Axis Stability Research Articles

Design and analysis for the multi-point flexible support structure of large and precision lens

In order to achieve accurate surface figure and optical axis stability of a large aperture lens in the ground-based telescope system which subject to various load case, a novel lens support with multi-point flexible support structure is proposed. Then, the parameters of the support structure are optimized based on low-order modal and system accuracy, and the sensitivity of the flexure element’s parameters, the impact on the optical axis inducted by assembly and machining error of the support structure and the stability of the lens under different load cases are analyzed, meanwhile the rigidity of the support structure is tested. The result show that: the support rigidity of the system is higher, the optical axis offset causing by gravity is less than 2 μm when the lens is mounted horizontally; lens wave-front aberration (RMS) is 11.07nm when thermal load is altered from reference temperature(+20 °C) to −20 °C. The results and practice indicate that the multi-point flexible support structure can improve lens surface figure, and the assembly design is practicable and extensible.

C1 Arch Reconstruction: A Novel Alternative to Fusion in Maintaining Mobility of the Atlanto-Axial Joint

First decribed by Sir Goeffrey Jefferson in London in 1924, the term Jefferson’s fracture has become an eponym for all fractures of the Atlas. Complex Jefferson fractures and unstable Jefferson fractures require surgical fusion to maintain stability of the spinal axis. This however results in debilitating loss of movement at the crucial C1C2 joint, the most versatile of spinal joints where stability and mobility are intricately balanced into a complex yet supremely agile structure. The desire to attempt in some way to preserve a degree of movement and to spare the patient the crippling loss of movement at this joint has led to many attempts at innovation, both surgical and technological. This has led to the discovery of C1 osteosynthesis. This revolutionary technique enables the anatomical fixation of the defect thus allowing motion preservation without compromising on stability, which is a major advantage given the extreme importance of both to the proper functioning of the C1C2 and C1C0 joints. We present a case report of a 54 year old man with an isolated Jefferson’s fracture which was treated successfully by this technique. We also present an overview of the biomechanics of C1 injury and the relevant review of literature regarding options for management of complex C1C2 injuries.

Magic angle spinning spheres.

Magic angle spinning (MAS) is commonly used in nuclear magnetic resonance of solids to improve spectral resolution. Rather than using cylindrical rotors for MAS, we demonstrate that spherical rotors can be spun stably at the magic angle. Spherical rotors conserve valuable space in the probe head and simplify sample exchange and microwave coupling for dynamic nuclear polarization. In this current implementation of spherical rotors, a single gas stream provides bearing gas to reduce friction, drive propulsion to generate and maintain angular momentum, and variable temperature control for thermostating. Grooves are machined directly into zirconia spheres, thereby converting the rotor body into a robust turbine with high torque. We demonstrate that 9.5-mm-outside diameter spherical rotors can be spun at frequencies up to 4.6 kHz with N2(g) and 10.6 kHz with He(g). Angular stability of the spinning axis is demonstrated by observation of 79Br rotational echoes out to 10 ms from KBr packed within spherical rotors. Spinning frequency stability of ±1 Hz is achieved with resistive heating feedback control. A sample size of 36 μl can be accommodated in 9.5-mm-diameter spheres with a cylindrical hole machined along the spinning axis. We further show that spheres can be more extensively hollowed out to accommodate 161 μl of the sample, which provides superior signal-to-noise ratio compared to traditional 3.2-mm-diameter cylindrical rotors.

Improved ADRC With ILC Control of a CCD-Based Tracking Loop for Fast Steering Mirror System

In order to improve the tracking accuracy of the fine tracking system of free-space optical communications, a proposed active disturbance rejection control (ADRC) with iterative learning control (ILC) strategy is designed to regulate the fast steering mirror (FSM) system. First, based on the open-loop frequency response results of the system, we can approximately confirm the system transfer function and prepare for the design of the controller. Then, an improved ADRC that using sliding mode control instead of the traditional nonlinear state error feedback method is proposed to attenuate the influence of the unknown and unmolded parts. In addition, the ILC method is used to compensate the hysteresis of piezoelectric actuators and improve the overall system performance. The experimental results indicate that the tracking accuracy of the system is 1 μrad at 1k sampling frequency. In addition, the recommended method shows the better disturbance suppression performance than traditional ADRC in simulation and experimental investigations. This method has a very high application value in the field of visual axis stability, adaptive optics, and other fields.

