scholarly journals Age-dependent and radial sectional differences in the dynamic viscoelastic properties of bamboo culms and their possible relationship with the lignin structures

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Yoko Okahisa ◽  
Keisuke Kojiro ◽  
Hatsuki Ashiya ◽  
Takeru Tomita ◽  
Yuzo Furuta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Structural Variation ◽  
Thermal Softening ◽  
Peak Temperature ◽  
Outer Side ◽  
Phyllostachys Pubescens ◽  
Age Dependence ◽  
Age Dependent ◽  
S Peak

Abstract Age is an important factor that dictates bamboo’s mechanical properties. In Japan, bamboo plants aged 3–5 years are selected for use as materials because of their robustness and decorative or craft-friendly characteristics. In this study, the age-dependent and radial sectional differences in bamboo’s dynamic viscoelastic properties in relation to lignin structural variation, were evaluated. We used Phyllostachys pubescens samples at the current year and at 1.5, 3.5, 6.5, 9.5, 12.5, and 15.5 years of age. There was a clear age dependence in the peak temperature of tan δ and in the yield of thioacidolysis products derived from β-O-4 lignin structures. The highest peak temperature tan δ value was detected in 3.5-year-old bamboo, which contained the highest amount of the thioacidolysis products. Moreover, tan δ’s peak temperature was always higher on the outer side, and the ratio of S/G thioacidolysis products was always higher on the inner side of bamboo plants of all ages. These results suggest that changes in bamboo’s thermal softening properties from aging are caused by the maturation and degradation of lignin in bamboo.

scholarly journals Evolution of the viscoelastic properties of painting stratigraphies: a moisture weathering and nanoindentation approach

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Mathilde Tiennot ◽  
Davide Iannuzzi ◽  
Erma Hermens
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Cultural Heritage ◽  
Mechanical Behaviour ◽  
Viscoelastic Properties ◽  
Viscoelastic Behaviour ◽  
Storage And Loss Moduli ◽  
Heritage Studies ◽  
Paint Films ◽  
The Impact

AbstractIn this investigation on the mechanical behaviour of paint films, we use a new ferrule-top nanoindentation protocol developed for cultural heritage studies to examine the impact of repeated relative humidity variations on the viscoelastic behaviour of paint films and their mechanical properties in different paint stratigraphies through the changes in their storage and loss moduli. We show that the moisture weathering impact on the micromechanics varies for each of these pigment-oil systems. Data from the nanoindentation protocol provide new insights into the evolution of the viscoelastic properties dsue to the impact of moisture weathering on paint films.

Capturing Age-Dependent Properties of Human Skin Using Magnetorheological Elastomers

2018 ◽  
Author(s):  
Kyle Weaver ◽  
Jeong-Hoi Koo ◽  
Tae-Heon Yang ◽  
Young-Min Kim
Keyword(s):  
Mechanical Properties ◽  
Human Skin ◽  
Skin Testing ◽  
Filler Particle ◽  
Variable Stiffness ◽  
Particle Volume ◽  
Magnetorheological Elastomers ◽  
Age Dependent ◽  
Skin Samples

Artificial and synthetic skins are widely used in the medical field; used in applications ranging from skin grafts to suture training pads. There is a growing need for artificial skins with tunable properties. However, current artificial skins do not take into account the variability of mechanical properties between individual humans as well as the age-dependent properties of human skin. Furthermore, there has been little development in artificial skins based on these properties. Thus, the primary purpose of this research is to develop variable stiffness artificial skin samples using magnetorheological elastomers (MREs) whose properties that can be controlled using external magnetic fields. In this study, multiple MRE skin samples were fabricated with varying filler particle volume contents. Using a precision dynamic mechanical analyzer, a series of indenting experiments were performed on the samples to characterize their mechanical properties. The samples were tested using a spherical indenter that indented a total depth of 1 mm with a speed of 0.01 mm/s and unloaded at the same rate. The results show that the modulus or stiffness increases significantly as the iron percent (w/w) in the sample increases. Additionally, the stiffness of the sample increases proportional to the intensity of the applied external magnetic field. To assess the MRE samples’ variability of properties, the testing results were compared with in vivo human skin testing data. The results show the MRE samples are feasible to represent the age-dependent stiffness demonstrated in in vivo human skin testing. The MRE materials studied will be further studied as a variable-stiffness skin model in medical devices, such as radial pulse simulators.

scholarly journals Viscoelastic properties of nanocellulose based inks for 3D printing and mechanical properties of CNF/alginate biocomposite gels

