Rotation Mechanism Research Articles

Insights into the Associations Between Systolic Left Ventricular Rotational Mechanics and Left Atrial Peak Reservoir Strains in Healthy Adults from the MAGYAR-Healthy Study

Introduction: In systole, when the left ventricle (LV) twists, the left atrium (LA) behaves like a reservoir, having a special wall contractility pattern opposite to that of the LV wall. Accordingly, the objective of the present study was to investigate the associations between LV rotational mechanics and LA peak (reservoir) strains as assessed simultaneously by three-dimensional speckle-tracking echocardiography (3DSTE) under healthy conditions. Methods: In the present study, 157 healthy adults (mean age: 33.2 ± 12.7 years, 73 men) were involved. Complete two-dimensional Doppler echocardiography with 3DSTE-derived data acquisition were performed in all cases. The 3DSTE-derived LV rotational and LA strain parameters were determined at a later date. Results: Global LA peak reservoir circumferential (22.7 ± 6.4% vs. 27.6 ± 6.8%, p < 0.05) and area (57.8 ± 20.0% vs. 66.0 ± 22.7%, p < 0.05) strains proved to be reduced in the case of the highest vs. lowest basal LV rotation; other LA peak reservoir strains were not associated with increasing basal LV rotation. Global LA peak radial strain was highest in the case of the lowest vs. highest apical LV rotation (−19.2 ± 9.4% vs. −13.0 ± 8.2%, p < 0.05). Global LA peak reservoir 3D strain was lowest in the case of the highest vs. lowest apical LV rotation (−9.9 ± 6.8% vs. −5.0 ± 4.2%, p < 0.05). Only apical LV rotation proved to be significantly reduced in the case of the highest vs. lowest global LA peak reservoir 3D strain (8.12 ± 3.23° vs. 10.50 ± 3.44°, p < 0.05). Other global LA peak reservoir strains were not associated with basal and apical LV rotations. Conclusions: In LV systole, LV rotational mechanics is associated with LA deformation represented by LA peak (reservoir) strains even in healthy circumstances. While basal LV rotation is associated with LA widening, apical LV rotation is associated with LA thinning, suggesting the close cooperation of the LV and LA in systole even in healthy adults.

Plastic deformation and trace element mobility in sphalerite

Abstract Sphalerite (ZnS) is a sulfide found in a large variety of ore deposits and is frequently hosted in meta-morphic terranes that have undergone deformation and related recrystallization. However, the deformation mechanisms of sphalerite are still poorly understood because recrystallization evidence is barely visible under an optical microscope and may reflect complex and frequently multistage mechanisms. Furthermore, sphalerite may host up to a few thousands of parts per million of critical metals such as gallium (Ga), germanium (Ge), and indium (In). Metamorphic conditions and dynamic recrystallization may have induced local or total redistribution of these elements. Modern techniques such as electron backscattered diffraction analyses (EBSD) and laser-induced breakdown spectroscopy (LIBS) applied on sphalerite allow for the examination of grain boundaries, crystal-plastic deformation, and internal chemical diffusion, which classically reflect active deformation mechanisms. In this study, a microstructural and in situ chemical comparison between four sphalerite types (types 1, 2, 3, and 4) has been made for the first time. The four sphalerite types present different deformation imprints, although they are hosted in a similar geological setting: the Pyrenean Axial Zone and the Montagne Noire Variscan massifs (France). Based on EBSD and LIBS mapping, we describe two regional sphalerite growth stages composed of dark red crystals with polygonal shape (type 1, Bentaillou-Liat deposit) and light- to dark-brown euhedral crystals (type 3, Saint Salvy deposit). New investigation at microscale on sphalerite grains from the Saint-Salvy deposit shows late Cu-Ge-Ga enrichment not only in specific sector zonings but also along grain boundaries, growing crystal edges, and in low-angle misorientations or twin boundaries. Following a deformation event that probably occurred during the Pyrenean-Alpine orogeny, these two sphalerite mineralizations have both endured plastic deformation in a dislocation creep regime and dynamically recovered by subgrain rotation (SGR) mechanism. Two mechanisms of Cu-Ga-Ge spatial redistribution are observed and are key processes for the crystallization of Cu-Ga-Ge-rich minerals in sphalerite veins. The first mechanism involved the in situ redistribution of Cu-Ga-Ge contents from a pre-existing concentration in the sphalerite lattice (type 3, Arre deposit), creating Ge-sulfides (briartite), probably during Pyrenean-Alpine orogeny. Formation of this type of Ge-mineral may be related to solid-state diffusion processes. The second mechanism is associated with the circulation of a Cu-Ga-Ge-rich fluid in surrounding rocks. In the pre-existing polygonal sphalerite from Late-Variscan veins (type 2, Pale Bidau deposit), millimeter-size bands of small (<50 µm), recrystallized sphalerite grains are locally observed. Those domains contain inclusions of Cu (chalcopyrite) and Ga and Ge minerals (brunogeierite, carboirite). Fluid-induced diffusion in the polygonal sphalerite aggregates may occur with superimposed dynamic recrystallization, such as the Late-Variscan veins (type 2, Pale Bidau-type). During post-Variscan time, this fluid enriched in Cu-Ga-Ge largely circulated in the upper-crust of this Variscan terrane. This study highlights the key importance of coupled textural (EBSD) and in situ chemical analyses (LIBS) of diverse sphalerite types at a regional scale to indirectly unravel the origin of vein mineralization, and their related critical metal distribution.

