Integrated Optimization of Structure and Control for Fast Steering Mirrors.

This study concerns the problem of integrated optimization of structure and control based on a fast steering mirror, aiming to achieve simultaneous optimization of the mechanical structure and control system. The traditional research and development path of the fast steering mirror involves a lengthy process from the initial design to the final physical manufacture. In the prior process, it was necessary to produce physical prototypes for repeated debugging and iterative optimization to achieve design requirements, but this approach consumes a significant amount of time and cost. To expedite this process and reduce unnecessary experimental costs, this study proposes an integrated optimization of structure and control (IOSC) method. With the use of IOSC, it is possible to achieve simultaneous optimization of structure and control. Specifically, the use of non-dominated sorting genetic algorithm II (NSGA-II) obtains globally optimal controller parameters and mechanical structure parameters under certain performance indices. This achieves an effective balance between the resonance frequency generated by the system and the working bandwidth, providing a high-precision reference for the research and development of fast steering mirrors.

Transport mechanism of human bilirubin transporter ABCC2 tuned by the inter-module regulatory domain.

Bilirubin is mainly generated from the breakdown of heme when red blood cells reach the end of their lifespan. Accumulation of bilirubin in human body usually leads to various disorders, including jaundice and liver disease. Bilirubin is conjugated in hepatocytes and excreted to bile duct via the ATP-binding cassette transporter ABCC2, dysfunction of which would lead to Dubin-Johnson syndrome. Here we determine the structures of ABCC2 in the apo, substrate-bound and ATP/ADP-bound forms using the cryo-electron microscopy, exhibiting a full transporter with a regulatory (R) domain inserted between the two half modules. Combined with substrate-stimulated ATPase and transport activity assays, structural analysis enables us to figure out transport cycle of ABCC2 with the R domain adopting various conformations. At the rest state, the R domain binding to the translocation cavity functions as an affinity filter that allows the substrates of high affinity to be transported in priority. Upon substrate binding, the R domain is expelled from the cavity and docks to the lateral of transmembrane domain following ATP hydrolysis. Our findings provide structural insights into a transport mechanism of ABC transporters finely tuned by the R domain.

Gastrodia elata polysaccharide alleviates Parkinson's disease via inhibiting apoptotic and inflammatory signaling pathways and modulating the gut microbiota.

Parkinson's disease (PD) is a common, chronic, and progressive degenerative disease of the central nervous system for which there is no effective treatment. Gastrodia elata is a well-known food and medicine homologous resource with neuroprotective potential. Gastrodia elata polysaccharide (GEP), which is a highly active and safe component in Gastrodia elata, is an important ingredient in the development of functional products. In this study, GEP was administered to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice over 3 weeks to investigate its neuroprotective effects. The results showed that GEP significantly alleviated the motor dysfunction of PD mice, inhibited the accumulation of α-synuclein, and reduced the loss of dopaminergic neurons in the brain. Moreover, GEP increased the Bcl-2/Bax ratio and decreased the cleaved-caspase-3 level, suggesting that GEP may ameliorate PD by preventing MPTP-induced mitochondrial apoptosis. GEP also significantly inhibited the increase of GFAP and decreased the levels of TNF-α, IL-1ß, and IL-6 in the brain of PD mice, which may be the result of the inhibition of neuroinflammation by the inactivation of the TLR4/NF-κB pathway. Furthermore, the neuroprotective effects of GEP involve the gut-brain axis, as it has been shown that GEP regulated the dysbiosis of PD-related gut microbiota such as Akkermansia, Lactobacillus, Bacteroides, Prevotella, and Faecalibacterium, increased the content of microbial metabolites SCFAs in the colon and increased the level of occludin that repairs the intestinal barrier of PD mice. In conclusion, this study is expected to provide a theoretical basis for the development and application of functional products with GEP from the perspective of neuroprotective effects.

