Abstract 440: Non-Invasive Quantification of Rat Vasculature Biomechanical Properties Under a Cardiovascular Challenge: Implications in Atherosclerosis Progression

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Paige E Castle ◽  
Joan M Greve
Keyword(s):  
Cyclic Strain ◽  
Biomechanical Properties ◽  
Human Condition ◽  
Infrarenal Aorta ◽  
Atherosclerosis Progression ◽  
Similar Work ◽  
Cine Frame ◽  
Vessel Wall Properties ◽  
Order Of Magnitude ◽  
Biomechanical Forces

Introduction: Measurements of cyclic strain give insight into vessel wall properties, offer a better understanding of the pathogenesis of atherosclerosis, and can be used in quantifying loss of vessel compliance. Using dobutamine stimulation to increase heart rate and cardiac output provides a clinically relevant means to begin to understand alterations in cyclic strain during a vascular challenge which mimics some aspects of exercise. Similar work has been completed in murine models, but translating these methods to a species that is an order of magnitude larger allows for a better understanding of how these results could allometrically scale to the human condition. We hypothesize that using a pharmacological cardiovascular stimulant will cause cyclic strain shifts that vary between species. Materials and Methods: Cyclic strain was non-invasively quantified using MRI. Young rats and mice were anesthetized using isoflurane and imaged at 7T. 2D and 3D gradient echo data were used to plan ECG-gated acquisitions that included 12 CINE frames across the cardiac cycle, in the infrarenal aorta pre- and post- dobutamine infusion. Vessel strain was quantified in each CINE frame. Results: Baseline strain in rats was 17% and 16%, for males and females respectively (A, C). In mice, baseline strain was 22% in males and 18% in females (B, D). After infusion of dobutamine, strain in rats increased to 26% in males and 27% in females, while in mice strain increased to 36% in males and 32% in females. Conclusions: In conclusion, there are evident variations in cyclic strain under a cardiovascular challenge between species. With this insight, a clearer understanding of the biomechanical forces experienced by the vasculature in different species may lead to improved extrapolation from mouse to human in understanding the effects of atherosclerosis on vessel compliance and developing therapeutic approaches.

Towards Non-Invasive Pressure Assessment

2010 ◽  
Author(s):  
Nathalie Bijnens ◽  
Bart Beulen ◽  
Peter Brands ◽  
Marcel Rutten ◽  
Frans van de Vosse
Keyword(s):  
Wall Thickness ◽  
Vessel Wall ◽  
Biomechanical Properties ◽  
Vessel Diameter ◽  
Local Pressure ◽  
Vessel Wall Thickness ◽  
Non Invasive ◽  
Vascular Impedance ◽  
Vessel Wall Properties ◽  
Invasive Techniques

In clinical practice, ultrasound is frequently applied to non-invasively assess blood velocity, blood volume flow and blood vessel wall properties such as vessel wall thickness and vessel diameter waveforms. To convert these properties into relevant biomechanical properties that are related to cardiovascular disease (CVD), such as elastic modulus and compliance of the vessel wall, local pressure has to be assessed simultaneously with vessel wall thickness and vessel diameter waveforms. Additionally, accurate estimates of vascular impedance (transfer function between pressure and blood flow) can be a valuable tool for the estimation of the condition of the vessel, e.g., to diagnose stenosis. Studies of arterial impedance in humans, however, are hampered by the lack of reliable non-invasive techniques to simultaneously record pressure and flow locally as a function of time. Local pressure assessment together with flow has great potential for improving the ability to diagnose and monitor CVD.

scholarly journals Conducting PEEK Nanocomposites with Electrophoretically Deposited Bioactive Coating for Bone Tissue Regeneration and Multi-Modal Therapeutic Applications

2020 ◽  
Author(s):  
Miaomiao He ◽  
Ce zhu ◽  
Huan Xu ◽  
dan Sun ◽  
Chen Chen ◽  
...  
Keyword(s):  
Bone Tissue ◽  
Tissue Regeneration ◽  
Bone Repair ◽  
Graphene Nanosheets ◽  
Biomechanical Properties ◽  
Bone Diseases ◽  
Bone Tissue Regeneration ◽  
Order Of Magnitude

