Insights into elastic properties of coarse-grained DNA models: q-stiffness of cgDNA vs cgDNA.

Coarse-grained models have emerged as valuable tools to simulate long DNA molecules while maintaining computational efficiency. These models aim at preserving interactions among coarse-grained variables in a manner that mirrors the underlying atomistic description. We explore here a method for testing coarse-grained vs all-atom models using stiffness matrices in Fourier space (q-stiffnesses), which are particularly suited to probe DNA elasticity at different length scales. We focus on a class of coarse-grained rigid base DNA models known as cgDNA and its most recent version, cgDNA+. Our analysis shows that while cgDNA+ closely follows the q-stiffnesses of the all-atom model, the original cgDNA shows some deviations for twist and bending variables, which are rather strong in the q → 0 (long length scale) limit. The consequence is that while both cgDNA and cgDNA+ give a suitable description of local elastic behavior, the former misses some effects that manifest themselves at longer length scales. In particular, cgDNA performs poorly on twist stiffness, with a value much lower than expected for long DNA molecules. Conversely, the all-atom and cgDNA+ twist are strongly length scale dependent: DNA is torsionally soft at a few base pair distances but becomes more rigid at distances of a few dozen base pairs. Our analysis shows that the bending persistence length in all-atom and cgDNA+ is somewhat overestimated.

Analyzing the changing trend of corneal biomechanical properties under different influencing factors in T2DM patients.

To analyze the changing trend of CH and CRF values under different influencing factors in T2DM patients. A total of 650 patients with T2DM were included. We discovered that the course of T2DM, smoking history, BMI, and FBG, DR, HbA1c, TC, TG, and LDL-C levels were common risk factors for T2DM, while HDL-C levels were a protective factor. Analyzing the CH and CRF values according to the course of diabetes, we discovered that as T2DM continued to persist, the values of CH and CRF gradually decreased. Moreover, with the increase in FBG levels and the accumulation of HbA1c, the values of CH and CRF gradually decreased. In addition, in patients with HbA1c (%) > 12, the values of CH and CRF decreased the most, falling by 1.85 ± 0.33 mmHg and 1.28 ± 0.69 mmHg, respectively. Compared with the non-DR group, the CH and CRF values gradually decreased in the mild-NPDR, moderate-NPDR, severe-NPDR and PDR groups, with the lowest CH and CRF values in the PDR group. In patients with T2DM, early measurement of corneal biomechanical properties to evaluate the change trend of CH and CRF values in different situations will help to identify and prevent diabetic keratopathy in a timely manner.

Tobacco price elasticity by socioeconomic characteristics in Ecuador.

Smoking is a worldwide epidemic and increased prices are one of the most cost-effective measures to reduce tobacco consumption. This article aims to estimate the price and income elasticity of cigarettes for different population groups in Ecuador. The National Survey of Urban and Rural Household Income and Expenditures (ENIGHUR) 2011-2012 was used, which has information on household cigarette consumption and its sociodemographic characteristics. Deaton's Almost Ideal Demand System, which decouples the effect of quality on the price of the good, was applied. The elasticities were calculated for several groups: urban/rural, income levels (tertiles), education level, sex and age ranges of the household head, and frequency of cigarette purchases in households. The estimated price elasticity nationwide is -0.89 and the income elasticity is 0.41, both statistically significant. Households headed by women (-2.22) are more sensitive to an increase in cigarette prices than those headed by men (-0.65) and households headed by people between 20 and 40 years of age (-2.32) have a higher price elasticity compared to country-level estimations. Differences within other groups are not statistically significant.

Effect of table tennis balls with different materials and structures on the hardness and elasticity.