Helicobacter pylori infection prevalence declined among an urban health check-up population in Chengdu, China: a longitudinal analysis of multiple cross-sectional studies.

Objectives: The efficacy of updated health policy in improving the generalization of Helicobacter pylori screening and eradication in southwest China was assessed in a longitudinal analysis of multiple cross-sectional studies from an institution. Methods: In the periods 2009-2010, 2013-2014, and 2019-2021, 8,365, 16,914, and 18,281 urban observations from health check-ups at West China Hospital were analyzed, respectively. The 14C-urea or 13C-urea breath test was consistently used for H. pylori detection. The protocol has been reported elsewhere (PROSPERO Registration number: CRD42019120764). Results: The overall prevalence of H. pylori dramatically decreased from 53.1% to 30.7% over the past decade (OR = 0.39, 95% CI 0.37-0.41), with a similar decline in all sex-specific and age-specific subgroups. The age-specific prevalence consistently increased before 40 years of age and always peaked at 50-59 years. Longitudinal clearance increased along with aging, and prevalence dropped to 22.6%, 25.1%, and 23.6% in the 40-49, 50-59, and 60-69 years initial age groups, respectively. Conclusion: The generalization of H. pylori screening and eradication could greatly contribute to the control of H. pylori infection among urban health check-up populations and lower gastric cancer incidence.

Placing steroid hormones within the human ABCC3 transporter reveals a compatible amphiphilic substrate-binding pocket.

The human ABC transporter ABCC3 (also known as MRP3) transports a wide spectrum of substrates, including endogenous metabolites and exogenous drugs. Accordingly, it participates in multiple physiological processes and is involved in diverse human diseases such as intrahepatic cholestasis of pregnancy, which is caused by the intracellular accumulation of bile acids and estrogens. Here, we report three cryogenic electron microscopy structures of ABCC3: in the apo-form and in complexed forms bound to either the conjugated sex hormones ß-estradiol 17-(ß-D-glucuronide) and dehydroepiandrosterone sulfate. For both hormones, the steroid nuclei that superimpose against each other occupy the hydrophobic center of the transport cavity, whereas the two conjugation groups are separated and fixed by the hydrophilic patches in two transmembrane domains. Structural analysis combined with site-directed mutagenesis and ATPase activity assays revealed that ABCC3 possesses an amphiphilic substrate-binding pocket able to hold either conjugated hormone in an asymmetric pattern. These data build on consensus features of the substrate-binding pocket of MRPs and provide a structural platform for the rational design of inhibitors.

Clinical guideline on magnetically controlled capsule gastroscopy (2021 edition).

With the development and generalization of endoscopic technology and screening, clinical application of magnetically controlled capsule gastroscopy (MCCG) has been increasing. In recent years, various types of MCCG are used globally. Therefore, establishing relevant guidelines on MCCG is of great significance. The current guidelines containing 23 statements were established based on clinical evidence and expert opinions, mainly focus on aspects including definition and diagnostic accuracy, application population, technical optimization, inspection process, and quality control of MCCG. The level of evidence and strength of recommendations were evaluated. The guidelines are expected to guide the standardized application and scientific innovation of MCCG for the reference of clinicians.

New insight into the geochemical mechanism and behavior of heavy metals in soil and dust fall of a typical copper smelter.

