Internal Contacts Research Articles

Nonlinear mechanics of horseshoe microstructure-based lattice design

Enhancing buffering capacity, flexibility, and energy absorption to withstand large deformations in structure remains a challenge. Bio-inspired horseshoe lattice structures, with their curved trusses, exhibit distinct mechanical characteristics compared to conventional metamaterials. However, their mechanical properties under in-plane compression have been rarely explored. This study characterised and modelled three types of novel 3D-printed horseshoe lattice structures, totalling 12 configurations, with unit cell geometry varying based on cell-wall angles ranging from 120°to 210°. The implementation of the FE simulation based on the three-network viscoplastic (TNV) model showed good agreement with the experiments. The results demonstrated that the cell-wall angle in the geometry and the cross-lap joint topology were significantly associated with the failure mechanism of the unit cell and the overall non-linear mechanical behaviour. Increasing the cell-wall angles can prevent beams from failing due to bending and buckling fractures, facilitate the initiation of internal contacts and stretching during in-plane compression. This reveals a configurable mechanism where the flexibility and stability of the lattice structure can trigger strain hardening, resulting in an increase in load-bearing capacity. The sensitivity to strain hardening varies depending on the order of cross-laps within the topology. A colour-pattern tracking method was employed to monitor the progressive stabilisation of lattice structures, and offering a novel approach for the future design of flexible, configurable, and programmable horseshoe-based lattice structures.

AbMelt: Learning antibody thermostability from molecular dynamics

Antibody thermostability is challenging to predict from sequence and/or structure. This difficulty is likely due to the absence of direct entropic information. Herein, we present AbMelt where we model the inherent flexibility of homologous antibody structures using molecular dynamics simulations at three temperatures and learn the relevant descriptors to predict the temperatures of aggregation (Tagg), melt onset (Tm,on), and melt (Tm). We observed that the radius of gyration deviation of the complementarity determining regions at 400 K is the highest Pearson correlated descriptor with aggregation temperature (rp = −0.68 ± 0.23) and the deviation of internal molecular contacts at 350 K is the highest correlated descriptor with both Tm,on (rp = −0.74 ± 0.04) as well as Tm (rp = −0.69 ± 0.03). Moreover, after descriptor selection and machine learning regression, we predict on a held-out test set containing both internal and public data and achieve robust performance for all endpoints compared with baseline models (Tagg R2 = 0.57 ± 0.11, Tm,on R2 = 0.56 ± 0.01, and Tm R2 = 0.60 ± 0.06). In addition, the robustness of the AbMelt molecular dynamics methodology is demonstrated by only training on <5% of the data and outperforming more traditional machine learning models trained on the entire data set of more than 500 internal antibodies. Users can predict thermostability measurements for antibody variable fragments by collecting descriptors and using AbMelt, which has been made available.

Dynamic Fall Recovery Control for Legged Robots via Reinforcement Learning.

Falling is inevitable for legged robots when deployed in unstructured and unpredictable real-world scenarios, such as uneven terrain in the wild. Therefore, to recover dynamically from a fall without unintended termination of locomotion, the robot must possess the complex motor skills required for recovery maneuvers. However, this is exceptionally challenging for existing methods, since it involves multiple unspecified internal and external contacts. To go beyond the limitation of existing methods, we introduced a novel deep reinforcement learning framework to train a learning-based state estimator and a proprioceptive history policy for dynamic fall recovery under external disturbances. The proposed learning-based framework applies to different fall cases indoors and outdoors. Furthermore, we show that the learned fall recovery policies are hardware-feasible and can be implemented on real robots. The performance of the proposed approach is evaluated with extensive trials using a quadruped robot, which shows good effectiveness in recovering the robot after a fall on flat surfaces and grassland.

Optimization of a tetrahedron compliant spherical joint via computer-aided engineering tools

This article focuses on enhancing the range of motion (ROM) of the Tetra II joint, a spherical compliant joint consisting of three internally interconnected tetrahedron-shaped elements that achieve motion through elastic deformation. Despite its excellent precision, this specific design is constrained in terms of ROM due to internal contacts among the tetrahedral elements. To overcome this limitation, this study utilizes a computer-aided engineering (CAE) framework to optimize the configuration of the Tetra II joint and enhance its ROM. The resultant optimized joint, referred to as Tetra III, is subsequently compared to Tetra II in terms of both ROM and center shift. Finite element models (FEM) are employed to validate the optimization results and examine how various tetrahedron-shaped geometries impact the joint’s performance. The newly optimized joint exhibits a significantly higher ROM compared to the previous version, while maintaining excellent precision and overall smaller dimensions. Finally, to demonstrate its manufacturability, the Tetra III joint is produced using selective laser sintering (SLS) technology, with Duraform PA serving as the construction material. The successful fabrication serves as a demonstrative example of the improved design of the Tetra III joint.