Angular-Dependent Radius Measurements at Rotating Objects Using Underdetermined Sensor Systems

Precise and contactless shape measurements of rotating objects is important, e.g., for monitoring and controlling the manufacturing quality in lathes. For this purpose, multisensor and single-sensor approaches based on optical distance and surface velocity measurements are state-of-the-art techniques. Two- and single-sensor systems are particularly promising to measure the angular-dependent radius of the cross section of the rotating object in a scanning regime with minimal optical access. Since a comparison between the different sensor systems is missing, the potential of these underdetermined sensor systems is unclear. In addition, displacements of the rotational axis and sensor misalignments are suspected to be crucial error sources, but the error is unknown. For this reason, an error analysis is performed regarding the resulting systematic error and the random error for the two- and single-sensor systems. As a result, the different sensor systems have an equal cross-sensitivity with respect to lateral displacements of the rotational axis from the sensor axes, but the two-sensor approach has the lowest sensitivity regarding sensor misalignments. For the studied measurement conditions, the systematic error dominates the sensor noise for the two-sensor system and the single-sensor system with combined distance and velocity measurement at an object mean radius >6 mm. The smallest total measurement uncertainty is obtained with the two-sensor system. Finally, the relevance of systematic error depends on the utilization, i.e., for instance on the absolute rotor radius, the stability of the rotor axis, the sensor position, the accuracy of the sensor alignment, and the uncertainty of the distance and/or velocity measurements.

Research on the method to improve the vibration stability of vibratory cylinder gyroscopes under temperature variation

Due to the material defects, manufacture errors and internal stress, the vibration axis stability of the vibratory cylinder gyroscope is highly influenced by environment temperature. According to the influencing rule of the internal stress on the vibrating axis, a special resonator structure is proposed which can generate oriented thermal stress to reduce the temperature drift of vibrating axis of the resonator. Firstly, the drift trend of the vibrating axis under varying temperature is analyzed. Secondly, thermal stress structures with holes and grooves are fabricated in special direction at the bottom of the resonator. Those thermal stress structures can generate thermal stress to make the vibrating axis rotate in the opposite direction, which can reduces the gyroscope’s temperature drift. Finally, simulations and experiments are conducted and results show that the proposed method can give good compensation effect for temperature drift of the vibratory cylinder gyroscope.

Mitochondrial dynamics controls anti-tumour innate immunity by regulating CHIP-IRF1 axis stability

Macrophages, dendritic cells and other innate immune cells are involved in inflammation and host defense against infection. Metabolic shifts in mitochondrial dynamics may be involved in Toll-like receptor agonist-mediated inflammatory responses and immune cell polarization. However, whether the mitochondrial morphology in myeloid immune cells affects anti-tumor immunity is unclear. Here we show that FAM73b, a mitochondrial outer membrane protein, has a pivotal function in Toll-like receptor-regulated mitochondrial morphology switching from fusion to fission. Switching to mitochondrial fission via ablation of Fam73b (also known as Miga2) promotes IL-12 production. In tumor-associated macrophages, this switch results in T-cell activation and enhances anti-tumor immunity. We also show that the mitochondrial morphology affects Parkin expression and its recruitment to mitochondria. Parkin controls the stability of the downstream CHIP–IRF1 axis through proteolysis. Our findings identify mechanisms associated with mitochondrial dynamics that control anti-tumor immune responses and that are potential targets for cancer immunotherapy.