The desorption mechanism of heavy metals (HMs) in soil around the mining region are complex and affected by multiple pollution sources, including sewage discharge and atmospheric deposition. Meanwhile, pollution sources would change soil physical and chemical properties (mineralogy and organic matter), thus affecting the bioavailability of HMs. This study aimed to investigate the pollution source of HMs (Cd, Co, Cu, Cr, Mn, Ni, Pb, and Zn) in soil near mining, and further evaluate influence mechanism of dust fall on HMs pollution in soil by desorption dynamics processes and pH-dependence leaching test. Result presented that dust fall is the primary pollution source to HMs accumulation in soil. Additionally, the result of mineralogical analysis in dust fall revealed that quartz, kaolinite, calcite, chalcopyrite, and magnetite are the major mineralogical phases by XRD and SEM-EDS. Meanwhile, the abundance of kaolinite and calcite in dust fall is higher than in soil, which is the primary reason of higher acid-base buffer capacity of dust fall. Correspondingly, the weakened or disappeared of hydroxyl after the adding acid extraction (0-0.4 mmol· g-1) demonstrated that hydroxyl is the main participants of HMs absorption in soil and dust fall. These combined findings suggested that atmospheric deposition not only increases the pollution loading of HMs in soil, but also changes the mineral phase composition of soil, which would increase the adsorption capacity and bioavailability of HMs in soil. This is very remarkable that heavy metals in soil influenced by dust fall pollution could be released preferentially when soil pH is changed. The present results of this study would provide efficient and scientific targeted strategies for pollution control of HMs in soil near mining areas.

Occurrence, distribution and risk assessment of microplastics and polycyclic aromatic hydrocarbons in East lake, Hubei, China.

The pollution of microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) in the environment is a global problem, which has attracted extensive attention of many researchers. In present study, MPs and PAHs are investigated to study the impact of human activities and their possible relationship in China's second largest urban lake, East Lake. The abundance of MPs are 3329.19 ± 2059.26 particles/m3 and 2207.56 ± 1194.04 particles/kg in water and sediment, respectively. MPs are predominantly characterized by fibers, polypropylene (PP) and polyethylene (PE), colorlessness in water and sediment. The abundance of MPs in water with frequent human activities is higher, which is reversed in sediments, indicating that disturbance is not conducive to the enrichment of MPs in sediments. The concentration of 16 PAHs are 36.95 ± 13.76 ng/L and 897.08 ± 232.34 ng/g in water and sediment, respectively. PAHs in water are mainly 2-3-ring, while there are 4-ring PAHs in sediments. The good corresponding relationship between MPs and PAHs indicates that human activities have an important impact on the distribution of pollutants compared to the interaction of pollutants. In addition, the significant positive correlation between lakeshore length and water MPs abundance indicates that surface runoff may be an important source of water MPs. The pollution load index shows that MPs in sediment has reached moderate to severe pollution level, while the water is slightly polluted level. The potential ecological risk assessment results show that more than half of the sediment sites are at dangerous to very dangerous ecological risk level.

Bioavailability and regional transport of PM2.5 during heavy haze episode in typical coal city site of Fenwei Plain, China.

Despite the decrease in anthropogenic emissions, haze episodes were still frequent in the Fenwei Plain, which was identified as one of the three key areas for air pollution control. Herein, PM2.5 samples were collected to investigate the influence of festival effect during the Chinese Spring Festival from February 2rd to 13th, 2019, in Linfen on the Fenwei Plain. The characteristics of element pollution, enrichment factor, source apportionment, regional transport of PM2.5, and health risk assessment were discussed. Meanwhile, the simulated lung fluid method (SLF) was carried out to accurately assess the inhalation risks of heavy metals (HMs). Results indicated that the average concentration of PM2.5 was 195.6 µg·m-3 during the studying period. Road fugitive dust (15.6%), firework burning source (25.6%), industrial emission (30.5%), and coal combustion (28.3%) were identified by positive matrix factorization (PMF) modeling. Using the HYSPLIT trajectory model, air masses from the central Shaanxi, southern Hebei, and northern Henan were the dominant transport paths during the Spring Festival, which contributed 21.9 and 41.2% of total trajectories, respectively. The findings that high PSCF and CWT levels were found in central Shaanxi, southern Hebei, and northern Henan were confirmed. The SLF mean bioaccessibility (%) of the solubility of particulate metals was in order of Mn > Ni > Sb > Ba > Zn > Pb > Cr. However, the carcinogenic risk value of Cr was the highest, exceeding the maximum acceptable risk. The present study provided important information for further analyzing the air pollution cause of Fenwei Plain.

