Average Rupture Force Research Articles

Preparation and performance assessment of high-strength polyurea microcapsules

Formulation of microcapsules with high mechanical strength holds great significance for their application in high-pressure scenarios. In this study, polyurea (PU) was employed as the shell material to encapsulate perfume oil through interfacial polymerization. Subsequently, a systematic assessment of mechanical strength was conducted. The results indicated that the protective colloid, triethylenediamine (TEDA) concentration, core/shell ratio (perfume oil to polymethylene polyphenyl isocyanate (PAPI)), and reaction temperature, significantly influenced the mechanical strength of PU microcapsules. Notably, employing a concentration of 1.5 wt% polyvinyl alcohol (PVA), 0.5 wt% TEDA, a core/shell ratio of 10:1, and a reaction temperature of 70 °C resulted in PU microcapsules boasting an average rupture force of 1.92 ± 0.22 mN and a Young's modulus of 0.0195 ± 0.0013 GPa. Impressively, when contrasted with melamine-formaldehyde microcapsules, those with PU shells exhibited markedly enhanced mechanical properties.

Moisture dependent postharvest physical and textural characteristics of brown sesame seed (var. TMV-4)

Physical and textural characteristics are important in design and manufacturing of harvest and post harvest machines. Some postharvest physical and textural characteristics of brown sesame seed (var. TMV-4) were determined as a function of moisture content in the range of 4.3 per cent to 20 per cent (d.b). The axial dimensions, geometric mean diameter, surface area, volume, sphericity and aspect ratio were found to be increasing linearly for all studied moisture levels. Furthermore, the thousand seed mass, true density, porosity and the angle of repose also increased linearly whereas, bulk density decreased linearly with the increase of moisture content under study. The results showed that the static coefficient of friction on four different surfaces of plywood, mild steel, galvanized iron and glass also increased linearly for all level of moisture. The initial cracking force, average rupture force and average rupture energy decreased linearly with increased moisture content of 4.3 to 20 per cent (d.b.).

Effect of Short-Term Storage Temperature on Mechanical Properties of ‘Istanbul’ Medlar

The study investigated the effect of short-term storage time on the mechanical (rupture force, rupture energy, deformation) properties of the ‘Istanbul’ medlar cultivar grafted on Quince A (QA) and Quince Province BA29 (BA29) quince clone rootstock. The study gives the average values of the physical properties (weight, size, geometric mean diameter, sphericity, surface area, true density, bulk density, and porosity) of the ‘Istanbul’ medlar cultivar. The changes in breaking force, breaking energy, and deformation values of 'Istanbul' medlar varieties stored at room temperature (251 °C) and cold storage (41 °C) for 5 days were investigated. Separate measurements were made for skin and skinless fruits. The average rupture force value of fruits of the ‘Istanbul’ medlar cultivar stored at 25 °C was determined as 8.82 N, deformation 4.66 mm, and rupture energy 0.035 J. The average rupture force value of the fruits of the ‘Istanbul’ medlar cultivar stored at 4 °C was determined as 10.06 N, deformation 5.16 mm, and rupture energy 0.043 J. It was found that the storage conditions had a statistically significant effect on the rupture force, rupture energy, and deformation values of the QA and BA29 rootstocks of the ‘Istanbul’ medlar cultivar (P≤0.001).

Temperature Difference in Loading Area (Tarmac) during Handling of Air Freight Operations and Distance of Production Area Affects Quality of Fresh Mango Fruits (Mangifera indica L. ‘Nam Dok Mai Si Thong’)

Mango (Mangifera indica L.) ‘Nam Dok Mai Si Thong’ is an important cultivar for export from Thailand. Export mainly takes place via air transport, but for about 2 h at the loading area (tarmac), unit loading devices (ULDs) are exposed to ambient environmental conditions. In this research, the effects of different temperature conditions at the loading area (tarmac) and the distance of the production area from the tarmac on the quality of fresh mango fruits were studied. The treatments included three temperature conditions for 2 h (simulated handling in tarmac)—constant temperature (20 °C), non-insulated or insulated and exposed to sun—and two distances of the tarmac from the production area—short distance (i.e., transport occurring 53 h after harvest) and long distance (i.e., transport occurring 70 h after harvest). The temperature variation in the boxes exposed to the sun was greater in the non-insulated than in the insulated boxes, but this effect was more pronounced in fruit from the short-distance production area (28.1 °C insulated and 36.9 °C non-insulated) than in fruit from the long-distance production area (34.2 °C insulated and 38 °C non-insulated). Insulation and short distance increased the shelf life, decreased weight loss, delayed the decrease in average firmness and rupture force, etc. The insulation of mango fruit boxes mitigates the deleterious effect of exposure to 2 h of direct sun by reducing the increase in temperature, thus improving the shelf life and quality of mango fruit.