Spatial orientation and postural control in patients with Parkinson’s disease

Postural instability is one of the most disabling and risky symptoms of advanced Parkinson's disease (PD). The purpose of this study was to investigate whether and how this is mediated by a centrally impaired spatial orientation. Therefore, we performed a spatial orientation study in 21 PD patients (mean age 68years, SD 8.5 years, 9 women) in a medically on condition and 21 healthy controls (mean age 68.9years, SD 5.5years, 14 women). We compared their spatial responses to the horizontal axis (Sakashita's visual target cancellation task), the vertical axis (bucket-test), the sagittal axis (tilt table test) and postural stability using the Fullerton Advanced Balance Scale (FAB). We found larger deviations on the vertical axis in PD patients, although the direct comparisons of performance in PD patients and healthy controls did not reveal significant differences. While the total scores of the FAB Scale were significantly worse in PD (25.9 points, SD 7.2 points) compared to controls (35.1 points, SD 2.3 points, p<0.01), the results from the spatialorientation task did not correlate with the FAB Scale. In summary, our results argue against a relation between perceptional deficits of spatial information and postural control in PD. These results are in favor of a deficit in higher order integration of spatial stimuli in PD that might influence balance control.

Orogen-parallel brittle extension as a major tectonic imprint in the Neogene evolution of the south-western Alpine arc

We present a new analysis of the late Alpine brittle deformation in the southern branch of the western Alpine arc, focusing on the stack of internal metamorphic nappes east of the Argentera external crystalline massif. The regional-scale fault network is dominated by a NW–SE-striking right-lateral fault system that follows the general curvature of the arc and controls the overall morphology of the area. A second fault set strikes N–S and is mainly represented by normal faults which accommodate orogen-parallel extension. Structural analysis and paleostress tensors derived from inversion of fault-slip data reveal a complex pattern of deformation involving extensional and strike-slip deformation events. The orogen-parallel extension previously described in the internal zones at the east of the Pelvoux massif is confirmed further south, and we show that it is combined with right-lateral strike-slip deformation that increases in intensity towards the south-west. The stability of the minimum stress axis (σ3) direction suggests that extensional and transcurrent regimes are contemporaneous and highlights regional interferences between inner brittle extension, parallel to the strike of the belt, and the strike-slip strain field driven by the counterclockwise rotation of the Apulia–Adria plate. The curved geometry of the belt constrains the direction of extension and the coupling relationship between the internal and external Alpine zones. We propose that the Neogene tectonic history is a result of the unique curved tectonic architecture of the south-western Alps with respect to the rotation of the Apulia–Adria indenting plate. The southern tip of the western Alpine arc represents a transitional zone between extension in the inner chain and strike-slip/compression in the outer parts.

EXPERIMENTAL RESEARCH REGARDING THE INFLUENCE OF THE FRICTION FORCE FROM LINEAR ROLLING GUIDEWAYS ON THE POSITIONING PRECISION OF KINEMATIC FEED CHAINS USED ON CNC MACHINE TOOLS

&lt;p&gt;Friction represents one of the major sources of disturbing forces which affect the functioning of the kinematic feed chains from CNC machine tools. Its influence reflects on the positioning precision values, having a negative impact on the table movement and leading to stationary errors, stick-slip motion and trajectory errors. The present paper presents an experimental analysis regarding the influence of the friction forces which appear in the linear rolling guideways on the positioning precision of kinematic feed chains. The rolling guideways present the advantages of a good behavior in terms of axis stability at low speeds and also for achieving high positioning speeds. Concerning the friction coefficient values, rolling and hydrostatic guideways are most suitable for the construction of high speed and high precision kinematic feed chains; in these cases, the friction coefficient has small values, which maintain quasi-constant against the feed rate. &lt;/p&gt;

Lorentz force filtering and fast steering mirror optical compensation in optical axis stability control for photoelectric mast

