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This paper aims to address the tracking control problem for the steer-by-wire (SbW) system with uncertain nonlinearity and parameter uncertainty. First, the adaptive fuzzy logic system (FLS) is constructed to realize the intelligent modeling of the SbW system. In addition, an adaptive higher-order sliding mode (AHOSM) control with dynamic gain is designed to overcome the lumped uncertainties including inaccurate model-parameter and fuzzy logic system approximation error, and has the advantage of eliminating the gain-overestimation phenomenon effectively without the prior knowledge about the bounds of approximation error and parameter uncertainty. Furthermore, theoretical analysis based on Lyapunov stability theory is provided to verify that the real sliding mode can be established. Finally, simulations and vehicle experiments are given to evaluate the effectiveness and superiority of the proposed methods.

The eye, an anatomical extension of the central nervous system (CNS), exhibits many molecular and cellular parallels to the brain. Emerging research demonstrates that changes in the brain are often reflected in the eye, particularly in the retina1. Still, the possibility of an immunological nexus between the posterior eye and the rest of the CNS tissues remains unexplored. Here, studying immune responses to herpes simplex virus in the brain, we observed that intravitreal immunization protects mice against intracranial viral challenge. This protection extended to bacteria and even tumours, allowing therapeutic immune responses against glioblastoma through intravitreal immunization. We further show that the anterior and posterior compartments of the eye have distinct lymphatic drainage systems, with the latter draining to the deep cervical lymph nodes through lymphatic vasculature in the optic nerve sheath. This posterior lymphatic drainage, like that of meningeal lymphatics, could be modulated by the lymphatic stimulator VEGFC. Conversely, we show that inhibition of lymphatic signalling on the optic nerve could overcome a major limitation in gene therapy by diminishing the immune response to adeno-associated virus and ensuring continued efficacy after multiple doses. These results reveal a shared lymphatic circuit able to mount a unified immune response between the posterior eye and the brain, highlighting an understudied immunological feature of the eye and opening up the potential for new therapeutic strategies in ocular and CNS diseases.

This study proposes a novel AC vector magnetometer developed using a low-resource magneto-impedance sensor for China’s Feng-Yun meteorological satellite (FY-3E). It was calibrated and characterized to determine its performance parameters. The total weight of the AC vector magnetometer is 51 g (the aluminum box excluded), while the total power consumption is 310 mW. The proposed AC vector magnetometer can detect magnetic field variations in the range of ±1000 nT and noise power spectral density of ⩽ 50 pT/Hz1/2@ 1 Hz. Furthermore, the proposed device has a maximum nonlinearity of ⩽ 0.71‰ over the entire range and a nonorthogonality error of 3.07 nT or 0.15% (root mean square). The total dose hardness of the sensor is ⩾ 30 krad (Si). Furthermore, we propose the first survey results of a magnetometer equipped aboard a Chinese FY-3E satellite in a Sun-synchronous orbit. The data revealed that the AC vector magnetometer can detect transient physical signals such as quasistatic field-aligned currents (~50 nT) and waves at the auroral latitudes. These features render the proposed AC vector magnetometer suitable for space-based applications, particularly those involving the study of geomagnetic activity.

With consideration of tire force saturation in vehicle motions, a novel path-following controller is developed for autonomous vehicles with unknown-bound disturbances and unknown actuator parameters. An adaptive sliding-mode fault-tolerant control (ASM-FTC) strategy is designed to stabilize the path-following errors without any information of disturbance boundaries, actuator fault boundaries and steering ratio from the steering wheel to the front wheels. By selecting the distance from the center of gravity to the center of percussion as the preview length, the effects of the lateral rear-tire force are decoupled and cancelled out, and then the preview error, which represents the path-following performance, can be only commanded by the front-tire force. To further address the issue of unknown tire-road friction limits, a modified ASM-FTC strategy is presented to improve the path-following performance as the lateral tire force is saturated. Simulation results show that the modified ASM-FTC controller demonstrates superior tracking performance over the normal ASM-FTC while the autonomous vehicle follows desired paths.

As one of steering systems, the steer-by-wire (SbW) system plays a significant role in the automobile. This paper investigates the study of the adaptive discrete-time neural network (NN) steering tracking control of the SbW system based on angular velocity observer. First, the continuous second-order SbW system is discretized by the Euler approximation approach. Before the control design, an adaptive discrete-time angular velocity observer is constructed to estimate the value of angular velocity signal. Then, an adaptive discrete-time control via a backstepping scheme is proposed to achieve the exact steering tracking performance, where the unknown nonlinear function, as well as the control coefficient, are incorporated into the lumped uncertainty and approximated by one NN. The main advantages of the proposed control scheme can be concluded that: (1) without using the exact prior knowledge of system uncertainty and angular position signal, the discrete-time tracking control is achieved and (2) the noncausal problem is overcome without transforming the original system into a predictor form. Finally, the Lyapunov stability theory shows that the tracking error converges to a small neighborhood of zero. Simulations and experiments illustrate the effectiveness and superiority of the proposed adaptive discrete-time NN control.

This paper investigates the problem of accurate voltage tracking control for direct current-direct current (DC-DC) boost converter under unknown system parameters and load. Firstly, uncertainties caused by the perturbation of the inductor, capacitor, input voltage and load are approximated by neural networks. Meanwhile, a finite-time observer is proposed to obtain the estimates of lumped uncertainty without any true parameters of the system. Finally, to improve the convergence of output voltage, a finite-time control scheme is proposed for the DC-DC boost converter. It is proven that all signals of the closed-loop system are bounded and both the estimate errors and tracking errors can converge to a small neighborhood of the origin in finite time. Numerical simulations and real-time experiments are presented to demonstrate the effectiveness and superiority of the proposed controller.

