Rotation Mechanism Research Articles

Mechanism of proton-powered c-ring rotation in a mitochondrial ATP synthase

Proton-powered c-ring rotation in mitochondrial ATP synthase is crucial to convert the transmembrane protonmotive force into torque to drive the synthesis of adenosine triphosphate (ATP). Capitalizing on recent cryo-EM structures, we aim at a structural and energetic understanding of how functional directional rotation is achieved. We performed multi-microsecond atomistic simulations to determine the free energy profiles along the c-ring rotation angle before and after the arrival of a new proton. Our results reveal that rotation proceeds by dynamic sliding of the ring over the a-subunit surface, during which interactions with conserved polar residues stabilize distinct intermediates. Ordered water chains line up for a Grotthuss-type proton transfer in one of these intermediates. After proton transfer, a high barrier prevents backward rotation and an overall drop in free energy favors forward rotation, ensuring the directionality of c-ring rotation required for the thermodynamically disfavored ATP synthesis. The essential arginine of the a-subunit stabilizes the rotated configuration through a salt bridge with the c-ring. Overall, we describe a complete mechanism for the rotation step of the ATP synthase rotor, thereby illuminating a process critical to all life at atomic resolution.

KULEX-Wrist: Design and Analysis of Linkage-Driven Exoskeleton for Wrist Assistance

Abstract This paper presents a wrist exoskeleton called the KIST Upper-Limb EXoskeleton (KULEX)-wrist for activities of daily living assistance of the elderly and the disabled. A novel linkage-based structure of the rotational mechanism with three degrees-of-freedom is proposed. The proposed wrist mechanism is composed of two prismatic-universal-spherical serial chains and one revolute-revolute-revolute spherical chain. Besides, a combination of a planar slider-crank and spherical four-bar linkages was employed as a drive mechanism for power transmission. Kinematic analysis was conducted to understand its working principle. Then, the dimensions of all the linkages were synthesized to meet the structural design suitable for the wearable exoskeleton and the transmission quality. In addition, motion twists and wrenches were geometrically derived. Finally, a prototype of the KULEX-wrist was designed, and then its performance of mechanical stiffness, motion capability, and power assistance was verified.

Stability Analysis of Three-Dimensional Tunnel Face Considering Linear and Nonlinear Strength in Unsaturated Soil

The shear strength of unsaturated soils exhibits significant nonlinearity, while previous studies often simplified it with linear strength models. The objective of this paper is to investigate the distinctions in the stability of three-dimensional (3D) tunnel faces when using linear and nonlinear strength models. A new 3D rotational failure mechanism and an extended form of the Mohr–Coulomb (M-C) failure criterion were integrated into the kinematically limited analysis (KLA) framework to describe the failure characteristics of tunnel faces. Subsequently, the factor of safety (FS) of the 3D tunnel faces was calculated using the strength reduction method (SRM). In the discussion section, the impacts of nonlinear shear strength, matric suction in the unsaturated soils, and the 3D geometric parameters of the tunnel on the stability of the tunnel face were analyzed. The outcomes indicate that, in unsaturated soil conditions, diverse nonlinear strength calculation models and soil types exert disparate influences on the FS of 3D tunnel faces. The main novelty of this study lies in establishing an effective method for assessing the stability of tunnel faces in unsaturated soils.

PoT quantization and rotational update mechanism for optimizing equalization in passive optical networks

We propose a low-complexity real-time equalization scheme for passive optical networks (PONs), which provides equalization with similar performance and ultra-low digital signal processing (DSP) resource usage compared to traditional schemes in experimental verification. With the help of the proposed scheme, FIR equalizers with multiple taps can be equivalent to equalizers with only two active taps, while other taps are quantified and stored, which can replace complex multiplications with simple shift operations. We introduce powers-of-two (PoT) non-uniform quantization technology to real-time transmission at the physical layer, which helps to save quantization precision and simplify multiplication complexity. We propose the rotational update mechanism (RUM), which solves the problem that the weight value after PoT non-uniform quantization is difficult to update. The proposed scheme with PoT and RUM greatly reduces the required hardware resources and power consumption, and the optical modules can use existing resources to support the additional number of taps required for higher baud rates. We verified the proposed scheme in decision-directed least mean square (DDLMS) equalization. The improved equalization scheme is implemented in the XCVU9P-FLGB2104-2-I Xilinx FPGA with a clock frequency of 230.4 MHz. The results show that the proposed equalization scheme can reduce up to 99.5% DSP resource usage compared to a normal DDLMS equalizer with 15 taps. We successfully realized 29.4912 Gbit/s PAM4 real-time IM/DD transmission over 25-km SSMF with a BER below the KP4 threshold utilizing the proposed DDLMS with PoT and RUM. The innovation of this paper lies in two aspects: (1) the introduction of the PoT quantization method in real-time equalization of PON transmission and (2) proposing RUM for real-time updating of weights in equalizers, which moves the quantification process from offline to real time, making the equalizers more robust for time-varying channels.