Cellulose ◽  
2018 ◽  
Vol 26 (1) ◽  
pp. 581-595 ◽  
Author(s):  
Ellinor B. Heggset ◽  
Berit L. Strand ◽  
Kristin W. Sundby ◽  
Sébastien Simon ◽  
Gary Chinga-Carrasco ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Viscoelastic Properties

Effects of myostatin on the mechanical properties of muscles during repeated active lengthening in the mouse

2019 ◽  
Vol 44 (4) ◽  
pp. 381-388
Author(s):  
Danguole Satkunskiene ◽  
Aivaras Ratkevicius ◽  
Sigitas Kamandulis ◽  
Tomas Venckunas
Keyword(s):  
Mechanical Properties ◽  
Isometric Force ◽  
Muscle Stiffness ◽  
Repeated Loading ◽  
Relative Reduction ◽  
Muscle Type ◽  
Age Dependent ◽  
Exercise Induced ◽  
Edl Muscle ◽  
Early Phases

The aim of the present study was to investigate how myostatin dysfunction affects fast and slow muscle stiffness and viscosity during severe repeated loading. Isolated extensor digitorum longus (EDL) and soleus muscles of young adult female mice of the BEH (dysfunctional myostatin) and BEH+/+ (functional myostatin) strains were subjected to 100 contraction–stretching loading cycles during which contractile and mechanical properties were assessed. BEH mice exhibited greater exercise-induced muscle damage, although the effect was muscle- and age-dependent and limited to the early phases of simulated exercise. The relative reduction of the EDL muscle isometric force recorded during the initial 10–30 loading cycles was greater in BEH mice than in BEH+/+ mice and exceeded that of the soleus muscle of either strain. The induced damage was associated with lower muscle stiffness. The effects of myostatin on the mechanical properties of muscles depend on muscle type and maturity.

scholarly journals Effects of Nitrogen Flow Ratio on Structures, Bonding Characteristics, and Mechanical Properties of ZrNx Films

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 476 ◽  
Author(s):  
Yi-En Ke ◽  
Yung-I Chen
Keyword(s):  
Mechanical Properties ◽  
Photoelectron Spectroscopy ◽  
Structural Variation ◽  
Nitrogen Flow ◽  
Flow Ratio ◽  
X Ray ◽  
Direct Current Magnetron Sputtering ◽  
Nanoindentation Hardness ◽  
Bonding Characteristics ◽  
Dominant Phase

ZrNx (x = 0.67–1.38) films were fabricated through direct current magnetron sputtering by a varying nitrogen flow ratio [N2/(Ar + N2)] ranging from 0.4 to 1.0. The structural variation, bonding characteristics, and mechanical properties of the ZrNx films were investigated. The results indicated that the structure of the films prepared using a nitrogen flow ratio of 0.4 exhibited a crystalline cubic ZrN phase. The phase gradually changed to a mixture of crystalline ZrN and orthorhombic Zr3N4 followed by a Zr3N4 dominant phase as the N2 flow ratio increased up to >0.5 and >0.85, respectively. The bonding characteristics of the ZrNx films comprising Zr–N bonds of ZrN and Zr3N4 compounds were examined by X-ray photoelectron spectroscopy and were well correlated with the structural variation. With the formation of orthorhombic Zr3N4, the nanoindentation hardness and Young’s modulus levels of the ZrNx (x = 0.92–1.38) films exhibited insignificant variations ranging from 18.3 to 19.0 GPa and from 210 to 234 GPa, respectively.

scholarly journals Microtubule aging probed by microfluidics-assisted tubulin washout

2016 ◽  
Vol 27 (22) ◽  
pp. 3563-3573 ◽  
Author(s):  
Christian Duellberg ◽  
Nicholas Ian Cade ◽  
Thomas Surrey
Keyword(s):  
Molecular Mechanism ◽  
Growth Phase ◽  
Morphological Changes ◽  
Threshold Model ◽  
Theoretical Models ◽  
Age Dependence ◽  
Microtubule Depolymerization ◽  
Microtubule Stability ◽  
Age Dependent

Microtubules switch stochastically between phases of growth and shrinkage. The molecular mechanism responsible for the end of a growth phase, an event called catastrophe, is still not understood. The probability for a catastrophe to occur increases with microtubule age, putting constraints on the possible molecular mechanism of catastrophe induction. Here we used microfluidics-assisted fast tubulin washout experiments to induce microtubule depolymerization in a controlled manner at different times after the start of growth. We found that aging can also be observed in this assay, providing valuable new constraints against which theoretical models of catastrophe induction can be tested. We found that the data can be quantitatively well explained by a simple kinetic threshold model that assumes an age-dependent broadening of the protective cap at the microtubule end as a result of an evolving tapered end structure; this leads to a decrease of the cap density and its stability. This analysis suggests an intuitive picture of the role of morphological changes of the protective cap for the age dependence of microtubule stability.