Energetic electron measurement is of great significance to theoretical space physics research and space weather applications. Current energetic electron detectors must cooperate with a spin-stabilized satellite platform to achieve high angular resolution in pitch angle distribution and three-dimensional (3D) imaging measurement of energetic electrons. This article introduces a cross-type quasi-3D imaging electron spectrometer (IES) based on pinhole imaging technology developed in the laboratory. The imager is composed of five imaging units, including a nine-pixel area array Si-PIN detector imaging unit in the middle and four three-pixel linear array Si-PIN detector imaging units placed in a cross-shape around it. The combination of five imaging units forms two orthogonal nine-pixel linear array detectors (with a common pixel in the middle). There are four pixels with a view angle of 20° × 20° in the 45° oblique directions of the cross-type detection array. There are 21 imaging pixels in the entire cross-type sensor head, corresponding to 21 directions. Two multichannel integrated preamplifier ASICs are integrated in the sensor head to realize particle signal readout from 21 pixels. With a back-end electronics system, each pixel can achieve high energy resolution detection of 50–600 keV electrons. Radioactive sources and electron accelerators are used to calibrate the cross-type imaging sensor head, and results demonstrate its good energy and directional detection characteristics (the energy resolution reaches 6.9 keV for the incident 200 keV electron beam). We performed simulations on the imaging sensor head’s ability to measure the electron pitch angle distribution on the three-axis stabilized platform, and the results show that the sensor head can perform quasi-three-dimensional detection of electrons incident within 2π solid angles on the three-axis stabilized satellite platform, with an average angular resolution of the electron pitch angle distribution of less than 6°.

This paper addresses the prescribed tracking performance control problem for uncertain steer-by-wire (SbW) systems with input nonlinearity (including dead-zone and actuator fault) and the limitation of controller-area-network (CAN) bandwidth. An adaptive interval type-2 fuzzy logic system (IT2 FLS) is introduced to approximate the lumped model uncertainty, and a switching event-triggering mechanism (ETM) is applied to save the communication resources. Combining the backstepping approach and barrier Lyapunov function techniques, a prescribed tracking performance control method is proposed for SbW systems, where the initial values of state errors are no longer required in the controller design. Theoretical analysis shows that the tracking error can converge to the predefined residual set within preset time instead of the time tending infinite, while the closed-loop system is semi-globally stable. Simulations and vehicle experiments are presented to verify the effectiveness of the proposed control method.

This article introduces a robust H-infinity fuzzy static output feedback (RHF-SOF) control with norm-bounded strategy to enhance the path-following performance for the four-wheel-independent-driven electric vehicles (FWID-EVs). Firstly, taking the parameter uncertainties including vehicle mass, moment of inertia, longitudinal velocity, and tire cornering stiffness into account, a fuzzy optimization model is constructed to approximate the nonlinear characteristic of the vehicle system using both the parameter uncertainty reduction strategy and polytope reduction strategy. Secondly, with consideration of the difficulty of the online lateral velocity measurement, a Lyapunov stability-based RHF-SOF control with the gain scheduling method is proposed to control the variables of the path following. Thirdly, since the actuator saturation can deteriorate the control performances, a norm-bounded strategy is designed to address the nonlinear saturation problem. The proposed controller is verified and evaluated through the hardware-in-the-loop experimental test with different maneuvers.

This article addresses the steering control problem for steer-by-wire (SbW) systems subject to the unknown uncertainty, external disturbance and unavailable variable. Before the controller design, an adaptive neural network-based observer and a disturbance observer are constructed to estimate the angular velocity signal and the compound disturbance, respectively. Then, to guarantee the transient and steady-state performance of steering tracking error within the quantitative boundary, a prescribed performance function is constructed by user-designed tracking accuracy and settling time. Finally, the controller is designed based on the backstepping scheme and the neural network with a composite learning scheme is proposed for the approximation of lumped uncertainty. The Lyapunov stability theory shows that the signals involved in the system are semi-global uniformly ultimately bounded and the tracking error converges to a preset range at finite time. Different numerical simulations and experiments are implemented to verify the effectiveness of the developed control scheme.

ABSTRACTInvestigating the function of delicate mammalian eyes often requires chemical fixation, histological sectioning, immunohistochemistry (IHC) and in situhybridization (ISH). One of the long-standing challenges in the ocular histology field is the limited success of maintaining intact morphology via cryo- or paraffin procedures. Although our latest protocol significantly improved the morphology of mouse eyeball sections, the window technique is time-consuming and requires extensive practice to avoid damage while making windows. In this study, we present a novel glyoxal fixative that is suitable for a freeze-substitution approach to improve both morphology and molecular target preservation of mouse eyes. The method prevents morphology distortion in all tested eyeballs. Therefore, it suits a variety of research needs from morphological examination to investigation of single-molecule RNA expression, using hematoxylin and eosin (H&E) stain, IHC, and ISH assays on either frozen (cryo) or paraffin-infiltrated tissue sections. In addition, this method can be easily performed in many histology laboratories.

ABSTRACTThe central tenet of scientific research is the rigorous application of the scientific method to experimental design, analysis, interpretation, and reporting of results. In order to confer validity to a hypothesis, experimental details must be transparent and results must be reproducible. Failure to achieve this minimum indicates a deficiency in rationale, design, and/or execution, necessitating further experimental refinement or hypothesis reformulation. More importantly, rigorous application of the scientific method advances scientific knowledge by enabling others to identify weaknesses or gaps that can be exploited by new ideas or technology that inevitably extend, improve, or refine a hypothesis. Experimental details, described in manuscript materials and methods, are the principal vehicle used to communicate procedures, techniques, and resources necessary for experimental reproducibility. Recent examination of the biomedical literature has shown that many published articles lack sufficiently detailed methodological information to reproduce experiments. There are few broadly established practice guidelines and quality assurance standards in basic biomedical research. The current paper provides a framework of best practices to address the lack of reporting of detailed materials and methods that is pervasive in histological slide-based assays. Our goal is to establish a structured framework that highlights the key factors necessary for thorough collection of metadata and reporting of slide-based assays.

