Increased Bending Rigidity Research Articles

Direction-dependent bending resistance of 3D printed bio-inspired composites with asymmetric 3D articulated tiles

Inspired by the protective armors in nature, composites with asymmetric 3D articulated tiles attached to a soft layer are designed and fabricated via a multi-material 3D printer. The bending resistance of the new designs are characterized via three-point bending experiments. Bending rigidity, strength, and final deflection of the designs are quantified and compared when loaded in two different in-plane and two different out-of-plane directions. It is found that in general, the designs with articulated tiles show direction-dependent bending behaviors with significantly increased bending rigidity, strength, and deflection to final failure in certain loading directions, as is attributed to the asymmetric tile articulation (asymmetric about the mid-plane of tiles) and an interesting sliding-induced auxetic effect. Analytical, numerical, and experimental analyses are conducted to unveil the underlying mechanisms.

An Ivestigation on Abrasion Resistance And Bending Rigidity of Recycled Nonwovens Including Blanket Trimmings

In this study blanket trimmings and mechanically recycled fibers were blended and softly pre-needlepunched to be used as innerlayers of conventional needle-punched nonwovens. The outer layers from three types of raw materials (polypropylene, recycled polyester and mechanically recycled fibers) and the control groups were produced by classical needle-punching at two different needle-punch densities. Abrasion resistance and bending properties of the end products were investigated considering recycled layer ratio, raw material type and needle-punching density through standard test methods. Among all types, the highest abrasion cycles and bending rigidity values were observed for the PP outer layered products. Increase in needling density increased the abrasion cycles between 10%-20% and increased bending rigidity 3%-8% among the overall. Comparing the fabrics with recycled layer of 20% to control groups, abrasion resistance was preserved between 67% -75% and bending rigidity was preserved between 86%-93% at overall.

Structural Design for Improving the Strength of Flat Wooden Pallets

The purpose of this study is to develop a new pallet structure using the inexpensive hinoki wood, which is produced in the Ehime Prefecture, having the same strength as the conventional Oregon pine wood. A new pallet structure was proposed for achieving high-strength by improving the flexural stiffness and compressive stiffness and achieving high-cost performance by using the inexpensive hinoki wood. The results obtained in this study are summarized as follows: deflection of the new type is reduced compared to the standard type, due to the increased bending rigidity of the edge board and deck board; compressive displacement of the new model decreases, as the compressive stiffness of the pallet legs increases; new mold pattern 6 made is higher in strength and rigidity than the standard mold; cost of the new type #6 is 72% of that of the standard type pallet, and cost can be reduced by 28%.

Blood bank storage of red blood cells increases RBC cytoplasmic membrane order and bending rigidity.

Blood banks around the world store blood components for several weeks ensuring its availability for transfusion medicine. Red blood cells (RBCs) are known to undergo compositional changes during storage, which may impact the cells’ function and eventually the recipients’ health. We extracted the RBC’s cytoplasmic membrane (RBCcm) to study the effect of storage on the membranes’ molecular structure and bending rigidity by a combination of X-ray diffraction (XRD), X-ray diffuse scattering (XDS) and coarse grained Molecular Dynamics (MD) simulations. Blood was stored in commercial blood bags for 2 and 5 weeks, respectively and compared to freshly drawn blood. Using mass spectrometry, we measured an increase of fatty acids together with a slight shift towards shorter tail lengths. We observe an increased fraction (6%) of liquid ordered (lo) domains in the RBCcms with storage time, and an increased lipid packing in these domains, leading to an increased membrane thickness and membrane order. The size of both, lo and liquid disordered (ld) lipid domains was found to decrease with increased storage time by up to 25%. XDS experiments reveal a storage dependent increase in the RBCcm’s bending modulus κ by a factor of 2.8, from 1.9 kBT to 5.3 kBT. MD simulations were conducted in the absence of proteins. The results show that the membrane composition has a small contribution to the increased bending rigidity and suggests additional protein-driven mechanisms.

Sclerostin antibody increases trabecular bone and bone mechanical properties by increasing osteoblast activity damaged by whole-body irradiation in mice.

