Age-Dependent Regional Mechanical Properties of the Rat Hippocampus and Cortex

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Benjamin S. Elkin ◽  
Ashok Ilankovan ◽  
Barclay Morrison
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Brain Injury ◽  
Brain Tissue ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Tissue Stiffness ◽  
Adult Rats ◽  
Age Dependent ◽  
Indentation Strain

Age-dependent outcomes following traumatic brain injury motivate the study of brain injury biomechanics in experimental animal models at different stages of development. Finite element models of the rat brain are used to better understand the mechanical mechanisms behind these age-dependent outcomes; however, age- and region-specific rat brain tissue mechanical properties are required for biofidelity in modeling. Here, we have used the atomic force microscope (AFM) to measure region-dependent mechanical properties for subregions of the cortex and hippocampus in P10, P17, and adult rats. Apparent elastic modulus increased nonlinearly with indentation strain, and a nonlinear Ogden hyperelastic model was used to fit the force-deflection data. Subregional heterogeneous distributions of mechanical properties changed significantly with age. Apparent elastic modulus was also found to increase overall with age, increasing by >100% between P10 and adult rats. Unconfined compression tests (ε=−0.3) were performed on whole slices of the hippocampus and cortex of P10, P17, and adult rats to verify the mechanical properties measured with the AFM. Mean apparent elastic modulus at an indentation strain of 30% from AFM measurements for each region and age correlated well with the long-term elastic modulus measured from 30% unconfined compression tests (slope not significantly different from 1, p>0.05). Protein, lipid, and sulfated glycosaminoglycan content of the brain increased with age and were positively correlated with tissue stiffness, whereas water content decreased with age and was negatively correlated with tissue stiffness. These correlations can be used to hypothesize mechanistic models for describing the mechanical behavior of brain tissue as well as to predict relative differences between brain tissue mechanical properties of other species, at different ages, and for different regions based on differences in tissue composition.

Stabilization of clayey subgrade with waste pumice for road infrastructure

2015 ◽  
Vol 22 (5) ◽  
Author(s):  
Ömür Çimen ◽  
Mehmet Saltan ◽  
S. Nilay Keskin
Keyword(s):  
Mechanical Properties ◽  
Road Construction ◽  
High Plasticity ◽  
Test Results ◽  
Index Properties ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Swelling Potential ◽  
Project Costs ◽  
High Plasticity Clay

AbstractHigh-plasticity clayey subgrade, which is unsuitable for road construction, may sometimes occur along highway routes. In such cases, engineers need to change the route of a highway project, resulting in an increase in road length and project costs. In this study, waste pumice was examined for stabilization of high-plasticity clayey subgrade, which is inappropriate for road construction. For this purpose, the physical and index properties of clay and pumice were determined. Then, the pumice was mixed with high plasticity clay at different ratios by weight. By performing standard Proctor compaction tests on the mixtures, the effects of adding pumice on compaction were also studied. Unconfined compression tests and California bearing ratio (CBR) tests were performed on all pumice-clay mixtures, and the test results and the CBR ratios were compared for each sample, respectively. The results showed that pumice stabilization improved the mechanical properties and reduced the swelling potential of high plasticity clayey subgrade.

NANOINDENTATION AND ASH CONTENT STUDY OF AGE DEPENDENT CHANGES IN PORCINE CORTICAL BONE

2015 ◽  
Vol 15 (05) ◽  
pp. 1550074 ◽  
Author(s):  
MICHAEL CHITTENDEN ◽  
AHMAD RAEISI NAJAFI ◽  
JUN LI ◽  
IWONA JASIUK
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Age Groups ◽  
Structure Property ◽  
Micro Computed Tomography ◽  
Mineral Contents ◽  
Age Related ◽  
Age Dependent ◽  
Composition Structure