The new material introduced by the ITTF in 2014 for table tennis balls has attracted significant attention from players and coaches. Changes in both material selection and production procedures are likely to have affected the static performance of the ball. However, the raw data regarding the elasticity and hardness of these new material balls, encompassing various brands and structures, often lacks practical information crucial for players' rapid adaptation and daily training. The static properties tested in this study were provided by the ITTF, covering both hardness and elasticity. Based on computed variables, this study revealed that the hardness of seam balls at the equator was not consistently higher than that at the pole. Additionally, the study confirmed that the hardness and bounce height of new material balls exceeded those of celluloid. Furthermore, correlation analysis was conducted to examine the relationship between these two properties, revealing a significant correlation between the hardness of seamless balls and their elasticity. This study provides an analysis of the static performance of various types of new material balls, aiding players and coaches in better understanding official event balls and offering a theoretical foundation for the formulation of diverse training and game strategies.

Own price elasticities of the demand for sugar-sweetened beverages in Bangladesh.

BACKGROUND: Consumption of sugar-sweetened beverages (SSB) is a major global public health problem. Increasing the price of SSBs through taxation is an effective tool to reduce SSB consumption. Price-elasticity estimates are useful in measuring the effect of taxation on consumption. We estimated the own price elasticities of demand for SSBs in Bangladesh, which will inform how SSB taxes could affect behaviour. METHODS: We used Household Income and Expenditure Survey (HIES) 2016 data, which is a nationally representative dataset at the household level across the country and is conducted using stratified random sampling method. Deaton's method was used to estimate the price elasticities for SSBs in Bangladesh. RESULTS: We found that the own price elasticity for SSBs varied between - 0.53% to -1.17% by types of SSBs in Bangladesh. The price elasticity for soft drinks was - 1.17, indicating that if the price of soft drinks increases by 10% via taxes, the quantity consumed of these beverages would reduce by 11.7%. CONCLUSION: This is the first study that estimates the own price elasticities of demand for SSBs in Bangladesh. Our results suggest to raise SSB prices through increased taxation in order to reduce SSB consumption and ensure public health gains in Bangladesh.

Superelastic carbon aerogels with anisotropic and hierarchically-enhanced cellular structure for wearable piezoresistive sensors.

Elastic carbon aerogels have promising applications in the field of wearable sensors. Herein, a new strategy for preparing carbon aerogels with excellent compressive strength and strain, shape recovery, and fatigue resistance was proposed based on the structure design and carbonization optimization of nanocellulose-based precursor aerogels. By the combination of directional freezing and zinc ion cross-linking, bacterial cellulose (BC)/alginate (SA) composite aerogels with high elasticity and compressive strength were first achieved. The existance of zinc ions also significantly improved the carbon retention rate and inhibited structural shrinkage, thus making the carbon aerogels retain ultra-high elasticity and fatigue resistance after compression. Moreover, the carbon aerogel possessed excellent piezoresistive pressure sensing performance with a wide detection range of 0-7.8 kPa, high sensitivity of 11.04 kpa-1, low detection limit (2 % strain), fast response (112 ms), and good durability (over 1,000 cycles). Based on these excellent properties, the carbon aerogel pressure sensors were further successfully used for human motion monitoring, from joint motion to and speech recognition.

Label-free Brillouin endo-microscopy for the quantitative 3D imaging of sub-micrometre biology.

This report presents an optical fibre-based endo-microscopic imaging tool that simultaneously measures the topographic profile and 3D viscoelastic properties of biological specimens through the phenomenon of time-resolved Brillouin scattering. This uses the intrinsic viscoelasticity of the specimen as a contrast mechanism without fluorescent tags or photoacoustic contrast mechanisms. We demonstrate 2 µm lateral resolution and 320 nm axial resolution for the 3D imaging of biological cells and Caenorhabditis elegans larvae. This has enabled the first ever 3D stiffness imaging and characterisation of the C. elegans larva cuticle in-situ. A label-free, subcellular resolution, and endoscopic compatible technique that reveals structural biologically-relevant material properties of tissue could pave the way toward in-vivo elasticity-based diagnostics down to the single cell level.

Measuring mechanical cues for modeling the stromal matrix in 3D cell cultures.