• The weight recursive least squares are employed to update SCN in real time. • SCN-based cascade GPC (SCN-CGPC) for the MST is derived. • Simplification of the KKT conditions saves iterative process. • Industrial application illustrates its practicality and effectiveness. The main steam temperature (MST) in power plants suffers from nonlinearity and large time delay, which cause large overshoot and long settling time under widely used cascade proportion integration differentiation (PID) controller. In order to cope with the negative effects, we propose a stochastic configuration network (SCN) based cascade generalized predictive control (GPC) scheme to improve the performance of the MST. A three-layer SCN is employed to model the MST process. The SCN is constructed by two phases, i.e., initial phase and real-time phase. The initial phase determines the structure and primary parameters of the learner model using the stochastic configuration algorithm. The real-time phase employs weighted recursive least squares (WRLS) for building the real-time MST process model for GPC design. Taking into account some constraints of the MST process, Karush–Kuhn–Tucker (KKT) conditions are applied for solving the constrained receding-horizon optimization problem. The derived explicit solutions of GPC avoid the implicit form which usually has to be solved iteratively. Comparative simulations demonstrate the superiority of the proposed SCN based cascade GPC (SCN-CGPC). Finally, the proposed SCN-CGPC is implemented via a standalone external MST control system in a power plant. The effectiveness and practicability are validated with the real-world application. [ABSTRACT FROM AUTHOR]

ABSTRACTIn recent years, the problem of cancer resistance has become more and more prominent, seriously affecting treatment efficiency. Circular RNAs (circRNAs) play an important role in cell progression and cancer mechanisms. However, there is a lack of systematic studies on its function in non-small cell lung cancer (NSCLC) resistance. CircPTK2, microRNA-942 (miR-942), and Tripartite motif 16 (TRIM16) levels were detected by Real-time quantitative reverse transcriptase PCR (qRT-PCR). Extracellular acidification rate (ECAR), glucose consumption, and lactate production were assessed using the Seahorse XF96 Glycolysis Analyzer, glucose, and lactate assay kits, respectively. The protein expression was measured with the western bolt Transwell assay was used to determine migration and invasion of transfected cells. (4-5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry were applied to carry out cell proliferation and apoptosis, respectively. The relationship among circPTK2, miR-942, and TRIM16 were determined by using the dual-luciferase reporter assay and RIP assay. circPTK2 (hsa_circ_0008305) and TRIM16 were low expressed, while miR-942 was significantly highly expressed in NSCLC tissues and cell lines. Moreover, overexpression of circPTK2 remarkably inhibited cell growth, metastasis, and glycolysis in A549/CDDP and H1299/CDDP cells. Promotion of miR-942 or inhibition of TRIM16 could reverse the effects of high circPTK2 expression on cell growth, metastasis, and glycolysis in A549/CDDP and H1299/CDDP cells. CircPTK2 overexpression inhibited the growth of A549/CDDP cells in vivo. Furthermore, circPTK2 weakened CDDP resistance of NSCLC through modulating miR-942/TRIM16 axis, providing a novel sight for the treatment of NSCLC and improving the understanding of the CDDP resistance mechanism of NSCLC.

This paper proposes a fuzzy modeling and event-triggered adaptive sliding mode control for steer-by-wire (SbW) systems subject to uncertain nonlinearity, time-varying perturbation, actuator fault, and limited communication resources. First, an interval type-2 fuzzy logic system (IT2 FLS) based on Lyapunov's adaptive scheme is built to model the uncertain nonlinearity. Then, an event-triggered adaptive sliding mode control method is designed to overcome the limited communication resources, time-varying perturbation, and actuator fault. This method eliminates the chattering phenomenon by utilizing nested adaptive technology and has practical finite-time stability. Theoretical analysis shows that the Zeno phenomenon is excluded. Finally, the validity of the methods is evaluated using simulations and vehicle experiments.

The steering-by-wire (SbW) system is one of the main subsystems of automatic vehicles, realizing the steering control of autonomous vehicles. This paper proposes an event-triggered adaptive sliding mode control for the SbW system subject to the uncertain nonlinearity, time-varying disturbance, and limited communication resources. Firstly, an event-triggered nested adaptive sliding mode control is proposed for SbW systems. The uncertain nonlinearity is approximated by the interval type-2 fuzzy logic system (IT2 FLS). The time-varying disturbance, modeling error, and event-triggering error can be offset by robust terms of sliding mode control. The key advantage is that the high-frequency switching of sliding mode control only appears on the time derivate of control input without increasing the input-output relative degree of closed-loop SbW systems, such that the chattering phenomenon can be eliminated. Finally, theoretical analysis shows that the practical finite-time stability of the closed-loop SbW system can be achieved, and communication resources in the controller-to-actuator channels can be saved while avoiding the Zeno-behavior. Numerical simulations and experiments are given to evaluate the effectiveness of the proposed method.

In this study, as-cast low alloy wear-resistant steels with Ti contents of 0.6 and 3.0?wt-% were prepared at different solidification cooling rates, and the effects of TiC formation on their microstructures, hardness values, and wear resistances were investigated. The obtained phase diagrams and experimental data revealed that the TiC phase was formed via a divorced eutectic reaction in a residual liquid phase during solidification. The larger Ti content promoted the formation of TiC particles, while the solidification cooling rate represented the main influencing factor. Moreover, the produced TiC phase increased the wear resistance of the studied steel and decreased the matrix hardness, suggesting a new method for enhancing its mechanical properties through the formation of a hard ceramic phase.

ABSTRACTCOVID-19 disease in humans, caused by the novel SARS-CoV-2 virus, was first reported in the city of Wuhan, China in December 2019. This disease has quickly developed into a global pandemic, resulting in over 350,000 deaths worldwide and over 5 million confirmed infections in a matter of 6 months. Although the genome of this novel viral RNA was sequenced quickly and testing kits were manufactured to assist in combatting COVID-19, the diagnosis and treatment will remain relatively unsuccessful until the pathology of this disease is fully understood. Histotechnology plays an important role in understanding the pathology of many diseases, including COVID-19. The first postmortem biopsy of a COVID-19 patient was collected on 27 January 2020, and the pathology finding was published in mid-February 2020. Since then, more studies have been published in scientific literatures as the global outbreak continues. This mini-review summarizes the published articles in which histotechnology aspects were utilized with the intent to understand the pathology of COVID-19. In addition, it is anticipated there will be more molecular and immunohistochemical studies to further understand the mechanism of the disease in the near future.