Composition-structure-property relations of bone provide fundamental understanding of bone quality. The objective of this paper was to investigate age dependent changes in the composition, structure and mechanical properties of porcine femoral cortical bone at mid-diaphysis region from six age groups (1, 3.5, 6, 12, 30, 48 months). This study was motivated by the fact that limited data is available in the literature on young porcine cortical bone. Nanoindentation technique with Berkovich fluid cell tip was employed to measure the elastic modulus and hardness. Individual lamellae were indented in the longitudinal direction of bone in different microstructural components (osteonal, interstitial and plexiform bone). A grid of indentations was also made on one bone sample to obtain spatial variations in the elastic modulus and hardness. Ash and water content tests were performed to measure water, organic and mineral contents of bone as a function of age. Finally, high resolution micro-computed tomography was used to measure porosity and visualize three-dimensional void structures. We found that the elastic modulus and hardness of bone increased with age but at different rates in each microstructural component. The mineral content increased correspondingly with age while the porosity decreased. The obtained structure, composition, and mechanical properties data give new insights on the age related changes in young cortical bone and can serve as inputs for and validation of multiscale models of bone.

Influence of Experimental Protocols on the Mechanical Properties of the Intervertebral Disc in Unconfined Compression

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Maximilien Recuerda ◽  
Simon-Pierre Coté ◽  
Isabelle Villemure ◽  
Delphine Périé
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Nucleus Pulposus ◽  
Annulus Fibrosus ◽  
Young's Modulus ◽  
Viscoelastic Model ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Experimental Conditions ◽  
Experimental Protocols

The lack of standardization in experimental protocols for unconfined compression tests of intervertebral discs (IVD) tissues is a major issue in the quantification of their mechanical properties. Our hypothesis is that the experimental protocols influence the mechanical properties of both annulus fibrosus and nucleus pulposus. IVD extracted from bovine tails were tested in unconfined compression stress-relaxation experiments according to six different protocols, where for each protocol, the initial swelling of the samples and the applied preload were different. The Young’s modulus was calculated from a viscoelastic model, and the permeability from a linear biphasic poroviscoelastic model. Important differences were observed in the prediction of the mechanical properties of the IVD according to the initial experimental conditions, in agreement with our hypothesis. The protocol including an initial swelling, a 5% strain preload, and a 5% strain ramp is the most relevant protocol to test the annulus fibrosus in unconfined compression, and provides a permeability of 5.0 ± 4.2e−14m4/N·s and a Young’s modulus of 7.6 ± 4.7 kPa. The protocol with semi confined swelling and a 5% strain ramp is the most relevant protocol for the nucleus pulposus and provides a permeability of 10.7 ± 3.1 e−14m4/N·s and a Young’s modulus of 6.0 ± 2.5 kPa.

Mechanical Properties of an Amorphous or Partially Crystallized Zirconium Based Metallic Glass

2007 ◽  
Vol 539-543 ◽  
pp. 2036-2042 ◽  
Author(s):  
Jean Marc Pelletier ◽  
Sébastien Gravier ◽  
Jean Jacques Blandin
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Elastic Modulus ◽  
Metallic Glass ◽  
Amorphous Material ◽  
Compression Tests ◽  
Mechanical Spectroscopy ◽  
Transition Range ◽  
Temperature Ranges ◽  
Partial Crystallization

The effect of partial crystallization on the mechanical properties of a Zr based bulk metallic glass (Vitreloy 1) is investigated. Viscoelastic properties are studied by mechanical spectroscopy in large frequency and temperature ranges, both below or above the glass transition temperature (Tg), whereas viscoplastic properties are investigated by compression tests . To study the interaction between crystallization and mechanical properties at high temperature, nanocomposites are produced thanks to appropriate heat treatments. Formation of nanocrystalline particles induces an increase of the storage elastic modulus, especially in the glass transition range, where this modulus is very low in the amorphous material. It also results in a decrease of the loss elastic modulus, corresponding to a decrease of the atomic mobility. Finally, partial crystallization induces very large hardening revealed by the compression tests but the hardening extent depends strongly on the applied strain rate.

scholarly journals Experimental Study on the Influence of Moisture Content on the Mechanical Properties of Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mingxing Gao ◽  
Yongli Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Moisture Content ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Triaxial Compression ◽  
Test System ◽  
Poisson's Ratio ◽  
Compression Tests