A breast-cancer tumor develops within a stroma, a tissue where a complex extracellular matrix surrounds cells, mediating the cancer progression through biomechanical and -chemical cues. Current materials partially mimic the stromal matrix in 3D cell cultures but methods for measuring the mechanical properties of the matrix at cell-relevant-length scales and stromal-stiffness levels are lacking. Here, to address this gap, we developed a characterization approach that employs probe-based microrheometry and Bayesian modeling to quantify length-scale-dependent mechanics and mechanical heterogeneity as in the stromal matrix. We examined the interpenetrating network (IPN) composed of alginate scaffolds (for adjusting mechanics) and type-1 collagen (a stromal-matrix constituent). We analyzed viscoelasticity: absolute-shear moduli (stiffness/elasticity) and phase angles (viscous and elastic characteristics). We determined the relationship between microrheometry and rheometry information. Microrheometry reveals lower stiffness at cell-relevant scales, compared to macroscale rheometry, with dependency on the length scale (10 to 100 µm). These data show increasing IPN stiffness with crosslinking until saturation (≃15 mM of Ca2+). Furthermore, we report that IPN stiffness can be adjusted by modulating collagen concentration and interconnectivity (by polymerization temperature). The IPNs are heterogeneous structurally (in SEM) and mechanically. Interestingly, increased alginate crosslinking changes IPN heterogeneity in stiffness but not in phase angle, until the saturation. In contrast, such changes are undetectable in alginate scaffolds. Our nonlinear viscoelasticity analysis at tumor-cell-exerted strains shows that only the softer IPNs stiffen with strain, like the stromal-collagen constituent. In summary, our approach can quantify the stromal-matrix-related viscoelasticity and is likely applicable to other materials in 3D culture.

Size effect in polymeric lattice materials with size-dependent Poisson's ratio caused by Cosserat elasticity.

Polymeric lattice materials with micro/nano-structures are attractive for applications in a wide range of bioengineering systems. Resent experimental results show that elastic constitutive law of polymer materials is in line with the Cosserat elasticity. In this work, a Cosserat continuum spectral element method is employed to explore the size-dependent mechanical performance of polymer polymeric lattice with horseshoe microstructures, efficiently. The mechanical performance predicted by the proposed method agrees very well with the experiment data. Our results demonstrate that size effects are significant in polymeric lattice materials. The size-dependent negative Poisson's ratio is found in the polymeric lattice materials with the same topological structure due to the size effect caused by the Cosserat elasticity of the polymer materials. It could be implied that it is possible to continuously adjust the negative Poisson's ratio of the polymeric lattice material over a wide range by only changing its microstructural size.

Evaluating Novel SP-B and SP-C Synthetic Analogues for Pulmonary Surfactant Efficacy.

Pulmonary surfactants, a complex assembly of phospholipids and surfactant proteins such as SP-B and SP-C, are critical for maintaining respiratory system functionality by lowering surface tension (ST) and preventing alveolar collapse. Our study introduced five synthetic SP-B peptides and one SP-C peptide, leading to the synthesis of CHAsurf candidates (CHAsurf-1 to CHAsurf-5) for evaluation. We utilized a modified Wilhelmy balance test to assess the surface tension properties of the surfactants, measuring spreading rate, surface adsorption, and ST-area diagrams to comprehensively evaluate their performance. Animal experiments were performed on New Zealand white rabbits to test the efficacy of CHAsurf-4B, a variant chosen for its economic viability and promising ST reduction properties, comparable to Curosurf®. The study confirmed that higher doses of SP-B in CHAsurf-4 are associated with improved ST reduction. However, due to cost constraints, CHAsurf-4B was selected for in vivo assessment. The animal model revealed that CHAsurf-4B could restore alveolar structure and improve lung elasticity, akin to Curosurf®. Our research highlights the significance of cysteine residues and disulfide bonds in the structural integrity and function of synthetic SP-B analogues, offering a foundation for future surfactant therapy in respiratory disorders. This study's findings support the potential of CHAsurf-4B as a therapeutic agent, meriting further investigation to solidify its role in clinical applications.

Evaluation of anorectal function using real-time tissue elastography before and after preoperative chemoradiotherapy.