The photoelectric mast equipped on the underwater vehicle is the key equipment for photoelectric tracking. While the vehicle moves under water, especially, at high speed, more complex vortexes are generated at the surface, which will give rise to great disturbance to the stability of optical axis. In this paper, firstly, based on the basic control equations of electromagnetic field and fluid mechanics, the effects of the Lorentz force on flow field structure and vortex induced vibration are numerical simulated with using the finite volume method with hierarchy grids. Secondly, the structural characteristics, transfer functions and PID control strategies of fast steering mirror (FSM) are analyzed. Finally, combining the transfer function of FSM and the force characteristics, the effect of the composite control on the stability of submarine photoelectric tracking system is discussed by MATLAB. The results show that the Lorentz force can adjust the boundary layer and suppress vortex induced vibration, based on which the FSM can be used to further improve the accuracy of the optical tracking system. This research offers a new exploration in the field of electromagnetic fluid control, as well as a novel development of the traditional research direction of fluid mechanics. Therefore it appears to have a certain scientific significance and practical value.

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

The near-Earth asteroid (3200) Phaethon is an intriguing object: its perihelion is at only 0.14 au and is associated with the Geminid meteor stream. We aim to use all available disk-integrated optical data to derive a reliable convex shape model of Phaethon. By interpreting the available space- and ground-based thermal infrared data and Spitzer spectra using a thermophysical model, we also aim to further constrain its size, thermal inertia, and visible geometric albedo. We applied the convex inversion method to the new optical data obtained by six instruments and to previous observations. The convex shape model was then used as input for the thermophysical modeling. We also studied the long-term stability of Phaethon's orbit and spin axis with a numerical orbital and rotation-state integrator. We present a new convex shape model and rotational state of Phaethon: a sidereal rotation period of 3.603958(2) h and ecliptic coordinates of the preferred pole orientation of (319$^{\circ}$, $-$39$^{\circ}$) with a 5$^{\circ}$ uncertainty. Moreover, we derive its size ($D$=5.1$\pm$0.2 km), thermal inertia ($\Gamma$=600$\pm$200 J m$^{-2}$ s$^{-1/2}$ K$^{-1}$), geometric visible albedo ($p_{\mathrm{V}}$=0.122$\pm$0.008), and estimate the macroscopic surface roughness. We also find that the Sun illumination at the perihelion passage during the past several thousand years is not connected to a specific area on the surface, which implies non-preferential heating.

A Dynamic Kinetic C–P Cross–Coupling for the Asymmetric Synthesis of Axially Chiral P,N Ligands

The Pd-catalyzed enantioselective C–P cross-coupling between racemic, configurationally stable heterobiaryl triflates and trialkylsilyldiaryl(dialkyl)phosphines has been used for the synthesis of several families of enantiomerically enriched heterobiaryl phosphines including QUINAP, PINAP, and QUINAZOLINAP analogues, which can be performed with good yields and enantioselectivities using JOSIPHOS-type bidentate phosphines. The strategy relies on two key assumptions: (I) The N atom of the heterocycle is a better ligand than triflate, and upon oxidative addition, it incorporates into the coordination sphere of the PdII center to form cationic cyclic intermediates. (II) The geometry of the palladacycle results in a widening of the angles involved in the stabilization of the stereogenic axis, facilitating a fast interconversion of diastereomeric structures and, hence, a dynamic kinetic C–P cross-coupling reaction. These starting hypotheses are supported by experimental and computational studies.

Synthesis of Naphthylpyridines from Unsymmetrical Naphthylheptadiynes and the Configurational Stability of the Biaryl Axis.

A series of different unsymmetrically substituted naphthyl-based diynes were synthesized. These substrates formed the foundation for the assembly of novel biaryls containing pyridine moieties with differently substituted five-membered rings in the backbone of the newly formed heterobiaryl system. The key step for their efficient construction was the photo- and cobalt-catalyzed [2 + 2 + 2] cycloaddition reaction between the corresponding naphthyldiyne and aceto- or benzonitrile. The heterobiaryl products have been isolated and investigated with respect to the configurational stability of their biaryl axis using dynamic chiral HPLC; subtle effects of the substitution pattern on the stability of the axis were observed. For several compounds the activation barriers (ΔG(‡)) of racemization were determined. Suitable substitution of the five-membered ring backbone exemplarily allowed the Co-catalyzed enantioselective cyclization to yield the enantiomerically enriched heterobiaryl.

