Cyclic Force Research Articles

Plexin-B2 Mediates Orthodontic Tension-Induced Osteogenesis via the RhoA/F-Actin/YAP Pathway.

This study aims to investigate the role of Plexin-B2 in tension-induced osteogenesis of periodontal ligament stem cells (PDLSCs) and its biomechanical mechanism. In vitro, cyclic tension simulated orthodontic forces to assess Plexin-B2 expression in PDLSCs. We then knocked out Plexin-B2 using lentivirus to explore its role in tension-induced osteogenesis. Invivo, we used nickel-titanium springs to establish orthodontic tooth movement (OTM) models in mice. Local periodontal Plexin-B2 expression was knocked down using adeno-associated viruses (AAVs) to study its influence on new bone formation under mechanical tension in OTM models. Molecular mechanisms were elucidated by manipulating Plexin-B2 and RhoA expression, assessing related proteins, and observing F-actin and Yes-associated protein (YAP) through immunofluorescence. Plexin-B2 expression in PDLSCs increased under cyclic tension. Decrease of Plexin-B2 reduced the expression of osteogenic protein in PDLSCs and negatively affected new bone formation during OTM. RhoA expression and phosphorylation of ROCK2/LIMK2/Cofilin decreased in Plexin-B2 knockout PDLSCs but were reversed by RhoA overexpression. The level of F-actin decreased in Plexin-B2 knockout PDLSCs but increased after RhoA rescue. Nuclear YAP was reduced in Plexin-B2 knockout PDLSCs but increased after RhoA overexpression. Plexin-B2 is involved in tension-induced osteogenesis. Mechanistically, the RhoA signaling pathway, the F-actin arrangement, and the nuclear translocation of YAP are involved in the mechanotransduction of Plexin-B2.

Mechanosensory entities and functionality of endothelial cells.

The endothelial cells of the blood circulation are exposed to hemodynamic forces, such as cyclic strain, hydrostatic forces, and shear stress caused by the blood fluid's frictional force. Endothelial cells perceive mechanical forces via mechanosensors and thus elicit physiological reactions such as alterations in vessel width. The mechanosensors considered comprise ion channels, structures linked to the plasma membrane, cytoskeletal spectrin scaffold, mechanoreceptors, and junctional proteins. This review focuses on endothelial mechanosensors and how they alter the vascular functions of endothelial cells. The current state of knowledge on the dysregulation of endothelial mechanosensitivity in disease is briefly presented. The interplay in mechanical perception between endothelial cells and vascular smooth muscle cells is briefly outlined. Finally, future research avenues are highlighted, which are necessary to overcome existing limitations.

Study of Capacity Calsium Board – Styrofoam Sandwich Panels on Wall Systems under Cyclic Lateral Force

Study of Capacity Calsium Board – Styrofoam Sandwich Panels on Wall Systems under Cyclic Lateral Force

Machine-learning assisted analysis on the seismic performance of steel reinforced concrete composite columns

This paper presents the data-driven analysis on the seismic performance of steel reinforced concrete (SRC) composite columns by using machine learning (ML) algorithms. A total of 248 test data of SRC columns subjected to the combined axial compressive force and low reversed cyclic horizontal force was collected from the published literatures to form the database. Since the seismic action triggers the SRC columns to suffer from different failure mode and hence exhibit quite different load bearing mechanism, six ML algorithms were employed to facilitate the failure mode classification and bearing capacity prediction. It was found that the Random Forest (RF) model predicts the failure mode most accurately, while XGBoost model delivers the best estimation of bearing capacity. To further evaluate the feasibility of ML models and unveil the interaction between different variables, interpretability analysis of ML models was carried out. In comparison with the conventional empirical judgement and theoretical derivation, ML model delivers enhanced accuracy and robustness to predict the seismic performance of SRC columns, and hence it could be used as a promising alternative for the preliminary design and analysis of SRC columns.

Intramedullary nailing at different distal tibial fracture levels: A biomechanical study.