PURPOSE: This study aimed to clarify the relationship between changes in elasticity and anorectal function before and after chemoradiotherapy. METHODS: This is a single-center prospective cohort study (Department of Surgical Oncology, The University of Tokyo). We established a technique to quantify internal anal sphincter hardness as elasticity using transanal ultrasonography with real-time tissue elastography. Twenty-seven patients with post-chemoradiotherapy rectal cancer during 2019-2022 were included. Real-time tissue elastography with transanal ultrasonography was performed before and after chemoradiotherapy to measure internal anal sphincter hardness as "elasticity" (hardest (0) to softest (255); decreased elasticity indicated sclerotic changes). The relationship between the increase or decrease in elasticity pre- and post-chemoradiotherapy and the maximum resting pressure, maximum squeeze pressure, and Wexner score were the outcome measures. RESULTS: A decrease in elasticity was observed in 16/27 (59.3%) patients after chemoradiotherapy. Patients with and without elasticity decrease after chemoradiotherapy comprised the internal anal sphincter sclerosis and non-sclerosis groups, respectively. The maximum resting pressure post-chemoradiotherapy was significantly high in the internal anal sphincter sclerosis group (63.0 mmHg vs. 47.0 mmHg), and a majority had a worsening Wexner score (60.0% vs. 18.2%) compared with that of the non-sclerosis group. Decreasing elasticity (internal anal sphincter sclerosis) correlated with a higher maximum resting pressure (r = 0.36); no correlation was observed between the degree of elasticity change and maximum squeeze pressure. CONCLUSION: Internal anal sphincter sclerosis due to chemoradiotherapy may correlate to anorectal dysfunction.

Continuous Softening as a State of Hyperelasticity: Examples of Application to the Softening Behavior of the Brain Tissue.

The continuous softening behavior of the brain tissue, i.e., the softening in the primary loading path with an increase in deformation, is modeled in this work as a state of hyperelasticity up to the onset of failure. That is, the softening behavior is captured via a core hyperelastic model without the addition of damage variables and/or functions. Examples of the application of the model will be provided to extant datasets of uniaxial tension and simple shear deformations, demonstrating the capability of the model to capture the whole-range deformation of the brain tissue specimens, including their softening behavior. Quantitative and qualitative comparisons with other models within the brain biomechanics literature will also be presented, showing the clear advantages of the current approach. The application of the model is then extended to capturing the rate-dependent softening behavior of the tissue by allowing the parameters of the core hyperelastic model to evolve, i.e., vary, with the deformation rate. It is shown that the model captures the rate-dependent and softening behaviors of the specimens favorably and also predicts the behavior at other rates. These results offer a clear set of advantages in favor of the considered modeling approach here for capturing the quasi-static and rate-dependent mechanical properties of the brain tissue, including its softening behavior, over the existing models in the literature, which at best may purport to capture only a reduced set of the foregoing behaviors, and with ill-posed effects.

Correlation analysis between texture features and elasticity of skin hyperspectral images in the near-infrared band.

BACKGROUND/PURPOSE: Skin elasticity was used to evaluate healthy and diseased skin. Correlation analysis between image texture characteristics and skin elasticity was performed to study the feasibility of assessing skin elasticity using a non-contact method. MATERIALS AND METHODS: Skin images in the near-infrared band were acquired using a hyperspectral camera, and skin elasticity was obtained using a skin elastimeter. Texture features of the mean, standard deviation, entropy, contrast, correlation, homogeneity, and energy were extracted from the acquired skin images, and a correlation analysis with skin elasticity was performed. RESULTS: The texture features, and skin elasticity of skin images in the near-infrared band had the highest correlation on the side of eye and under of arm, and the mean and correlation were features of texture suitable for distinguishing skin elasticity according to the body part. CONCLUSION: In this study, we performed elasticity and correlation analyses for various body parts using the texture characteristics of skin hyperspectral images in the near-infrared band, confirming a significant correlation in some body parts. It is expected that this will be used as a cornerstone of skin elasticity evaluation research using non-contact methods.

Intrinsic Lipid Curvature and Bilayer Elasticity as Regulators of Channel Function: A Comparative Single-Molecule Study.

