STED/AFM as a tool to investigate mechanical and adhesive properties of migrating keratinocytes

Fibronectins (FNs) are a major component of the extracellular matrix (ECM), and provide important binding sites for a variety of ligands outside and on the surface of the cell. Similar to other ECM proteins, FNs are consistently subject to mechanical stress in the ECM. Therefore, it is important to study their structure and binding properties under mechanical stress and understand how their binding and mechanical properties might affect each other. Although certain FN modules have been extensively investigated, no simulation studies have been reported for the FN type I (Fn1) domains, despite their prominent role in binding of various protein modules to FN polymers in the ECM. Using equilibrium and steered molecular dynamics simulations, we have studied mechanical properties of Fn1 modules in the presence or the absence of a specific FN-binding peptide (FnBP). We have also investigated how the binding of the FnBP peptide to Fn1 might be affected by tensile force. Despite the presence of disulfide bonds within individual Fn1 modules that are presumed to prevent their extension, it is found that significant internal structural changes within individual modules are induced by the forces applied in our simulations. These internal structural changes result in significant variations in the accessibility of different residues of the Fn1 modules, which affect their exposure, and, thus, the binding properties of the Fn1 modules. Binding of the FnBP appears to reduce the flexibility of the linker region connecting individual Fn1 modules (exhibited in the form of reduced fluctuation and motion of the linker region), both with regard to bending and stretching motions, and hence stabilizes the inter-domain configuration under force. Under large tensile forces, the FnBP peptide unbinds from Fn1. The results suggest that Fn1 modules in FN polymers do contribute to the overall extension caused by force-induced stretching of the polymer in the ECM, and that binding properties of Fn1 modules can be affected by mechanically induced internal protein conformational changes in spite of the presence of disulfide bonds which were presumed to completely abolish the capacity of Fn1 modules to undergo extension in response to external forces.

Optimizing horizontal well placement is often not limited to identifying the most favorable reservoir, but also identifying the ideal target window within that reservoir. In unconventional reservoirs, the ideal target window must have both appropriate reservoir quality and the mechanical rock properties conducive to effective hydraulic fracturing. This paper presents two case studies from the Permian Basin. The first study directly compares wireline logs and core data with drilling vibration analysis. Analyzing drill bit vibrations, one can process mechanical rock property data. This process is called drill bit geomechanics. These high-resolution drill-bit-derived data were first calibrated to wireline and core data, then applied to target future landing zones. The second case study compares drill bit geomechanics data across three neighboring 10,000-ft horizontal wells, all of which landed in the same target zone. Based on the drill bit geomechanics data, the three wells showed notable differences in mechanical rock quality. The operator found the three wells’ production responses also differed. High frequency measurements of drilling-induced vibrations were recorded through several producing Permian reservoirs. In the pilot well, the recording tool was run behind a coring assembly to obtain mechanical data at in-situ pressure and temperature. Elastic stress-strain relationships were used to solve for the stiffness coefficients and determine relative values of mechanical properties (i.e., Young's Modulus (YM) and Poisson's Ratio (PR)). The resulting mechanical data were compared directly to core analysis, wireline dipole sonic logs, and wireline image logs. In general, the mechanical rock properties derived from drilling vibrations compared well with those from the sonic log and core analysis. One can attribute differences between the datasets to fluid effects and differences in resolution. The drill-bit-derived mechanical properties showed fine-scale changes and thinly-bedded intervals that were not identified by the sonic log. Using sonic measurements to determine in-situ mechanical properties can have non-uniqueness. Analyzing cores also includes challenges of translating exhumed core properties to those of in-situ conditions. Combining the in-situ measurement of mechanical properties from drilling vibrations with the traditional sonic log and core analysis minimized uncertainties. Increased understanding of mechanical properties in the pilot well informed the landing zone target intervals for the horizontal well development plan. Understanding mechanical properties is also critical to effective hydraulic fracture stimulation design and execution. Even within a landing zone, mechanical properties can vary laterally. Measuring and understanding these variations in mechanical properties can improve completions and lead to increased well productivity. Gathering drill bit geomechanics data provides a lower cost and lower risk method to acquire mechanical rock properties in long, horizontal wellbores. These near-wellbore variations in mechanical rock properties are ideal for use in identifying target landing zones for horizontal wells. One can use the data to create high-resolution, laterally variable fracture simulation and reservoir models. By integrating these data sets with mechanical rock properties recorded while drilling, operators can have significantly higher confidence in choosing a target landing zone and improving completions.