Combining Simple Deformations to Elicit Complex Motions and Directed Swimming of Smart Organic Crystals with Controllable Thickness

The lack of control over the crystal growth in a systematic way currently stands as an unsurmountable impediment to the preparation of dynamic crystals as soft robots; in effect, the mechanical effects of molecular crystals have become a subject of scattered reports that pertain only to specific crystal sizes and actuation conditions, often without the ability to establish or confirm systematic trends. One of the factors that prevents the verification of such performance is the unavailability of strategies for effectively controlling crystal size and aspect ratio, where crystals of serendipitous size are harvested from crystallization solution. Here we devised a water‐assisted precipitation method to prepare crystals of chemical variants of 9‐anthracene derivative (chemical substitution of the 9th carbon) crystals with various thicknesses that respond to ultraviolet light with simple mechanical effects, including bending, splintering, and rotation. By capitalizing on the robust mechanical flexibility and deformability of crystals, we demonstrate systematic variations in crystal deformation that are further elevated in complexity to construct crystal‐based robots capable of motions reminiscent of controllable sailing and humanoid movements. The results illustrate an approach to eliminate a critical obstacle towards complete control over the motility of dynamic molecular crystals as microrobots in nonaerial environments.

Combining Simple Deformations to Elicit Complex Motions and Directed Swimming of Smart Organic Crystals with Controllable Thickness.

The lack of control over the crystal growth in a systematic way currently stands as an unsurmountable impediment to the preparation of dynamic crystals as soft robots; in effect, the mechanical effects of molecular crystals have become a subject of scattered reports that pertain only to specific crystal sizes and actuation conditions, often without the ability to establish or confirm systematic trends. One of the factors that prevents the verification of such performance is the unavailability of strategies for effectively controlling crystal size and aspect ratio, where crystals of serendipitous size are harvested from crystallization solution. Here we devised a water-assisted precipitation method to prepare crystals of chemical variants of 9-anthracene derivative (chemical substitution of the 9th carbon) crystals with various thicknesses that respond to ultraviolet light with simple mechanical effects, including bending, splintering, and rotation. By capitalizing on the robust mechanical flexibility and deformability of crystals, we demonstrate systematic variations in crystal deformation that are further elevated in complexity to construct crystal-based robots capable of motions reminiscent of controllable sailing and humanoid movements. The results illustrate an approach to eliminate a critical obstacletowards complete control over the motility of dynamic molecular crystals as microrobots in nonaerial environments.