Perturbations in bilayer material properties (thickness, lipid intrinsic curvature and elastic moduli) modulate the free energy difference between different membrane protein conformations, thereby leading to changes in the conformational preferences of bilayer-spanning proteins. To further explore the relative importance of curvature and elasticity in determining the changes in bilayer properties that underlie the modulation of channel function, we investigated how the micelle-forming amphiphiles Triton X-100, reduced Triton X-100 and the HII lipid phase promoter capsaicin modulate the function of alamethicin and gramicidin channels. Whether the amphiphile-induced changes in intrinsic curvature were negative or positive, amphiphile addition increased gramicidin channel appearance rates and lifetimes and stabilized the higher conductance states in alamethicin channels. When the intrinsic curvature was modulated by altering phospholipid head group interactions, however, maneuvers that promote a negative-going curvature stabilized the higher conductance states in alamethicin channels but destabilized gramicidin channels. Using gramicidin channels of different lengths to probe for changes in bilayer elasticity, we found that amphiphile adsorption increases bilayer elasticity, whereas altering head group interactions does not. We draw the following conclusions: first, confirming previous studies, both alamethicin and gramicidin channels are modulated by changes in lipid bilayer material properties, the changes occurring in parallel yet differing dependent on the property that is being changed; second, isolated, negative-going changes in curvature stabilize the higher current levels in alamethicin channels and destabilize gramicidin channels; third, increases in bilayer elasticity stabilize the higher current levels in alamethicin channels and stabilize gramicidin channels; and fourth, the energetic consequences of changes in elasticity tend to dominate over changes in curvature.

DFT-based finite element analysis of compressive response in armchair phosphorene nanotubes.

In this paper, the finite element method is utilized to evaluate the behavior of the armchair phosphorene nanotubes under the compressive loading. The energy equations of the molecular and structural mechanics are used to obtain the elemental properties. The critical compressive forces of various armchair phosphorene nanotubes are computed with clamped-clamped and clamped-free boundary conditions. Results show that the stability of armchair phosphorene nanotubes increases with increasing nanotube aspect ratio, particularly under clamped-clamped boundary conditions. Finally, the buckling mode shapes of armchair phosphorene nanotubes under different boundary conditions are compared. Our work offers valuable insights into how these nanotubes respond to mechanical stress, helps determine elemental properties, and investigates the effects of nanotube geometry and different boundary conditions on their stability. This knowledge has broad applications in fields like nanotechnology, materials science, and nanomechanics, advancing the understanding of nanoscale materials and their potential for various practical uses.

Magnetic tweezers characterization of the entropic elasticity of intrinsically disordered proteins and peptoids.

Understanding the conformational behavior of biopolymers is essential to unlocking knowledge of their biophysical mechanisms and functional roles. Single-molecule force spectroscopy can provide a unique perspective on this by exploiting entropic elasticity to uncover key biopolymer structural parameters. A particularly powerful approach involves the use of magnetic tweezers, which can easily generate lower stretching forces (0.1-20 pN). For forces at the low end of this range, the elastic response of biopolymers is sensitive to excluded volume effects, and they can be described by Pincus blob elasticity model that allow robust extraction of the Flory polymer scaling exponent. Here, we detail protocols for the use of magnetic tweezers for force-extension measurements of intrinsically disordered proteins and peptoids. We also discuss procedures for fitting low-force elastic curves to the predictions of polymer physics models to extract key conformational parameters.

Tunable structure and linear viscoelastic properties of poly(glycerol adipate urethane)-based elastomeric composites for tissue regeneration.