The use of polyetheretherketone (PEEK) has grown exponentially in the biomedical field in recent decades due to its outstanding biomechanical properties. However, its lack of bioactivity/osteointegration remains an unresolved issue towards its wide use in orthopedic applications. In this work, graphene nanosheets have been incorporated into PEEK to obtain multifunctional nanocomposites. Due to the formation of electrical percolation network and the π-π* conjugation between graphene and PEEK, the resulting composites have achieved twelve order of magnitude enhancement in its electrical conductivity, and have enabled electrophoretic deposition of bioactive/anti-bacterial coating consisting of stearyltrimethylammonium chloride (STAC) modified hydroxyapatite (HA). The coated composite implant showed significant boosting of BMSC cell proliferation in vitro. In addition, the strong photothermal conversion effect of the graphene nanofillers have enabled laser induced heating of our nanocomposite implants, where the temperature of the implant can reach 45 oC in 150 s. The unique multi-functionality of our composite implant has also been demonstrated for photothermal applications such as enhancing bacterial (E. coli and S. aureus) eradication and tumor cell (MG63) inhibition, as well as bone tissue regeneration in vivo. The results suggest the strong potential of our multi-functional implant in bone repair applications as well as multi-modal therapy of challenging bone diseases such as osteosarcoma and osteomyelitis

scholarly journals Effects of Cyclic Strain and Growth Factors on Vascular Smooth Muscle Cell Responses

2009 ◽  
Vol 3 (1) ◽  
pp. 28-38 ◽  
Author(s):  
Soujanya Kona ◽  
Prithiviraj Chellamuthu ◽  
Hao Xu ◽  
Seth R Hills ◽  
Kytai Truong Nguyen
Keyword(s):  
Smooth Muscle ◽  
Growth Factors ◽  
Growth Factor ◽  
Vascular Smooth Muscle ◽  
Transforming Growth Factor ◽  
Growth Factor Receptor ◽  
Cyclic Strain ◽  
Transforming Growth Factor Β ◽  
Positive Influence ◽  
Biomechanical Forces

Under physiological and pathological conditions, vascular smooth muscle cells (SMC) are exposed to different biochemical factors and biomechanical forces. Previous studies pertaining to SMC responses have not investigated the effects of both factors on SMCs. Thus, in our research we investigated the combined effects of growth factors like Bfgf (basic fibroblast growth factor), TGF-β (transforming growth factor β) and PDGF (platelet-derived growth factor) along with physiological cyclic strain on SMC responses. Physiological cyclic strain (10% strain) significantly reduced SMC proliferation compared to static controls while addition of growth factors bFGF, TGF-β or PDGF-AB had a positive influence on SMC growth compared to strain alone. Microarray analysis of SMCs exposed to these growth factors and cyclic strain showed that several bioactive genes (vascular endothelial growth factor, epidermal growth factor receptor, etc.) were altered upon exposure. Further work involving biochemical and pathological cyclic strain stimulation will help us better understand the role of cyclic strain and growth factors in vascular functions and development of vascular disorders.

scholarly journals High Pulsatile Load Decreases Arterial Stiffness: An ex vivo Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Cédric H. G. Neutel ◽  
Giulia Corradin ◽  
Pauline Puylaert ◽  
Guido R. Y. De Meyer ◽  
Wim Martinet ◽  
...  
Keyword(s):  
Arterial Stiffness ◽  
Blood Vessel ◽  
Pulse Pressure ◽  
Ex Vivo ◽  
Strong Predictor ◽  
Biomechanical Properties ◽  
Aortic Tissue ◽  
Infrarenal Aorta ◽  
Pulsatile Load