Poly(vinyl alcohol) has not previously been examined in much detail as a controlled release polymer for use in pharmaceutical formulations. However, this food grade polymer has barrier and tensile properties which make it attractive for such applications. The effects of several diluents and fillers on Poly(vinyl alcohol) (PVAL) coatings have been determined using both mechanical property and water vapor permeability measurements. It has been found that the alcohol ethoxylate Neodol 23-6.5 (CH3(CH2)11–O(CH2–CH2–O)6–H) acts as a plasticizer for PVAL only up to 15–20 wt% in contrast to 600 molecular weight Polyethylene Glycol (PEG 600), which continuously plasticizes PVAL. The effects of Neodol on PVAL mechanical properties and water vapor permeability at higher concentrations can be explained in terms of Neodol phase separation and has been confirmed with DSC. The inert filler and whitener titanium dioxide (TiO2) monotonically degrades film mechanical properties and increases water vapor permeability of the coating. Attempts to correlate coating dust generated during particle attrition tests with mechanical property measurements were unsuccessful. A correlation between accelerated granule stability and water vapor permeability of the PVAL coating was established.

The main objective of this study was to measure the properties of the carrot to design carrot (Daucus carota L.) harvesting mechanism. Physical properties were beneficial to fix the relative position of carrot harvesting mechanism and mechanical properties were helping in functionality of the carrot combine harvester mechanism. Three carrot cultivars namely Pusa Keshar, Pusa Rudhira and Nantes cultivar were taken for the study. Length of carrot, effective foliage length (stem node), carrot head (crown) above soil surface; weight and upper root diameter were included in physical properties measurement. Pulling and tensile force were included in mechanical properties measurement. The foliage length was found in the range from 46 to 90cm, however, the crown height was observed at 1.5 cm above the soil surface. Carrot root length of Pusa Keshar, Pusa Rudhira and Nantes were 23.10 ± 3.71, 21.68 ± 4.14 and 18.64 ± 3.49 cm, respectively. Average pulling force in undisturbed (unloosen) raised bed highest was observed with Pusa Rudhira (148.93 ± 73.46 N) followed by Pusa Keshar (133.10 ± 62.15) and Nantes (118.18 ± 41.72). While, the pulling force for loosen raised bed were observed in following order Pusa Rudhira (22.41 ± 7.64 N) >Pusa Keshar (21.35 ± 5.84 N) >Nantes (20.21 ± 5.52 N). The loosen soil imposed 5 to 6 time lesser resistance on pulling carrot than unloosen raised bed. Average foliage detachment force (tensile force) from carrot crown was 236.13 ± 20.66, 211.95 ± 16.81 and 243.35 ± 47.73 N for Pusa Keshar, Nantes and Pusa Rudhira, respectively. It was observed that pulling force in loose raised bed was around 10 times lesser than the foliage detachment force.

Manipulation of individual viruses: friction and mechanical properties

The objective of this work was to develop a method for repeated same-site measurement of mechanical properties suitable for the detection of degenerative changes in a biologically active explant model after a single blunt impact injury. Focal blunt impact injuries to articular surfaces lead to local cartilage degeneration and loss of mechanical properties. We employed a repeated measurement methodology to determine variations in mechanical same-site properties before and after injury in living cartilage, with the hypothesis that normalization with initial mechanical properties may provide a clearer evaluation of impact effects and improve our understanding of the biologic responses to impact injury. Bovine osteochondral explants were cultured for up to 14 days after impact injury. Indentation tests were performed before and after impact injury to assess relative changes in mechanical properties. Creep strain increased significantly in impacted explants after 7 days and in both impacted and control explants after 14 days. Further analysis at 14 days revealed decreases in stretch factor beta, creep time constant and local compressive modulus. A repeated measures methodology reliably detected changes in the mechanical behaviour of viable osteochondral explants after a single impact injury.

