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Polar molecules confined in an optical lattice are a versatile platform to explore spin-motion dynamics based on strong, long-range dipolar interactions 1 , 2 . The precise tunability 3 of Ising and spin-exchange interactions with both microwave and d.c. electric fields makes the molecular system particularly suitable for engineering complex many-body dynamics 4 – 6 . Here we used Floquet engineering 7 to realize new quantum many-body systems of polar molecules. Using a spin encoded in the two lowest rotational states of ultracold 40 K 87 Rb molecules, we mutually validated XXZ spin models tuned by a Floquet microwave pulse sequence against those tuned by a d.c. electric field through observations of Ramsey contrast dynamics. This validation sets the stage for the realization of Hamiltonians inaccessible with static fields. In particular, we observed two-axis twisting 8 mean-field dynamics, generated by a Floquet-engineered XYZ model using itinerant molecules in two-dimensional layers. In the future, Floquet-engineered Hamiltonians could generate entangled states for molecule-based precision measurement 9 or could take advantage of the rich molecular structure for quantum simulation of multi-level systems 10 , 11 . A study demonstrates the application of Floquet Hamiltonian engineering to ultracold trapped polar molecules to realize interactions relevant to quantum metrology and many-body physics.

We introduce a notion of stability for non-autonomous Hamiltonian flows on two-dimensional annular surfaces. This notion of stability is designed to capture the sustained twisting of particle trajectories. The main Theorem is applied to establish a number of results that reveal a form of irreversibility in the Euler equations governing the motion of an incompressible and inviscid fluid. In particular, we show that nearby general stable steady states (i) all fluid flows exhibit indefinite twisting (ii) vorticity generically exhibits gradient growth and wandering. We also give examples of infinite time gradient growth for smooth solutions to the SQG equation and of smooth vortex patches that entangle and develop unbounded perimeter in infinite time.

Filopodia are actin-rich structures, present on the surface of eukaryotic cells. These structures play a pivotal role by allowing cells to explore their environment, generate mechanical forces or perform chemical signaling. Their complex dynamics includes buckling, pulling, length and shape changes. We show that filopodia additionally explore their 3D extracellular space by combining growth and shrinking with axial twisting and buckling. Importantly, the actin core inside filopodia performs a twisting or spinning motion which is observed for a range of cell types spanning from earliest development to highly differentiated tissue cells. Non-equilibrium physical modeling of actin and myosin confirm that twist is an emergent phenomenon of active filaments confined in a narrow channel which is supported by measured traction forces and helical buckles that can be ascribed to accumulation of sufficient twist. These results lead us to conclude that activity induced twisting of the actin shaft is a general mechanism underlying fundamental functions of filopodia. The authors show how tubular surface structures in all cell types, have the ability to twist and perform rotary sweeping motion to explore the extracellular environment. This has implications for migration, sensing and cell communication.

Advances in material architectures have enabled endowing materials with exotic attributes not commonly available in the conventional realm of mechanical engineering. Twisting, a mechanism whereby metamaterials are used to transform static axial load into twist motion, is of particular interest to this study. Herein, computations based on the finite element method, corroborated by a theoretical approach derived from applying Lagrange’s equations to a monoatomic spring-mass system, are employed to explore the longitudinal-twist (L-T) conversion exhibited by a chiral tetragonal-beam metamaterial. Firstly, we perform an eigenvalue analysis taking into account the polarization states to highlight the contribution of the longitudinal mode in the L-T conversion. We contrast the twisting behavior of the chiral cell with that of other homogeneous medium, octagonal-tube, and non-chiral cells. Moreover, we demonstrate the influence of the cell’s chirality on the L-T conversion using both time-domain and frequency-domain studies. The findings indicate that at least a portion of the longitudinally propagating wave is transformed into twist throughout a broad frequency range and even quasi-totally converted at distinct frequencies.

The connecting cable between the inter-satellite link (ISL) antenna and the deployment arm of geosynchronous Earth orbit (GEO) telecommunication satellites undergoes continuous two-dimensional twisting motion, with up to 30,000 rotations during the entire on-orbit lifetime. By establishing a two-dimensional twisting mechanical performance verification platform, we obtained the resistance torque and lifetime characteristics of the extravehicular cable installed using traditional methods. Experiment results showed that the satellite extravehicular cable installed using traditional methods cannot effectively resist mechanical damage caused by antenna twisting throughout the entire life cycle. Therefore, this paper proposes a strength-enhanced cable based on a combination of metal hoses and polyimide films to resist two-dimensional twisting motion. Accelerated lifetime tests have verified the mechanical strength and twisting characteristics of this cable, which can be applied to the external cable of the ISL antenna of GEO telecommunication satellites, effectively improving satellite reliability.