On adjustable and lossless suppression to disturbances and uncertainties for nonminimum-phase laser pointing system.

This paper focuses on the nonminimum-phase laser pointing system's disturbances and uncertainties rejection problems on moving platforms. Moving platforms cause a variety of noticeable vibrations that substantially impair pointing accuracy. Additionally, the disturbance-observer-based control approaches currently in use sacrifice the desired disturbance suppression effects, stability margins, or tracking characteristics due to the nonminimum-phase laser pointing system. This paper suggests an adjustable disturbance-observer-based control strategy with dual filters to obtain lossless and adjustable disturbance suppression effects without sacrificing stability margins or tracking characteristics. The closed-loop controller and forward plant are presented to reduce the laser pointing system's nonminimum-phase properties. An additional flexible filter is added to deal with the weakened nonminimum-phase system. Both filters are uniformly proposed depending on various disturbances brought on by moving platforms and work together to accomplish lossless desired disturbance suppression effects. The analyses and experiments show that the suggested approach can accomplish the lossless and adjustable disturbance suppression effects in the nonminimum-phase laser pointing system, which cancels out many more disturbances and uncertainties than the current methods.

Influence of temperature and precipitation on the fate of polycyclic aromatic hydrocarbons: simulation experiments on peat cores from a typical alpine peatland in Central China.

The corresponding relationships between temperature, precipitation, and polycyclic aromatic hydrocarbon (PAH) concentration in a typical ombrotrophic peatland in Dajiuhu, Shennongjia, were quantitatively characterized by field sampling tests validated with simulation experiments. The PAH concentrations of peat cores in Dajiuhu peatland ranged from 262 to 977 ng·g-1, with a mean value of 536 ± 284 ng·g-1. PAHs were mainly composed of 2-3 ring PAHs, accounting for 31.7% ± 2.00% and 31.7% ± 5.00%, respectively. The concentration of PAHs in peat cores showed a significant decrease with increasing temperature, while the low molecular weight PAHs (LMW-PAHs) were more sensitive to temperature changes compared to the high molecular weight PAHs (HMW-PAHs). Besides, with the increase of quantity and velocity of leaching liquid, PAHs in peat were first transferred in the form of attached large-size particles and then gradually entered the aqueous phase. According to the IPCC projections of global warming, Dajiuhu peatland will release 956 ± 26.3 kg·°C-1 PAHs into gas phase during 2030-2052, and a conservative projection based on local temperature trends showed that 459 ± 12.6 kg·°C-1 PAHs will be released into gas phase by 2047 in Dajiuhu peatland. The projected release fluxes of PAHs in Dajiuhu peatland with precipitation volume and precipitation velocity are 381 ± 201 kg·100 mm-1 and 1052 ± 167 kg·min·mL-1, respectively, which are primarily from peat into particulate and aqueous phase.

The characteristics of polycyclic aromatic hydrocarbons and heavy metals in water and sediment of dajiuhu subalpine wetland, shennongjia, central China, 2018-2020: Insights for sources, sediment-water exchange, and ecological risk.

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) are persistent environmental issues. Secondary emissions are produced as a result of climate change and human activity. To observe spatio-temporal variations of PAHs and HMs and to discuss the sources as well as the source or sink of PAHs for sediment and peat, twelve surface sediment and surface water sites were chosen along the direction of the flow to down hole in the Dajiuhu area, simultaneously, surface peat and water samples were collected in peatland. Samples were continuously taken for three years (Sep. 2018, Sep. 2019, and Sep. 2020, respectively). The results showed that PAHs and HMs are common in sediment and peat. PAHs concentration is generally higher in peat and water, while HMs concentration is relatively higher in water and relatively low in sediment and peat, and the ecological risk of sediment was low. HMs in sediment are mainly affected by rock weathering, while PAHs are mainly affected by atmospheric deposition, biomass and coal combustion and vehicle emission. HMs and PAHs can be used as an indicator of rock weathering and human activity in Dajiuhu area, respectively. A water-sediment fugacity analysis revealed that peat is a sink for PAHs, confirming that it has a high capacity for adsorbing organic contaminants, and that sediments are secondary sources of PAHs that can release them into water. Attention should be paid to the increased fugacity fraction (ff) value in peatland, indicating that peat might be converted from a sink to a source of PAHs.