To solve the uncertainties in permanent magnet synchronous motor (PMSM) driven steer-by-wire (SbW) system, a prescribed-performance-control (PPC) based finite-time fuzzy controller is proposed. Specifically, the dynamics of SbW system driven by PMSM is analyzed, and combine PPC technology to transform the tracking error coordinates. Then, the velocity signal is obtained from the sigmoid function-based tracking differentiator by using the position signal. To solve the problem of mismatched disturbance, fuzzy logic system (FLS) are used as a universal approximator to estimate the lumped nonlinear friction and other unknown functions, the boundary of lumped disturbance is estimated by the designed adaptive updating law. By fusing the designed virtual controller and the intermediate control law, the controller needs no precise parameters of system, under which the effect of uncertainty of control gain can be compensated completely. Finally, rigorous theoretical analysis based on the Lyapunov stability theory is provided to demonstrate the finite-time stability of the closed-loop system under consideration. Simulation and experiment results are presented to show the effectiveness of the developed control approach, and some comparisons are given to show the rapid and accurate position tracking control performance.

Background: Avascular necrosis is a common organ damage in SLE patients, which can influence patients’ life quality. Conflicting results exist in risk factors of AVN in SLE patients. The aim of this study was to illustrate risk factors predicting the occurrence of avascular necrosis (AVN), also known as osteonecrosis, in systemic lupus erythematosus (SLE) patients in Chinese SLE Treatment and Research Group (CSTAR), a multi-center cohort of Chinese SLE patients. Methods: SLE patients in CSTAR without existing AVN at registration were included. At least two follow-ups and an observation period of no less than 2 years for AVN event were required. Univariate and multivariate Cox regression analyses were used to evaluate risk factors for AVN in SLE patients. Coefficient B was transformed to risk score for the development of a risk stratification model. Results: One hundred six (2.59%) of 4091 SLE patients were diagnosed AVN during follow-ups of no less than 2 years. Multi-variate Cox regression analysis suggested that SLE onset age ≤ 30 (HR 1.616, p0.023), arthritis (HR 1.642, p0.018), existing organ damage (SDI ≥ 1) at registration (HR 2.610, p< 0.001), positive anti-RNP (HR 1.709, p0.006), and high glucocorticoid maximum daily dose at registration (HR 1.747, p0.02) were independent risk factors. A risk stratification system was developed according to the risk factors, and patients were divided into high risk (3–6) and low risk (0–2). The AUC of 0.692 indicated moderate discrimination. The calibration curve in internal validation was drawn. Conclusion: Patients with SLE onset age ≤ 30, arthritis, existing organ damage (SDI ≥ 1) at registration, positive anti-RNP, and high glucocorticoid maximum daily dose at registration are at high risk for AVN and require attention.

The hematopoietic stem cell (HSC) microenvironment, termed the niche, supports the proliferation, self-renewal, and differentiation abilities of HSCs. The definitive HSCs emerge from the hemogenic endothelium in the aorta-gonad-mesonephros (AGM) region after E10.5, and then migrate to the fetal liver (FL) after E12.5 for expansion. After E18.5, HSCs migrate to the bone marrow where they reside for the postnatal stage and adulthood. Because the fetal liver is thought to be a harbor for the rapid expansion of HSCs, numerous studies have focused on the FL-HSC niche in the search for novel niche factors and niche cells that support HSC expansion. However, to our knowledge thus far, there have been no successes in translating the niche factors to a clinical application for the expansion of HSCs ex vivo. In this study, we use cutting-edge spatial transcriptomics to comprehensively investigate the transcriptomics and interactions between HSCs and the niche cells in the fetal liver. As a result, we have uncovered two distinct niches: the portal-vessel (PV) niche and the sinusoidal niche.

ABSTRACTMelanomas represent the malignant transformation of melanocytes, cells found primarily in the skin to protect epithelium and underlying connective tissues from harmful effects of ultraviolet light. Melanomas vary greatly in morphology and may continue to produce melanin markedly, mildly, or not at all. Performing and evaluating hematoxylin and eosin stains as well as immunohistochemical stains on pigmented melanomas has been a long-standing challenge due to the obscuring pigment. Protocols for removing melanin to reveal cellular morphology have been used successfully for years, but coupling these protocols with stains for immunohistochemistry represents an added challenge. In this study, the investigators evaluated results of various melanin bleaching protocols on tissue morphology, completeness of melanin removal, and immunohistochemistry staining quality. It was found that 1% formamide in 3% H2O2under bright light without heating outperformed other tested protocols.

ABSTRACTThe BaseScope™ assay is a novel, highly sensitive RNA in situhybridization (ISH) technique, allowing detection of short RNA sequences as well as discrimination between single-nucleotide alterations. Multiplexing BaseScope™ ISH with immunofluorescence assay has proven challenging because the diffusion of colorimetric dyes such as Fast Red in aqueous solutions degrades spatial resolution. In this study, we explore alkaline phosphatase-based fluorescent signal detection methods and integrate it with BaseScope™ RNA ISH. We found that Fast Blue BB/NAMP can be used in BaseScope™ ISH for signal detection. Additionally, we found that the calcium binding fluorochromes calcein and xylenol orange can be used to localize alkaline phosphatase activity in both immunohistochemistry (IHC) and BaseScope™ ISH assays. When applied to mouse brain and intestine tissue sections, we successfully detected circular RNA molecules and cell proliferation antigen Ki-67 proteins. This technological advance expanded the substrate selection of alkaline phosphatase-based BaseScope™ RNA ISH to allow researchers and clinical professionals accurately assess RNA targets with immunofluorescent multiplexing.

