Twist Mechanics Research Articles

The cellulose–lignin balance mediated by auxin signal transduction affects the twisted growth of Yunnan pine trunk

Trunk twisting, a special phenomenon observed during plant growth, leads to remarkable changes in plant phenotypic plasticity and adaptability. However, it is a debate whether the trunk twisting belongs to environmental alteration or genetic variation. To understand the mechanisms underlying trunk twisting in Yunnan pine (Pinus yunnanensis Franch.), through a diallel cross experiment, we first determined that trunk twisting was controlled by recessive genes. Anatomical analysis identified that straight and twisty types differed significantly in xylem and phloem. RNA-seq of materials enriched by laser microdissection revealed several metabolic pathways with significant enrichment in twisty pines, including auxin signal transduction, photosynthetic carbon fixation and sucrose metabolism, etc. Application of exogenous auxin and auxin transport inhibitors (TIBA) can only change the growth rate, but cannot change the twisted or straight of the trunk. When auxin signaling inhibitors (auxinole) were added, the straight pines produce a tendency to twisty growth. Combined with enzyme activity assay and immunohistochemistry, we propose a working model. ARF can not only downregulate POR to block chlorophyll synthesis and photosynthesis but also upregulated Susy expression, and allows a large amount of sucrose to synthesize cellulose. Nevertheless, due to downregulated CBH expression and abnormal cellulolysis, cellulose accumulates and the lignin content decreases, eventually making the trunk highly prone to twisted growth. These results reveal the molecular mechanism of trunk twisting, and suggest that ARF expression method can be vital in trunk shape screening during the early growth stages of Yunnan pines.

Numerical investigation of the compressive behavior of 2.5D woven carbon-fiber (2.5D-CFRP) honeycomb and experimental validation

In this work, the quasi-static compression behavior of a 2.5D woven carbon-fiber (2.5D-CFRP) honeycomb was numerically investigated by using two optimized models based on a conventional macro-mechanical model and the representative volume element (RVE) model. We introduced a viscosity regularization criterion into the conventional macro-mechanical model to improve the accuracy of the simulations. The relationship between the viscosity coefficient and simulation accuracy was analyzed using the displacement-load profile of the 2.5D-CFRP honeycomb under quasi-static compression. We further clarified the damage mechanism during the crushing of the 2.5D-CFRP honeycomb. An RVE model simulation was performed by using the combined VUMAT subroutine, which represented the damage state of fibers in different lay-up directions of the 2.5D-CFRP honeycomb. The results showed that the modified macro-mechanical model represented the twisting and folding mechanism of the honeycomb walls during quasi-static compression rather than the damage of the fibers at the intersection of the honeycomb walls.

Development of a Butterfly Fractional-Order Backlash-Like Hysteresis Model for Dielectric Elastomer Actuators

Differential equation-based hysteresis model is an efficient approach to predict the hysteresis effect with less modeling parameters. Available differential equation-based hysteresis models mainly focus on describing the single-loop hysteresis effect and fail to describe the butterfly hysteresis effect. In this article, a butterfly fractional-order backlash-like hysteresis model is proposed to describe the butterfly hysteretic behavior. To this end, a twist mechanism is developed to transform the single-loop backlash-like hysteresis model into the one that is capable of representing the butterfly hysteresis. To further improve the modeling accuracy, a fractional-order expression is integrated into the butterfly backlash-like hysteresis model. In addition, considering the buckling threshold characteristic of the elastomer membrane in dielectric elastomer actuators, a buckling threshold selector is designed and incorporated into the model as well. Experiments are conducted to validate the effectiveness of the proposed model.

FRET-based fluorescent probe with favorable water solubility for simultaneous detection of SO2 derivatives and viscosity

The intracellular viscosity is an important parameter of the microenvironment and SO2 is a vital gas signal molecule. At present, some dual-response fluorescence probes for simultaneous measurements of viscosity and SO2 derivatives (HSO3−/SO32−) possessed poor water solubility. In this work, we developed a water-soluble fluorescence probe CIJ (0.0864 g/100 mL of water at 20 °C) for simultaneous measurements of viscosity and SO2 derivatives. CIJ exhibited a sensitive fluorescence enhancement to environmental viscosity from 0.97 to 28.04 cP based on a twisted intramolecular charge transfer mechanism and was applied to effective measurement of viscosity in vitro and in vivo. CIJ could also respond to SO2 derivatives with a low detection limit (44 nM) and a fast response time (5 min) based on the nucleophilic addition reaction. Furthermore, CIJ was applied to monitor SO2 derivatives in ratiometric response manner in living cells.