Distal tibial fractures remains a significant challenge in orthopedic trauma surgery. As the fracture level approaches the joint, alternative fixation options instead of intramedullary nailing (IMN) come to the fore. The present study aimed to assess the biomechanical stability of IMN at different distal tibial fracture levels and the number of locking screws required. Using a total of 21 sawbone models, 3 different tibial fracture levels (3, 4.5, and 6 cm proximally to the talocrural joint) were created and the fractures were fixed using 2, 3, or 4 distal locking screws. A single compression force at a speed of 30 mm/min with a maximum force of 800 Newton and a cyclic compression force of 60 cycles at a speed of 60 mm/min was applied to all tibia models. The applied weight and displacements from the fracture lines were recorded and evaluated. There was no statistically significant difference in fixation with 2 distal locking screws in groups 1, 2, and 3 (single test P =.9689) (cyclic test P =.8050). Therefore, if 2 distal screws are used, the fracture level does not affect the strength of fixation. In fractures located 6 cm proximal to the talocrural joint, all 4 holes of the nail can be used to insert screws, which provides a stronger fixation. When 2 screws are used, a statistically weaker fixation is obtained than with 3 or 4 screws. However, there is no significant difference between using 3 or 4 screws. Our findings support the use of IMN with 2 distal locking screws as a viable option for the management of distal tibial fractures. We found that it provides sufficient fixation regardless of the fracture level, suggesting that there is no need to choose an alternative fixation technique due to concerns of inadequate fixation as the fracture line moves distally. In cases where more stable fixation is desired, an additional locking screw can be used, but the potential increase in procedure and fluoroscopy time should be considered.

Role of STIM1 in stretch-induced signaling in human airway smooth muscle.

Alteration in the normal mechanical forces of breathing can contribute to changes in contractility and remodeling characteristic of airway diseases, but the mechanisms that mediate these effects in airway cells are still under investigation. Airway smooth muscle (ASM) cells contribute to both contractility and extracellular matrix (ECM) remodeling. In this study, we explored ASM mechanisms activated by mechanical stretch, focusing on mechanosensitive piezo channels and the key Ca2+ regulatory protein stromal interaction molecule 1 (STIM1). Expression of Ca2+ regulatory proteins, including STIM1, Orai1, and caveolin-1, mechanosensitive ion channels Piezo-1 and Piezo-2, and NLRP3 inflammasomes were upregulated by 10% static stretch superimposed on 5% cyclic stretch. These effects were blunted by STIM1 siRNA. Histamine-induced [Ca2+]i responses and inflammasome activation were similarly blunted by STIM1 knockdown. These data show that the effects of mechanical stretch in human ASM cells are mediated through STIM1, which activates multiple pathways, including Piezo channels and the inflammasome, leading to potential downstream changes in contractility and ECM remodeling.NEW & NOTEWORTHY Mechanical forces on the airway can contribute to altered contractility and remodeling in airway diseases, but the mechanisms are not clearly understood. Using human airway smooth muscle cells exposed to cyclic forces with static stretch to mimic breathing and static pressure, we found that the effects of stretch are mediated through STIM1, resulting in the activation of multiple pathways, including Piezo channels and the inflammasome, with potential downstream influences on contractility and remodeling.

Nonlinear Slippage of Tensile Armor Layers of Unbonded Flexible Riser Subjected to Irregular Loads

The unbonded flexible riser has been increasingly applied in the ocean engineering industry to transport oil and gas resources from the seabed to offshore platforms. The slippage of helical layers, especially the tensile armor layers of unbonded flexible risers, contribute to the nonlinear hysteresis phenomenon, which is a research hotspot and difficulty. In this paper, on the basis of a typical eight-layer unbonded flexible riser model, the nonlinear slippage of a tensile armor layer and the corresponding nonlinear behavior of an unbonded flexible riser subjected to irregular external loads are studied by numerical modeling with detailed cross-sectional properties of the helical layers, and are verified through a theoretical method considering the coupled effect of the external loads on the unbonded flexible riser. Firstly, the balance equation of each layer considering the effect of external loads is established based on functional principles, and the overall theoretical model of the unbonded flexible riser is set up in consideration of the contact between adjacent layers. Secondly, the numerical modeling of each separate layer within the unbonded flexible riser, including the actual geometry of the carcass and pressure armor layer, is established, and solid elements are applied to all the interlayers, thus simulating the nonlinear contact and friction between and within interlayers. Finally, after verification through test data, the behavior of the unbonded flexible riser under the cyclic axial force, torsion, bending moment, and irregular external and internal pressure is studied. The results show that the tensile armor layer can slip under irregular loads. Additionally, some suggestions related to the analysis of unbonded flexible risers under irregular loads are drawn in the end.