Irradiation therapy causes bone deterioration and increased risk for skeletal-related events. Irradiation interferes with trabecular architecture through increased osteoclastic activity, decreased osteoblastic activity, and increased adipocyte expansion in the bone marrow (BM), which further compounds bone-related disease. Neutralizing antibodies to sclerostin (Scl-Ab) increase bone mass and strength by increasing bone formation and reducing bone resorption. We hypothesized that treatment with Scl-Ab would attenuate the adverse effects of irradiation by increasing bone volume and decreasing BM adipose tissue (BMAT), resulting in better quality bone. In this study, 12-week-old female C57BL/6J mice were exposed to 6Gy whole-body irradiation or were non-irradiated, then administered Scl-Ab (25mg/kg) or vehicle weekly for 5weeks. Femoral μCT analysis confirmed that the overall effect of IR significantly decreased trabecular bone volume/total volume (Tb.BV/TV) (2-way ANOVA, p<0.0001) with a -43.8% loss in Tb.BV/TV in the IR control group. Scl-Ab independently increased Tb.BV/TV by 3.07-fold in non-irradiated and 3.6-fold in irradiated mice (2-way ANOVA, p<0.0001). Irradiation did not affect cortical parameters, although Scl-Ab increased cortical thickness and area significantly in both irradiated and non-irradiated mice (2-way ANOVA, p<0.0001). Femoral mechanical testing confirmed Scl-Ab significantly increased bending rigidity and ultimate moment independently of irradiation (2-way ANOVA, p<0.0001). Static and dynamic histomorphometry of the femoral metaphysis revealed osteoblast vigor, not number, was significantly increased in the irradiated mice treated with Scl-Ab. Systemic alterations were assessed through serum lipidomic analysis, which showed that Scl-Ab normalized lipid profiles in the irradiated group. This data supports the theory of sclerostin as a novel contributor to the regulation of osteoblast activity after irradiation. Overall, our data support the hypothesis that Scl-Ab ameliorates the deleterious effects of whole-body irradiation on bone and adipose tissue in a mouse model. Our findings suggest that future research into localized and systemic therapies after irradiation exposure is warranted.

Ultrasonically Assisted In Situ Deposition of ZnO Nano Particles on Cotton Fabrics for Multifunctional Textiles

Zinc oxide (ZnO) nano particles have great importance in textile industry, because of remarkable efficiency and multiple applications such as antibacterial, UV protection, self-cleaning etc. The aim of this research work was in situ growth of ZnO nano particles on 100 % cotton fabrics with the help of ultrasonic acoustic waves. Zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and sodium hydroxide (NaOH) were used as precursors for ZnO growth. Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) were done to examine the surface morphology and characteristics of deposited nano particles. Furthermore the functional properties i.e. antibacterial, UPF rating, self cleaning, air permeability and bending rigidity of the developed samples were evaluated. The results regarding SEM, EDS, XRD and FTIR confirmed the deposition of ZnO nanoparticles on cotton fabric with pure hexagonal wurtzite crystalline structure. The developed samples showed excellent results for antibacterial, UPF rating and self cleaning with increased bending rigidity and slightly decreased in air permeability.

Analysis of ride comfort of high-speed train based on a train-seat-human model in the vertical direction

A rigid-flexible coupled train-seat-human model was developed for studying ride comfort of rail vehicles. The weighted acceleration r.m.s. value at the seat pan was used for assessing ride comfort. The contribution of different modes of the carbody to ride comfort was defined from the perspective of power spectral density. The role of first bending mode was more important than other bending modes when bogie and seat positions are far from the nodes of first bending mode. Under this situation, the bogie spacing filter effect of first bending mode can be adopted to predict peaks and troughs of the equivalent acceleration on the floor or human-seat interface varying with speed or first bending frequency. The incorporation of human-seat system was necessary in order to accurately evaluate ride comfort. The ride comfort exhibited a global trend of improvement with increased bending rigidity or reduced speed. Increasing the damping ratio of bending modes improved ride comfort effectively. Increasing stiffness or decreasing damping of human-seat vertical contact on the seat pan worsened ride comfort. Equivalent accelerations at symmetrical seat positions showed analogous tendency as the speed. Ride comfort was worst at two ends whatever the speed was, followed by carbody centre at high speed.