AFM Study of Nanoscale Membrane Perturbation Induced by Antimicrobial Lipopeptide C14 KYR.

Lipopeptides have been extensively studied as potential antimicrobial agents. In this study, we focused on the C14-KYR lipopeptide, a modified version of the KYR tripeptide with myristic acid at the N-terminus. Here, membrane perturbation of live E. coli treated with the parent KYR and C14-KYR peptides was compared at the nanoscale level using AFM imaging. AFM analyses, including average cellular roughness and force spectroscopy, revealed the severe surface disruption mechanism of C14-KYR. A loss of surface roughness and changes in topographic features included membrane shrinkage, periplasmic membrane separation from the cell wall, and cytosolic leakage. Additional evidence from synchrotron radiation FTIR microspectroscopy (SR-FTIR) revealed a marked structural change in the membrane component after lipopeptide attack. The average roughness of the E. coli cell before and after treatment with C14-KYR was 129.2 ± 51.4 and 223.5 ± 14.1 nm, respectively. The average rupture force of the cell treated with C14-KYR was 0.16 nN, four times higher than that of the untreated cell. Our study demonstrates that the mechanistic effect of the lipopeptide against bacterial cells can be quantified through surface imaging and adhesion force using AFM.

Functionalization of Diamond‐Like Carbon Surfaces to Access High Rupture Forces in Single‐Molecule Force Spectroscopy of Covalent Bonds

AbstractSingle‐molecule force spectroscopy is a powerful tool to experimentally probe the effect of mechanical force on individual bonds. With increasing mechanical stability of the target bond, however, this becomes exceedingly challenging, as mechanical activation of the mechanophore competes with rupture of the surface anchor. Here we investigate and systematically modify a functionalization protocol which is based on diamond‐like carbon (DLC) surfaces. We perform dynamic force spectroscopy on heterobifunctional polyethylene glycol molecules which are covalently anchored to the functionalized DLC surfaces and analyze the changes in rupture forces, distances at which single rupture events occur, as well as the properties of unspecific adhesion caused by modifications in the functionalization protocol. Average rupture forces of 1.7 nN are achieved, and 5.7 % of the rupture events yield rupture forces above 3 nN. Both values are significantly higher than for the widely used silane‐based surface anchors.

Determination of the mechanical properties of polymeric microneedles by micromanipulation

Precise characterization of the mechanical properties of polymeric microneedles is crucial for their successful penetration into skin and delivery of the loaded active ingredients. However, most available strategies for this purpose are based on compression of the whole patch, which only provide the average rupture force of the needles and can not give information on the variations across individual microneedles in the patch. In this study, we determined the mechanical strength of individual microneedles of two types of hyaluronic acid microneedles with or without loaded model drugs using a micromanipulation technique. The applied force as a function of displacement of the microneedles was recorded, which was used to determine the rupture displacement, rupture force, and then to derive and calculate normal stress-deformation curve, rupture stress and Young′s modulus of individual microneedles. The obtained data suggest that the molecular weight of the polymer and the loading of drug into the microneedles can significantly affect the rupture behavior and mechanical properties of the microneedles, which provides a foundation for preparing sufficiently strong microneedles for controlled drug delivery.

Orientation Dependence of Inter-NCP Interaction: Insights into the Behavior of Liquid Crystal Phase and Chromatin Fiber Organization.

We report equilibrium and nonequilibrium molecular dynamics (MD) simulations of two nucleosome core particles (NCPs) stacked with their dyad axes oriented in parallel or antiparallel fashion. From the equilibrium trajectories, we determine the bridging behavior of different histone tails and observe that different sets of histone tails play important roles in the two orientations in stabilizing the NCP stack. While the H4 and H2A tails play important intermediary roles in the parallel stack, the H3 and H2B tails are important in the antiparallel stack. We use steered MD simulations to unstack the two NCPs and find a stark difference in their unstacking pathways. While the average rupture force was found to be higher for the parallel stack, the work done for complete unstacking was similar for both orientations. We use Jarzynski equality to determine the PMF profiles along the unstacking pathway, relate our findings to the behavior of NCP mesophases, and derive insights into the enigmatic nucleosomal organization in the chromatin fiber.

Mechanical properties of P-selectin PSGL-1 bonds.