Measuring arterial stiffness has recently gained a lot of interest because it is a strong predictor for cardiovascular events and all-cause mortality. However, assessing blood vessel stiffness is not easy and the in vivo measurements currently used provide only limited information. Ex vivo experiments allow for a more thorough investigation of (altered) arterial biomechanical properties. Such experiments can be performed either statically or dynamically, where the latter better corresponds to physiological conditions. In a dynamic setup, arterial segments oscillate between two predefined forces, mimicking the diastolic and systolic pressures from an in vivo setting. Consequently, these oscillations result in a pulsatile load (i.e., the pulse pressure). The importance of pulse pressure on the ex vivo measurement of arterial stiffness is not completely understood. Here, we demonstrate that pulsatile load modulates the overall stiffness of the aortic tissue in an ex vivo setup. More specifically, increasing pulsatile load softens the aortic tissue. Moreover, vascular smooth muscle cell (VSMC) function was affected by pulse pressure. VSMC contraction and basal tonus showed a dependence on the amplitude of the applied pulse pressure. In addition, two distinct regions of the aorta, namely the thoracic descending aorta (TDA) and the abdominal infrarenal aorta (AIA), responded differently to changes in pulse pressure. Our data indicate that pulse pressure alters ex vivo measurements of arterial stiffness and should be considered as an important variable in future experiments. More research should be conducted in order to determine which biomechanical properties are affected due to changes in pulse pressure. The elucidation of the underlying pulse pressure-sensitive properties would improve our understanding of blood vessel biomechanics and could potentially yield new therapeutic insights.

scholarly journals Solanales Stem Biomechanical Properties Are Primarily Determined by Morphology Rather Than Internal Structural Anatomy and Cell Wall Composition

Plants ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 678
Author(s):  
Ilana Shtein ◽  
Alex Koyfman ◽  
Amnon Schwartz ◽  
Zoë A. Popper ◽  
Benny Bar-On
Keyword(s):  
Cell Wall ◽  
Ipomoea Batatas ◽  
Biomechanical Properties ◽  
Cell Wall Composition ◽  
Morning Glory ◽  
Specific Cell ◽  
Minor Variation ◽  
Plant Groups ◽  
Order Of Magnitude ◽  
Growth Habits

Self-supporting plants and climbers exhibit differences in their structural and biomechanical properties. We hypothesized that such fundamental differences originate at the level of the material properties. In this study, we compared three non-woody members of the Solanales exhibiting different growth habits: (1) a self-supporting plant (potato, Solanum tuberosum), (2) a trailing plant (sweet potato, Ipomoea batatas), and (3) a twining climber (morning glory, Ipomoea tricolor). The mechanical properties investigated by materials analyses were combined with structural, biochemical, and immunohistochemical analyses. Generally, the plants exhibited large morphological differences, but possessed relatively similar anatomy and cell wall composition. The cell walls were primarily composed of hemicelluloses (~60%), with α-cellulose and pectins constituting ~25% and 5–8%, respectively. Immunohistochemistry of specific cell wall components suggested only minor variation in the occurrence and localization between the species, although some differences in hemicellulose distribution were observed. According to tensile and flexural tests, potato stems were the stiffest by a significant amount and the morning glory stems were the most compliant and showed differences in two- and three-orders of magnitude; the differences between their effective Young’s (Elastic) modulus values (geometry-independent parameter), on the other hand, were substantially lower (at the same order of magnitude) and sometimes not even significantly different. Therefore, although variability exists in the internal anatomy and cell wall composition between the different species, the largest differences were seen in the morphology, which appears to be the primary determinant of biomechanical function. Although this does not exclude the possibility of different mechanisms in other plant groups, there is apparently less constraint to modifying stem morphology than anatomy and cell wall composition within the Solanales.

scholarly journals Comparison of biphasic material properties of equine articular cartilage from stress relaxation indentation tests with and without tension-compression nonlinearity

2018 ◽  
Vol 4 (1) ◽  
pp. 485-488
Author(s):  
Thomas Reuter ◽  
Christof Hurschler
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Material Properties ◽  
Collagen Matrix ◽  
Biomechanical Properties ◽  
Resolution Parameter ◽  
Marquardt Algorithm ◽  
Mesh Resolution ◽  
Indentation Tests ◽  
Order Of Magnitude