Elasticity and phase behaviour of biomimetic membrane systems containing tetraether archaeal lipids

Archaeal single-cell microorganisms are characterised by particularly strong resistance to harsh environments at extreme temperature ranges, pH values, high pressure and salinity. The recognition of molecules rendering the archaeal membranes stable in such conditions represents an important step towards understanding the molecular mechanisms, which underlie the cellular survival, in order to effectively exploit them in biomedicine and bionanotechnology. Here we report on the bending elasticity and phase behaviour of model lipid membranes containing tetraether archaeal lipids. The bending elasticity modulus of membranes composed of palmitoyl-oleoyl phosphatidylcholine and glycerol dialkyl glycerol tetraether extract from the archaeon Thermoplasma acidophilum’s plasma membrane is measured by analysis of the thermal shape fluctuations of nearly spherical giant unilamellar vesicles (tens of micrometers in size). The bending rigidity is reported to non-monotonically depend on the archaeal lipids’ concentration in the bilayer. At 50 wt% of tetraether lipids in the membrane we measure around 20% decrease of the bending modulus compared to the studied single-component phosphocholine bilayer. The membrane resistance to bending increases at archaeal lipids’ content higher than 70 wt%. These findings support the hypothesis about a probable looping conformation at very low amounts of bipolar lipids in the membrane and prevailing spanning tetraether molecules at higher concentrations. Fluorescence microscopy reveals structural phase coexistence at low temperatures (6 °C) for 75 wt% of bolalipids in the bilayer. Laurdan spectroscopy measurements of large unilamellar vesicles (hundreds of nanometers in size) provide evidences for increased lipid ordering at the glycerol level induced by the presence of up to 90 wt% of bolalipid in the bilayer. At this archaeal lipid content we measure increased bending rigidity of the membrane. The fatty acyl chain mobility probed by DPH fluorescence spectroscopy is significantly reduced in the presence of bolalipids. The lipid ordering decreases with increasing the temperature to an extent depending on the bolalipid content in the membrane. The presence of bipolar lipids in the bilayer affects the lipid packing more strongly at the glycerol level compared to the hydrophobic core of the membrane. By elucidating the effect of tetraether lipids on the structural and mechanical properties of the bilayer, the reported results are expected to help in advancing on liposome-based pharmaceuticals and biomedical applications as well as for developments in sensorics and nanotechnology.

Combined bending-tension/compression deformation of micro-bars accounting for strain-driven long-range interactions

The paper aims to investigate combined bending-tension/compression deformation of a micro-bar. The strain-driven nonlocal differential model which involves information about long-range interactions between atoms is used to develop the mechanical model and theoretical formulations. Subsequently, effects of internal long-range scale parameter, length of micro-bar, external loads and bending rigidity on combined deformation are shown and discussed. In particular, the upper bound of internal longrange scale parameter and the buckling load are achieved during bending-compression analyses. It is demonstrated that the existence of internal scale parameter or axial tensile load decreases combined deformation. The deflection at the midpoint reduces with increasing bending rigidity, while it rises with increasing length of the microbar. Additionally, an effect of the acting position of transverse load on combined deformation is discussed and deflection at the symmetry point of transverse acting position is achieved. When the long-range interaction is taken into consideration, the equivalent stiffness of the micro-bar subjected to combined bending-tension is stiffer than that predicted by classical mechanics, and it validates the existing nonlocal hardening model. The combined bending-compression of the micro-bar reveals that the deflection may increase or decrease with an increase in the long-range scale or structural length, which verifies both the nonlocal softening and hardening models.

