ◽  
Tumor Size ◽  
Critical Role ◽  
Evaluation Criteria ◽  
Soft Tissue Tumors ◽  
Resonance Imaging ◽  
Benign Soft Tissue Tumors ◽  
Response To Chemotherapy

: Differentiation of malignant from benign soft tissue tumors is challenging with imaging alone, including that by magnetic resonance imaging and computed tomography. However, the accuracy of this differentiation has increased owing to the development of novel imaging technology. Detailed patient history and physical examination remain essential for differentiation between benign and malignant soft tissue tumors. Moreover, measurement only of tumor size based on Response Evaluation Criteria In Solid Tumors criteria is insufficient for the evaluation of response to chemotherapy or radiotherapy. Change in metabolic activity measured by 18F-fluorodeoxyglucose positron emission tomography or dynamic contrast enhanced-derived quantitative endpoints can more accurately evaluate treatment response compared to change in tumor size. Magnetic resonance imaging can accurately evaluate essential factors in surgical planning such as vascular or bone invasion and “tail sign”. Thus, imaging plays a critical role in the diagnosis and treatment of soft tissue tumors.

Ionized gas kinematics and luminosity profiles of Low-z Lyman Alpha Blobs

2019 ◽  
Vol 15 (S359) ◽  
pp. 413-414
Author(s):  
María P. Agüero ◽  
Rubén Díaz ◽  
Mischa Schirmer
Keyword(s):  
Emission Line ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Lyman Alpha ◽  
Gas Kinematics ◽  
The Universe ◽  
Very High ◽  
The Continuum

AbstractThis work is focused on the characterization of the Seyfert-2 galaxies hosting very large, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2−0.34. With a space density of 4.4 Gcp−3 at z ∼ 0.3, these “Low Redshift Lyman-α Blob” (LAB) host galaxies are amongst the rarest objects in the universe, and represent an exceptional and short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). We present the study of GMOS spectra for 13 LAB galaxies covering the rest frame spectral range 3700–6700 Å. Predominantly, the [OIII]λ5007 emission line radial distribution is as widespread as that of the continuum one. The emission line profiles exhibit FWHM between 300–700 Km s−1. In 7 of 13 cases a broad kinematical component is detected with FWHM within the range 600–1100 Km s−1. The exceptionally high [OIII]λ5007 luminosity is responsible for very high equivalent width reaching 1500 Å at the nucleus.

scholarly journals Cloning and characterization of cDNA for mitochondrial GTP:AMP phosphotransferase of bovine liver

1989 ◽  
Vol 264 (32) ◽  
pp. 19192-19199
Author(s):  
M Yamada ◽  
M Shahjahan ◽  
T Tanabe ◽  
F Kishi ◽  
A Nakazawa
Keyword(s):  
Bovine Liver
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