An imaging energetic electron spectrometer built by the Peking University team (BD-IES) onboard a Chinese navigation satellite in an inclined GEO orbit has been launched successfully in September 2015, which measures the spectra of the energetic electrons with the energy range of 50–600 keV in nine directions. In this study, Monte Carlo simulations of the BD-IES sensor head were performed using Geant4 and the corresponding characteristic responses to the isotropic energetic particles were derived. The effective geometric factors were estimated using the typical electron and proton spectra in the GEO orbit and the corresponding simulated sensor head responses. It was found that the average effective geometric factors of nine directions are close to the nominal geometric factors calculated with the traditional method, but the effective geometric factor decreases as the center energy of the energy channel decreases. The BD-IES sensor head also responses to the energetic protons, but the average contamination rate of all 72 channels is about 2%, which means that the proton contamination is acceptable. The spectra of the energetic electrons measured by BD-IES are derived using the effective geometric factors of the sensor head and are comparable with the spectra measured by the magnetic electron ion spectrometer (MagEIS) instrument onboard Van Allen Probes.

In Earth's high‐latitude ionosphere, the poleward motion of east–west elongated auroral arcs has been attributed to standing hydromagnetic waves, especially when the auroral arcs appear quasi‐periodically with a recurrence time of a few minutes. The validation of this scenario requires spacecraft observations of ultra‐low‐frequency hydromagnetic waves in the magnetosphere and simultaneous observations of poleward‐moving auroral arcs near the spacecraft footprints. Here we present the first observational evidence from the multi‐spacecraft THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission and the conjugated all‐sky imager to support the scenario that standing hydromagnetic waves can generate the quasi‐periodic appearance of poleward‐moving auroral arcs. In this specific event, the observed waves were toroidal branches of the standing hydromagnetic waves, which were excited by a pulse in the solar wind dynamic pressure. Multi‐spacecraft measurements from THEMIS also suggest higher wave frequencies at lower L shells (consistent with the distribution of magnetic field line eigenfrequencies), which indicates that the phase difference across latitudes would increase with time. As time proceeds, the enlarged phase difference corresponds to a lower propagation speed of the auroral arcs, which agrees very well with the ground‐based optical data.

Sudden changes of the solar wind dynamic pressure have significant impacts on the dynamics of the magnetosphere‐ionosphere system. On 18 February 2011, a sudden decrease in solar wind dynamic pressure was observed by the Wind satellite, which drove the entire magnetosphere‐ionosphere system as recorded in many ground‐based and space‐based measurements. In the magnetosphere, Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft observed a counterclockwise plasma flow vortex propagating tailward. Near the magnetic footprints of the THEMIS spacecraft, the ground magnetometers observed magnetic field variations that corresponded to a counterclockwise vortex in the equivalent ionospheric currents, which in turn indicated the presence of upward field‐aligned currents. The all‐sky imager at RANK station near the THEMIS footprints also observed a simultaneous enhancement of the auroral brightness. Therefore, this comprehensive case study demonstrates a causal chain that links the solar wind dynamic pressure variations to magnetospheric, ionospheric, and auroral activities. In the near‐Earth space, the shape and dynamics of the magnetosphere and the ionosphere are strongly affected by solar wind variations. There have been numerous studies demonstrating the effects of magnetospheric compression caused by a sudden enhancement in the solar wind dynamic pressure. However, the opposite case with sudden decrease in the solar wind dynamic pressure has been rarely investigated. Here we perform a comprehensive, observational study to demonstrate the consequences of sudden decrease of solar wind dynamic pressure in the entire magnetosphere‐ionosphere system, which include the formation of magnetospheric flow vortices, generation of field‐aligned currents, perturbations of the geomagnetic field, and enhancement of auroral brightness near the magnetic footprints of the magnetospheric flow vortices. In other words, this case study provides a causal chain that shows the magnetospheric, ionospheric, and auroral responses to a sudden decrease of the solar wind dynamic pressure. Small‐scale auroral brightening is observed after a sudden decrease in solar wind dynamic pressureSolar wind discontinuity produces a tailward‐moving magnetospheric flow vortex associated with field‐aligned currentsClear relationship between upward field‐aligned currents, ionospheric currents, and auroral activities are presented

Electric vehicles have the potential to reduce oil dependency and decrease emissions. Electric vehicles with four-wheel independent drive have become a promising vehicle architecture. The yaw moment control has been widely applied to improve the performance of four-wheel independent drive electric vehicles. This study develops a new ideal vehicle model as a reference, which has a logarithmic functional relationship between wheel cornering stiffness and the controlled electric vehicles. A control method based on H∞theory and Moore–Penrose inverses property is used to produce the optimal yaw moment to match the ideal vehicle model. The simulation results show that the yaw speed of the controlled electric vehicles increases with lower speed, and the yaw speed and slip angle decrease with a higher speed. The steering performance is efficiently improved when the four-wheel independent drive electric vehicles can accurately match the ideal vehicle model.

The energetic electron measurement is one of the most important issues to understand dynamics in space physics and the applications for space weather. In this study, the principle and functional components of the imaging energetic electron spectrometer (IES) onboard a Chinese navigation satellite in the inclined GEO orbit (IGSO) was introduced. The IES instrument is developed by the team in Peking University (BeiDa), thus it is named as BD-IES. Based on the pin-hole technique, the instrument can measure 50–600 keV electrons incident from 9 directions over a range of 180° in polar angle. With pulse height analysis (PHA), the spectrum can be determined for each direction. The energy and angular calibrations were performed, which show the good energy and angular characteristics of BD-IES. Monte Carlo simulations show that the anti-proton design of BDIES can effectively decrease the proton contamination on the electron measurements in the inclined GEO orbit. The primary results of BD-IES verify the successful design of this instrument.