Evaluation of Rotation Capacity and Bauschinger Effect Coefficient of I-Shaped Beams Considering Loading Protocol Influences

Recent catastrophic earthquake events have reinforced the necessity of evaluating the seismic performance of buildings. Notably, the buildings can go into the plastic phase during a striking earthquake disaster. Under this condition, the current design codes assume seismic response reduction by virtue of the energy dissipation capacity of the structural members. In the strong-column–weak-beam design, which involves I-shaped beams and boxed columns, the mechanism is defined as a standard design scheme to prevent the building from collapsing. Therefore, energy dissipation relies highly on the I-shaped beam performance. However, the I-shaped beam performance can differ depending on the loading history experienced, whereas this effect is untouched in the prevailing evaluation equation. Hence, this study first performs cyclic loading tests of 11 specimens using different loading protocols. The experimental results clarify the fluctuation in the structural performance of I-shaped beams depending on the applied loading hysteresis, proving the necessity of considering the stress history for proper assessment. Furthermore, the database of experimental results is constructed based on the previous experimental studies. Ultimately, the novel evaluation equation is proposed to reflect the influences of the loading protocol. This equation is demonstrated to effectively assess the member performance retrieved from the experiment of 65 specimens, comprising 11 specimens from this investigation and 54 specimens from the database. The width–thickness ratio, shear span-to-depth ratio, and loading protocols are utilized as the evaluation parameters. Moreover, the prediction equation of the Bauschinger effect coefficient is newly established to convert the energy dissipation capacity under monotonically applied force into hysteretic energy dissipation under the cyclic forces.

Cannulated screws versus nitinol staple for tarsometatarsal fusion: A cadaveric biomechanical comparison model

BackgroundThe objective of this study was to evaluate the biomechanical stability of a medially placed nitinol staple compared to two crossed-screws in the first TMT-1 joint fusion in a cadaveric cyclic loading model. MethodsSeven matched pairs (N = 7) of lower limb cadaveric specimens were utilized. TMT-1 joints from each donor were fixed with a medially placed nitinol staple or dorsally placed two 3.5 mm partially threaded cannulated crossed-screws. Specimens were tested in a 4-point bending setting with increasing cyclic forces. ResultsThe mean plantar gapping was not significantly different between the two groups at any loading stage below 200 N. Specimens fixed with a nitinol staple failed at a mean load of 305 ± 57 N. Conversely, those fixed with crossed-screws failed at 373 ± 86 N. (P = .09). ConclusionThere was no statistical difference between a medially placed nitinol staple and dorsally placed crossed-screws in failure loads and plantar gapping under cyclic loads at the TMT-1 joint, however, the staple fixation was much more variable. Level of evidenceLevel V, basic science study, biomechanics

Structural behavior of steel tube reinforced resilient RAC shear walls under static cyclic loading

This paper proposed a method to enhance the energy dissipation capacity of recycled aggregate concrete (RAC) shear walls reinforced with ultra-high strength bars (UHSB). The proposed method encases circular steel tubes within the boundary elements of walls. With the presence of steel tubes, steel fibers and axial load level as primary research variables, five RAC shear walls were fabricated and tested under reversed cyclic lateral force and constant axial compression to verify the effectiveness of the proposed method. The test results showed that the presence of steel tubes upgraded lateral resistance and enhanced energy dissipation capacity, while causing some subtle splitting cracks. Due to the yielding of the steel tubes, the encasement of the steel tube increased residual drift ratio at large drift, but the measured residual drift ratios of test walls still were kept less than 0.5 % until 2.5 % drift ratio. The addition of steel fibers delayed cracking, constrained the cover concrete and reduced damage to the specimens. Test results also indicated that increasing concrete strength and axial compression level could enhance the lateral resistance of the proposed wall. In addition, a numerical analytical method is presented to analyze the cyclic behavior of the proposed shear walls. Good agreement was observed between the measured and calculated hysteretic loops.

Boosted charge transfer in a naturally formed Ca(Al2Si2O8)/Fe2O3 heterojunction for piezocatalytical formation of H2O2 and solidification of U(VI)

Energy and environmental issues make the generation of H2O2 and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al2Si2O8)/Fe2O3 heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H2O2 with a high yield of 196.7 μmol·g−1 in 4 h, which further solidifies U(VI) to form a solid of UO2O2. The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al2Si2O8)/Fe2O3 and provides a new idea for piezocatalytic extraction of uranium.