A novel 1,8-naphthalimide-based fluorescent chemosensor for the detection of HSA in living cells.

Human serum albumin (HSA) is an essential protein for maintaining human health. Accurate detection and quantification of HSA are of great significance for disease diagnosis and biochemical research. Here, a new HSA fluorescent probe BNPE based on the 1,8-naphthalimide fluorophore was designed and synthesized. The probe could recognize HSA through a twisted intramolecular charge transfer mechanism, effectively avoid the interference of most substances, and realize HSA fluorescence imaging in living cells.

Vis–NIR Electrochromism and NIR–Green Electroluminochromism in Dual Functional Benzothiadiazole‐Arylamine Mixed‐Valence Compounds

AbstractElectrochromism/electrofluorochromism is the reversible tuning of the absorption/photoluminescence by redox processes. Dual functional electrochromic/electrofluorochromic materials can be exploited in, for example, smart windows, encryption/anticounterfeiting technologies, displays, and biomedical sensors. While electrofluorochromic materials showing tunable fluorescence intensity are relatively widespread, those with tunable color emission are not. Moreover, electrofluorochromic materials with tunable emission in the near‐infrared (NIR) range are seldom encountered. Here, this work shows a new molecular approach to afford both the above functionalities, in addition to red–NIR electrochromism, by combining the properties of highly stable arylamine radical cation mixed valence species, with those of donor–acceptor systems exhibiting the photoinduced twisted intramolecular charge transfer mechanism.

Evaluation of the impact of successful percutaneous balloon mitral valvuloplasty on the left ventricular twist and untwist mechanics by the two dimensional speckle tracking imaging

Background: MS is one of the most prevalent valve abnormalities in people with chronic rheumatic heart disease (RHD). The effect of Inoue and multi-track successful percutaneous balloon mitral valvuloplasty (PBMV) on the twist and untwist mechanisms of the left ventricle was evaluated using non-invasive two-dimensional speckle tracking imaging (STI). Methods: This study was conducted on patients with mitral stenosis of rheumatic origin fulfilling the criteria for PBMV. Cases were categorized into two equal groups; group 1: 30 Patients underwent PBMV using Inoue technique and group 2: 30 Patients underwent PBMV using multi-track technique. All patients were subjected to full history and clinical examination, twelve leads surface electrocardiogram (ECG) before and after the procedure, two-dimensional and Doppler echocardiography, LV twist and untwist measured by the 2D the two-dimensional speckle tracking imaging (STI) before and after the procedure and PBMV. Results: In both techniques; the mitral valve area (MVA) was highly significantly increased after balloon mitral valvuloplasty (BMV), while mean pressure gradient (MPG) and the estimated systolic pulmonary artery pressure (PAP) were highly significantly decreased. The apical rotation, basal rotation, twist and untwist were highly significantly decreased after the procedure in each technique.

Moiré Tuning of the Dynamic Behavior of a Twisted Bilayer van der Waals Material Resonator

Abstract Fully atomistic simulations and a sandwich plate model are used to study the dynamic behavior of twisted 3R-MoS2 bilayers. The simulations demonstrate that for a very small twist angle, the Moiré pattern leads to the symmetry breaking of the interlayer van der Waals energy on the scale of tens of nanometers and causes the dynamic behavior of twisted 3R-MoS2 bilayers to show strong position dependence. In particular, obvious mode pair splitting is observed in twisted 3R-MoS2 bilayer resonators where the interlayer van der Waals energy distribution is nonaxisymmetric. An analysis of the results of these molecular dynamic calculations shows that this behavior can be well explained using the sandwich plate model considering the nonuniform interlayer shear effect. Moreover, the twisted 3R-MoS2 bilayer relaxation mechanism involves the transition from AA stacking order with higher interlayer van der Waals potential energy to AB or BA stacking order, resulting in local buckling in the bilayers. The natural frequencies of resonators dominated by AA domains are much lower than those of resonators dominated by AB domains and even less than those of single-layer 3R-MoS2. Furthermore, as the radius increases, the frequency shows an abnormal trend, and a frequency gap is observed in the resonators dominated by AA domains.