Integrity of structural components depends on the deformation and fracture behavior of materials. For evaluating the material condition in-service, it is generally not feasible or practical or advisable to cut samples from operating structures. Non-destructive testing (NDT) techniques are required to evaluate the mechanical properties. Although several NDT techniques such as ultrasound, magnetic strength, Barkhausen noise, microhardness etc., are employed for estimating the mechanical property degradation, these methodologies are generally empirical and indirect. Automated Ball Indentation (ABI) is a non-destructive testing technique for direct measurement of mechanical and fracture properties of metallic engineering materials. Because of the small area over which the test is carried out, it is possible to determine point to point variations in the mechanical and fracture properties, such as those that exist in weldments. Although ABI technique is non-intrusive, it is a state-of-the-art mechanical test that measures directly the current/local deformation behavior of the material. In this paper, we present results from studies on the application of ABI technique to determine tensile and fracture properties of ferritic steels, an austenitic stainless steel, a nickel base superalloy and Zircaloy in different thermo-mechanical conditions. The effects of aging and cold work on these properties were determined from the ABI tests. Gradients in mechanical properties of ferritic steel welds, particularly in the narrow heat-affected zone, were clearly established. ABI technique was found to be useful in determining the anisotropy in the tensile properties of Zircaloy cladding tubes. The technique has potential as a non-destructive method for assessing structural integrity of aged components.

Influence of manufacturing conditions on measurement of mechanical material properties on thermoplastic micro tensile bars

This work is aimed to study the possibility of recycling plastic waste (polypropylene (PP)) as aggregate instead of sand in the manufacturing of mortar or concrete. For this, an experimental study was carried out to evaluate the influence of nano‐SiO2 and recycled PP plastic particles′ content on physical, mechanical, and shrinkage properties and microstructure of the mortars with recycled PP plastic particles. The sand is substituted with the recycled PP plastic particles at dosages (0%, 20%, 40%, and 60% by volume of the sand). The nano‐SiO2 content is 5% by weight of cement. The physical (porosity, water absorption, and density), mechanical (compressive and flexural strength) and shrinkage properties of the mortars were evaluated, and a complementary study on microstructure of the interface between cementitious matrix and PP plastic particles was made. The measurements of physical and mechanical properties showed that PP‐filled mortar had lower density and better toughness (higher ratio of flexural strength to compressive strength). However, the compressive strength and flexural strength of PP‐filled mortar is reduced, and the porosity, water absorption, autogenous shrinkage, and dry shrinkage increased as compared to normal cement mortar. The addition of nano‐SiO2 reduced the porosity, water absorption, and drying shrinkage of PP‐filled mortar and effectively improved the mechanical properties, but increased its autogenous shrinkage. A microscopic study of the interfacial zone (plastic‐binder) has shown that there is poor adhesion between PP plastic particles and cement paste. From this work, it is found that recycled PP plastic waste has a great potential to be a construction material. It can be used as partial replacement of natural aggregates instead.

Two-dimensional (2D) materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties, making them a focal point in nanotechnology research. Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications. However, their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties. Among the in situ characterization techniques, atomic force microscopy (AFM) has gained widespread applications in exploring the mechanical behaviour of nanomaterials, because of the easy measurement capability of nano force and displacement from the AFM tips. Specifically, AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials. This review comprehensively details the methods based on normal force spectroscopy, which are utilized to test and characterize the elastic and fracture properties, adhesion, and fatigue of 2D materials. Additionally, the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials, including surface friction of 2D materials, shear behaviour of interlayers as well as nanoflake-substrate interfaces. The influence of various factors, such as testing methods, external environments, and the properties of test samples, on the measured mechanical properties is also addressed. In the end, the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed, which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.