A cautionary tale of basic azo photoswitching in dichloromethane finally explained

Many studies of azobenzene photoswitches are carried out in polar aprotic solvents as a first principles characterization of thermal isomerization. Among the most convenient polar aprotic solvents are chlorinated hydrocarbons, such as DCM. However, studies of azobenzene thermal isomerization in such solvents have led to spurious, inconclusive, and irreproducible results, even when scrupulously cleaned and dried, a phenomenon not well understood. We present the results of a comprehensive investigation into the root cause of this problem. We explain how irradiation of an azopyridine photoswitch with UV in DCM acts not just as a trigger for photoisomerization, but protonation of the pyridine moiety through photodecomposition of the solvent. Protonation markedly accelerates the thermal isomerization rate, and DFT calculations demonstrate that the singlet-triplet rotation mechanism assumed for many azo photoswitches is surprisingly abolished. This study implies exploitative advantages of photolytically-generated protons and finally explains the warning against using chlorinated solvent with UV irradiation in isomerization experiments.

The implementation of speckle tracking echocardiography for cardiac resynchronization therapy optimization. A rotational myocardial mechanics interpretation

Abstract Background Cardiac resynchronization therapy (CRT) has an additive therapeutic influence on left ventricular (LV) function in heart failure (HF) patients, but the underlying mechanisms through which it works are not completely explained. Our aim was to further elucidate the role of this intervention via rotational mechanics using 2D speckle tracking echocardiography (2D-STE). Methods We investigated 46 patients (65 ± 9 years) who received CRT. All enrolled patients were assessed on admission by 2D-STE and 6 min walk test (6m WT) and followed in the outpatient device clinic by 2D-STE (at one week and 6 months post-implantation) and 6m WT (at 6 months post-implantation). On their first appointment all biventricular systems were optimized by atrioventricular delay optimization and by changing the temporal activation of ventricular electrodes aiming to reach the highest effective LV stroke volume (eff SV) across all activation options. A new 2D-STE based index (twist integral – TI) targeting to assess the rotational mechanics of the whole cardiac cycle was also measured to further explain the CRT response. For the calculation of LV TI of the full cardiac cycle, serial isochronal apical and basal rotation measurements (in degrees) were exported to a worksheet Excel file and the final algebraic summation was calculated by the formula: Twist Integral = (systolic twist integral – diastolic twist integral) Σ twisti= twist1+twist2+...+twistn (table 1). Results Twenty-two (48%) patients with dilated cardiomyopathy as the predominant aetiology of HF were responders at 6-month follow-up. The commonest selected mode that was related with the greatest LV performance response was the simultaneous activation of the 2 ventricular leads (39%). The strongest predictor of CRT response was the improvement of eff SV between admission and first appointment at clinic, followed by the improvement of TI, the non-existence of CAD, and the improvement of peak systolic twist (table 2). Conclusions Additional CRT optimization via changing the temporal activation of ventricular electrodes is beneficial for LV performance in HF patients. Rotational mechanics essentially explain the beneficial CRT contribution to these patients.

Achieving high piezoelectric performance in Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric single crystals through pulse poling technique

To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals.

Interface-packing analysis of F1-ATPase using integral equation theory and manifold learning

It has been shown that the translational entropy of water plays a key role in biological processes such as protein folding and ligand binding. Under the physiological condition, tightly packed protein conformations like native structures are achieved so that the translational entropy of water is maximized. In this study, we investigate the rotation mechanism of a rotary protein motor, F1-ATPase, by analyzing the packing at the interfaces between the subunits. The packing at the interface between a subunit pair is analyzed using the change in the solvent entropy upon forming subunit pair, ∆S. It is found that as the γ subunit rotates, the ∆S value of a α-β subunit pair decrease because the interface packing becomes loose. However, because the interface packing of another α-β subunit pair becomes tighter upon the rotation, ∆S of this α-β subunit pair increases, leading to a compensation of the decrease in ∆S. Such compensation would be necessary to maximize the solvent entropy of F1-ATPase. In this study, packing at the interfaces between the subunits is also analyzed using a manifold-learning technique, and it is suggested a possibility that a qualitative estimation of the ∆S values of some α-β subunit pairs can be predicted using a manifold-learning technique.