Atom-based optical polarization modulator.

In this work, we employ 87Rb atoms as rotation media to manipulate the polarization of optical fields in both magnetic and magnetic-free environments. Employing the nonlinear magneto-optical rotation mechanism, we achieve a state-of-the-art magneto-optical rotation coefficient of 1.74×108 rad⋅T-1⋅m-1 which is four orders of magnitude higher than commonly employed materials. Additionally, in a magnetic-free environment, we achieve all-optical cross-polarization modulation between the pump and probe light via Rb atoms. The nonlinear magneto-optical rotation configuration introduces inventive techniques for a new type of magneto-optical modulator while the all-optical configuration paves the way for exploring photonic integrated circuit (PIC) devices free from disruptions caused by electrical or magnetic crosstalk.

Theoretical Understanding of the Long-Range Proton Transfer Mechanism in 7-Hydroxy Quinoline-Based Molecular Switches: Varma's Proton Crane and Its Analogues.

Herein, the detailed mechanism of intramolecular proton transfer in molecular switches, constructed from 7-hydroxy quinoline substituted in the eight-position C-C single axle, connected to three different proton cranes (morpholine, piperidine, and 1,3,5-dioxazine), was investigated by means of theoretical chemistry. The theoretical interpretation of the rotational mechanism and its stable structures were proposed for the well-known Varma's proton crane, based on morpholine molecule. The reliability of the theoretical simulations was confirmed by the available literature data from time-dependent IR measurements.

Right Ventricular Longitudinal Shortening is not Associated with Left Ventricular Rotational Mechanics in Healthy Adults - Insights from the Three-dimensional Speckle-tracking Echocardiographic MAGYAR-Healthy Study.

The left ventricle (LV) not only contracts, but its rotational mechanics have a significant role in systolic ejection, whereas the right ventricle (RV) is substantially different in shape and function, and its contractility is not accompanied by rotational features. Simple M-mode echocardiography-based tricuspid annular plane systolic excursion (TAPSE) reflects RV longitudinal contraction or shortening. The aim of the present study was to examine the relationship between the parameters characterizing the rotational mechanics of the LV as assessed by three-dimensional speckle-tracking echocardiography (3DSTE) and the TAPSE. The effects of different degrees of these parameters on each other were also examined. The present retrospective analysis evaluated the results of 80 healthy adult individuals with an average age of 28.1 6.3 years (33 males) with LV rotational mechanics being directed normally. All cases have undergone complete two-dimensional Doppler echocardiography with the measurement of TAPSE and 3DSTE. None of the LV volumes and rotational parameters showed any differences in healthy cases with TAPSE 18-21 mm vs. TAPSE 22 mm. Similarly, right atrial (RA) volumetric parameters did not differ either. TAPSE showed no associations with the degree of basal LV rotation. RA volumes were slightly increased with higher basal LV rotation. Similar to basal LV rotation, TAPSE did not change with the degree of apical LV rotation and a tendentious increase of RA volumes could be demonstrated with increasing apical LV rotation. No correlation could be demonstrated between apical and basal LV rotations and TAPSE. 3DSTE-derived LV rotational parameters and TAPSE are not associated suggesting that LV twist is independent of RV longitudinal shortening in healthy circumstances.

The Simons Observatory: Cryogenic half wave plate rotation mechanism for the small aperture telescopes.

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀0.42m) and large (⌀6m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 μrad s. During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance.

Angle-resolved X-ray emission spectroscopy facility realized by an innovative spectrometer rotation mechanism at SPring-8 BL07LSU.