Mechanical Properties of Composite Hydrogels for Tissue Engineering

2018 ◽  
Vol 18 (14) ◽  
pp. 1214-1223 ◽  
Author(s):  
Ramon Rial ◽  
J.F. Armando Soltero ◽  
Pedro V. Verdes ◽  
Zhen Liu ◽  
Juan M. Ruso
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Viscoelastic Properties ◽  
Theoretical Models ◽  
Biologically Active ◽  
Nanoparticle Concentration ◽  
Mechanical Stiffness ◽  
Gelatin Hydrogel ◽  
Frequency Sweeps ◽  
Gel Network

Tissue engineering provides solutions that require medicine to restore damaged tissues or even complete organs. This discipline combines biologically active scaffolds, cells and molecules; being the addition of nanoparticles into the scaffolds, one of the techniques that is attracting more interest these days. In this work, Hydroxyapatite Nanorods (HA) were added to the network of Gelatin hydrogel (GE), and the particular properties resulting from their interaction were studied. Specifically, viscoelastic properties were characterized as a function of gel and nanoparticle concentration, varying ratios and temperatures. Oscillatory Time Sweeps (OTS) provided the necessary information about how the timeresolved material property/structure alteration. A wide variety of Continuous Flow Tests and Frequency Sweeps were used to describe the mechanical properties of the material, proving that the presence of nanoparticles led to a reinforcement of the gel network, mechanical stiffness and strength. The thixotropic nature of the gels was also evaluated and the most common theoretical models were described and commented. The attributes inferred from the data, showed a material that can allow the natural growth of bone tissue whilst withstanding properly the mechanical efforts; resulting in a material with an outstanding suitability to be used in regenerative medicine.

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.

scholarly journals Chronic hypoxic decreases in soluble guanylate cyclase protein and enzyme activity are age dependent in fetal and adult ovine carotid arteries

2006 ◽  
Vol 100 (6) ◽  
pp. 1857-1866 ◽  
Author(s):  
James M. Williams ◽  
Charles R. White ◽  
Melody M. Chang ◽  
Elisha R. Injeti ◽  
Lubo Zhang ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Carotid Arteries ◽  
Chronic Hypoxia ◽  
Soluble Guanylate Cyclase ◽  
Mrna Translation ◽  
Mrna Levels ◽  
Age Dependence ◽  
Age Dependent ◽  
Cgmp Analog ◽  
Reduced Activity

The present study tests the hypothesis that chronic hypoxia enhances reactivity to nitric oxide (NO) through age-dependent increases in soluble guanylate cyclase (sGC) and protein kinase G (PKG) activity. In term fetal and adult ovine carotids, chronic hypoxia had no significant effect on mRNA levels for the β1-subunit of sGC, but depressed sGC abundance by 16% in fetal and 50% in adult arteries, through possible depression of rates of mRNA translation (15% in fetal and 50% in adult) and/or increased protein turnover. Chronic hypoxia also depressed the catalytic activity of sGC, but only in fetal arteries (63%). Total sGC activity was reduced by chronic hypoxia in both fetal (69%) and adult (37%) carotid homogenates, but this effect was not observed in intact arteries when sGC activity was measured by timed accumulation of cGMP. In intact arteries treated with 300 μM 3-isobutyl-1-methylxanthine (IBMX), chronic hypoxia dramatically enhanced sGC activity in fetal (186%) but not adult (89%) arteries. This latter observation suggests that homogenization either removed an sGC activator, released an sGC inhibitor, or altered the phosphorylation state of the enzyme, resulting in reduced activity. In the absence of IBMX, chronic hypoxia had no significant effect on rates of cGMP accumulation. Chronic hypoxia also depressed the ability of the cGMP analog, 8-( p-chlorophenylthio)-cGMP, to promote vasorelaxation in both fetal (8%) and adult (12%) arteries. Together, these results emphasize the fact that intact and homogenized artery studies of sGC activity do not always yield equivalent results. The results further suggest that enhancement of reactivity to NO by chronic hypoxia must occur upstream of PKG and can only be possible if changes in cGMP occurred in functional compartments that afforded either temporal or chemical protection to the actions of phosphodiesterase. The range and age dependence of hypoxic effects observed also suggest that some responses to hypoxia must be compensatory and homeostatic, with reactivity to NO as the primary regulated variable.

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