Approximate upper- and lower-bound analyses of translational rainfall-induced landslides in curvilinear hillslopes

Increased frequency of rainfall-induced landslides (RILs) with global climate change is expected to be a huge challenge. Previous studies have focused on RILs encompassing the examination of rotational failure mechanisms and straightforward slope geometries, notably those pertaining to planar or cutting slopes. However, instability issues of curvilinear hillslopes have received less attention, although they are of great significance for early warning landslides in more common natural slopes. This study presents a progressive failure mechanism for curvilinear hillslopes in which the local failure initiates at the steepest zone and gradually extends to upslope/downslope flat regions. By means of upper- and lower-bound analyses, approximate criteria for the onset of a translational landslide with respect to the critical wetting front depth and the failure positions are derived. Unlike traditional theories, upper- and lower-bound analyses are unaffected by slope topology, self-weight of soil and cohesion effects. By conducting a case study at the end of the study, the suggested criteria are found to exhibit notable merits in their straightforward implementation for evaluating the stability of curvilinear natural slopes under varying precipitation patterns.

Competing excitation quenching and charge exchange in ultracold Li-Ba+ collisions

Abstract Hybrid atom-ion systems are a rich and powerful platform for studying chemical reactions, as they feature both excellent control over the electronic state preparation and readout as well as a versatile tunability over the scattering energy, ranging from the few-partial wave regime to the quantum regime. In this work, we make use of these excellent control knobs, and present a joint experimental and theoretical study of the collisions of a single 138Ba+ ion prepared in the 5d 2D3/2,5/2 metastable states with a ground state 6Li gas near quantum degeneracy. We show that in contrast to previously reported atom-ion mixtures, several non-radiative processes, including charge exchange, excitation exchange and quenching, compete with each other due to the inherent complexity of the ion-atom molecular structure. We present a full quantum model based on high-level electronic structure calculations involving spin-orbit couplings. Results are in excellent agreement with observations, highlighting the strong coupling between the internal angular momenta and the mechanical rotation of the colliding pair, which is relevant in any other hybrid system composed of an alkali-metal atom and an alkaline-earth ion.

EDRP-GTDQN: An adaptive routing protocol for energy and delay optimization in wireless sensor networks using game theory and deep reinforcement learning

Routing protocols, as a crucial component of the internet of things (IoT), play a significant role in data collection and environmental monitoring tasks. However, existing clustering routing protocols suffer from issues such as uneven network energy consumption, high communication delays, and inadequate adaptation to topology changes. To address these issues, this study proposes an adaptive routing algorithm to balance energy consumption and delay using game theory and deep Q-network (DQN) algorithms (EDRP-GTDQN). Specifically, EDRP-GTDQN evaluates the importance of node positions using node centrality and integrates a game-theoretic-based approach to select optimal cluster heads in terms of node centrality and residual energy. Moreover, graph convolutional networks (GCN) and DQN are incorporated to construct transmission paths for cluster heads, adapt to network topology changes, and balance energy consumption and performance. Furthermore, a cluster rotation mechanism is employed to optimize overall network energy consumption and prevent the formation of hotspots. Experimental results demonstrate that EDRP-GTDQN achieves average performance improvements of 19.76%, 30.04%, 44.2%, and 61.42% in average energy consumption, network lifetime, and average end-to-end delay compared to conventional routing protocols such as EECRAIFA, MRP-GTCO, DEEC, and MH-LEACH. Therefore, EDRP-GTDQN is undoubtedly an effective solution to reduce energy consumption and enhance service quality in wireless sensor networks.