Transplantation of hematopoietic stem cells (HSCs) from human umbilical cord blood (hUCB) holds great promise for treating a broad spectrum of hematological disorders including cancer. However, the limited number of HSCs in a single hUCB unit restricts its widespread use. Although extensive efforts have led to multiple methods for ex vivo expansion of human HSCs by targeting single molecules or pathways, it remains unknown whether it is possible to simultaneously manipulate the large number of targets essential for stem cell self-renewal. Recent studies indicate that N6-methyladenosine (m6A) modulates the expression of a group of mRNAs critical for stem cell-fate determination by influencing their stability. Among several m6A readers, YTHDF2 is recognized as promoting targeted mRNA decay. However, the physiological functions of YTHDF2 in adult stem cells are unknown. Here we show that following the conditional knockout (KO) of mouse Ythdf2the numbers of functional HSC were increased without skewing lineage differentiation or leading to hematopoietic malignancies. Furthermore, knockdown (KD) of human YTHDF2led to more than a 10-fold increase in the ex vivo expansion of hUCB HSCs, a fivefold increase in colony-forming units (CFUs), and more than an eightfold increase in functional hUCB HSCs in the secondary serial of a limiting dilution transplantation assay. Mapping of m6A in RNAs from mouse hematopoietic stem and progenitor cells (HSPCs) as well as from hUCB HSCs revealed its enrichment in mRNAs encoding transcription factors critical for stem cell self-renewal. These m6A-marked mRNAs were recognized by Ythdf2 and underwent decay. In Ythdf2KO HSPCs and YTHDF2KD hUCB HSCs, these mRNAs were stabilized, facilitating HSC expansion. Knocking down one of YTHDF2′s key targets, Tal1mRNA, partially rescued the phenotype. Our study provides the first demonstration of the function of YTHDF2 in adult stem cell maintenance and identifies its important role in regulating HSC ex vivo expansion by regulating the stability of multiple mRNAs critical for HSC self-renewal, thus identifying potential for future clinical applications.

Biologists have long been fascinated with the organization and function of intricate protein complexes. Therefore, techniques for precisely imaging protein complexes and the location of proteins within these complexes are critically important and often require multidisciplinary collaboration. A challenge in these explorations is the limited resolution of conventional light microscopy. However, a new microscopic technique has circumvented this resolution limit by making the biological sample larger, thus allowing for super-resolution of the enlarged structure. This ‘expansion’ is accomplished by embedding the sample in a hydrogel that, when exposed to water, uniformly expands. Here, we present a protocol that transforms thick expansion microscopy (ExM) hydrogels into sections that are physically expanded four times, creating samples that are compatible with the super-resolution technique structured illumination microscopy (SIM). This super-resolution ExM method (ExM–SIM) allows the analysis of the three-dimensional (3D) organization of multiprotein complexes at ~30-nm lateral (xy) resolution. This protocol details the steps necessary for analysis of protein localization using ExM–SIM, including antibody labeling, hydrogel preparation, protease digestion, post-digestion antibody labeling, hydrogel embedding with tissue-freezing medium (TFM), cryosectioning, expansion, image alignment, and particle averaging. We have used this approach for 3D mapping of in situ protein localization in the Drosophilasynaptonemal complex (SC), but it can be readily adapted to study thick tissues such as brain and organs in various model systems. This procedure can be completed in 5 d.

During February 15–16, 2014, the energetic electron spectrogram for four successive inner radiation belt crossing show clearly the electron zebra structures and their time evolution which last for about 17 h. Unfortunately, the time of flight (TOF) in RBSPICE measurement is turned off below 3RE, and the ion measurement is contaminated by electrons. Thus in this study we studied the differences between the ion and electron zebra stripe structures and their time evolution using simple theory and test particle simulation, combining the electron measurement from RBSIPICE onboard Van Allen Probes. Theoretical analysis predicts that the ion zebra stripe structures should lie at a higher energy range than the corresponding electron zebra stripe structures due to that the directions of gradient B drift and corotation E×Bdrift are the same for electrons while opposite for ions. Test particle simulation with the dipole magnetic field and Volland-Stern electric field model have shown that the ion and electron zebra stripe structures could be produced by the convection electric field penetrating into the inner magnetosphere in this event, with their time evolution determined by total drift velocity that are different for ions and electrons. The predicted differences between the ion and electron zebra stripe structures are partially verified through observation. The ion zebra stripe structures could have potential influence to the ring current.

Rheumatoid arthritis patients are at higher risk of developing comorbidities. The main objective of this study was to evaluate the prevalence of major comorbidities in Chinese rheumatoid arthritis patients. We also aimed to identify factors associated with these comorbidities. Baseline demographic, clinical characteristics and comorbidity data from RA patients enrolled in the Chinese Registry of rhEumatoiD arthrITis (CREDIT) from Nov 2016 to August 2017 were presented and compared with those from five other registries across the world. Possible factors related to three major comorbidities (cardiovascular disease, fragility fracture and malignancy) were identified using multivariate logistic regression analyses. A total of 13,210 RA patients were included (80.6% female, mean age 52.9 years and median RA duration 4.0 years). Baseline prevalence rates of major comorbidities were calculated: CVD, 2.2% (95% CI 2.0–2.5%); fragility fracture, 1.7% (95% CI 1.5–1.9%); malignancy, 0.6% (95% CI 0.5–0.7%); overall major comorbidities, 4.2% (95% CI 3.9–4.6%). Advanced age was associated with all comorbidities. Male gender and disease duration were positively related to CVD. Female sex and longer disease duration were potential risk factors for fragility fractures. Ever use of methotrexate (MTX) was negatively related to baseline comorbidities. Patients with rheumatoid arthritis in China have similar prevalence of comorbidities with other Asian countries. Advanced age and long disease duration are possible risk factors for comorbidities. On the contrary, MTX may protect RA patients from several major comorbidities, supporting its central role in the management of rheumatoid arthritis.