Elastomeric biocomposites based on poly(glycerol adipate urethane) and hydroxyapatite were fabricated for tissue regeneration. The poly(glycerol adipate urethane) (PGAU) elastomeric composite matrices were obtained by chemical crosslinking of the poly(glycerol adipate) prepolymer (pPGA) with diisocyanate derivative of L-lysine. Two series of composites varying in the amount of L-lysine diisocyanate ethyl ester (LDI) used as a crosslinking agent were manufactured. As a ceramic filler both unmodified and L-lysine surface-modified hydroxyapatite (HAP) particles were used. The novelty of our research consists in the manufactured elastomeric materials and characterization of their linear viscoelastic (LVE) properties. The LVE properties of the composites were investigated by means of dynamic thermomechanical analysis. Frequency sweep and amplitude sweep measurements were performed in shear mode. The influence of the crosslinking agent (LDI) amount, HAP content and surface modification of HAP on the LVE properties of the composites was determined based on the analysis of the master curves of storage (G') and loss (G″) moduli and of tanδ of the composites. Depending on the amount of LDI, HAP and surface modification, the materials differ in the values of rubber elasticity plateau modulus (G0) and G' and G″ determined at selected shear frequencies and at the glassy state. G0 ranges from 278 kPa to 3.98 MPa, G' in the glassy state is within the range of 219 MPa-459 MPa. The G0 values of the PGAU-based composites are within the stiffness range of soft tissue. In view of the choice of HAP as the ceramic component and the G0 values, elastomeric composites have the potential to be used as filling materials in small bone defects (due to their mechanical similarity to osteoid) as well as materials for cartilage tissue regeneration.

Anisotropic plates with architected tendon network.

We synthesize geometrically tailorable anisotropic plates by combining button shaped fish-scale like features on soft substrates, then lacing them with high-stiffness strings. This creates a new type of biomimetic architectured structure with multiple broken symmetries. First, the tendons and substrate together break the symmetry of the bending response between the concave and convex curvature. Next, the weave pattern of the tendons further breaks symmetry along the two directors of plates. The anisotropy is clearly evident in 3-point bending experiments. Motivated by these experiments and the need for design, we formulate an analytical energy-based model to quantify the anisotropic elasticity. The derived architecture-property relationships can be used to design architected tendon plates with desirable properties.

Energy evolution mechanism of structural surfaces in sandstones with different dips based on the energy principle.

A uniaxial compression test was conducted on sandstone specimens at various inclination angles to determine the energy evolution characteristics during deformation and damage. Based on the principle of minimum energy dissipation, an intrinsic model incorporating the damage threshold was developed to investigate the mechanical properties of sandstone at different inclination angles, and the energy damage evolution during deformation and damage. This study indicated that when the inclination angle of the structural surface remained below 40°, sandstone exhibited varying mechanical properties based on different inclination angles. The peak strain was positively correlated with the inclination angle, whereas the compressive strength and modulus of elasticity showed negative correlations. From an energy perspective, the deformation and damage of sandstone under external loading entail processes of energy input, accumulation, and dissipation. Moreover, higher inclination angles of the structural surface resulted in a smaller absorbed peak strain and a reduced proportion of dissipated energy relative to the energy input, thereby affecting the evolution of energy damage throughout the process. As the inclination angle of the structural surface increased, the absorbed total strain at the peak value decreased, whereas the proportion of the dissipated energy increased. Additionally, the damage threshold and critical value of the rock specimens increased with the inclination angle. The critical value, a composite index comprising the peak strain, compressive strength, and elastic modulus, also increased accordingly. These findings can offer a novel perspective for analyzing geological disasters triggered by fissure zones within underground rock formations.

Heterogeneous elasticity drives ripening and controls bursting kinetics of transcriptional condensates.

Many biomolecular condensates, including transcriptional condensates, are formed in elastic mediums. In this work, we study the nonequilibrium condensate dynamics in a chromatin-like environment modeled as a heterogeneous elastic medium. We demonstrate that the ripening process in such an elastic medium exhibits a temporal power-law scaling of the average condensate radius, depending on the local stiffness distribution and different from Ostwald ripening. Moreover, we incorporate an active process to model the dissolution of transcriptional condensates upon RNA accumulation. Intriguingly, three types of kinetics of condensate growth emerge, corresponding to constitutively expressed, transcriptional-bursting, and silenced genes. Furthermore, the simulated burst frequency decreases exponentially with the local stiffness, through which we infer a lognormal distribution of local stiffness in living cells using the transcriptome-wide distribution of burst frequency. Under the inferred stiffness distribution, the simulated distributions of bursting kinetic parameters agree reasonably well with the experimental data. Our findings reveal the interplay between biomolecular condensates and elastic mediums, yielding far-reaching implications for gene expression.