Discovery of Novel Anti-Resistance AR Antagonists Guided by Funnel Metadynamics Simulation.

Androgen receptor (AR) antagonists are widely used for the treatment of prostate cancer (PCa), but their therapeutic efficacy is usually compromised by the rapid emergence of drug resistance. However, the lack of the detailed interaction between AR and its antagonists poses a major obstacle to the design of novel AR antagonists. Here, funnel metadynamics is employed to elucidate the inherent regulation mechanisms of three AR antagonists (hydroxyflutamide, enzalutamide, and darolutamide) on AR. For the first time it is observed that the binding of antagonists significantly disturbed the C-terminus of AR helix-11, thereby disrupting the specific internal hydrophobic contacts of AR-LBD and correspondingly the communication between AR ligand binding pocket (AR-LBP), activation function 2 (AF2), and binding function 3 (BF3). The subsequent bioassays verified the necessity of the hydrophobic contacts for AR function. Furthermore, it is found that darolutamide, a newly approved AR antagonist capable of fighting almost all reported drug resistant AR mutants, can induce antagonistic binding structure. Subsequently, docking-based virtual screening toward the dominant binding conformation of AR for darolutamide is conducted, and three novel AR antagonists with favorable binding affinity and strong capability to combat drug resistance are identified by in vitro bioassays. This work provides a novel rational strategy for the development of anti-resistant AR antagonists.

Evolutionary dynamics of a lattice dimer: a toy model for stability vs. affinity trade-offs in proteins

Understanding how a stressor applied on a biological system shapes its evolution is key to achieving targeted evolutionary control. Here we present a toy model of two interacting lattice proteins to quantify the response to the selective pressure defined by the binding energy. We generate sequence data of proteins and study how the sequence and structural properties of dimers are affected by the applied selective pressure, both during the evolutionary process and in the stationary regime. In particular we show that internal contacts of native structures lose strength, while inter-structure contacts are strengthened due to the folding-binding competition. We discuss how dimerization is achieved through enhanced mutability on the interacting faces, and how the designability of each native structure changes upon introduction of the stressor.

O.4.4-9 Organized sport and physical activity for older adults – salutogenic settings-based recommendations

Abstract Sport and physical activity is important to address healthy aging. There are recommendations on how much physical activity people should do, but no recommendations for how organizations should organize activities to suit as many as possible. The purpose of this study was to explore the characteristics of sport and physical activity initiatives that older adults participate in. Different ongoing sport and physical activity initiatives that involve older adults were investigated regarding their focus, organization, intensity and organizer, and in relation to their costs, booking opportunities and recruitment. The study was conducted with a cross-sectional design using the Salutogenic Physical Activity Health Resources Questionnaire (SPAHRQ). The study included 27 different initiatives with 372 participants (60% women) ranging from 60 to 96 years of age. A health-promoting, salutogenic, settings-based approach, and specifically the concepts drop-in, drop-through and drop-over (Geidne and Quennerstedt, 2021) were used in discussing recommendations for the organization of sport and physical activity for older adults. The main findings were that who (sports clubs or senior associations) organizes the sport and physical activity initiative seems to affect the characteristics of how (for example intensity and characteristics of the activities) it is organized and what characterizes the participants in it. Despite the differing characters of sport and physical activity initiatives, the majority of older adults are recruited by internal contacts like friends and family. The lowest costs are found in senior associations, leisure-focused initiatives, individual initiatives, and low-intensity activities. In senior associations, most activities were booked per semester 60%. In sport clubs the most common booking system was per occasion, 40%. In team sports (almost always in sport clubs), the most common way of booking was per semester (46%). Which older adults participate in which initiatives is explained mostly by the age and gender of the participants. In conclusion, to attract as many older adults as possible, organizations should work with lowering the thresholds into, as well as within and between, organizations, and raise the threshold for dropping out of sports and physical activity. Support/Funding Source The study was funded in a PhD-project at Örebro University.

The characteristics of organized sport and physical activity initiatives for older adults in Sweden.