The X-ray emission spectrometer at SPring-8 BL07LSU has recently been upgraded with advanced modifications that enable the rotation of the spectrometer with respect to the scattering angle. This major upgrade allows the scattering angle to be flexibly changed within the range of 45-135°, which considerably simplifies the measurement of angle-resolved X-ray emission spectroscopy. To accomplish the rotation system, a sophisticated sample chamber and a highly precise spectrometer rotation mechanism have been developed. The sample chamber has a specially designed combination of three rotary stages that can smoothly move the connection flange along the wide scattering angle without breaking the vacuum. In addition, the spectrometer is rotated by sliding on a flat metal surface, ensuring exceptionally high accuracy in rotation and eliminating the need for any further adjustments during rotation. A control system that integrates the sample chamber and rotation mechanism to automate the measurement of angle-resolved X-ray emission spectroscopy has also been developed. This automation substantially streamlines the process of measuring angle-resolved spectra, making it far easier than ever before. Furthermore, the upgraded X-ray emission spectrometer can now also be utilized in diffraction experiments, providing even greater versatility to our research capabilities.

Structural Design and Mechanism Analysis of Palm Oil Harvester

Plantation of palm oil in Malaysia is one of the top contributor of the economy. In order to match the supply of palm oil fruit with demand, different harvesting methods are used such as the existing motorized cutter. Although it can reduce the harvesting time and the number of labors involved in harvesting process, the tight arrangement of oil palm fronds and long manually adjusted harvesting pole may cause the inconvenient to the labors. Therefore, this project studies the design of a circular cutter and automatically adjusted telescopic pole with rotational mechanism. The concept development of harvester is based on the scientific study on the limitations, customer requirement and engineering characteristics of existing harvesters. It is followed with the selection of best design of harvester that can solve the problems that faced by labors in existing harvester. The analysis of rotational speed, deflection and bending moment for different components in the palm oil harvester. The design of harvester is done with the aid of CAD software in form of part detail design, orthographic view and exploded view. With the rotational cutting mechanism, the harvester can easily reach and harvest the oil palm fresh fruit bunches from the bottom of the bunches.

Scalable Optical Frequency Rulers with the Faraday Effect

Optical frequency rulers (OFRs) can be used as optical wavelengths or frequency references for spectra modulation or to determine unknown wavelengths. In the past, difficult-to-perform and complicated mechanisms were used to make OFRs, such as double slits with a high-speed fluid or an external circuit to control the liquid crystal birefringence. Since then, a later research study introduced a simple structure for producing OFRs by utilizing the optical activity block and two polarizers. This achieved a movable OFR that was controllable by simply rotating one of the polarizers. However, this mechanical rotation hindered its high-speed applicability. In this article, a more advanced, scalable OFR scheme using the Faraday effect is proposed. It is controlled by varying the magnetic field intensity, which is not a mechanical method, and it can be changed at high speeds. The numerical results demonstrate that those OFR spectral ticks can be scaled to reach a higher or lower tick density, greatly benefiting the wavelength decision jobs.

Operating an electric motor in saturation – mechanical vibrations and other effects

This paper addresses some of the effects of running an electric motor near and in the saturation zone of the electromagnetic hysteresis curve, namely mechanical effects such as mechanical vibrations and rotation speed apart from the classic electrical and thermal effects. Mechanical vibrations are intrinsically characteristic of rotating machines, and other turbomachine characteristics, such as rotor unbalance, non-linearity and shaft variable stiffness can introduce severe disturbances in the operation of the machine. Rotation speed is also affected by electric parameters, when the mechanical machine is connect to an electric machine, meaning both the electric machine type and the process by which it is driven affects both the value of speed and its constancy.

