scholarly journals Inverse elastographic method for analyzing the ocular lens compression test

2017 ◽  
Vol 10 (06) ◽  
pp. 1742009 ◽  
Author(s):  
Matthew A. Reilly ◽  
Andre Cleaver
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Molecular Basis ◽  
Human Lens ◽  
Ocular Lens ◽  
Loss Of Function ◽  
Manual Compression ◽  
Wild Type ◽  
Genetic Manipulations ◽  
Good Agreement

The ocular lens stiffens dramatically with age, resulting in a loss of function. However, the mechanism of stiffening remains unknown, at least in part due to difficulties in making reliable measurements of the intrinsic mechanical properties of the lens. Recent experiments have employed manual compression testing to evaluate the stiffness of murine lenses which have genotypes pertinent to human lens diseases. These experiments compare the extrinsic stiffness of lenses from the genotype of interest to the wild-type lens in an effort to reach conclusions regarding the cellular or molecular basis of lens stiffening. However, these comparisons are confounded by alterations in lens size and geometry which invariably accompany these genetic manipulations. Here, we utilize manual lens compression to characterize the stiffness of a porcine lens and a murine lens. An inverse elastographic technique was then developed to estimate the intrinsic shear modulus of each lens as well as the elastic modulus of the lens capsule. The results were in good agreement with the previous literature values.

Modelling the nano indentation behaviour of recast layer and heat affected zone on reverse micro EDMed hemispherical feature

2021 ◽  
pp. 1-15
Author(s):  
Tribeni Roy ◽  
Anuj Sharma ◽  
Prabhat Ranjan ◽  
R. Balasubramaniam
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Heat Affected Zone ◽  
Parent Material ◽  
Recast Layer ◽  
Machined Surface ◽  
Nano Indentation ◽  
Fea Simulation ◽  
Load Displacement ◽  
Good Agreement

Abstract Electrical discharge machined surfaces inherently possess recast layer on the surface with heat affected zone (HAZ) beneath it and these have a detrimental effect on the mechanical properties viz. hardness, elastic modulus, etc. It is very difficult to experimentally characterise each machined surface. Therefore, an attempt is made in this study to numerically calculate the mechanical properties of the parent material, HAZ and the recast layer on a hemispherical protruded micro feature fabricated by reverse micro EDM (RMEDM). In the 1st stage, nano indentation was performed to experimentally determine the load-displacement plots, elastic modulus and hardness of the parent material, HAZ and the recast layer. In the 2nd stage, FEA simulation was carried out to mimic the nano indentation process and determine the load-displacement plots for all the three cases viz. parent material, recast layer and HAZ. Results demonstrated that the load'displacement plots obtained from numerical model in each case was in good agreement with that of the experimental curves. Based on simulated load-displacement plots, hardness was also calculated for parent material, HAZ and the recast layer. A maximum of 11% error was observed between simulated values of hardness and experimentally determined values.

Estimation of the Elastic Modulus and Moisture Absorption of Sisal Fibre

2013 ◽  
Vol 750-752 ◽  
pp. 204-209
Author(s):  
Yiou Shen ◽  
Yan Li ◽  
Feng Lv
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Moisture Absorption ◽  
Single Fibre ◽  
Geometrical Model ◽  
Natural Fibre ◽  
Sisal Fibre ◽  
Dimensional Parameters ◽  
Longitudinal Modulus ◽  
Good Agreement

Microstructures of sisal fibres were revealed optically. Statistics on dimensional parameters for sisal fibres were used to establish a geometrical model in order to estimate the elastic modulus and moisture absorption capability of sisal fibres. The single fibre tensile test was conducted on the sisal. The predicted longitudinal modulus and water absorption was in good agreement with experimental results. It was found that the lumen ratio is a significant factor in determine the mechanical properties of the natural fibre.

Nanoindentation of Multi-Wall CNT Reinforced Al Composites

2010 ◽  
Vol 447-448 ◽  
pp. 549-553 ◽  
Author(s):  
Jin Zhi Liao ◽  
Jian Jun Pang ◽  
Ming Jen Tan
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Carbon Nanotube ◽  
Transverse Direction ◽  
Transverse Section ◽  
Hot Extrusion ◽  
Mechanical Tests ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Good Agreement

This work used nanoindentation to characterize the local mechanical properties of the multi-wall carbon nanotube (MWCNT) reinforced aluminum (Al) composites. The Al-MWCNT (0.5, 1.0 and 2.0 wt.%) specimens were fabricated by spark plasma sintering (SPS) followed by hot extrusion. Different local regions of the as-extruded and tensile-fractured specimen over the longitudinal and transverse section were studied by nanoindentation. The nanoindentation results were compared with the conventional macro- and mircoscopic mechanical tests, and were found in good agreement. The values of hardness (H) and elastic modulus (E) obtained reached maximum at the 0.5 wt.% MWCNT adding Al samples. E was highest in the necking region then decreased with increasing distance from the localized deformed region; while H varied in different regions. In the same region, H and V were higher in the longitudinal than those in the transverse direction, due to the texture hardening and alignment of CNT.