Morphological stability of an elastic tumor–host interface

Abstract The ability of tumors to metastasize is preceded by morphological instabilities such as chains or fingers that invade the host environment. Therefore, parameters that control the morphology of the tumor may also contribute to its invasive ability. Previous analyses on morphological changes were performed using surface energy of the tumor–host interface. In an effort to understand the role the interface stiffness plays on tumor evolution, here we model the tumor–host interface as an elastic membrane governed by the Helfrich bending energy. Using an energy variation approach, we derive a modified Laplace–Young condition for the stress jump across the interface in the Stokes equation. We then perform a linear stability analysis and investigate how physical parameters such as viscosity, bending rigidity, and apoptosis affect the morphological instability. Results show that increased bending rigidity versus mitosis rate contributes to a more stable morphological tumor behavior. On the other hand, increasing tumor viscosity or apoptosis may lead to invasive fingering morphologies. Comparison with experimental data on glioblastoma spheroids shows good agreement especially for tumors with high adhesion and low proliferation.

Dynamics of driven translocation of semiflexible polymers.

We study translocation of semiflexible polymers driven by force f_{d} inside a nanometer-scale pore using our three-dimensional Langevin dynamics model. We show that the translocation time τ increases with increasing bending rigidity κ. Similarly, the exponent β for the scaling of τ with polymer length N,τ∼N^{β}, increases with increasing κ as well as with increasing f_{d}. By comparing waiting times between semiflexible and fully flexible polymers we show that for realistic f_{d} translocation dynamics is to a large extent, but not completely, determined by the polymer's elastic length measured in number of Kuhn segments N_{Kuhn}. Unlike in driven translocation of flexible polymers, friction related to the polymer segment on the trans side has a considerable effect on the resulting dynamics. This friction is intermittently reduced by buckling of the polymer segment in the vicinity of the pore opening on the trans side. We show that in the experimentally relevant regime where viscosity is higher than in computer simulation models, the probability for this buckling increases with increasing f_{d}, giving rise to a larger contribution to the trans side friction at small f_{d}. Similarly to flexible polymers, we find significant center-of-mass diffusion of the cis side polymer segment which speeds up translocation. This effect is larger for smaller f_{d}. However, this speedup is smaller than the slowing down due to the trans side friction. At large enough N_{Kuhn}, the roles can be seen to be reversed, and the dynamics of flexible polymers can be reached. However, for example, polymers used in translocation experiments of DNA are elastically so short that the finite-length dynamics outlined here applies.

A study on the thermal and physical properties of nylon fabric treated by metal sputtering (Al, Cu, Ni)

This research was conducted for an in-depth analysis of changes in thermal properties and in comfortability as well as physical properties before and after sputtering on fabrics. It was found that the sputtering treatment could give significant effects on the heat transfer of nylon without much loss in its shear property, water vapor transmission, and bending property, which suggested that sputtering treatment with metals on the surface of fabric helped reduce the surface temperature by releasing body heat. When the metal coating layers of the sputtered fabrics were pointed toward the cold air (15℃), the surface temperature was lowered drastically from 35℃ to 22.07℃ by depending on metals. Also, the computed surface temperatures based on the heat transfer theory displayed a high level of consistency with the measured values. The conductive fabric, which was used for comparison, showed an increased bending rigidity after sputtering, making the fabric stiffer. In the future, a metal-sputtered fabric is expected to be used as a special material by utilizing its surface temperature-controlling function in the high-functional clothing material field.

Increased bending rigidity of wool fabric imparted by hybrid organic-inorganic sol–gel coatings

Hybrid organic–inorganic coatings prepared by the sol–gel method can impart desirable properties to textiles, but may adversely affect properties such as bending rigidity. This study investigated the causes of increased bending rigidity. Woven wool fabric was pad coated with formulations of methyltriethoxysilane (MTES) and Hercosett polyamide resin, examined by scanning electron microscopy, and the bending rigidities were determined. MTES coatings of up to 3.0% solids on mass of wool did not impart unacceptable bending rigidity. The coatings were not uniform on the fiber surfaces, and the increases in fabric bending rigidity could be partially attributed to inter-fiber bonding. In addition, the coatings “pinned” the edges of the cuticle scales, making individual fibers harder to bend. These effects are only weakly dependent on the Young's moduli of the coating materials.