The accurate determination of the mechanical properties of P-selectin and PSGL-1 is crucial for design and optimization of applications utilizing such bonds, e.g. biosensors and targeted drug delivery systems, as adhesion and mechanical interactions play a critical role in several key functions of biological cells. In current work, the spring constant and rupture force of a single P-selectin PSGL-1 ligand receptor bond and the Young's modulus of a layer made of these ligand receptors are reported. The work-of-adhesion of the P-selectin PSGL-1 interface is also characterized. In the reported experiments, PSGL-1 coated particles are deposited on a P-selectin coated substrate and their transient nanometer scale out-of-plane displacements are acquired employing a laser Doppler vibrometer as they are excited by an ultrasonic field. From the spectral response of a single particle, the resonance frequencies of its vibrational motion are identified, and with help of a particle adhesion model, the average rupture force and stiffness of a single P-selectin PSGL-1 ligand receptor are determined as Frupt = 171 ± 56 pN and kb = 0.56 ± 0.04 mN/m, respectively. Furthermore, the Young's modulus and work-of-adhesion of a layer of P-selectin PSGL-1 ligand receptors are extracted as E = 28.74 ± 3.96 MPa and WA = 70.0 ± 8.0 mJ/m2, respectively. Unlike Atomic Force Microscopy (AFM) and other probe-based techniques, the reported approach eliminates the need for direct contact with the sample, which could compromise the accuracy of the results by imposing unspecified additional contact interactions. Further, the current technique can be employed for measurements under various fluid flow conditions.

Abstract 596: Disruption of Cholesterol Metabolism and Substrate Stiffness Coordinate to Regulate Cellular Biomechanics and Induce Cytoskeletal Remodeling in Vascular Smooth Muscle Cells

Cholesterol is the main culprit contributing to the development of atherosclerosis by inducing the endothelial dysfunction, triggering the inflammatory response in the blood vessel wall, and deposition in the foam cell at the atherosclerotic plaque. However, growing evidence suggests that the role cholesterol plays during the process of atherogenesis is not only triggering the inflammation, but also plays an important role as a regulator of cellular mechanics, cell spreading, and cell migration, which is the critical step in atherogenesis. In addition, the mechanical environment of the VSMCs in blood vessel undergoes progressive stiffening along with aging, which may potentially affect the development of atherosclerosis. In this study, our main hypothesis is that membrane cholesterol affects the VSMCs migration during the progression of atherosclerosis by regulating the integrin- and cadherin-mediated cell adhesion and this effect highly depends on the mechanical properties of extracellular matrix (ECM). VSMCs used were enzymatically isolated from the descending thoracic aorta of male Sprague-Dawley rats. Cell mechanics was measured using an atomic force microscope (AFM). F-actin cytoskeleton was visualized with confocal microscopy and AFM imaging. 1 μM fluvastatin was used to reduce the endogenous cellular cholesterol. Our results showed that fluvastatin treatment dramatically decreased cell E-modulus, but, significantly increased the average rupture force of collagen I-, fibronectin-, and N-cadherin-mediated cell adhesion. In addition, the confocal microscopy and AFM imaging studies showed that the fluvastatin treatment significantly disrupted the actin stress fiber organization. Interestingly, the effect of fluvastatin on the biomechanics and the architecture of cytoskeleton of VSMCs decreased on the soft substrate. These results indicate that cholesterol and ECM stiffness play the roles synergistically in biomechanics, cytoskeleton architecture, and thus in migration of VSMCs. The knowledge that we obtained in this project will lead to a novel therapeutic strategy to prevent the VSMCs migration and then formation of atherosclerotic plaque by regulating VSMCs biomechanics.

Single Molecule Force Spectroscopy Reveals the pH-Dependent Mechanical Strength of the Alkynyl-Gold Bond.

Alkynyl groups are widely used as the gold-binding motifs for many applications, including the stabilization of gold nanoparticles, surface protection and surface chemical conjugation. However, at the fundamental level, the strength and binding mechanism of the alkynyl-gold bonds were yet to be revealed. Here, we use atomic force microscopy (AFM) based single molecule force spectroscopy to directly quantify the mechanical strength of the alkynyl-gold bond one bond at a time. We find that alkynyl-gold bonds are relatively strong with rupture forces in a broad range from 200 pN to 400 pN, which are stronger than many coordination bonds studied so far but weaker than a thiol-gold bond under similar experimental conditions. More interestingly, we find that the dissociation forces of alkynyl-gold bonds depend on the pH of the solution, suggesting a heterolytic rupture mechanism. The average rupture forces decrease from ∼270 pN at pH 7.4 to ∼100 pN at pH 3.4. Moreover, we find that the solvent conditions can also significantly affect the dissociation of alkynyl-gold bonds, indicating the existence of different binding modes and different dissociation pathways. Together, our results provide direct quantification of the mechanical strength of alkynyl-gold bonds and reveal the complex bond dissociation mechanism. This study may shed new light on the modulation of the stabilities of alkynyl-gold bonds at the bulk level for various biomedical and nanotechnological applications.