Beyond "Mega": Origin of the "Giga" Stokes Shift for Triazolopyridiniums.

Over the past decade, fluorophores that exhibit "mega" Stokes shifts, defined to be Stokes shifts of greater than 100 nm, have gained considerable attention due to their potential technological applications. A subset of these fluorophores have Stokes shifts of at least 10,000 cm-1, for whom we suggest the moniker "giga" Stokes shift. The majority of "giga" Stokes shifts reported in the literature arise from the twisted intramolecular charge transfer mechanism, but this mechanism does not fit empirical characterization of triazolopyridinium (TOP). This observation inspired a density functional theory (DFT) and time-dependent DFT study of TOP, and several related fluorophores, to elucidate the novel photophysical origin for the "giga" Stokes shift of TOP. The resulting computational models revealed that photoexcitation of TOP yields a zwitterionic excited state that undergoes significant structural relaxation prior to emission. Most notably, TOP has two orthogonal moieties in the ground state that adopt a coplanar geometry in the excited state. According to Hückel's rule, both the heterocycle and phenyl moieties of TOP should be aromatic in an orthogonal ground state. However, according to Baird's rule, these individual moieties should be anti-aromatic in the excited state. By relaxing to a coplanar conformation in the excited state, TOP likely forms a single aromatic system consisting of both the heterocycle and phenyl moieties.

Fabrication and experimental characterisation of a bistable tensegrity-like unit for lattice metamaterials

The peculiar nonlinear mechanical behaviour of tensegrity structures and their engineering applications have attracted considerable interest in the last two decades. However, the difficulties in their traditional fabrication and assembling methods represent current limitations to their widespread use. This paper presents a novel design and fabrication procedure for bistable tensegrity-like units. Starting from the classical triangular tensegrity prism and using stereolithography technology, a double tensegrity-like unit was designed and realised monolithically as a compliant mechanism. High repeatability of compression tests confirmed the activation of the designed bistable twisting mechanism in large displacements, proving that the bistability of a tensegrity-like unit with null selfstress and no cables can dependably be achieved. Numerical simulations showed that a reduced-order stick-and-spring model is able to provide predictions on the nonlinear mechanical behaviour of the unit in close agreement with experimental results. Low relative density and bistable characteristics make this type of tensegrity-like unit suitable to manufacture highly-customisable multistable metamaterials. The proposed procedure could be applied to transform and additively manufacture other types of tensegrity structures with different nonlinear responses into corresponding tensegrity-like versions. • Stereolithography fabrication of tensegrity-like units without pin-joints or cables. • Experimental investigation on the compressive behaviour of a tensegrity-like unit. • Bistable response of the designed unit confirmed by experimental results. • Design procedure suitable to lightweight metamaterials with nonlinear behaviour. • Tessellation of units for multistable metamaterials and control of compact waves.

On the Aeroelasticity of the Active Span and Passive Pitching Polymorphing Wing: A Parametric Study

This paper presents an aeroelastic analysis of a polymorphing wing capable of active span extension and passive pitch variation. The wing is split into two segments: an inboard segment responsible for span extension/retraction and an outboard segment capable of pitch variation. The two segments are connected through an overlapping spar and a torsional spring. A finite element aeroelastic model is developed where the wing structure is discretized into Euler–Bernoulli beam elements and the aerodynamic loads are calculated using Theodorsen’s unsteady model. A comprehensive parametric analysis is carried out with and without span extension to analyze the effect of varying critical design parameters, such as elastic axis position of outboard section and torsional spring rigidity, and conditions for aeroelastic phenomena of flutter and divergence are studied. A gust load analysis is carried out to quantify the capability of the outboard wing passive twist mechanism to alleviate loads. Finally, a nonlinear analysis is carried out by replacing the linear torsional spring with a nonlinear cubic spring to study the effects of cubic hardening and softening on the aeroelasticity of the polymorphing wing.