Alpha-SGANet: A multi-attention-scale feature pyramid network combined with lightweight network based on Alpha-IoU loss.

The design of deep convolutional neural networks has resulted in significant advances and successes in the field of object detection. However, despite these achievements, the high computational and memory costs of such object detection networks on the edge or in mobile scenarios are one of the most significant barriers to their broad adoption. To solve this problem, this paper introduces an improved lightweight real-time convolutional neural network based on YOLOv5, called Alpha-SGANet: A multi-attention-scale feature pyramid network combined with a lightweight network based on Alpha-IoU loss. Firstly, we add one more prediction head to detect different-scale objects, design a lightweight and efficient feature extraction network using ShuffleNetV2 in the backbone, and reduce information loss using the SPP module with a smaller convolutional nucleus. Then, cleverly, employ GAFPN to improve feature transition processing in the neck region, including the usage of the Ghost module to construct efficient feature maps to help prediction. The CBAM module was further integrated to find areas of interest in the scene; finally, combined with Alpha-IOU loss for model supervision training, the biggest performance improvement was achieved. The experiment results show that, compared with YOLOv5s, our proposed method can achieve higher accuracy with fewer parameters and has real-time speed through verification on the PASCAL VOC dataset and MS COCO dataset.

Impact of short-term control measures on air quality: A case study during the 7th Military World Games in central China.

The 7th Military World Games held in Wuhan (WH) in Oct 2019 provided an opportunity to clarify the impact of short-term control measures on air quality. Fine particulate matters (PM2.5) were collected in WH, Huangshi (HS), and Huanggang (HG) during the control (Oct 13-28, 2019) and non-control periods (Oct 29- Nov 5, 2019). The results showed that air quality was good during the control period, with the concentrations of PM2.5 and gaseous pollutants being below the Grade Ⅱ of China Ambient Air Quality Standard. Concentrations of PM2.5 and its major chemical components in the control period were significantly lower than those in the non-control period, with reductions ranging from 17% (trace elements) to 46% (elemental carbon). However, higher contributions of secondary components such as SO42-, NO3-, NH4+ and secondary organic carbon (SOC) to PM2.5 were observed during the control period, suggesting the important role of secondary transformation. Potential source contribution function (PSCF) of PM2.5 showed that the main source regions were potentially located in surrounding cities Hubei Province, but regional transport can't be ignored. Six sources were identified by positive matrix factorization (PMF) for both control and non-control period. The contributions of combustion emissions and vehicle emissions were amplified in the control period, while the contribution of construction dust increased significantly when the control measures ended. Emission reductions contributed more to PM2.5 concentration decrease in WH (55%) than that in HS (51%) and HG (49%), which was consistent with the stricter control measures implemented in WH. These results indicated that short-term controls were effective at lowering PM2.5 concentration. However, the elevated contributions of secondary aerosols and the influence of regional transport on the study areas also need to be paid attention for air quality improvement in the future.

Structural basis of substrate recognition and translocation by human very long-chain fatty acid transporter ABCD1.