Wide-Angle Beam Steering Closed-Form Pillbox Antenna Fed by Substrate-Integrated Waveguide Horn for On-the-Move Satellite Communications

Wide-angle mechanical beam steering for on-the-move satellite communications is presented in this paper based on a closed-form pillbox antenna system. It includes three main parts: a fixed-feed part, which is a substrate-integrated waveguide (SIW) horn with an extended aperture attached to a parabolic reflector; a novel quasi-optical system, which is a single coupling slot alongside and without spacing from the parabolic reflector; and a radiating disc, which is a leaky-wave metallic pattern. To make the antenna compact, pillbox-based feeding is implemented underneath the metallic patterns. The antenna is designed based on a substrate-guided grounded concept using leaky-wave metallic patterns operating at 20 GHz. Beam scanning is achieved using mechanical rotation of the leaky-wave metallic patterns. The proposed antenna has an overall size of 340 × 335 × 2 mm3, a gain of 23.2 dBi, wide beam scanning range of 120°, from −60° to +60° in the azimuthal plane, and a low side lobe level of −17.8 dB at a maximum scan angle of 60°. The proposed antenna terminal is suitable for next-generation ubiquitous connectivity for households and small businesses in remote areas, ships, unmanned aerial vehicles, and disaster management.

Rotation and Confined Eruption of a Double Flux-rope System

We perform a data-constrained simulation with the zero-β assumption to study the mechanisms of strong rotation and failed eruption of a filament in active region 11474 on 2012 May 5 observed by Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The initial magnetic field is provided by nonlinear force-free field extrapolation, which is reconstructed by the regularized Biot–Savart laws and magnetofrictional method. Our simulation reproduces most observational features very well, e.g., the filament large-angle rotation of about 130°, the confined eruption, and the flare ribbons, allowing us to analyze the underlying physical processes behind observations. We discover two flux ropes in the sigmoid system, an upper flux rope (MFR1) and a lower flux rope (MFR2), which correspond to the filament and hot channel in observations, respectively. Both flux ropes undergo confined eruptions. MFR2 grows by tether-cutting reconnection during the eruption. The rotation of MFR1 is related to the shear-field component along the axis. The toroidal field tension force and the nonaxisymmetry forces confine the eruption of MFR1. We also suggest that the mutual interaction between MFR1 and MFR2 contributes to the large-angle rotation and the eruption failure. In addition, we calculate the temporal evolution of the twist and writhe of MFR1, which is a hint of probable reversal rotation.

The Formation of Supramolecular Chiral Materials from Achiral Molecules Using a Liquid-Crystallin System: Symmetry Breaking, Amplification, and Transfer

Recently, the formation of chiral materials by the self-organization of achiral small molecules has attracted much attention. How can we obtain chirality without a chiral source? Interesting approaches, such as mechanical rotation, circularly polarized light, and asymmetric reaction fields, have been used. We describe recent research developments in supramolecular chirality in liquid crystals, focusing primarily on our group’s experimental results. We present the following concepts in this review. Spontaneous mirror symmetry breaking in self-assembled achiral trimers induces supramolecular chirality in the soft crystalline phase. Two kinds of domains with opposite handedness exist in non-equal populations. The dominant domain is amplified to produce a homochiral state. Chirality is transferred to a polymer film during the polymerization of achiral monomers by using the homochiral state as a template. Finally, we discuss how the concepts obtained from this liquid crystal research relate to the origin of homochirality in life.

Functional anatomy of the orbit in strabismus surgery: Connective tissues, pulleys, and the modern surgical implications of the "arc of contact" paradigm.

Oculomotricity is a multidimensional domain characterised by a delicate interplay of anatomical structures and physiological processes. This manuscript meticulously dissects the nuances of this interplay, bringing to the fore the integral role of the extraocular muscles (EOMs) and their intricate relationship with the myriad orbital connective tissues as it harmoniously orchestrates binocular movements, ensuring synchronised and fluid visual tracking. Historically, the peripheral oculomotor apparatus was conceptualised as a rudimentary system predominantly driven by neural directives. While widely accepted, this perspective offered a limited view of the complexities inherent in ocular movement mechanics. The twentieth century heralded a paradigm shift in this understanding. With advances in anatomical research and imaging techniques, a much clearer picture of the gross anatomy of the EOMs emerged. This clarity challenged traditional viewpoints, suggesting that the inherent biomechanical properties of the EOMs, coupled with their associated tissue pulleys, play a pivotal role in dictating eye movement dynamics. Central to this revised understanding is the "arc of contact" paradigm. This concept delves deep into the mechanics of eye rotation, elucidating the significance of the point of contact between the EOMs and the eyeball. The arc of contact is not just a static anatomical feature; its length and orientation play a crucial role in determining the effective torque generated by a muscle, thereby influencing the amplitude and direction of eye rotation. The dynamic nature of this arc, influenced by the position and tension of the muscle pulleys, offers a more comprehensive model for understanding ocular kinematics. Previously overlooked in traditional models, muscle pulleys have now emerged as central players in the biomechanics of eye movement. These anatomical structures, formed by dense connective tissues, guide the paths of the EOMs, ensuring that their pulling angles remain optimal across a range of gaze directions. The non-linear paths resulting from these pulleys provide a more dynamic and intricate understanding of eye movement, challenging two-dimensional, linear models of orbital anatomy. The implications of these revelations extend beyond mere theoretical knowledge. The insights garnered from this research promise transformative potential in the realm of strabismus surgery. Recognising the pivotal role of muscle pulleys and the "arc of contact" paradigm allows for more precise surgical interventions, ensuring better post-operative outcomes and minimising the risk of complications. Surgical procedures that previously relied on basic mechanical principles now stand to benefit from a more nuanced understanding of the underlying anatomical and physiological dynamics. In conclusion, this manuscript serves as a testament to the ever-evolving nature of scientific knowledge. Challenging established norms and introducing fresh perspectives pave the way for more effective and informed clinical interventions in strabismus surgery.