We identified 28 discrete electron events (DEEs) with enhanced fluxes at ∼50–200 keV in the high-altitude cusp/polar cap/lobe, using the electron measurements by the BeiDa Image Electron Spectrometer (BD-IES) instrument onboard an inclined (55°) geosynchronous orbit (IGSO) satellite from October 2015 to January 2016. We find that among the 28 DEEs, 22 occur in the nightside and mostly in the northern cusp/polar cap/lobe, while 6 occur in the dayside and all in the southern cusp; 24 events correspond to an average interplanetary magnetic field (IMF) component Bz>0, 3 correspond to an average IMF Bz<0, and 1 has no OMNI IMF data. In these DEEs, the observed average omnidirectional electron differential flux generally fits well to a power-law spectrum, J∼E−γ, with the spectral index γranging from 2.6 to 4.6, while the average electron flux varies over three orders of magnitude from event to event. The spectral index of these cusp DEEs are (strongly) larger than the spectral index of solar wind superhalo electrons (radiation belt electrons) observed by the WIND 3D Plasma & Energetic Particle instrument (the BD-IES). At ∼110 keV, the electron flux of DEEs in the cusp/polar cap/lobe shows a weak positive correlation with the solar wind superhalo electron flux but no obvious correlation with the radiation belt electron flux. These results suggest that these DEEs probably originate from transient processes acting on the solar wind superhalo electrons, e.g., the mid/high-latitude reconnection.

The purpose of this paper is to understand how low energy plasmaspheric electrons respond to ULF waves excited by interplanetary shocks impinging on magnetosphere. It is found that both energy and pitch angle dispersed plasmaspheric electrons with energy of a few eV to tens of eV can be generated simultaneously by the interplanetary shock. The subsequent period of successive dispersion signatures is around 40 s and is consistent with the ULF wave period (third harmonic). By tracing back the energy and pitch angle dispersion signatures, the position of the electron injection region is found to be off-equator at around ?32° in the southern hemisphere. This can be explained as the result of injected electrons being accelerated by higher harmonic ULF waves (e.g. third harmonic) which carry a larger amplitude electric field off-equator. The dispersion signatures are due to the flux modulations (or accelerations) of “local” plasmaspheric electrons rather than electrons from the ionosphere. With the observed wave-borne large electric field excited by the interplanetary shock impact, the kinetic energy can increase to a maximum of 23 percent in one bouncing cycle for plasmaspheric electrons satisfying the drift-bounce resonance condition by taking account of both the corotating drift and bounce motion of the local plasmaspheric electron.

A lunar roving vehicle is of great significance in the processing of manned lunar exploration for long-duration space exploration missions. The mechanical model of the lunar roving vehicle’s wheel directly affects the mobility performance. However, the wheel of lunar roving vehicle is a special one with the metal mesh surface, and the soil can penetrate through its surface. In this paper, the mechanical model of a rigid normal wheel is deduced, and four stress correction coefficients are introduced to obtain the mechanical model of the lunar roving vehicle’s wheel. These four stress correction coefficients are identified in several groups of experiment of the lunar roving vehicle’s wheel, and using the functional coefficients can have a high precision for the mechanical model of the lunar roving vehicle’s wheel.

The efficacy and safety of the oral Janus kinase inhibitor peficitinib were investigated in Asian patients with rheumatoid arthritis (RA).

The tribological properties of the self-lubricating polymer were improved by strengthening the properties of the transfer film. The graphene oxide (GO) reinforced polytetrafluoroethylene (PTFE)/poly-p-phenylene terephthamide (PPTA) composites (GPPs) were prepared by dual-size synthesis. The tribological properties of GPPs were studied on a ball-on-disk tribometer. GPPs have low friction coefficient (minimum = 0.061) and hydrophobicity (maximum = 137.1385°). The structure–property relationships and the practical effect of transfer film enhancement induced by GO were revealed. We attempt to provide guidance for the GO reinforced self - lubricating polymers design. Finally, in light of the excellent properties of GPPs, this study provides guidance for the GO reinforced self - lubricating polymers design.

We present joint observations of a substorm injection event on 5 February 2016. The enhancements of energetic electron (∼30 to ∼300 keV) fluxes, the drift echoes of the injected electrons, and the quasi‐monochromatic ultralow frequency oscillations embedded in the flux variations were simultaneously observed by the BeiDa Imaging Electron Spectrometer and the Van Allen Probe B. These vivid features of substorm injection were concretely captured by multiple spacecraft within the geosynchronous distance for the first time. The radial separation of the spacecraft (∼0.3 RE) allowed for a quantitative comparison of the electron flux and phase space density (PSD) across different drift shells. It is found that a more intense increase of equatorial PSD occurred at the lower L‐shell (L* ∼5.5), which indicated a non‐adiabatic acceleration of the injected electrons in the inner magnetosphere. Energetic charged particles can be transported from the magnetotail into the inner magnetosphere via a process named substorm injection. The injection process is usually considered adiabatic, as the magnetic moment of the particles remained conserved. In this study, however, we present observational evidence of non‐adiabatic acceleration of substorm injected electrons. Specifically, we derive the radial gradient of electron phase space density using the dual‐spacecraft data obtained by BeiDa Imaging Electron Spectrometer and Van Allen Probe B. The phase space density gradient turned into negative by the arrival of the injected electrons, which is indicative of a non‐adiabatic acceleration. Substorm injection of energetic electrons was simultaneously observed by radially separated spacecraft within the geosynchronous distanceThe radial phase space density gradient turned into negative by the arrival of the injected electronsThe negative phase space density gradient indicated a non‐adiabatic acceleration of the injected electrons Substorm injection of energetic electrons was simultaneously observed by radially separated spacecraft within the geosynchronous distance The radial phase space density gradient turned into negative by the arrival of the injected electrons The negative phase space density gradient indicated a non‐adiabatic acceleration of the injected electrons

In cases where substorm injections can be observed simultaneously by multiple spacecraft, they can help elucidate the potential mechanisms of particle transport and energization, of great importance to understanding and modeling the magnetosphere. In this paper, using data returned from the BeiDa-IES (BD-IES) instrument onboard a satellite in an inclined (55°) geosynchronous orbit (IGSO), in combination with two geo-transfer orbiting (GTO) satellite Van Allen Probes (A and B), we analyze a substorm injection event that occurred on the 16th of October 2015. During this substorm injection, the IGSO onboard BD-IES was outbound, while both Van Allen Probe satellites (A and B) were inbound, a configuration of multiple trajectories that provides a unique opportunity to simultaneously investigate both the inward and outward radial propagation of substorm injection. Indicated by AE/AL indices, this substorm was closely related to an IMF/solar wind discontinuity that showed a sharp change in IMF Bzdirection to the north. The innermost signature of this substorm injection was detected by Van Allen Probes A and B at L-3.7, while the outermost signature was observed by the onboard BD-IES instrument at L~10. These data indicate that the substorm had a global, rather than just local, effect. Finally, we suggest that electric fields carried by fast-mode compressional waves around the substorm injection are the most likely candidate mechanism for the electron injection signatures observed in the inner- and outermost inner magnetosphere.