Stretching instability of intrinsically curved semiflexible biopolymers: A lattice model approach**Project supported by the Funds from MOST and “National" Center for Theoretical Physics (NCTS).

We apply a Monte Carlo simulation method to lattice systems to study the effect of an intrinsic curvature on the mechanical property of a semiflexible biopolymer. We find that when the intrinsic curvature is sufficiently large, the extension of a semiflexible biopolymer can undergo a first-order transition at finite temperature. The critical force increases with increasing intrinsic curvature. However, the relationship between the critical force and the bending rigidity is structure-dependent. In a triangle lattice system, when the intrinsic curvature is smaller than a critical value, the critical force increases with the increasing bending rigidity first, and then decreases with the increasing bending rigidity. In a square lattice system, however, the critical force always decreases with the increasing bending rigidity. In contrast, when the intrinsic curvature is greater than the critical value, the larger bending rigidity always results in a larger critical force in both lattice systems.

Modulation of Membrane Rigidity by Human and Yeast Homologs of the Vesicle Trafficking Protein Sar1

Understanding how proteins manipulate the shape and form of membranes is crucial to intracellular cargo trafficking, yet the mechanical activities of trafficking proteins remain poorly understood. using an optical-trap based assay involving dynamic membrane deformations and fluorescence recovery after photobleaching (FRAP) to measure protein mobility on in vitro endoplasmic reticulum mimic membranes, we examined the behavior of the two human paralogs of Sar1, a key component of the COPII family of vesicle coat proteins. Like their yeast (S. cerevisiae) counterpart, the human Sar1 proteins can lower the mechanical rigidity of the membranes to which they bind. Unlike the yeast Sar1, the rigidity is not a monotonically decreasing function of concentration. At high concentrations, we find increased bending rigidity and decreased protein mobility. These features imply a model in which protein clustering influences membrane mechanical properties. Additionally we are investigating other membrane-associated proteins known to cluster in order to further our understanding of the model and the effects these proteins have on rigidity and mobility.

Modulation of membrane rigidity by the human vesicle trafficking proteins Sar1A and Sar1B

The sculpting of membranes into highly curved vesicles is central to intracellular cargo trafficking, yet the mechanical activities of trafficking proteins remain poorly understood. Using an optical trap based assay that measures in vitro membrane response to imposed deformations, we examined the behavior of the two human paralogs of Sar1, a key component of the COPII family of vesicle coat proteins. Like their yeast counterpart, the human Sar1 proteins can lower the mechanical rigidity of the membranes to which they bind. Unlike the yeast Sar1, the rigidity is not a monotonically decreasing function of concentration. At high concentrations, we find increased bending rigidity and decreased protein mobility. These features imply a model in which protein clustering governs membrane mechanical properties.

Influence of Particle Shape on Bending Rigidity of Colloidal Monolayer Membranes and Particle Deposition during Droplet Evaporation in Confined Geometries

We investigate the influence of particle shape on the bending rigidity of colloidal monolayer membranes (CMMs) and on evaporative processes associated with these membranes. Aqueous suspensions of colloidal particles are confined between glass plates and allowed to evaporate. Confinement creates ribbonlike air-water interfaces and facilitates measurement and characterization of CMM geometry during drying. Interestingly, interfacial buckling events occur during evaporation. Extension of the description of buckled elastic membranes to our quasi-2D geometry enables the determination of the ratio of CMM bending rigidity to its Young's modulus. Bending rigidity increases with increasing particle anisotropy, and particle deposition during evaporation is strongly affected by membrane elastic properties. During drying, spheres are deposited heterogeneously, but ellipsoids are not. Apparently, increased bending rigidity reduces contact line bending and pinning and induces uniform deposition of ellipsoids. Surprisingly, suspensions of spheres doped with a small number of ellipsoids are also deposited uniformly.