Water injection in coal seams will lead to the increase of moisture content in coal, which plays an essential role in the physical and mechanical properties of coal. In order to study the influence of moisture content on the mechanical properties of soft media, the forming pressure (20 MPa) and particle size ratio (0-1 mm (50%), 1-2 mm (25%), and 2-3 mm (25%)) during briquette preparation were firstly determined in this paper. Briquettes with different moisture contents (3%, 6%, 9%, 12%, and 15%) were prepared by using self-developed briquettes. Uniaxial and triaxial compression tests were carried out using the RMT-150C rock mechanics test system. The results show that the uniaxial compressive strength and elastic modulus of briquette samples increase first and then decrease with the increase of briquette water, while Poisson’s ratio decreases first and then increases with the increase of briquette water. When the moisture content is around 9%, the maximum uniaxial compressive strength is 0.866 MPa, the maximum elastic modulus is 1.385 GPa, and Poisson’s ratio is at the minimum of 0.259. The compressive strength of briquettes increases with the increase of confining pressure. With the increase of moisture content, the cohesion and internal friction angle of briquettes first increased and then decreased.

An Artificial Material for Simulating Champlain Clays

1973 ◽  
Vol 10 (3) ◽  
pp. 489-503 ◽  
Author(s):  
F. A. Tavenas ◽  
M. Roy ◽  
P. La Rochelle
Keyword(s):  
Mechanical Properties ◽  
Effective Stress ◽  
Sampling Technique ◽  
Model Material ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Failure Envelope ◽  
Synthetic Material ◽  
Strain Behavior

As part of an investigation on the behavior of Champlain clays, full scale penetrometer and vane tests had to be performed in the laboratory to observe the behavior of the soil during such tests. Since it was impossible to obtain samples of the necessary size, it was decided to develop a synthetic material which would model the mechanical properties of the Champlain clays.Such a model material has been defined. It consists of a mixture of kaolinite, bentonite, cement, and water. It is first shown to have a stress–strain behavior identical to that of the clay in unconfined compression tests, provided it is aged for 16 days. It is also shown to simulate very well all other mechanical properties of the Champlain clays, and more particularly the peculiar shape of the failure envelope in effective stress as well as the preconsolidation pressure.This material has been used successfully for laboratory penetrometer tests. It can also be used for the installation of instruments in situ or for the analysis of any testing or sampling technique.

Experimental study on the mechanical properties of biological hydrogels of different concentrations

2020 ◽  
Vol 28 (6) ◽  
pp. 685-695
Author(s):  
Khurshid Alam ◽  
Anwarul Hasan ◽  
Muhammad Iqbal ◽  
Jamal Umer ◽  
Sujan Piya
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Precise Measurement ◽  
Three Dimensional ◽  
Crosslinking Density ◽  
Compression Tests ◽  
Cell Functions ◽  
Wide Range ◽  
Tension And Compression ◽  
Cellular Mechanobiology

BACKGROUND: Biological hydrogels provide a conducive three-dimensional extracellular matrix environment for encapsulating and cultivating living cells. Microenvironmental modulus of hydrogels dictates several characteristics of cell functions such as proliferation, adhesion, self-renewal, differentiation, migration, cell morphology and fate. Precise measurement of the mechanical properties of gels is necessary for investigating cellular mechanobiology in a variety of applications in tissue engineering. Elastic properties of gels are strongly influenced by the amount of crosslinking density. OBJECTIVE: The main purpose of the present study was to determine the elastic modulus of two types of well-known biological hydrogels: Agarose and Gelatin Methacryloyl. METHODS: Mechanical properties such as Young’s modulus, fracture stress and failure strain of the prescribed gels with a wide range of concentrations were determined using tension and compression tests. RESULTS: The elastic modulus, failure stress and strain were found to be strongly influenced when the amount of concentration in the hydrogels was changed. The elastic modulus for a lower level of concentration, not considered in this study, was also predicted using statistical analysis. CONCLUSIONS: Closed matching of the mechanical properties of the gels revealed that the bulk tension and compression tests could be confidently used for assessing mechanical properties of delicate biological hydrogels.