AbstractThe mechanical parameters of articular cartilage estimated from indentation tests depend on the constitutive model adopted to analyze the data. In this study, we present a 3D-FE-based method to determine the biomechanical properties of equine articular cartilage from stress relaxation indentation tests (ε = 6 %, t = 1000 s) whereby articular cartilage is modeled as a biphasic material without (BM) and with tension-compression nonlinearity (BMTCN). The FEmodel computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg-Marquardt-algorithm. The R² of the fit results varies between 0.695 and 0.930 for the BMmodel and between 0.877 and 0.958 for the BMTCN-model. The differences of the R² occur from the more exact description of the initial stress relaxation behaviour by the fiber modulus from the BMTCN-model. The fiber modulus defines the collagen matrix of cartilage. Furthermore, for both models the determined values of Young’s modulus and permeability were in the same order of magnitude.

scholarly journals Novel minimally invasive tape suture osteosynthesis for instabilities of the pubic symphysis: a biomechanical study

2021 ◽  
Author(s):  
Adrian Cavalcanti Kußmaul ◽  
Fanny Schwaabe ◽  
Manuel Kistler ◽  
Clara Gennen ◽  
Sebastian Andreß ◽  
...  
Keyword(s):  
Minimally Invasive ◽  
Pubic Symphysis ◽  
Biomechanical Properties ◽  
Current Treatment ◽  
Biomechanical Study ◽  
Open Book ◽  
Biomechanical Stability ◽  
Vertical Loading ◽  
Biomechanical Forces ◽  
Symphyseal Plating

Abstract Introduction Open book fractures are challenging injuries oftentimes requiring surgical treatment. The current treatment of choice is symphyseal plating, which requires extensive surgery and entirely limits physiological movement of the symphyseal joint, frequently resulting in implant failure. Therefore, we investigated the biomechanical properties of a semi-rigid implant (modified SpeedBridge™) as a minimally invasive tape suture construct for the treatment of open book fractures and evaluated the superiority of two techniques of implementation: criss-cross vs. triangle technique. Materials and methods Nine synthetic symphyseal joints were dissected creating an open book fracture. The different osteosynthesis methods (plating, modified SpeedBridge™ in criss-cross/triangle technique) were then applied. All constructs underwent horizontal and vertical loading, simulating biomechanical forces while sitting, standing and walking. For statistical analysis, dislocation (mm) and stiffness (N/mm) were calculated. Results Symphyseal plating for the treatment of open book fractures proved to be a rigid osteosynthesis significantly limiting the physiological mobility of the symphyseal joint (dislocation: 0.08 ± 0.01 mm) compared to the tape sutures (dislocation: triangle technique 0.27 ± 0.07 mm, criss-cross technique 0.23 ± 0.05 mm) regarding horizontal tension (p < 0.01). Both modified SpeedBridge™ techniques showed sufficient biomechanical stability without one being superior to the other (p > 0.05 in all directions). Considering vertical loading, no statistical difference was found between all osteosynthesis methods (caudal: p = 0.41; cranial: p = 0.61). Conclusions Symphyseal plating proved to be the osteosynthesis method with the highest rigidity. The modified SpeedBridge™ as a semi-rigid suture construct provided statistically sufficient biomechanical stability while maintaining a minimum of symphyseal movement, consequently allowing ligamental healing of the injured joint without iatrogenic arthrodesis. Furthermore, both the criss-cross and the triangle technique displayed significant biomechanical stability without one method being superior.

Intermediate Temperature, Low-Cycle Fatigue Behavior of Coated and Uncoated Nickel Base Superalloys in Air and Corrosive Sulfate Environments

1984 ◽  
Vol 106 (1) ◽  
pp. 43-49 ◽  
Author(s):  
G. A. Whitlow ◽  
R. L. Johnson ◽  
W. H. Pridemore ◽  
J. M. Allen
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Aluminide Coating ◽  
Cyclic Strain ◽  
Fracture Morphology ◽  
Cycle Fatigue ◽  
Coated Alloy ◽  
Order Of Magnitude ◽  
Nickel Base ◽  
Udimet 720