X-FEL Quadrupole with Gradient of 100 T/m

The paper describes an XFEL quadrupole with a gradient of 100 T/m. The magnets of this quadrupole are designed for installation in the free space between the XFEL undulators to maintain the high quality of the electron beam at an energy of 10 - 20GeV, which requires high stability of the magnetic axis of the lens. The available size of the aperture of the lens is R = 8 mm. The stability of the quadrupole magnetic axis is better than 5 um for ±10% of the gradient range; the magnetic field quality is good (ΔВ/В < 10-3).

Система пространственной стабилизации оси диаграммы направленности лазерного излучения в атмосферной линии связи

Система пространственной стабилизации оси диаграммы направленности лазерного излучения в атмосферной линии связи

抗失谐高光轴稳定度激光器

抗失谐高光轴稳定度激光器

Control of peripheral tolerance by regulatory T cell-intrinsic Notch signaling.

Notch receptors direct the differentiation of T helper (TH) cell subsets, but their influence on regulatory T (Treg) cell responses is obscure. We here report that lineage-specific deletion of components of the Notch pathway enhanced Treg cell-mediated suppression of TH1 responses, and protected against their TH1 skewing and apoptosis. Expression in Treg cells of gain of function transgene encoding Notch1 intracellular domain resulted in lymphoproliferation, exacerbated TH1 responses and autoimmunity. Cell-intrinsic canonical Notch signaling impaired Treg cell fitness, promoted the acquisition by Treg cells of a TH1 cell-like phenotype, whereas Rictor-dependent non-canonical Notch signaling activated the AKT-Foxo1 axis and impaired Foxp3 epigenetic stability. These findings establish a critical role for Notch signaling in controlling peripheral Treg cell functions.

Comparison of GC/time-of-flight MS with GC/quadrupole MS for halocarbon trace gas analysis

Abstract. We present the application of time-of-flight mass spectrometry (TOF MS) for the analysis of halocarbons in the atmosphere after cryogenic sample preconcentration and gas chromatographic separation. For the described field of application, the quadrupole mass spectrometer (QP MS) is a state-of-the-art detector. This work aims at comparing two commercially available instruments, a QP MS and a TOF MS, with respect to mass resolution, mass accuracy, stability of the mass axis and instrument sensitivity, detector sensitivity, measurement precision and detector linearity. Both mass spectrometers are operated on the same gas chromatographic system by splitting the column effluent to both detectors. The QP MS had to be operated in optimised single ion monitoring (SIM) mode to achieve a sensitivity which could compete with the TOF MS. The TOF MS provided full mass range information in any acquired mass spectrum without losing sensitivity. Whilst the QP MS showed the performance already achieved in earlier tests, the sensitivity of the TOF MS was on average higher than that of the QP MS in the "operational" SIM mode by a factor of up to 3, reaching detection limits of less than 0.2 pg. Measurement precision determined for the whole analytical system was up to 0.2% depending on substance and sampled volume. The TOF MS instrument used for this study displayed significant non-linearities of up to 10% for two-thirds of all analysed substances.

Stability and dynamic analyses of a horizontal axis washing machine with a ball balancer

A mathematical model of a horizontal axis washing machine with a ball balancer is built. The Floquet multipliers are employed for judging the stability of the system based on which a special continuation program considering the influence of gravity is developed. Stability analysis is carried out with stable and unstable regions above 4Hz discovered. Influences of several parameters on variations of the boundaries between the regions are discussed. Dynamics of the spinning cycle in Stable region 1 are studied. The phenomenon that the tub's axis moves along the lateral surface of a cone is discovered based on which equilibrium of the centrifugal forces is discussed and a potential method for getting a smaller vibration angle is proposed. A ball balancer is produced for experiment with its lubrication and defects due to friction discussed. Quantitative experiment is done on a commercial washing machine with instability of the balancer, the cone shape trajectory of the tub's axis and the method of obtaining a smaller vibration angle validated.