Cyclic response and mechanical model of a rotational viscoelastic damper

This paper investigated the cyclic response of a new viscoelastic damper that utilized a rotational mechanism to enhance shear deformation in the viscoelastic material and increase its energy dissipation. Three damper prototypes were fabricated and subjected to displacement-controlled cyclic excitations with varying strain amplitudes and frequencies. For comparison, three conventional viscoelastic dampers, each containing an equivalent volume of viscoelastic material to the proposed damper, were also fabricated and tested. Results indicated that the proposed damper had up to three times larger loss factor and five times larger damping coefficient than the tested conventional viscoelastic damper. This study also presented two analytically driven equations to estimate the proposed damper's rotational stiffness and damping coefficient. A finite element model was proposed for simulating the damper in software, and its effectiveness was demonstrated.

Hybrid rotational cavity optomechanics using an atomic superfluid in a ring

We introduce a hybrid optomechanical system containing an annularly trapped Bose-Einstein condensate (BEC) inside an optical cavity driven by Lauguerre-Gaussian (LG) modes. Spiral phase elements serve as the end mirrors of the cavity such that the rear mirror oscillates torsionally about the cavity axis through a clamped support. As described earlier in a related system [P. Kumar , ], the condensate atoms interact with the optical cavity modes carrying orbital angular momentum which create two atomic side modes. We observe three peaks in the output noise spectrum corresponding to the atomic side modes and rotating mirror frequencies, respectively. We find that the trapped BEC's rotation reduces quantum fluctuations at the mirror's resonance frequency. We also find that the atomic side modes-cavity coupling and the optorotational coupling can produce bipartite and tripartite entanglements between various constituents of our hybrid system. We reduce the frequency difference between the side modes and the mirror by tuning the drive field's topological charge and the condensate atoms' rotation. When the atomic side modes become degenerate with the mirror, the stationary entanglement between the cavity and the mirror mode diminishes due to the suppression of cooling. Our proposal, which combines atomic superfluid circulation with mechanical rotation, provides a versatile platform for reducing quantum fluctuations and producing macroscopic entanglement with experimentally realizable parameters. Published by the American Physical Society 2024

Prediction of conformational states in a coronavirus channel using Alphafold-2 and DeepMSA2: Strengths and limitations

The envelope (E) protein is present in all coronavirus genera. This protein can form pentameric oligomers with ion channel activity which have been proposed as a possible therapeutic target. However, high resolution structures of E channels are limited to those of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), responsible for the recent COVID-19 pandemic. In the present work, we used Alphafold-2 (AF2), in ColabFold without templates, to predict the transmembrane domain (TMD) structure of six E-channels representative of genera alpha-, beta- and gamma-coronaviruses in the Coronaviridae family. High-confidence models were produced in all cases when combining multiple sequence alignments (MSAs) obtained from DeepMSA2. Overall, AF2 predicted at least two possible orientations of the α-helices in E-TMD channels: one where a conserved polar residue (Asn-15 in the SARS sequence) is oriented towards the center of the channel, ‘polar-in’, and one where this residue is in an interhelical orientation ‘polar-inter’. For the SARS models, the comparison with the two experimental models ‘closed’ (PDB: 7K3G) and ‘open’ (PDB: 8SUZ) is described, and suggests a ∼60˚ α-helix rotation mechanism involving either the full TMD or only its N-terminal half, to allow the passage of ions. While the results obtained are not identical to the two high resolution models available, they suggest various conformational states with striking similarities to those models. We believe these results can be further optimized by means of MSA subsampling, and guide future high resolution structural studies in these and other viral channels.