Physical characteristics of baru tree fruit aimed at kernel extraction

The baru tree fruit has a sustainable economical potential. However, the shelling process to release the whole kernel, the most valued part of the fruit, is still performed in a rather inefficient way. The objective of this investigation was to determine the physical-mechanical properties of the fruit to understand its behavior during shelling. Fruit and nut were characterized by unit mass, dimensions, volume and bulk, and real densities. Compression tests up to endocarp disruption were performed to determine maximum force, corresponding deformation, and deformation energy. X-ray tomography was used to identify potential nut internal dimension changes, affected by the treatments. Whole fruits and nuts showed average unit mass values of 28.20 ± 0.99 g and 16.52 ± 1.67 g, respectively. Their average dimensions, such as length, width, and thickness were 52.40 ± 4.48 mm, 38.31 ± 4.05 mm, and 28.64 ± 3.67 mm, and 50.78 ± 5.57 mm, 34.65 ± 5.14 mm, and 21.36 ± 2.86 mm, respectively. Average bulk and real densities values were 519.33 ± 49.63 kg/m3 and 918.87 ± 77.77 kg/m3, and 517.14 ± 41.88 kg/m3 and 1072.00 ± 187.01 kg/m3, respectively. Considering all treatments, the average rupture force ranged between 7926.7 and 9284.4 N, with corresponding widthwise specific deformation of 5.1% and 6.6%, to release 100% whole kernels of the tested nuts. Up to maximum force, deformation energy values ranged between 6.55 and 9.26J. There was no evidence of treatments’ effect on the internal dimension. Based on its mechanical behavior, showing that it is possible to open the endocarp and release the whole kernel, it was concluded that the baru nut has mechanized shelling potential.

Mechanical Behavior of Ensete ventricosum Fiber Under Tension Loading

ABSTRACTThe mechanical behavior of Ensete ventricosum fibers, expressed as the dependency of tension force in relation to the elongation, was determined for fibers with gauge length 50 mm and transformed into general linear mathematical model describing dependency of tension stress and strain. The average rupture force (10.88 ± 1.11) N, rupture stress (390.33 ± 21.96) MPa, rupture strain (0.021 ± 2 · 10–5), and volume energy (3.39 ± 0.22) J m−3 were also determined at this conducted study. Using image analyses, it was determined that the cross section of Ensete ventricosum fiber has circle shape and its dimension was specified. From the study, it implies that Ensete ventricosum fiber, with respect to its mechanical behavior under tension loading having regard to its density and to the fact that it is environmentally friendly, biodegradable and recyclable, could be used as a perspective construction material of the future. Determined model of mechanical behavior could be applied as background for further research focused on the Ensete fiber application.

Moisture dependent thermal properties of cassia

AbstractThermal and mechanical properties of cassia are primarily required in the study of its different thermal and mechanical operations. The thermal properties of cassia bark viz., specific heat, glass transition temperature (Tg), bulk thermal conductivity, and bulk thermal diffusivity were determined for a moisture range of 8–14% dry basis (d.b). Compression test was performed by Universal Testing Machine to examine the breaking characteristics of cassia along its three orthogonal directions at 11.10% d.b. moisture level. Results revealed that the specific heat increased from 1,553.12 to 3,232.90 J kg−1 °C−1 with an increase in moisture at 30°C. Whereas Tg decreased linearly from −66.67 to −86.09°C and the bulk thermal conductivity increased linearly from 0.10 to 0.14 W m−1 °C−1 with a rise in moisture content of the sample. Moreover, the bulk thermal diffusivity of cassia bark decreased from 2.75 × 10−7 to 1.62 × 10−7 m2 s−1 with an increase in moisture level. The average rupture forces for cassia ba...

A new approach to analyze the dynamic strength of eggs.

The mechanical behavior of eggshell was determined in terms of average rupture force and corresponding deformation. For the experiment, we selected goose eggs (Anser anser f. domestica). Samples of eggs were compressed along their x-axis and z-axis. The effect of the loading orientation can be described in terms of the eggshell contour curvature. Two different experimental methods were used: compression between two plates (loading rates up to 5mm/s) and the Hopkinson split pressure bar technique. This second method enables achieving loading rates up to about 17m/s. The response of goose eggs to this high loading rate was characterized also by simultaneous measurement of the eggshell surface displacements using a laser vibrometer and by the measurement of both circumferential and meridian strains.