Based on the data from the Medium-Energy Proton and Electron Detector (MEPED) onboard NOAA-17, 141 anomalies of a Chinese Sun-Synchronous satellite (SSO-X) that occurred between 02/01/2010 and 09/31/2012 were studied statistically. About 26 out of the 52 anomalies that occurred outside the South Atlantic Anomaly (SAA) were accompanied by energetic electron storms. Superposed Epoch Analysis (SEA) was used to analyze the properties of the anomalies and the dynamics of the space environments during these 26 events. Then, a Monte Carlo method was utilized to simulate the electron deposition and the interactions of the injected electrons with an aluminum shield and polyethylene dielectric. The average, median, and 75th percentile values of the maximum electric field strength inside the dielectric were calculated. The results showed the following. (1) SSO-X anomalies are more likely to occur within the SAA, as 89 out of 141 anomalies (63%) occurred there. (2) Twenty-six of the anomalies that occurred outside the SAA during energetic electron storms were located near the outer boundaries of the outer radiation belts, and these were more frequent in the Southern Hemisphere than in the Northern Hemisphere. (3) Electron flux enhancements occurred around the failure time at all energy levels but were more profound in the lower energy channels. The maximum fluxes of electrons >30 keV, >100 keV, and >300 keV were 106, 3.5×105, and 1.2×106cm-2s-1sr-1, respectively. (4) The average, median, and 75th percentile values of the maximum electric field strengths inside the dielectric for the aforementioned 26 events remained in the range from 106to 107V/m for long time periods, which suggests that the ‘potential hazards’ of internal discharges cause SSO-X anomalies. The above results can provide useful information for the design and protection of sun-synchronous spacecraft.

We investigate initial-boundary-value problem for three dimensional magnetohydrodynamic (MHD) system of compressible viscous heat-conductive flows and the three-dimensional full compressible Navier-Stokes equations. We establish a blowup criterion only in terms of the derivative of velocity field, similar to the Beale-Kato-Majda type criterion for compressible viscous barotropic flows by Huang et al. (2011). The results indicate that the nature of the blowup for compressible MHD models of viscous media is similar to the barotropic compressible Navier-Stokes equations and does not depend on further sophistication of the MHD model, in particular, it is independent of the temperature and magnetic field. It also reveals that the deformation tensor of the velocity field plays a more dominant role than the electromagnetic field and the temperature in regularity theory. Especially, the similar results also hold for compressible viscous heat-conductive Navier-Stokes flows, which extend the results established by Fan et al. (2010), and Huang and Li (2009). In addition, the viscous coefficients are only restricted by the physical conditions in this paper.

Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region (TCR) structure in southern plasma sheet boundary layer (PSBL) at 21:09 UT of September 19, 2001. We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method. Results show that C1 passed through part of a plasmoid, which compressed the lobe magnetic field and formed a TCR. The size of the whole plasmoid structure in Xdirection is estimated to be about 3 RE. Furthermore, using multi-spacecraft observations, we have found some detailed information about this structure. First, C1 observed bi-streaming electron components, which supports our suggestion that the spacecraft passed through closed field lines. Second, a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.

The attitude kinematic equations and measurement equations are the function of the orbit parameters, so the standard Extended Kaiman Filter (EKF) can't give optimal attitude estimation because of the orbit errors, especially for a magnetometer-based small satellite. A robust adaptive Kaiman filter was designed to deal with the disturbance from the orbit estimation errors. The principle of robust estimation was adopted for the adaptive filters, and the covariance matrix and observational noise were adjusted to get proper Kaiman gains, and then the approximately optimal filtering results were obtained. Based on EKF stable theory, RAKF was proved uniformly and stochastically stable if the system is asymptotically controllable and asymptotically observable. Simulation results indicate that RAKF can improve attitude estimation precision from 0.3° to 0.2°, and the filter is approved to be more effective and robust for attitude estimation. [ABSTRACT FROM AUTHOR]

Fructokinase is the main catalytic enzyme for fructose phosphorylation and can also act as a glucose receptor and signal molecule to regulate the metabolism of plants, which plays an important role in plant growth and development. In this study, the CaFRKgene family and their molecular characteristics are systematically identified and analyzed, and the specific expression of CaFRKsunder different tissues, abiotic stresses and hormone treatments were explored. Nine FRKgenes were authenticated in pepper genome database, which were dispersedly distributed on eight reference chromosomes and predicted to localize in the cytoplasm. Many cis-acting elements that respond to light, different stresses, hormones and tissue-specific expression were found in the promoters of CaFRKs. FRK proteins of four species including Capsicum annuum, Arabidopsis thaliana, Solanum lycopersicumand Oryza sativawere divided into four groups via phylogenetic analysis. The collinearity analysis showed that there were two collinear gene pairs between CaFRKsand AtFRKs. In addition, it was significantly found that CaFRK9expressed far higher in flower than other tissues, and the relative expression of CaFRK9was gradually enhanced with the development of flower buds in fertile accessions, 8B, R1 and F1. Nevertheless, CaFRK9hardly expressed in all stages of cytoplasmic male sterile lines. Based on the quantitative real-time PCR, most of CaFRKgenes showed significant up-regulation under low-temperature, NaCl and PEG6000 treatments. On the contrary, the expression levels of most CaFRKsrevealed a various trend in response to hormone treatments (IAA, ABA, GA3, SA and MeJA). This study systematically analyzed CaFRKgene family and studied its expression pattern, which lay the foundation of CaFRK genes cloning and functional verification response to abiotic stresses, and provides new insights into exploring the CaFRKgenes on the pollen development in pepper.