Physiological rotation patterns of the thoracolumbar spine across different ages: A detailed analysis using upright CT

BackgroundThe rotational motion of the spine plays a crucial role in daily activities. Understanding the mechanisms of spinal rotation is essential for evaluating normal spinal function, especially in standing positions due to the influence of gravity. However, previous studies on spinal rotation have been limited. Research QuestionWhat are the differences in thoracolumbar rotation during trunk rotation in a standing position among different age and gender groups? MethodsThis cross-sectional study involved 49 healthy volunteers without back pain, including 24 younger participants (13 males, 11 females) and 25 elderly participants (12 males, 13 females). Upright and trunk-rotated CT (right-rotated standing positions) scans were taken. Vertebral rotation was measured using the femoral head center as an axis. ResultsAnalysis of spinal alignment in the standing position revealed mild rotation from the lumbar to thoracic vertebrae. The lumbar spine exhibited left rotation at apex of L3 (L3: −1.3±3.8°, p=0.01), while the lower thoracic spine showed right rotation at apex of T8 (T8: 1.9±2.4°, p<0.001) and the upper thoracic spine showed left rotation at apex of T3 (T3: −2.6±2.9°, p<0.001). The lumbar spine showed minimal rotation during maximum trunk rotation, with significant rotation noted above T10 (16 % vs 84 %). The total thoracolumbar spinal rotation at T1 showed significant differences by gender and age (male vs. female: 23.9±° vs. 30.3±°, p=0.001; young vs. elderly: 29.2±° vs. 25.0±°, p=0.028; elderly male vs. elderly female: 19.2±° vs. 30.4±°, p<0.001). Younger participants did not show significant gender differences, while elderly females retained more rotation compared to males. SignificanceThis pioneering study provides the first detailed report on the range of spinal rotation in a physiological standing situation, highlighting significant differences by gender and age. These findings offer new insights into the natural patterns of spinal rotation and their potential implications for diagnosing and treating spinal disorders.

Design of Gearings from Involute-Bevel Gears

The article presents formulas for determining the dimensions of involute-bevel gears and the gearings composed of them. It examines the most general cases of gearings formation, consisting of two involute-bevel gears with crossing axes (hyperboloid gearings), with intersecting axes (bevel gearings), and with parallel axes (cylindrical gearings). Gearings composed of involute-bevel gears have design, technological, and operational advantages compared to gearings composed of conventional cylindrical and bevel gears. The use of involute-bevel gearings with crossing axes allows for achieving the required contact character of the teeth from localized contact to linear contact, reducing sensitivity to manufacturing and assembly errors, and increasing the load capacity of the gearing compared to helical gearings from cylindrical gears. Bevel gearings with involute-bevel gears allow for the creation of gearings with any desired small shaft angles, which is difficult to achieve with conventional bevel gears. The use of internal meshing bevel gearings with modified tooth profiles in planetary reducers allows for gearings comparable to harmonic drives in terms of power and kinematic characteristics, but with a higher operational life. The use of involute-bevel gears in cylindrical gearings improves the smoothness of the mechanism and allows for adjusting the center distance and backlash in the meshing, making them suitable for backlash-free drives. By combining the taper angles of the gears and the inclination of the teeth, it is possible to create a one-way rotation mechanism - a freewheel mechanism. Modern CAD systems do not take into account the geometry features of gearings composed of involute-bevel gears, which limits their application in technology. The article proposes an algorithm for calculating the main geometric parameters of gearings composed of involute-bevel gears with arbitrary axis placement in space. Examples of geometric calculations of various types of gearings based on the proposed algorithm are provided.

Physics-guided neural network-based framework for 3D modeling of slope stability

Physics-informed neural networks (PINN) have gradually attracted attention in the field of geotechnical engineering. This paper proposes a novel PINN-based framework for the three-dimensional (3D) stability analysis of soil slopes. Based on the fundamental theorem of plasticity and limit analysis, the partial differential equations (PDE) with regard to slope collapse are derived and integrated into the physics-guided loss function. A kinematically admissible failure mechanism that rigorously satisfies the Mohr-Coulomb associated flow rule is obtained by minimizing the loss function, thereby circumventing complex mathematical calculations. The discrete points generated by PINN are selected and refined through a series of procedures to represent the failure block of slopes using a two-dimensional matrix. The entire training process of the PINN-based framework is conducted without the need for any labeled data. The resulting discretized failure mechanism is meshfree and capable of accommodating spatially discrete data. A validation exercise is performed to verify the proposed framework by comparing it with the classical 3D rotational failure mechanism. To further consider the impact of external excitation on slope stability, a hybrid PINN framework is developed to assess the stability of slopes subjected to complex external environments. In addition to the PINN to generate a failure mechanism, a parallel PINN is employed to acquire the corresponding spatially discrete data of specified external excitations. The hybrid PINN framework for seismic stability assessment of slopes is demonstrated by way of example, indicating favorable feasibility and applicability of the developed approach. The proposed PINN-based framework provides innovative and promising avenues for 3D slope stability analysis.