Experimental and Numerical Analysis for Prediction of Mechanical Properties of Eggshell

Abstract Egg is a complete food package. Importance and quality of this sealed food package rely on its invulnerability to external contaminants. Therefore, eggshell with no cracks and high resistance against loads during transportation, packaging, and so on is recommended. There are two methods for measurement of shell resistance: destructive and nondestructive methods. Modeling and simulation of eggshell by computer and finite element software (FEM) is one of the nondestructive methods which was used in this study to measure eggshell resistance. ANSYS 10 software was utilized to perform finite element analysis. In destructive testing of 90 hen eggs, the average eggshell rupture force was determined to be 22.7 N at 0.144 mm displacement when applying parallel plate force. Results of the finite element analysis showed that for 0.144 mm displacement, the estimated rupture force was 21.7 N. Results of FE analysis showed that maximum stress and displacement occurred at the point of application of the force interface with the supports and at the equator. Stress value at failure point was 14.307 MPa for the first principal stress, 8.75 MPa for the second and –0.028 MPa for the third principal stress by finite element method.

Engineering properties of sunflower seed: Effect of dehulling and moisture content

AbstractThe study diagnosed engineering properties on varying moisture content of sunflower seed and kernel from 7.6 to 25% (wet basis). On increasing moisture, dimensional values increased for both seed and kernel. Bulk density, true density and porosity were found higher for kernel as compared to seed at each moisture content. On increasing the moisture content from 7.6 to 25%, true density, porosity and thousand kernel weight increased. Coefficient of static friction on plywood was found maximum for kernel at 25% moisture content, while it was minimum for seed on glass at 7.6% moisture content. The angle of repose was maximum for kernel as compared to seed. Initial cracking force, average rupture force and average rupture energy for seed and kernel decreased with an increase in the moisture content. The kernel was found to be more resistant to initial cracking than seed.

Effect of the loading rate on compressive properties of goose eggs.

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.

Characterization of Folic Acid and Poly(amidoamine) Dendrimer Interactions with Folate Binding Protein: A Force-Pulling Study.

Atomic force microscopy force-pulling experiments have been used to measure the binding forces between folic acid (FA) conjugated poly(amidoamine) (PAMAM) dendrimers and folate binding protein (FBP). The generation 5 (G5) PAMAM conjugates contained an average of 2.7, 4.7, and 7.2 FA per dendrimer. The most probable rupture force was measured to be 83, 201, and 189 pN for G5-FA2.7, G5-FA4.7, and G5-FA7.2, respectively. Folic acid blocking experiments for G5-FA7.2 reduced the frequency of successful binding events and increased the magnitude of the average rupture force to 274 pN. The force data are interpreted as arising from a network of van der Waals and electrostatic interactions that form between FBP and G5 PAMAM dendrimer, resulting in a binding strength far greater than that expected for an interaction between FA and FBP alone.

Nanoadhesion of Staphylococcus aureus onto Titanium Implant Surfaces

Adhesion of bacteria to dental implant surfaces is the critical initial step in the process of biofilm colonization; however, the specific nanoadhesive interactions occurring during the first contact between bacterial cells and biomaterial substrates remain poorly understood. In this report, we utilize single-cell force spectroscopy to characterize the dynamics of the initial interaction between living Staphylococcus aureus cells and machined titanium surfaces at the nanoscale. Values for maximum adhesion force were found to increase from 0-s (–0.27 ± 0.30 nN) to 60-s (–9.15 ± 0.78 nN) surface delays, with similar results observed for total adhesion work (7.39 ± 2.38 and 988.06 ± 117.08 aJ, respectively). Single unbinding events observed at higher surface delays were modeled according to the wormlike chain model, obtaining molecular contour-length predictions of 314.06 ± 9.27 nm. Average single-bond rupture forces of −0.95 ± 0.04 nN were observed at increased contact times. Short- and long-range force components of bacterial adhesion were obtained by Poisson analysis of single unbinding event peaks, yielding values of −0.75 ± 0.04 and −0.58 ± 0.15 nN, respectively. Addition of 2-mg/mL chlorhexidine to the buffer solution resulted in the inhibition of specific adhesive events but an increased overall adhesion force and work. These results suggest that initial attachment of S. aureus to smooth titanium is mostly mediated by short-range attractive forces observed at higher surface delays.