There is a common understanding that sport and physical activity can be important to address healthy aging. There are individual-level recommendations about how much physical activity people of different ages should engage in to gain health benefits, but at the same time there are no recommendations for how organizations should organize physical activities to suit as many people as possible for as long as possible. The purpose of this study was to explore the characteristics of sport and physical activity initiatives that older adults participate in. Different ongoing sport and physical activity initiatives that involve older adults were investigated regarding their focus, organization, intensity and organizer, and in relation to their costs, booking opportunities and recruitment. The study was conducted with a cross-sectional design using the Salutogenic Physical Activity Health Resources Questionnaire (SPAHRQ). The study included 27 different initiatives with 372 participants (60% women) ranging from 60 to 96 years of age. A health-promoting, salutogenic settings-based approach, and specifically the concepts drop-in, drop-through and drop-over were used in discussing recommendations for the organization of sport and physical activity for older adults. The main findings were that who organizes the sport and physical activity initiative seems to affect the characteristics of how it is organized and what characterizes the participants in it. Despite the differing characters of sport and physical activity initiatives, the majority of older adults are recruited by internal contacts like friends and family. Which older adults participate in which initiatives is explained mostly by the age and gender of the participants. In conclusion, to attract as many older adults as possible, organizations should work with lowering the thresholds, as well as within and between, organizations, and raise the threshold for dropping out of sports and physical activity.

Data-driven modelling with coarse-grid network models

We propose to use a conventional simulator, formulated on the topology of a coarse volumetric 3D grid, as a data-driven network model that seeks to reproduce observed and predict future well responses. The conceptual difference from standard history matching is that the tunable network parameters are calibrated freely without regard to the physical interpretation of their calibrated values. The simplest version uses a minimal rectilinear mesh covering the assumed map outline and base/top surface of the reservoir. The resulting CGNet models fit immediately in any standard simulator and are very fast to evaluate because of the low cell count. We show that surprisingly accurate network models can be developed using grids with a few tens or hundreds of cells. Compared with similar interwell network models (e.g., Ren et al., 2019, 10.2118/193855-MS), a typical CGNet model has fewer computational cells but a richer connection graph and more tunable parameters. In our experience, CGNet models therefore calibrate better and are simpler to set up to reflect known fluid contacts, etc. For cases with poor vertical connection or internal fluid contacts, it is advantageous if the model has several horizontal layers in the network topology. We also show that starting with a good ballpark estimate of the reservoir volume is a precursor to a good calibration.

On-Load Tap Changer Internal Contact Health Assessment Based on Ion Detection in Oil

Internal contact deterioration causes most electrical faults in on-load tap changers (OLTCs), which are difficult to diagnose promptly and accurately by traditional methods. This paper proposes a novel approach for internal contact condition evaluation based on metal ion detection. The variation of metal ions under the action of DC breakdown and natural corrosion for metal contacts with different materials are experimentally studied first. The formation mechanism of metal ions indicates that electric erosion is the primary cause of the short-term increase of characteristic ions. In addition, both chemical corrosion and electrochemical corrosion play a significant role in the long-term growth of metal ions. Based on the assumption of maximum damage to OLTC contacts, the characteristic metal ion concentration when the contacts require mandatory replacement is calculated. An early warning method for the damage condition of the internal contacts is proposed by combining the accumulated metal ion concentration and the relative metal ion growth rate. An on-site fault transformer case demonstrates that the multilevel warning value can well meet the requirements for the health status assessment of OLTC’s internal contacts.

Prismatic Spreading–Constriction Expression for the Improvement of Impedance Spectroscopy Models and a More Accurate Determination of the Internal Thermal Contact Resistances of Thermoelectric Modules

Thermoelectric (TE) devices can convert heat to electrical power or use electrical power to generate a temperature difference. Their characterization is essential to develop devices with higher efficiency. Impedance spectroscopy models have been developed in the last few years, and it has become a highly advantageous method for TE system characterization. Recently, it has been shown that this technique can also be used to determine internal thermal contacts (between the TE legs and the metallic strips that connect them and between the metallic strips and the outer layers). Here, we developed for the first time a spreading–constriction expression which does not assume cylindrical geometry. The enhanced model is also used to characterize four TE devices from different manufacturers, highlighting overestimations up to 13% when the previous cylindrical approximation is used. A code is provided in the Supporting Information ready to fit the experimental data. This study positions impedance spectroscopy as a powerful tool to detect and monitor issues during manufacturing or operation of TE devices, which typically occur at the contacts.