Study of Local Mechanical Properties of Fe78Al22 Alloy

2018 ◽  
Vol 784 ◽  
pp. 27-32 ◽  
Author(s):  
Vilma Buršíková ◽  
Vojtěch Homola ◽  
Yvonna Jirásková ◽  
Naděžda Pizúrová ◽  
Ivana Miháliková ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Grain Orientation ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Berkovich Indenter ◽  
Indentation Tests ◽  
Anisotropic Elastic ◽  
Crystallographic Orientations ◽  
Good Agreement

The local mechanical properties of Fe78Al22alloy were studied using nanoindentation techniques. Sharp Berkovich indenter was used to perform load-controlled nanoindentation experiments on the studied sample. Hardness and elastic modulus maps were created on the basis of the indentation tests carried out in different grains. The focus of the work was to study the dependence of mechanical properties on the grain orientation. The results were in good agreement with quantum-mechanical calculations of anisotropic elastic properties of the studied alloy. It was explained that the maximum detected elastic modulus values are likely for grains with [111] crystallographic orientations which we theoretically identified as the hard ones.

Evolution of Crystallographic Texture and Mechanical Properties during Annealing of Nanocrystalline Fe-50%Ni Alloy Foil

2007 ◽  
Vol 345-346 ◽  
pp. 781-784
Author(s):  
Jong Kweon Kim ◽  
Shi Hoon Choi ◽  
Yong Bum Park
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Crystallographic Texture ◽  
Elastic Moduli ◽  
Nanoindentation Test ◽  
Strong Decrease ◽  
Alloy Foil ◽  
Ni Alloy ◽  
Self Consistent ◽  
Good Agreement

The crystallographic texture and mechanical properties were investigated in a nanocrystalline Fe-50%Ni alloy fabricated by using an electrodeposition method. The as-deposited texture was characterized by strong <100>//ND and weak <111>//ND fibre components, and the occurrence of grain growth resulted in the strong development of the <111>//ND fibre components with the minor <100>//ND fibre components. The elastic modulus and hardness were measured by means of a nanoindentation test. The annealing led the specimen to an increase in the elastic modulus and a strong decrease in the hardness. The elastic modului measured were compared with the theoretic predictions based on an elastic self-consistent (ESC) polycrystal model. The theoretical values of the elastic moduli through the thickness direction in the sample were in a good agreement with the experimental results.

scholarly journals Mutations in fbiD (Rv2983) as a Novel Determinant of Resistance to Pretomanid and Delamanid in Mycobacterium tuberculosis

2020 ◽  
Vol 65 (1) ◽  
pp. e01948-20
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Content Type ◽  
Solid Media ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole prodrugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole-genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, of which 91% occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance, namely, fbiC (56%), fbiA (15%), ddn (12%), fgd (4%), and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983 (fbiD), a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals The NALCN Channel Regulator UNC-80 Functions in a Subset of Interneurons To Regulate Caenorhabditis elegans Reversal Behavior

2019 ◽  
Vol 10 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Chuanman Zhou ◽  
Jintao Luo ◽  
Xiaohui He ◽  
Qian Zhou ◽  
Yunxia He ◽  
...  
Keyword(s):  
Plant Hormone ◽  
Neuronal Excitability ◽  
Resting Membrane Potential ◽  
Loss Of Function ◽  
Wild Type ◽  
C Elegans ◽  
Link Type ◽  
Complex Functions ◽  
And Function ◽  
Multiple Loss

NALCN (Na+leak channel, non-selective) is a conserved, voltage-insensitive cation channel that regulates resting membrane potential and neuronal excitability. UNC79 and UNC80 are key regulators of the channel function. However, the behavioral effects of the channel complex are not entirely clear and the neurons in which the channel functions remain to be identified. In a forward genetic screen for C. elegans mutants with defective avoidance response to the plant hormone methyl salicylate (MeSa), we isolated multiple loss-of-function mutations in unc-80 and unc-79. C. elegans NALCN mutants exhibited similarly defective MeSa avoidance. Interestingly, NALCN, unc-80 and unc-79 mutants all showed wild type-like responses to other attractive or repelling odorants, suggesting that NALCN does not broadly affect odor detection or related forward and reversal behaviors. To understand in which neurons the channel functions, we determined the identities of a subset of unc-80-expressing neurons. We found that unc-79 and unc-80 are expressed and function in overlapping neurons, which verified previous assumptions. Neuron-specific transgene rescue and knockdown experiments suggest that the command interneurons AVA and AVE and the anterior guidepost neuron AVG can play a sufficient role in mediating unc-80 regulation of the MeSa avoidance. Though primarily based on genetic analyses, our results further imply that MeSa might activate NALCN by direct or indirect actions. Altogether, we provide an initial look into the key neurons in which the NALCN channel complex functions and identify a novel function of the channel in regulating C. elegans reversal behavior through command interneurons.

scholarly journals A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 830
Author(s):  
Julio Cesar Martinez-Garcia ◽  
Alexandre Serraïma-Ferrer ◽  
Aitor Lopeandía-Fernández ◽  
Marco Lattuada ◽  
Janak Sapkota ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymeric Nanocomposites ◽  
Mechanical Reinforcement ◽  
Future Studies ◽  
Three Phase ◽  
Theoretical Predictions ◽  
Filler Network ◽  
New Research ◽  
Good Agreement ◽  
Research Avenue

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

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