Low temperature hot corrosion effects on the low cycle fatigue (LCF) life and fracture morphology of a Udimet 720 alloy and the effectiveness of a protective coating in minimizing life degradation are reported. Strain controlled, continuous cycling (1 cpm) and 1 h hold (at maximum tensile strain) tests at 1350°F (732°C) in air revealed only small changes in life that could be attributed to creep during the 1 h hold. The presence of a corrosive salt environment, however, resulted in more than an order of magnitude degradation in life. In air and salt, the fracture was initially transgranular, but in salt it quickly changed to an intergranular mode, particularly at cyclic strains above 0.65 percent. These differences are attributed to reductions of 95 and 28 percent in the respective ductility and fatigue strength coefficients in the Coffin-Manson and Basquin relationships between cyclic strain and life. At cyclic strains ≤ ± 0.5 percent, a diffusion aluminide coating was protective in 1350°F (732° C) salt, with lives equivalent to those for the coated alloy in air; but at higher strains, coating failure occurred. Insignificant differences in fatigue life in air were noted for Udimet 720 and Udimet 710 alloys.

Designing Gas Turbine Packages for Reduced Installation Time

2002 ◽  
Author(s):  
Bryan K. Kendig ◽  
Ernest J. Pido
Keyword(s):  
Gas Turbine ◽  
Component Technology ◽  
Package Design ◽  
Similar Work ◽  
Air Inlet ◽  
Operating Environments ◽  
Order Of Magnitude ◽  
The Cost ◽  
And Control ◽  
Installation Time

Gas turbine users increasingly seek to install equipment in remote and harsh operating environments. Experience has shown that the cost of performing work in such an environment can be an order of magnitude greater than the cost of similar work performed in the manufacturer’s workshop. For this reason, gas turbine users have requested manufacturers to create package designs that minimize installation time. This paper describes changes made to aero-derivative gas turbine package design over the past seven years that achieve reduced installation time. Package changes have been permitted by advances in component technology affecting air inlet, exhaust, and control systems. Advances have also been made in piping, cable and baseplate designs. Component and package changes are described via a comparison of today’s standard aero-derivative gas turbine package to the standard package provided five to seven years ago. The comparison is made for a pipeline compressor application.

scholarly journals Multilayer Shielding Design for Intermediate Radioactive Waste Storage Drums: A Comparative Study between FLUKA and QAD-CGA

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Wenqian Li ◽  
Xuegang Liu ◽  
Ming Li ◽  
Yilin Huang ◽  
Sheng Fang
Keyword(s):  
Radioactive Waste ◽  
Variance Reduction ◽  
Dose Rates ◽  
Similar Work ◽  
Weighted Algorithm ◽  
Calculated Dose ◽  
Calculation Results ◽  
Order Of Magnitude ◽  
Intermediate Level Radioactive Waste ◽  
Shielding Design

To ensure that the outside dose rate of waste package is below the limitation of national laws and regulations, based on the standard 200L drum, a new drum with inner shielding was proposed for intermediate-level radioactive waste (ILW) storage. For comparison, FLUKA and QAD-CGA were used to verify the shielding design of the ILW storage drums produced in INET with multiple inner shielding layers. The flux and dose were calculated and analyzed for four different cases. In QAD-CGA calculation, it was found that different buildup factors can lead to the considerably different results. A weighted algorithm was proposed to correct QAD-CGA for multilayer shielding cases. In FLUKA calculation, parameter optimization and tailored variance reduction technique (VRT) were used. Quantitative efficiency evaluation of different FLUKA settings using the FOM factor was carried out. The differences in the calculated dose rates results between the FLUKA and QAD-CGA programs are within one order of magnitude. The results of QAD-CGA are generally higher than those of FLUKA. The analysis shows that appropriate corrections in QAD-CGA can make the trend of the calculation results more consistent with the theory. In FLUKA calculation, with optimized setting and VRT adopted, the calculation efficiency can be improved more than 20 times. The results of this study provide not only suggestions for the design of the ILW storage drums but also useful references for other similar work.

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