Internal Rotation Measurement of the Knee with Polymer-Based Capacitive Strain Gauges versus Mechanical Rotation Measurement Taking Gender Differences into Account: A Comparative Analysis.

With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge's electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee's surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii's tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark's length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor's initial 20% strain range. The comparison between length change and the knee's internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen.

Acid Violet 3: A Base-Activated Water-Soluble Photoswitch.

Acidic azo dyes are widely used for their vibrant colors. However, if their photophysics were better understood and controllable, they could be integrated into many more applications such as photosensing, photomedicine, and nonlinear optics. Here, the proton-controlled photophysics of a widely used acid, hydrazo dye, acid violet 3 (AV3) is explored. Density functional theory is used to predict the ground- and excited-state potential energy surfaces, and the proposed photoisomerization mechanism is confirmed with spectroscopic experiments. The ground-state and first two excited-state surfaces of the three readily accessible protonation states, AV3-H, AV3, and AV3+H, are investigated along both the dihedral rotation and inversion coordinates. The deprotonated AV3-H undergoes photoisomerization with blue light (λex = 453 nm) through a dihedral rotation mechanism. Upon the formation of the cis-isomer, the reversion of AV3-H is predicted to occur through a mixed rotational and inversion mechanism. In contrast, AV3 and its protonated form, AV3+H, do not undergo photoisomerization because there is no driving force for either the rotation or inversion of the azo bond in the excited state. In addition, when the azo bond is acidic, the ground-state dihedral rotation reversion mechanism barrier is lower. The mechanistic insights gained here through the combination of theory and experiment provide a roadmap to control the reactivity of AV3 across 11 orders of magnitude of proton concentration, making them interesting candidates for a range of pharmaceuticals.

In-situ EBSD observation of texture evolution and lattice rotation behavior in shear deformation of thin-walled aluminum alloy tubes

As shear stress plays a significant role in the deformation of tubular parts with complex shapes, investigation of the microstructue evolution of tubes under the shear stress state is beneficial to understanding the shear deformation mechanism and promoting the prediction accuracy of numerical simulation. In this paper, the shear experiments were conducted on thin-walled 5052 aluminum alloy tubes. The texture evolution and lattice rotation behavior of the tube during shear deformation were studied using in-situ electron back scatter diffraction (EBSD) technology. It is shown that the initial Cube texture remains stable, while a new Rot. Copper texture is formed in the shear deformation zone. The grains with the orientation of <100> parallel to the axial direction (AD) tend to stabilize, while several low-angle grain boundaries (LAGBs) are formed inside the grains with unstable initial orientations. Notably, the orientations of adjacent grains are more similar after shear deformation, and the high-angle grain boundaries (HAGBs) gradually transform to LAGBs showing the characteristics of polycrystalline cooperative deformation. By analyzing the lattice rotation mechanism under shear stress, it is found that the shear stress promotes the lattice rotation to a stable orientation parallel to the direction of the shear stress. This research provides theoretical guidance for predicting the forming of tubular parts with complex shapes.

Improved Units of Measure in Rotational Mechanics

Improved Units of Measure in Rotational Mechanics