Cyclic behaviour of circular CFT-SG columns under axial tension-compression: Novel FE modelling and design methods

The ultra-high concrete-filled steel tubular (CFT) power transmission tower is popularly applied in engineering practice, which may be under a typical cyclic axial tension-compression loading condition due to the dynamic wind load. Nonetheless, the CFT columns of the tower may be accompanied by significant gap defects due to the influence of structural feature, material property, and service environment. Hence, to figure out the performance of circular CFT columns with spherical-cap gaps (CFT-SG) subjected to cyclic axial tension-compression, this paper investigates a constitutive relationship for the gapped core concrete, which is verified by several existing experiments. A novel numerical modelling approach for simulating the irregular cross-section of the circular CFT-SG columns under cyclic axial load was following established based on the triangulation method and code programming. The influence of important parameters such as gap ratio, material strength, and diameter to thickness ratio on the hysteresis characteristics, load-bearing capacity, elastic stiffness, energy dissipation and ductility of circular CFT-SG columns under cyclic axial tension-compression force is studied. Moreover, the restoring force model of the circular CFT-SG columns under cyclic axial tension-compression is finally presented. Research results declare that the compressive bearing capacity, stiffness, ductility, and energy dissipation of circular CFT-SG columns under cyclic axial tension-compression are gradually weakened with the increment in the gap ratio. The numerical modelling approach and restoring force model proposed in this article can accurately evaluate the hysteresis performance of circular CFT-SG columns subjected to cyclic axial tension-compression.

Two‐Photon Laser Printing to Mechanically Stimulate Multicellular Systems in 3D

AbstractBiological activities take place in 3D environments, where cells interact in various directions in a defined, often microstructured, space. A sub‐millimeter‐sized stretching device is developed to mechanically stimulate a structurally restricted, soft multicellular microenvironment to investigate the effect of defined cyclic mechanical forces on a multicellular system. It consists of a multi‐material 3D microstructure made of Polydimethylsiloxane (PDMS) and gelatine‐based hydrogel, which is printed using the 2‐photon polymerization (2PP) method. The printed structures are first characterized microscopically and mechanically to study the effect of different printing parameters. Using 2PP, organotypic cell cultures are then directly printed into the hydrogel structures to create true 3D cell culture systems. These systems are mechanically stimulated with a cantilever by indenting at defined positions. The cells in the 3D organotypic cell culture change morphology and actin orientation when exposed to cyclic mechanical stretch, even within short timescales of 30 min. As proof of concept, a Medaka retinal organoid is encapsulated in the same structure to demonstrate that even preformed organoids can be stimulated by this method. The results highlight the capability of 2PP for manufacturing multifunctional soft devices to mechanically control multicellular systems at micrometer resolution and thus mimic mechanical stresses as they occur in vivo.

Construction risk analysis of cantilever casting mid-span closure of bridge in reservoir area

In order to assess the impact of frequent microseismic and cyclic water flow forces on the bridge cantilever casting construction in the Three Gorges reservoir area, a limited element-quantum-orthogonal experimental design-neural network-Monte Carlo simulation method was used to analyze the risk assessment of the construction. The orthogonal experimental design method is utilized to generate probability distribution samples of water velocity, water height, and microseismic acceleration. These samples are then combined with a finite element model and trained using a BP neural network. This approach aims to establish a nonlinear mapping relationship between each control parameter and the axial deviation value in the mid-span closure, and then the Monte Carlo simulation is used to generate the random influence parameter, which can be substituted into the trained BP neural network to predict the risk of the error in the mid-axial deviation. The results suggested that the risk probability of the medial axis deviation of the closure section due to the coupling effect of water flow force and high-frequency microseismicity had reached 5.06%, and the risk of line deviation of the cantilever casting construction of the bridge in the reservoir area needed to be paid sufficient attention and prevented. The risk of line deviation of the cantilever casting construction of the reservoir bridge needs to attract enough attention and precaution.