Determination of muscle strength and function in plesiosaur limbs: finite element structural analyses of Cryptoclidus eurymerus humerus and femur.

BackgroundThe Plesiosauria (Sauropterygia) are secondary marine diapsids. They are the only tetrapods to have evolved hydrofoil fore- and hindflippers. Once this specialization of locomotion had evolved, it remained essentially unchanged for 135 Ma. It is still controversial whether plesiosaurs flew underwater, rowed, or used a mixture of the two modes of locomotion. The long bones of Tetrapoda are functionally loaded by torsion, bending, compression, and tension during locomotion. Superposition of load cases shows that the bones are loaded mainly by compressive stresses. Therefore, it is possible to use finite element structure analysis (FESA) as a test environment for loading hypotheses. These include muscle reconstructions and muscle lines of action (LOA) when the goal is to obtain a homogeneous compressive stress distribution and to minimize bending in the model. Myological reconstruction revealed a muscle-powered flipper twisting mechanism. The flippers of plesiosaurs were twisted along the flipper length axis by extensors and flexors that originated from the humerus and femur as well as further distal locations.MethodsTo investigate locomotion in plesiosaurs, the humerus and femur of a mounted skeleton of Cryptoclidus eurymerus (Middle Jurassic Oxford Clay Formation from Britain) were analyzed using FE methods based on the concept of optimization of loading by compression. After limb muscle reconstructions including the flipper twisting muscles, LOA were derived for all humerus and femur muscles of Cryptoclidus by stretching cords along casts of the fore- and hindflippers of the mounted skeleton. LOA and muscle attachments were added to meshed volumetric models of the humerus and femur derived from micro-CT scans. Muscle forces were approximated by stochastic iteration and the compressive stress distribution for the two load cases, “downstroke” and “upstroke”, for each bone were calculated by aiming at a homogeneous compressive stress distribution.ResultsHumeral and femoral depressors and retractors, which drive underwater flight rather than rowing, were found to exert higher muscle forces than the elevators and protractors. Furthermore, extensors and flexors exert high muscle forces compared to Cheloniidae. This confirms a convergently evolved myological mechanism of flipper twisting in plesiosaurs and complements hydrodynamic studies that showed flipper twisting is critical for efficient plesiosaur underwater flight.

Exploring of blood viscosity in injured liver tissues of hyperlipidemic mice

Exploring the connection between blood viscosity and liver in it have great significance for the detection and treatment of hyperlipidemic. Therefore, we designed a new near-infrared viscosity sensitive fluorescent probe Vis-LW based on the twisted intramolecular charge transfer mechanism. The probe exhibited a strong dependence on viscosity as well as good anti-interference performance. With the aid of Vis-LW, we successfully detected the viscosity changes in chloroquine induced cells and realized the diagnosis of diseases in hyperlipidemic mice by utilizing blood viscosity as a diagnostic indicator for hyperlipidemia. Not only that, the increased liver viscosity of hyperlipidemic mice was found for the first time, the reduced blood and liver viscosity after treatment with lipid-lowering drug fenofibrate was also tracked. This work provides a new method for the diagnosis of hyperlipidemia and offered a new idea on the research and treatment of hyperlipidemia in the future.

4 Dimensional X-Strain Speckle Tracking Echocardiography: Assessment of Normal Values of Left Ventricular Rotation and Twist, in Healthy Indian Adults during Covid-19 Pandemic

Cardiac MRI and 2Dimensional speckle Tracking Echocardiography (2D STE) are the most sought-after methods to evaluate LV twist mechanics. LV rotational deformation resembles the wringing of a towel, and this deformation is referred as LV twist (LVT), and the subsequent recoil in diastole is known as LV untwist (LVUT). 2D/3D/4D twist mechanics assessment by STE is inherently associated with limitations. Recently introduced 4D XStrain STE has been used for evaluation of strain parameters because of better appraisal of contractile properties of LV, to analyse complex multi-dimensional LV rotational mechanics. This novel technology is a reliable, affordable, and simple tool for quantification of regional myocardial functions, particularly LV strain and rotation parameters. To evaluate and establish the normal values of LV rotation and twist by 4D XStrain STE in healthy Indian adults during the Covid-19 pandemic was the aim of the current study. 46 subjects were enrolled (34 males & 12 females). LA size, LV mass, CO, LVEDV and mitral E/A ratio were significantly greater in males (p<0.01) even though EF was higher in females (p<0.01). GLS, GCS, and GRS were increased in males (p<0.01). Peak basal rotation, peak twist, peak twist rate, and peak untwist rate were also greater in males (p<0.01), nonetheless, peak apical rotation and papillary muscle rotational velocity were greater in females (p<0.01). However, MV rotational velocity was increased in males (p<0.01). This is the first research publication of normal values of LV rotation and twists in healthy Indian adults by 4D XStrain STE.