scholarly journals Competition among oxidizable substrates in brains of young and adult rats. Whole homogenates

1984 ◽  
Vol 219 (1) ◽  
pp. 125-130 ◽  
Author(s):  
L M Roeder ◽  
J T Tildon ◽  
J H Stevenson
Keyword(s):  
Brain Tissue ◽  
Ketone Bodies ◽  
Adult Brain ◽  
Adult Rats ◽  
Young Rats ◽  
Age Dependent ◽  
14Co2 Production ◽  
Presence And Absence

The rates of conversion into 14CO2 of D-(-)-3-hydroxy[3-14C]butyrate, [3-14C]acetoacetate, [6-14C]glucose and [U-14C]glutamine were measured in the presence and absence of unlabelled alternative oxidizable substrates in whole homogenates from the brains of young and adult rats. The addition of unlabelled glutamine resulted in decreased 14CO2 production from [6-14C]glucose in brain homogenates from both young and adult rats. In contrast, glucose had no effect on [U-14C]glutamine oxidation. In suckling animals, both 3-hydroxybutyrate and acetoacetate decreased the rate of oxidation of [6-14C]glucose, but in adults only 3-hydroxybutyrate had an effect, and to a lesser degree. The addition of unlabelled glucose markedly enhanced the rates of oxidation of both ketone bodies in adult brain tissue and had little or no effect in the young. The rate of production of 14CO2 from [U-14C]glutamine was increased by the addition of unlabelled ketone bodies in brain homogenates from young, but not from adult rats. In the converse situation, unlabelled glutamine added to 14C-labelled ketone bodies diminished 14CO2 production in young rats, but had no effect in adult animals. These results revealed a complex age-dependent pattern of interaction in which certain substrates apparently competed with each other, whereas an enhanced rate of 14CO2 production was found with others.

Mechanical properties of the porcine growth plate and its three zones from unconfined compression tests

2009 ◽  
Vol 42 (4) ◽  
pp. 510-516 ◽  
Author(s):  
Kim Sergerie ◽  
Marc-Olivier Lacoursière ◽  
Martin Lévesque ◽  
Isabelle Villemure
Keyword(s):  
Mechanical Properties ◽  
Growth Plate ◽  
Compression Tests ◽  
Unconfined Compression

scholarly journals Experimental study on the effect of chitosan biopolymer on sandy soil stabilization

2020 ◽  
Vol 195 ◽  
pp. 06007
Author(s):  
Nader Shariatmadari ◽  
Mohammad Reza ◽  
Amiri Tasuji ◽  
Pooria Ghadir ◽  
A. Akbar Javadi
Keyword(s):  
Mechanical Properties ◽  
Sandy Soil ◽  
Contaminated Soils ◽  
Soil Stabilization ◽  
Soil Improvement ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Curing Conditions ◽  
Removal Of Heavy Metals ◽  
Chitosan Biopolymer

Due to the environmental impacts of conventional soil stabilization materials, such as cement, ongoing efforts have been carried out by different researchers to find alternative economical materials for substitution. Biopolymers are environmentally friendly materials that are widely used in different geoenvironmental applications such as removal of heavy metals from contaminated soils, reduction of soil hydraulic conductivity, erosion control, and soil improvement. In this research the feasibility of using chitosan biopolymer for sandy soil stabilization has been studied. The effects of biopolymer content, curing time, and curing conditions have investigated using unconfined compression tests. The results indicated that incorporation of chitosan has the potential to increase the interparticle cohesion between the particles and considerable improvement of sandy soil mechanical properties. After initial strengthening of the soil, some strength reduction over time was observed due to the degradation characteristics of the chitosan. With regards to the curing condition, better performances at dry condition compare to the wet and saturated environment were achieved. In addition to soil mechanical properties, the pore plugging effect of chitosan biopolymer on highly permeable sandy soil has been studied in this study.

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