Compressive strength is a key to understanding the internal structure of dust aggregates in protoplanetary disks and their resultant bodies, such as comets and asteroids in the solar system. Previous work has modeled the compressive strength of highly porous dust aggregates with volume filling factors lower than 0.1. However, a comprehensive understanding of the compressive strength from low (<0.1) to high (>0.1) volume filling factors is lacking. In this paper, we investigate the compressive strength of dust aggregates by using aggregate compression simulations resolving constituent grains based on Johnson-Kendall-Roberts theory to formulate the compressive strength comprehensively. We perform a series of numerical simulations with moving periodic boundaries mimicking the compression behavior. As a result, we find that the compressive strength becomes sharply harder when the volume filling factor exceeds 0.1. We succeed in formulating the compressive strength comprehensively by taking into account the rolling motion of aggregates for low volume filling factors and the closest packing of aggregates for high volume filling factors. We also find that the dominant compression mechanisms for high volume filling factors are sliding and twisting motions, while rolling motion dominates for low volume filling factors. We confirm that our results are in good agreement with previous numerical studies. We suggest that our analytical formula is consistent with the previous experimental results if we assume the surface energy of silicate is ≃210 ± 90 mJ m−2. Now, we can apply our results to properties of small compact bodies, such as comets, asteroids, and pebbles.

The formation mechanism of spicules is fundamentally important for understanding mass and energy transport from the chromosphere into the corona. Recent studies suggested that spicules may be powered by microfilament eruptions. However, direct observational evidence remains limited due to insufficient spatial resolution. Using high-resolution Hα broadband observations from the Visible Broadband Imager on board the Daniel K. Inouye Solar Telescope, we identify 30 spicule events triggered by microfilament eruptions in a quiet-Sun region near the solar disk center on 2023 August 29. The detected microfilaments have an average length of 0.93 ± 0.46 Mm and a minimum length of 0.17 Mm, substantially smaller than previously reported minifilaments. We identify two distinct morphological classes of ejecta: individual spicules associated with smaller microfilaments and enhanced spicular activities associated with larger microfilaments. Moreover, some events exhibit apparent twisting motions. All these high-resolution observations provide compelling evidence that spicules can be triggered by microfilament eruptions.

For large‐scale wind turbines, the long and flexible blades are prone to flapwise, edgewise, and twisting motions. The rigid‐blade assumption commonly used in conventional CFD (computational fluid dynamics) simulations may be insufficient for accurately predicting the aerodynamic characteristics of large‐scale wind turbines. To improve the physical realism of the CFD model, prescribed blade twisting motion is introduced, and its influence on the aerodynamic characteristics of a large‐scale wind turbine is investigated. Taking a three‐bladed wind turbine as the research object, large eddy simulation (LES) is adopted, and the blade rotation and the prescribed twisting motion are realized through sliding‐mesh and dynamic‐mesh techniques. The twisting frequency is set equal to the rotor rotational frequency (0.2867 Hz), and the blade‐tip twisting amplitudes are set to 0°, 2°, 4°, and 6° for parametric investigation. The results show that prescribed blade twisting causes periodic variations in torque and axial force. Compared with the no‐twist case, the average torque decreases by 0.94%, 3.53%, and 7.32% for blade‐tip twisting amplitudes of 2°, 4°, and 6°, respectively, while the corresponding reductions in average axial force are 0.57%, 1.97%, and 3.87%. Blade twisting also modifies the near‐wake velocity distribution, blade‐surface pressure distribution, and blade‐tip flow structure. These results indicate that prescribed blade twisting should be considered when evaluating the unsteady aerodynamic response of large‐scale wind turbines.

The nature and detailed properties of the heating of the million-degree solar corona are important issues that are still largely unresolved. Nanoflare heating might be dominant in active regions and quiet Sun, although direct signatures of such small-scale events are difficult to observe in the highly conducting, faint corona. The aim of this work is to test the theory of coronal heating by nanoflares in braided magnetic field structures. We analyze a 3D MHD model of a multistrand flux tube in a stratified solar atmosphere, driven by twisting motions at the boundaries. We show how the magnetic structure is maintained at high temperature and for an indefinite time, by intermittent episodes of local magnetic energy release due to reconnection. We synthesize the optically thin emission with SDO/AIA and MUSE and compare the synthetic observations with the intrinsic coronal plasma properties, focusing on the response to impulsive coronal heating. Currents’ buildup and their impulsive dissipation into heat are also investigated through different runs. In this first paper, we describe the proliferation of heating from the dissipation of narrow current sheets in realistic simulations of braided coronal flux tubes at unprecedented high spatial resolutions.

In this paper, we focus on the challenges of modeling deformable 3D objects from casual videos. With the popularity of NeRF, many works extend it to dynamic scenes with a canonical NeRF and a deformation model that achieves 3D point transformation between the observation space and the canonical space. Recent works rely on linear blend skinning (LBS) to achieve the canonical-observation transformation. However, the linearly weighted combination of rigid transformation matrices is not guaranteed to be rigid. As a matter of fact, unexpected scale and shear factors often appear. In practice, using LBS as the deformation model can always lead to skin-collapsing artifacts for bending or twisting motions. To solve this problem, we propose neural dual quaternion blend skinning (NeuDBS) to achieve 3D point deformation, which can perform rigid transformation without skin-collapsing artifacts. To register 2D pixels across different frames, we establish a correspondence between canonical feature embeddings that encodes 3D points within the canonical space, and 2D image features by solving an optimal transport problem. Besides, we introduce a texture filtering approach for texture rendering that effectively minimizes the impact of noisy colors outside target deformable objects.