An analysis of vibration signals is conducted to monitor the condition of the clutch of a centrifugal pump, employing ISO 10816 standards

Vibration in the shaft of a centrifugal pump arises from various factors, including the spacing between clutches, belt thickness, width, and their positioning within the clutch assembly. Vibration serves as a vital diagnostic tool for assessing machinery, offering insights into both motion and translation. Understanding vibrations and analyzing corresponding data are essential for effective maintenance and troubleshooting protocols. By leveraging this knowledge, companies can mitigate downtime, enhance productivity, and extend the operational lifespan of their machinery. Vibration stems from cyclic forces acting upon machine components, triggering energy release within the structure and resulting in oscillations. Excessive vibration not only generates noise but also compromises pump performance and jeopardizes critical components, notably the shaft and bearings. The objective of this study is to monitor and analyze vibration in centrifugal pumps equipped with modified belt connections. Various configurations of belt thickness, width, distance, and positioning were explored. Real-time data was gathered using accelerometer sensors to capture X, Y, and Z-axis values, subsequently converted from analog to digital format. Among the configurations tested, the Outside-Inside belt positioning, with belt dimensions of 6.5mm thickness, 150mm width, and a 40mm distance, exhibited the lowest average vibration value at 8.72mm/s. However, according to ISO 10816 standards, this measurement falls within the unsatisfactory category, indicating the need for further refinement in pump design and maintenance practices.

Actuation of Soft Thermoresponsive Hydrogels Mechanically Stimulates Osteogenesis in Human Mesenchymal Stem Cells without Biochemical Factors.

Mesenchymal stem cells (MSCs) have the potential to differentiate into multiple lineages and can be harvested relatively easily from adults, making them a promising cell source for regenerative therapies. While it is well-known how to consistently differentiate MSCs into adipose, chondrogenic, and osteogenic lineages by treatment with biochemical factors, the number of studies exploring how to achieve this with mechanical signals is limited. A relatively unexplored area is the effect of cyclic forces on the MSC differentiation. Recently, our group developed a thermoresponsive N-ethyl acrylamide/N-isopropylacrylamide (NIPAM/NEAM) hydrogel supplemented with gold nanorods that are able to convert near-infrared light into heat. Using light pulses allows for local hydrogel collapse and swelling with physiologically relevant force and frequency. In this study, MSCs are cultured on this hydrogel system with a patterned surface and exposed to intermittent or continuous actuation of the hydrogel for 3 days to study the effect of actuation on MSC differentiation. First, cells are harvested from the bone marrow of three donors and tested for their MSC phenotype, meeting the following criteria: the harvested cells are adherent and demonstrate a fibroblast-like bipolar morphology. They lack the expression of CD34 and CD45 but do express CD73, CD90, and CD105. Additionally, their differentiation potential into adipogenic, chondrogenic, and osteogenic lineages is validated by the addition of standardized differentiation media. Next, MSCs are exposed to intermittent or continuous actuation, which leads to a significantly enhanced cell spreading compared to nonactuated cells. Moreover, actuation results in nuclear translocation of Runt-related transcription factor 2 and the Yes-associated protein. Together, these results indicate that cyclic mechanical stimulation on a soft, ridged substrate modulates the MSC fate commitment in the direction of osteogenesis.

Piezo1 mediates abnormal type 2 immune response to aggravate ischemia–reperfusion acute lung injury which by regulating alveolar macrophages derived IL-33: A hypothesis

The pathogenesis of ischemia–reperfusion acute lung injury (IR-ALI) is not yet fully understood. We previously reported that unwonted increased type 2 immunity plays a key role in the pathogenesis and the pathophysiological process in acute haemorrhagic inducedlung injury. Progressive lung edema after ischemia reperfusion is accompanied by the change of lung cyclical hydrostatic force. The changed lung mechanical force could activate the mechanosensitive Piezo1 channel in alveolar macrophages. Furthermore, our group had elucidated that microenvironmental stiffness exacerbated hindlimb ischemia reperfusion injury by activating Piezo1 in bone marrow-derived macrophages. Considering early findings that IL-33 is a potent driver of pulmonary type 2 immunity, that Piezo1 plays an important role in regulating macrophages biological activity and that alveolar macrophages are involved in orchestrating the early abnormal detrimental type 2 inflammatory response in lung ischemia–reperfusion injury, we herein hypothesize that the change of mechanical force in lung after ischemia–reperfusion might activate Piezo1/IL-33/type 2 immunity axis and aggravate lung ischemic injury. Mechanistically, Piezo1 mediates extracellular Ca2+influx and activates Ca2+-dependent Calcineurin-NFAT signaling in alveolar macrophages, leading to transcriptional activation of IL-33, thereby promoting abnormal type 2 immune response and participating in the occurrence and development of IR-ALI. Future validation of these mechanisms could provide a deeper explanation of the new pathogenesis of IR-ALI and ultimately serve for clinical treatment.

Two classes of action-stabilizing synergies reflecting spinal and supraspinal circuitry.