The heterogeneity of porous features and different phases, especially porous features are important in the performance of ceramic coatings as thermal protection. In evaluation of mechanical properties of porous composite coatings by using nanoindentation, the effect of heterogeneity needs to be clarified. In this study, YSZ/Al 2 O 3 composite coatings prepared by EPD and sintered subsequently at high temperatures are investigated. Load-displacement curves are pores and particle fractures sensitive, but independent of different phases. The measured mechanical properties are strongly dependent on the penetration depth chosen. In order to cover all the microstructural features in the YSZ/Al 2 O 3 composite coatings, a penetration depth larger than 1000 nm was required to determine the global mechanical properties.

Experimental measurement and modeling analysis of active and passive mechanical properties of arterial vessel wall

In the present study, mechanical and water absorption properties of the nonwoven kenaf fiber (KF)/unsaturated‐polyester composites manufactured by resin transfer molding were investigated. Nonwoven KF mats with an aerial density of 1350 g/m2 were treated with a 6% NaOH solution for 3 h. The influence of the fiber treatment on the properties of the composites was investigated with Fourier transform‐infra red (FTIR), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), and dynamic contact angle technique (DCAT). Mechanical properties measurements were conducted via determination of flexure and fracture toughness. A general trend was observed whereby alkalized KF composites gave superior mechanical properties compared to as‐received KF composites. The XRD and DCAT results indicated an enhancement of the crystallinity index and surface energy of the alkali‐treated KF. SEM and AFM of the treated KF showed the removal of impurities and a reduction of roughness on the KF surface with alkalization. Water immersion induced a drastic loss of the mechanical properties of the composites albeit better retention of properties was observed in the case of alkalized KF composites. The fracture surfaces were inspected by SEM which confirmed the quality of the interface. POLYM. COMPOS., 37:3516–3526, 2016. © 2015 Society of Plastics Engineers

PurposeThis paper aims to find a suitable solution to treat the solidification paper by using hydroxypropyl cellulose (HPC) to improve the mechanical, physical and chemical properties of paper.Design/methodology/approachThe samples have gone several stages, starting with the manufacture of paper from the linen pulp and the same components of the hardened manuscript papers. It was subjected to artificial aging to reach an age comparable to the manuscript age, then it was subjected to natural aging by inoculation it with A. niger. Mechanical cleaning of the leaves was done with soft brushes. The samples have been consolidated by HPC 2%. Digital microscopy, scanning electron microscopy, mechanical properties measurement, color change, Fourier transform infrared and pH measurements were used to assess the effect of HPC on the qualities of leaves.FindingsHPC succussed in strengthening and restoring the natural, chemical and mechanical properties for the solidified leaves.Originality/valueThe solidified papers phenomenon constitutes severe suffering for manuscripts and books conservators. The paper consolidation initial stage is one of the most important conservation stages because paper has lost many natural, mechanical and chemical properties. The most important feature of this study is providing a solution to the hardened leaves strengthening problem and restoring their chemical, natural and mechanical properties.

En masse cell migration is more relevant than single cell migration in physiological processes of tissue formation, such as embryogenesis, morphogenesis and wound healing. In these situations, cells are influenced by the proximity of other cells including interactions facilitated by substrate mechanics. Here we found that when fibroblasts migrated en masse over a hydrogel, they established a well-defined deformation field by traction forces and migrated along a trajectory defined by field gradients. The mechanics of the hydrogel determined the magnitude of the gradient. For materials stiff enough to withstand deformation related to cellular traction forces, such patterns did not form. Furthermore, migration patterns functioned poorly on very soft matrices where only a minimal traction gradient could be established. The largest degree of alignment and migration velocity occurred on the gels with the largest gradients. Granulation tissue formation in punch wounds of juvenile pigs was correlated strongly with the modulus of the implanted gel in agreement with in vitro en masse cell migration studies. These findings provide basic insight into the biomechanical influences on fibroblast movement in early wounds and relevant design criteria for development of tissue-engineered constructs that aim to stimulate en masse cell recruitment for rapid wound healing.