Stacking and Twisting of Layered Materials Enabled by Screw Dislocations and Non-Euclidean Surfaces

ConspectusThe rise of van der Waals layered materials such as graphene, hexagonal boron nitride, and transition-metal dichalcogenides opens up enormous opportunities for exploring novel quantum phenomena at the two-dimensional (2D) atomic limit. The physical properties of van der Waals materials are often affected by the symmetry of the crystal lattices. For example, breaking the inversion symmetry can lead to a variety of phenomena, such as second-harmonic generation, valley polarization, and ferroelectricity. The symmetry and symmetry breaking of layered materials are determined by the atomic arrangements within the layer and the layer stackings. The screw-dislocation-driven growth mechanism is general to 2D materials and can provide effective kinetic pathways to influence the layer stacking and generate diverse and complex layer stackings with different symmetry.Furthermore, different van der Waals layered materials can also be stacked vertically to create artificial new structures. In such stacked structures, the interlayer twist angle between stacked layers results in the formation of large-scale moiré superlattices that manipulate the electronic structures of van der Waals materials and provide an additional degree of freedom for tuning their physical properties. The stacking and twisting of layered materials lead to observations of new quantum phenomena, such as unconventional superconductivity, tunable Mott insulators, moiré excitons, and various magnetic and ferroelectric orderings. Previously, such twisted 2D structures were often fabricated by mechanically stacking exfoliated layers, but it was recently demonstrated that twisted van der Waals structures can form via direct growth. Moreover, continuously twisted structures of 2D materials can be realized through two distinct mechanisms that involve screw dislocations. The Eshelby twist mechanism induced by the strain of screw dislocation gives rise to twisted van der Waals nanowires with small interlayer twists. Beyond the Eshelby twist mechanism, supertwisted spirals have recently been enabled by a non-Euclidean twist mechanism which arises from the mismatched geometry between van der Waals crystals and non-Euclidean (curved) surfaces.In this Account, we start with reviewing the stacking configurations in the diverse polytypic structures of layered materials using transition-metal dichalcogenides as examples. We further discuss the twisted structures of layered materials from a structural point of view. After introducing screw-dislocation-driven growth and showing its generality in the crystal growth of layered materials, we further discuss how the unique structures of screw dislocations influence the stacking and symmetry of layered materials. Moreover, we highlight how screw dislocations enable interlayer twisting through the Eshelby twist mechanism and the non-Euclidean twist mechanism. In the end, the challenges and future perspectives are discussed for the study of screw-dislocated layered materials to control the stacking and twist for exotic physical properties.

Left Ventricular Strains and Myocardial Work in Adolescents With Anorexia Nervosa

BackgroundAnorexia nervosa (AN) is accompanied by bradycardia, low blood pressure (BP) and cardiac morphological remodeling. Systolic and diastolic functions are relatively preserved when assessed by standard ultrasound methods. However, novel advances based on speckle tracking echocardiography (STE), that could detect subtle and early alterations of left ventricular (LV) function, remained poorly used in AN patients.ObjectiveThe aim of this study was to assess the cardiac function of AN patients by evaluating LV myocardial strains, myocardial work (MW) and LV mechanical dispersion. We hypothesized that LV strains and global myocardial work would be decreased and LV twisting mechanisms enhanced to preserve the systolic function.MethodsFifty-nine adolescents including 26 women AN patients (14.6 ± 1.9 yrs. old) with a mean duration of AN of 19 ± 9 months and 33 controls (14.1 ± 2.0 yrs. old) underwent STE to assess LV morphology and myocardial regional strains.ResultsThe global longitudinal strain (GLS) was higher in AN patients compared to controls (−18.8 ± 2.0 vs. −16.9 ± 2.8%, p = 0.006). The area under the pressure-strain loop, representing the global MW was not altered but was shifted to the left and downwards in AN patients, due to their lower BP and higher GLS. Intraventricular mechanical dispersion was similar in both groups. Circumferential strains, twisting/untwisting mechanics were preserved.ConclusionOur results strongly support that the cardiac morphological remodeling observed in our AN patients was associated with normal ventricular regional myocardial functions. Only GLS was higher in AN patients, but its clinical significance remains to be demonstrated.