Temperature‐Induced Nonlinear Elastic Behavior in Berea Sandstone Explained by a Modified Sheared Contacts Model

AbstractRocks commonly display a reduction in elastic modulus during an acoustic perturbation followed by a logarithmic recovery of the modulus to its original value. This nonlinear elastic behavior can also be induced by changes in temperature of the rock, although experimental data for this are sparse. In this paper, we utilize temperature perturbations to broaden our understanding of the causes and mechanisms of nonlinear elasticity in rocks. We perform laboratory experiments tracking the nonlinear response of a Berea sandstone under vacuum both during and following 10°C changes in temperature. Ultrasonic velocity decreases by up to 0.30 ± 0.02% during both temperature increases and decreases, before recovering in the following days. Continuous monitoring over a 2‐month period also reveals a longer‐term 0.78 ± 0.04% increase in velocity. To explain these observations, we modify a recent model for nonlinear elasticity based on the shearing and subsequent recreation of internal microscopic contacts. Application of this model to our data suggests that internal stresses from differential thermal expansion/contraction of mineral grains break contacts, inducing nonlinear weakening. The degree of weakening depends on the temperature gradient. Slow dynamics recovery in the ∼10 hr following a temperature change likely results from the recreation of broken contacts due to nanoscopic adhesive forces. In contrast, the long‐term velocity increase results from evaporation of bound water from clay minerals. In addition to furthering our understanding of nonlinear elasticity in rocks, our results imply that sudden changes of temperature in shallow crustal environments will induce nonlinear weakening that persists for hours to days.

Bulk resistance and internal contacts of carbon fiber paper determined via X-ray computed tomography

Owing to the challenge of irregular morphology, the impact of compressed carbon fiber paper (CFP) on fuel cell performance and durability is intricate. As a carbon-carbon composite, the internal contact state of CFP directly determines its mechanical and physical properties. In this paper, fiber distribution and intersection of uncompressed CFP are achieved by X-ray computed tomography. Then we established an analytical model of bulk resistance based on the electron transfer path and provided a function to describe the internal contact state with strain. The results imply that the increasing number of electron paths and the variation of the contact state are the main factors for the decrease in bulk resistance under compression. The turning points in the contact state curve divide the range of pressure into fiber contact, elastic-plastic deformation and fiber fracture region, which can be used to assess the mechanical properties of CFP and determine the optimal pressure for fuel cell assembly.

A Flexible Capacitance Strain Sensor with Stitched Contact Terminals

AbstractFlexible strain sensing in wearables and textiles, employs simple resistive sensor elements which suffer from high hysteresis. Textile compatible capacitive strain sensors that have low hysteresis and negligible cross‐axis sensitivity will be ideal for sensing human movement and shape change. In this work, a non‐MEMS based flexible interdigital capacitive strain sensor is proposed. The proffered sensor is built using flexible elastomer material with stitched conductive threads serving as internal and external contacts thereby making the sensor easily customizable. The developed sensor is amenable for fabrication using large scale textile sensor manufacturing techniques. The low sensitivity due to the low dielectric constant of most elastomers is addressed by employing high dielectric constant additives while molding the elastomer sections. The developed sensor is virtually insensitive to cross‐axis strain by design and is capable of withstanding stretching up to 160%. The prototype sensor built and tested has a sensitivity of and portrays a worst‐case nonlinearity error of &lt;±2.9%. An application, where the developed sensor was stitched on to a glove to sense finger movement is presented and discussed. The proposed fully stitch‐able sensors have the versatility to perform fabric‐based wearable strain sensing for body shape and movement analysis.

Micromechanical Origin of Plasticity and Hysteresis in Nestlike Packings.

Disordered packings of unbonded, semiflexible fibers represent a class of materials spanning contexts and scales. From twig-based bird nests to unwoven textiles, bulk mechanics of disparate systems emerge from the bending of constituent slender elements about impermanent contacts. In experimental and computational packings of wooden sticks, we identify prominent features of their response to cyclic oedometric compression: nonlinear stiffness, transient plasticity, and eventually repeatable velocity-independent hysteresis. We trace these features to their micromechanic origins, identified in characteristic appearance, disappearance, and displacement of internal contacts.

The genome organization of Neurospora crassa at high resolution uncovers principles of fungal chromosome topology.