Table-top laser-based terahertz high harmonic generation spectroscopy under magnetic fields and low temperatures.

We have developed a terahertz (THz) nonlinear spectrometer at low temperatures (1.5-300K) and under high magnetic fields (up to 10T) by combining the laser-driven table-top intense THz source with a superconducting magnet. The strong-field THz pump pulse was generated from LiNbO3 crystal using the tilted-pulse-front technique and tightly focused into the center of the magnet by an off-axis parabolic mirror and a THz lens. The electric fields at the focus can achieve 500kV/cm with a monocycle waveform and 30kV/cm with a multicycle waveform at 0.5THz. The sample was mounted on a low-temperature motorized rotation stage, which enables performing the polarization dependent measurements of the third harmonic generation (THG) intensity without rotating the incident THz pulses. The magnetic field direction can be rotated using a mechanical rotator, allowing for a convenient switch between Faraday and Voigt geometry. We demonstrate the excellent performance of our instrument by conducting THG measurements in the two-band superconductor MgB2 as a function of temperature, sample azimuth angle, as well as in-plane and out-of-plane magnetic fields. The successful combination of the strong field THz source with magnetic fields enables us to study a variety of materials with magnetic-field-dependent properties of interest.

Quantum enhanced mechanical rotation sensing using wavefront photonic gears

Quantum metrology leverages quantum correlations for enhanced parameter estimation. Recently, structured light enabled increased resolution and sensitivity in quantum metrology systems. However, lossy and complex setups impacting photon flux hinder true quantum advantage while using high dimensional structured light. We introduce a straightforward mechanical rotation quantum sensing mechanism, employing high-dimensional structured light and use it with a high-flux (45 000 coincidence counts per second) N00N state source with N = 2. The system utilizes two opposite spiral phase plates with topological charge of up to ℓ = 16 that converts mechanical rotation into wavefront phase shifts and exhibit a 16-fold enhanced super-resolution and 25-fold enhanced sensitivity between different topological charges, while retaining the acquisition times, and with negligible change in coincidence count. Furthermore, the high efficiency together with the high photon flux enables detection of mechanical angular acceleration in real-time. Our approach paves the way for highly sensitive quantum measurements, applicable to various interferometric schemes.

Snap-through mechanism of an elastic bimetal ring for rotary actuation

Smart materials responsive to stimuli and new rotary mechanisms have drawn much attention in recent years. This paper investigates a novel snap-through rotation mechanism of a thermal responsive bimetal ring confined inside the annular region constraint when subjected to the local curvature induced by thermal loading. The buckled ring has movable boundaries and keeps an invariant shape during the snap-through rotation so that it requires small energy input to drive the bistable transition. To uncover the elusive mechanism behind this intriguing snap-through phenomenon, a theory based on the bifurcation and energy principle is developed to predict the critical loading curvature and the critical loading temperature, which agrees with the experimental results. The effects of loading positions and the constraint width are studied and a map predicting the critical loading curvature with different geometrical parameters is demonstrated. The rotary buckled ring not only enables the bistable actuation, but also triggers various actuation applications such as the motor actuation and the pump actuation. Due to great advantages in terms of energy supply and actuation loading, this study exhibits great potential of the proposed snap-through mechanism in bistable structures and rotary actuation.