Fingertip Sensorless Force Control by Tendon-driven Two-joint Robotic Finger

In this paper, we designed an articulated robot finger with a round-belt twist mechanism combining a wire drive and a Twisted round-belt Actuator (TbA). This robot finger has the following two main features. First, we designed new mechanism，Variable-pitch Screw Module (VSM) to apply stretch to the round belt while adding twists to them at the same time. Second, we replaced acceleration sensors with encoders to stabilize output signals of joint angles. We explain the mechanism of this robot finger which are mentioned above. We show the results of experiments of fingertip force measurement. Finally, we show the results of a force-following control experiment for stepwise target values.

Development of 1-DOF robotic gripper with wrist twist mechanism

Development of 1-DOF robotic gripper with wrist twist mechanism

Anabolic Steroids Use Is Associated with Impairments in Atrial and Ventricular Cardiac Structure and Performance in Athletes.

Despite potential severe cardiac side effects, anabolic androgenic steroids (AAS) are increasingly used by strength athletes. However, previous echocardiographic studies focused on the left ventricular (LV) strains but did not assess LV twist and untwist mechanics. Moreover, left atrial (LA) function has been often neglected, and its stiffness, an important determinant of LA reservoir function, has never been challenged. The aim of this study was to investigate the effects of AAS on LA and LV morphologies and functions in strength athletes. Fifty subjects including 20 strength-trained young athletes age 32.0 ± 8.5 yr with a mean duration of AAS use of 4.7 ± 1.8 yr (users), 15 athletes with no history of AAS use (nonusers) and 15 sedentary controls underwent speckle tracking echocardiography to assess LA and LV morphology and function. Users showed higher LA reservoir dysfunction than nonusers (33.7% ± 10.9% vs 44.9% ± 9.9% respectively, P = 0.004) and higher LA stiffness (0.13 ± 0.05 vs 0.19 ± 0.08 A.U., respectively; P = 0.02), higher LV mass index and lower global and regional LV diastolic and systolic dysfunction (global longitudinal strain: -15.5% ± 3.2% vs -18.9% ± 1.8% respectively; P = 0.003), with a drop of LV twist-untwist mechanics (untwisting velocity: 61.5°·s-1 ± 20.2°·s-1 vs 73.7°·s-1 ± 16.1°·s-1 respectively, P = 0.04). There were significant correlations between LV mass and LV apical rotation (P = 0.003, r = 0.44) and diastolic longitudinal strain rate (P = 0.015, r = 0.33). Our results showing significant LA and LV remodeling and dysfunctions in young AAS using athletes are alarming. Screening echocardiography based on speckle tracking echocardiography parameters for early diagnosis, as well as a stronger awareness in athletes and in physicians are warranted in this context.

Coupled bend–twist mechanics of biomimetic scale substrate

We develop the mechanics of combined bending and twisting deformation of a one-dimensional filamentous structure with protruding stiff fish-scale-like plates embedded at an angle on the surface. We develop a Cosserat kinematic formulation along with scale contact constraints. This geometrically exact model allows us to bypass the limitations of small deflection finite element computations, thereby preserving the accuracy of scale kinematics. The derived structure–property relationships reveal, for the first time, the combined effect of bending and twisting on a slender fish-scale inspired substrate. The model subsumes previous models on pure bending and pure twisting, but also shows previously unobserved phenomena that arise due to the coupled effects of these loads. These include a new interpretation of kinematic locking behavior, multiple contact regimes, asymmetric sensitivities of one curvature over the other, and discontinuous transitions in the nonlinear moment–curvature and torque–twist behaviors, reflecting the complex scale engagement patterns.