The eukaryotic genome must be precisely organized for its proper function, as genome topology impacts transcriptional regulation, cell division, replication, and repair, among other essential processes. Disruptions to human genome topology can lead to diseases, including cancer. The advent of chromosome conformation capture with high-throughput sequencing (Hi-C) to assess genome organization has revolutionized the study of nuclear genome topology; Hi-C has elucidated numerous genomic structures, including chromosomal territories, active/silent chromatin compartments, Topologically Associated Domains, and chromatin loops. While low-resolution heatmaps can provide important insights into chromosomal level contacts, high-resolution Hi-C datasets are required to reveal folding principles of individual genes. Of particular interest are high-resolution chromosome conformation datasets of organisms modeling the human genome. Here, we report the genome topology of the fungal model organism Neurospora crassa at a high resolution. Our composite Hi-C dataset, which merges 2 independent datasets generated with restriction enzymes that monitor euchromatin (DpnII) and heterochromatin (MseI), along with our DpnII/MseI double digest dataset, provide exquisite detail for both the conformation of entire chromosomes and the folding of chromatin at the resolution of individual genes. Within constitutive heterochromatin, we observe strong yet stochastic internal contacts, while euchromatin enriched with either activating or repressive histone post-translational modifications associates with constitutive heterochromatic regions, suggesting intercompartment contacts form to regulate transcription. Consistent with this, a strain with compromised heterochromatin experiences numerous changes in gene expression. Our high-resolution Neurospora Hi-C datasets are outstanding resources to the fungal community and provide valuable insights into higher organism genome topology.

Accelerated beta radiation aging of interlayer titanium nitride in gallium nitride contacts

Currently, there is no good way to determine the influence of radiation on the aging of betavoltaic electrical contacts. This work tested a method to accelerate the aging of the contacts inside a betavoltaic by enhancing energy deposition within the interfacial region of interest. An electrical contact of gold-titanium on gallium nitride was aged by exposure to tritium beta particles and electrons in a beamline. The interface stoichiometry was compared to the electrical performance of the contact. The method to age the betavoltaic component could help predict the lifetime performance of the internal electrical contacts and provide assurance of deployment reliability.Graphic abstract

Phosphorylation tunes elongation propensity and cohesiveness of INCENP’s intrinsically disordered region

The inner centromere protein, INCENP, is crucial for correct chromosome segregation during mitosis. It connects the kinase Aurora B to the inner centromere allowing this kinase to dynamically access its kinetochore targets. However, the function of its central, 440-residue long intrinsically disordered region (IDR) and its multiple phosphorylation sites is unclear. Here, we determined the conformational ensemble of INCENP’s IDR, systematically varying the level of phosphorylation, using all-atom and coarse-grain molecular dynamics simulations. Our simulations show that phosphorylation expands INCENP’s IDR, both locally and globally, mainly by increasing its overall net charge. The disordered region undergoes critical globule-to-coil conformational transitions and the transition temperature non-monotonically depends on the degree of phosphorylation, with a mildly phosphorylated case of neutral net charge featuring the highest collapse propensity. The IDR transitions from a multitude of globular states, accompanied by several specific internal contacts that reduce INCENP length by loop formation, to weakly interacting and highly extended coiled conformations. Phosphorylation critically shifts the population between these two regimes. It thereby influences cohesiveness and phase behavior of INCENP IDR assemblies, a feature presumably relevant for INCENP’s function in the chromosomal passenger complex. Overall, we propose the disordered region of INCENP to act as a phosphorylation-regulated and length-variable component, within the previously defined “dog-leash” model, that thereby regulates how Aurora B reaches its targets for proper chromosome segregation.

A novel wireless charging system for GIS state observation video sensor

Because the gas insulated switchgear (GIS) is closed, it is impossible to directly see the actual position of internal contacts. The image recognition technology can be used to collect, analyze and process the images of the switches in different states, and finally obtain the actual opening and closing state. In addition, some potential flaws can also be identified in advance. Considering the particularity of the GIS internal environment, wireless charging system can be used to supply power for internal video sensor. In this paper, a new type of coupling coil structure, DC coil, is proposed, which supplies power for video sensor through GIS observation window by wireless power transfer (WPT) technology. The proposed DC coil is analyzed theoretically, optimized by genetic algorithm (GA), and verified by finite element method (FEM). The experimental results indicate that the proposed structure can achieve the same transfer performance in lateral and rotation misalignment, while the conductor and space is saved by 8.49% and 22.22% compared with the traditional DD coil. The proposed DC coil is feasible to be applied in the actual GIS scene.

Tunable frequency bandgaps in elastic metamaterials with internal contacts

We design an elastic metamaterial with internal contacts and study the tunable frequency band structure of the metamaterial. It is well-known that the frequency band of granule structures consisting of particles changes depending on the system's compression because of the nonlinearity of the contact between particles. We adopt this efficient tunning mechanism, i.e., contact, in the design of continuum type elastic metamaterials. We first design a unit cell structure showing internal contacts under compression and fabricate it using a 3D printer. We numerically and experimentally identify that the unit cell's stiffness suddenly increases when the internal contact happens. This sudden change of the stiffness induces a change of frequency characteristics of the structure. Here, we demonstrate that internal contacts are useful for designing various frequency bandgaps and tuning them efficiently.