Thermodynamics and bending energetics of toruslike micelles

The self-assembly of surfactants forming toruslike or toroidal micelles has been investigated from a theoretical point of view, in particular the structural behaviour and stability of tori in terms of the three bending elasticity constants spontaneous curvature ( H 0 ), bending rigidity ( k c ) and saddle-splay constant ( k ¯ c ). It is demonstrated that the size of toruslike micelles increases with an increasing bending rigidity, but is independent of both spontaneous curvature and saddle-splay constant. Similar to conventional micelles, toruslike micelles are found to be stable over bilayers as the spontaneous curvature times the surfactant layer thickness exceeds 1/4. Moreover, it is shown that toruslike micelles, in general, are favoured at the expense of long spherocylindrical micelles as a result of elimination of the unfavourable end-caps. However, conventional micelles that are able to grow with respect to both width and length (tablets) may be stable over tori as well as spheres in much wider regimes of different bending elasticity constants. As a result, toruslike micelles are predicted to be stable over conventional micelles, including rods, at large values of the effective bending constant k eff ≡ 2 k c + k ¯ c , i.e. in the same region where infinite cylinders are expected to be observed. This result is consistent with the fact that toruslike micelles have usually been observed to coexist with large networks of branched cylinders.

On the Formation of Discoidal versus Threadlike Micelles in Dilute Aqueous Surfactant/Lipid Systems

In a recent study, we showed that the surfactant 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000 (DSPE-PEG2000) induced mixed micelles of either threadlike or discoidal shape when mixed with different types of lipids. In this study, we have exchanged the PEG-lipid for the more conventional surfactants octaethylene glycol monododecyl ether (C12E8), hexadecyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Cryo-TEM investigations show that also these surfactants are able to induce the formation of long-lived discoidal micelles. Generally, the preference for either discoidal or threadlike micelles can be tuned by the choice of lipids and environmental conditions in much the same way as observed for the lipid/PEG-lipid system. Our investigation showed, furthermore, that the choice of surfactant may influence the type of mixed micelles formed. It is argued that the formation of discoidal rather than threadlike micelles may be rationalized as an effect of increasing bending rigidity. Our detailed theoretical model calculations show that the bending rigidity becomes significantly raised for aggregates formed by an ionic rather than a nonionic surfactant.

Rigidity and spontaneous curvature of lipidic monolayers in the presence of trehalose: a measurement in the DOPE inverted hexagonal phase

Trehalose is a sugar which plays an important protectant role in organisms against damage due to dehydration. To explore the basic molecular mechanism which governs the protective function exerted on lipid membranes, X-ray diffraction and osmotic stress experiments have been performed on L: -alpha-dioleoyl-phosphatidyl-ethanolamine (DOPE) in trehalose solutions of different concentrations. In pure water, DOPE forms an inverted hexagonal (H(II)) phase; in sugar solutions, a strong dehydration, which induces a large reduction of the H(II) lattice parameter, has been detected, but nevertheless no phase transitions occur. Structural data, directly obtained from reconstructed electron density maps, show that the bending of the lipid monolayer induced by the sugar is coupled to changes in the DOPE molecular shape. By osmotic stress, the work required to dehydrate the monolayer has been obtained and the overall free energy described as a function of trehalose concentration. Three results should be stressed: (1) dehydration experiments performed in the presence of sugar demonstrate that the protective effect cannot be purely osmotic; (2) the pivotal surface, that location on the molecule whose area is invariant upon isothermal bending, has been analyzed by two different methods: the approach by Rand and co-workers and the approach by Templer and co-workers; in both cases its presence along the DOPE molecule has been revealed and its position estimated; (3) the spontaneous radius of curvature and the rigidity constant of the lipid monolayer, measured at the pivotal plane, changes from 3.06 nm (in pure water) to 2.82 nm (in 1.4 M trehalose), and from 0.55 x 10(-19) to 0.74 x 10(-19) J, respectively. We assume that these modifications are related to direct interactions between trehalose and DOPE that alter the interface geometry, reducing the repulsion between the polar heads. However, the increased bending rigidity also accounts for the changes of the property of the aqueous compartment, reflecting the rigidity and stiffness of the sugar matrix around and inside the lipid phase.