Human ABC transporter ABCD1 transports very long-chain fatty acids from cytosol to peroxisome for ß-oxidation, dysfunction of which usually causes the X-linked adrenoleukodystrophy (X-ALD). Here, we report three cryogenic electron microscopy structures of ABCD1: the apo-form, substrate- and ATP-bound forms. Distinct from what was seen in the previously reported ABC transporters, the two symmetric molecules of behenoyl coenzyme A (C22:0-CoA) cooperatively bind to the transmembrane domains (TMDs). For each C22:0-CoA, the hydrophilic 3'-phospho-ADP moiety of CoA portion inserts into one TMD, with the succeeding pantothenate and cysteamine moiety crossing the inter-domain cavity, whereas the hydrophobic fatty acyl chain extends to the opposite TMD. Structural analysis combined with biochemical assays illustrates snapshots of ABCD1-mediated substrate transport cycle. It advances our understanding on the selective oxidation of fatty acids and molecular pathology of X-ALD.

Huge quantities of microplastics are "hidden" in the sediment of China's largest urban lake-Tangxun Lake.

Microplastics (MPs) pollution in Tangxun Lake, the largest urban lake in China, was investigated. The average MPs pollution in sediment (1.81 ± 1.75 × 104 items kg-1) is at a high level, while the MPs in lakeshore water (917.77 ± 742.17 items m-3) is in the middle to low level compared with existing studies, which is related to the government's protection. Fragments and fibers are the most common shapes in sediment and water, respectively. MPs size <1 mm dominates in the sediment, while the MPs in water has a larger size. The distribution of MPs in the inner lake shows that pellets tend to "hidden" in sediments. Suspected MPs are randomly selected for polymer detection by Micro-Raman microscopy. Polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET) are the most common polymer types in water, sediment and atmospheric deposition MPs samples. The input of wastewater, fishery and surrounding human activities are the main sources of MPs in sediment. Atmospheric deposition has a great impact on the distribution of MPs, while the contribution of surface runoff to lake MPs is not remarkable. In addition, MPs in sediments have exceeded the environmental carrying capacity. More attention should be focused on the sediment, where huge amounts of MPs are "hidden".

Variation of pollution sources and health effects on air pollution before and during COVID-19 pandemic in Linfen, Fenwei Plain.

Stringent pollution control measures are generally applied to improve air quality, especially in the Spring Festival in China. Meanwhile, human activities are reduced significantly due to nationwide lockdown measures to curtail the COVID-19 spreading in 2020. Herein, to better understand the influence of control measures and meteorology on air pollution, this study compared the variation of pollution source and their health risk during the 2019 and 2020 Spring Festival in Linfen, China. Results revealed that the average concentration of PM2.5 in 2020 decreased by 39.0% when compared to the 2019 Spring Festival. Organic carbon (OC) and SO42- were the primary contributor to PM2.5 with the value of 19.5% (21.1%) and 23.5% (25.5%) in 2019 (2020) Spring Festival, respectively. Based on the positive matrix factorization (PMF) model, six pollution sources of PM2.5 were indicated. Vehicle emissions (VE) had the maximum reduction in pollution source concentration (28.39 µg· m-3), followed by dust fall (DF) (11.47 µg· m-3), firework burning (FB) (10.39 µg· m-3), coal combustion (CC) (8.54 µg· m-3), and secondary inorganic aerosol (SIA) (3.95 µg· m-3). However, the apportionment concentration of biomass burning (BB) increased by 78.7%, indicating a significant increase in biomass combustion under control measures. PAHs-lifetime lung cancer risk (ILCR) of VE, CC, FB, BB, and DF, decreased by 44.6%, 43.2%, 34.1%, 21.3%, and 2.0%, respectively. Additionally, the average contribution of meteorological conditions on PM2.5 in 2020 increased by 20.21% compared to 2019 Spring Festival, demonstrating that meteorological conditions played a crucial role in located air pollution. This study revealed that the existing control measures in Linfen were efficient to reduce air pollution and health risk, whereas more BB emissions were worthy of further attention. Furthermore, the result was conducive to developing more effective control measures and putting more attention into unfavorable meteorological conditions in Linfen.

The mechanistic investigation of geochemical fractionation, bioavailability and release kinetic of heavy metals in contaminated soil of a typical copper-smelter.