We explored force-stabilizing synergies during accurate four-finger constant force production tasks in spaces of finger modes (commands to fingers computed to account for the finger interdependence) and of motor unit (MU) firing frequencies. The main specific hypothesis was that the multifinger synergies would disappear during unintentional force drifts without visual feedback on the force magnitude, whereas MU-based synergies would be robust to such drifts. Healthy participants performed four-finger accurate cyclical force production trials followed by trials of constant force production. Individual MUs were identified in the flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC). Principal component analysis was applied to motor unit frequencies to identify robust MU groups (MU-modes) with parallel scaling of the firing frequencies in FDS, in EDC, and the combined MUs of FDS + EDC. The framework of the uncontrolled manifold hypothesis was used to quantify force-stabilizing synergies when visual feedback on the force magnitude was available and 15 s after turning the visual feedback off. Removing visual feedback led to a force drift toward lower magnitudes, accompanied by the disappearance of multifinger synergies. In contrast, MU-mode synergies were minimally affected by removing visual feedback off and continued to be robust for the FDS and for the EDC, while being absent for the (FDS + EDC) analysis. We interpret the findings within the theory of hierarchical control of action with spatial referent coordinates. The qualitatively different behavior of the multifinger and MU-mode-based synergies likely reflects the difference in the involved neural circuitry, supraspinal for the former and spinal for the latter.NEW & NOTEWORTHY Two types of synergies, in the space of commands to individual fingers and in the space of motor unit groups, show qualitatively different behaviors during accurate multifinger force-production tasks. After removing visual feedback, finger force synergies disappear, whereas motor unit-based synergies persist. These results point at different neural circuitry involved in these two basic classes of synergies: supraspinal for multieffector synergies, and spinal for motor unit-based synergies.

Solar cycle as a distinct line of evidence constraining Earth’s transient climate response

Severity of warming predicted by climate models depends on their Transient Climate Response (TCR). Inter-model spread of TCR has persisted at ~ 100% of its mean for decades. Existing observational constraints of TCR are based on observed historical warming response to historical forcing and their uncertainty spread is just as wide, mainly due to forcing uncertainty, and especially that of aerosols. Contrary, no aerosols are involved in solar-cycle forcing, providing an independent, tighter, constraint. Here, we define a climate sensitivity metric: time-dependent response regressed against time-dependent forcing, allowing phenomena with dissimilar time variations, such as the solar cycle with 11-year cyclic forcing, to be used to constrain TCR, which has a linear time-dependent forcing. We find a theoretical linear relationship between the two. The latest coupled atmosphere-ocean climate models obey the same linear relationship statistically. The proposed observational constraint on TCR is about 1/3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{1}}/{{3}}$$\\end{document} as narrow as existing constraints. The central estimate, 2.2 oC, is at the midpoint of the spread of the latest generation of climate models, which are more sensitive than those of the previous generations.

Synchrotron X-ray operando study and multiphysics modelling of the solidification dynamics of intermetallic phases under electromagnetic pulses

In this paper, we used synchrotron X-ray radiography and tomography to study systematically and in operando conditions the growth dynamics of the primary Al3Ni intermetallic phases in an Al-15wt%Ni alloy in the solidification process with magnetic pulses of up to 1.5 T. The real-time observations clearly revealed the growth dynamics of the intermetallics in time scale from millisecond to minutes, including phase growth instability, side branching, fragmentation and orientation alignment under different magnetic pulse fluxes. A multiphysics numerical model was also developed to calculate the alternating and cyclic Lorentz forces and stresses acting on the Al3Ni phases and the nearby melt due to the applied pulses. Combining the results of the operando experiments and modelling, for the first time, the differential forces between the growing Al3Ni phases and the nearby melt were quantified. The forces can create slip dislocations at the growing crystal front which can further develop into nm and µm crystal steps for initiating phase branching. Furthermore, the magnitudes of the shear stresses are strongly related to the size, morphological and geometric features of the growing Al3Ni phases. Dependent on the magnitude of the shear stresses, phase fragmentation could occur in a single pulse period or in multiple pulse periods via fatigue mechanism. This systematic research work elucidate some of the long-time debated hypotheses concerning intermetallic phases growth instability and phase fragmentation in pulse magnetic fields. The research establishes a robust theoretical framework for quantitative understanding of the intermetallic phase growth dynamics in solidification under pulse magnetic fields.