Identifying the bioavailability and release-desorption mechanism of heavy metals (HMs) in soil is critical to understand the release risk of HMs. Simultaneously, the mechanistic investigation of affecting the bioavailability of HMs in soil is necessary, such as the grain-size distribution and soil mineralogy. Herein, the bioavailability of HMs (Cu, Cd, Ni, Pb, and Zn) in different area soils near a typical copper-smelter was evaluated by the sequential extraction technique (BCR), diffusive gradients in thin-films (DGT), and DGT-induced fluxes in sediments (DIFS) model. Results showed that the HMs proportion of the residual fraction in all soils was the highest. The average bioavailability concentration (CDGT) of Cu and Cd in industrial soil was the highest, with 45.12 µg· L-1 and 9.06 µg· L-1. The result of DIFS model revealed that the decreased order of the mean value of desorption rate constant (K-1) was Cd > Zn > Ni > Cu > Pb, 5.91 × 10-5, 4.96 × 10-5, 2.89 × 10-5, 9.64 × 10-6, and 8.69 × 10-6, respectively. According to the spatial distribution of release potential (R-value), the release potential of labile-Cu in agricultural soil was the highest, which was mainly attributed to fertilizer application in farmland. Simultaneously, the reduced hydroxyl was also related to the agricultural activities, resulting in the weakened adsorption capacity of HMs by soil. Redundancy analysis (RDA) results showed that the bioavailability of Cd, Ni, and Zn was mainly driven by soil pH, while the bioavailability of Cu and Pb was primarily driven by dissolved organic carbon (DOC). Meanwhile, carbonate minerals had a positive correlation with the bioavailability of Cd, Ni, and Zn, which could promote the release of HMs in mining soil as chemical weathering progresses. In conclusion, this study provides a structured method which can be used as a standard approach for similar scenarios to determine the geochemical fractionation, bioavailability, and release kinetics of heavy metals in soils.

Robust Risley prism control based on disturbance observer for system line-of-sight stabilization.

In this paper, a robust control based on disturbance observer is proposed to improve the tracking accuracy of the Risley prism system (RPS). Applying the flexible thin-wall ring mechanism in the RPS causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the RPS. Two different observer-based control methods are proposed to guarantee the tracking precision of the RPS. Moreover, the disturbance observation and compensation (DOC) performance of the proposed methods is analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially the DOC-expanded state observer control mode, obtain the best performance for disturbance rejection in the RPS.

Status and prospects of atmospheric microplastics: A review of methods, occurrence, composition, source and health risks.

The global pollution of microplastics (MPs) has attracted widespread attention, and the atmosphere was an indispensable media for the global transmission of MPs. With the growing awareness of MPs, atmospheric microplastics (AMPs) have been proposed as a new topic in recent years. Compared with the extensive studies on MPs in Marine and terrestrial environments, the studies of AMPs remain limited. In this study, sampling and analysis methods, occurrence, source analysis and health risk of AMPs were summarized and discussed. According to the different sampling methods, AMPs can be divided into suspension microplastics (SAMPs) and deposition microplastics (DAMPs). Previous studies have shown that SAMPs and DAMPs differ in composition and abundance, with SAMPs generally having a higher fraction of fragments. The mechanism of the migration of AMPs between different media was not clear yet. We further collated global data on the composition characteristics of MPs in soil and fresh water, which showed that the fragment MPs in soil and fresh water was higher than that in the atmosphere. Polymers in soil and fresh water were mainly PP and PE, while AMPs in the atmosphere were mainly PET. The shape composition of the MPs in both atmospheric and freshwater systems suggests that there may be the same dominant factor. The transport of AMPs and source apportionment were the important issues of current research, but both of them were at the initial stage. Therefore, AMPs needs to be further studied, especially for the source and fate, which would be conducive to understand the global distribution of AMPs. Furthermore, a standardized manual on sampling and processing of AMPs was also necessary to facilitate the comparative analysis of data between different studies and the construction of global models.