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The signal delay caused by the troposphere layer plays a key role in many applications. It is not only a significant error source in space geodetic techniques such as GNSS and InSAR, but also a valuable data product in meteorological applications, such as climate research and weather forecasting. Hence, the community needs key troposphere-related parameters and models to support data processing, for correcting tropospheric delays or retrieving water vapor content. For this purpose, the GNSS Meteorological Ensemble Tools (GMET) online service () was developed, constituting three modules and using state-of-art methods and data sources. The module for custom products is defined by a specific user input and generates various parameters, including meteorological parameters, mapping function coefficients, and tropospheric corrections for specific regions or sites using numerical weather models (NWMs) or radiosonde data. The module for model products is designed to distribute gridded products via File Transfer Protocol (FTP). Finally, the tropospheric parameter monitoring module provides visualizations of routinely processed zenith tropospheric delay (ZTD) products from about 500 GNSS stations. To facilitate online services, we describe here algorithms and strategies used for the product generation and data processing. All the services are free and open to all users, and feedback from users is welcome for continuing service improvements. [ABSTRACT FROM AUTHOR]

Convolutional neural network (CNN)-based object detectors perform excellently but lack global feature extraction and cannot establish global dependencies between object pixels. Although the Transformer is able to compensate for this, it does not incorporate the advantages of convolution, which results in insufficient information being obtained about the details of local features, as well as slow speed and large computational parameters. In addition, Feature Pyramid Network (FPN) lacks information interaction across layers, which can reduce the acquisition of feature context information. To solve the above problems, this paper proposes a CNN-based anchor-free object detector that combines transformer global and local feature extraction (GLFT) to enhance the extraction of semantic information from images. First, the segmented channel extraction feature attention (SCEFA) module was designed to improve the extraction of local multiscale channel features from the model and enhance the discrimination of pixels in the object region. Second, the aggregated feature hybrid transformer (AFHTrans) module combined with convolution is designed to enhance the extraction of global and local feature information from the model and to establish the dependency of the pixels of distant objects. This approach compensates for the shortcomings of the FPN by means of multilayer information aggregation transmission. Compared with a transformer, these methods have obvious advantages. Finally, the feature extraction head (FE-Head) was designed to extract full-text information based on the features of different tasks. An accuracy of 47.0% and 82.76% was achieved on the COCO2017 and PASCAL VOC2007 + 2012 datasets, respectively, and the experimental results validate the effectiveness of our method. [ABSTRACT FROM AUTHOR]

Copyright of Frontiers of Information Technology & Electronic Engineering is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cooperative trajectory planning of aerial-ground systems is a fundamental and challenging problem, which aims to leverage the aerial information to assist the ground tasks. Existing methods often suffer from suboptimal trajectories or computation burden. In this paper, we address cooperative trajectory planning of aerial-ground systems in which an unmanned ground vehicle (UGV) plans its local trajectory in real-time with the assistance of an unmanned aerial vehicle (UAV). Firstly, the UAV generates guidance trajectory using nonlinear model predictive control (NMPC), which considers the obstacle distribution density as a factor reflecting the coupling effect of multiple obstacles on the UGV, thereby avoiding local minima problem and improving the feasibility of the planned trajectory. Secondly, a null-space-based behavioral control (NSBC) framework is employed to merge the guidance trajectory into the UGV’s own planned one as a task. Finally, an event triggering task supervisor is developed for the UGV to decide the priorities of all tasks, which reduces the switching frequency of task priorities brought by traditional rule-based task supervisors. Both simulation and experiment results show that the proposed approach has superior trajectory planning performance in terms of trajectory error, on-line computation time and the success rate of task execution. [ABSTRACT FROM AUTHOR]

The BeiDou global navigation satellite system (GNSS) of China (BDS-3) had full operation capacity on July 31, 2020, and started providing free precise point positioning (PPP) service on B2b signals. Although GNSS community has conducted many evaluations on the PPP-B2b products and its user performance, comprehensive evaluations of real-time PPP solutions using the BDS-3 PPP service at kinematic and highly kinematic platforms are still absent. We present a general evaluation of a real-time PPP performance exploiting the PPP-B2b corrections in various user situations represented with static stations, a car, an offshore vessel and an aircraft. We found that errors of the PPP-B2b corrections are less stable and higher approximately by a factor of two for GPS compared to BDS-3 medium earth orbit (MEO) satellites. An average convergence time of 28.5 and 12.9 min can be achieved with a standalone BDS-3 and BDS-3 + GPS solution for a low-speed object, such as a permanent station, a car, and a ship, in real time when using the PPP-B2b corrections. For a high-kinematic airborne platform, the convergence time is much longer, reaching 48.9 min. The 95% positioning errors after convergence are less than 20 and 35 cm in horizontal and vertical directions for all the experiments. We conclude that the PPP-B2b service offered by the BDS-3 is prospective for real-time kinematic positioning applications. [ABSTRACT FROM AUTHOR]

In this work, a behavior-based adaptive dynamic programming (BADP) method is proposed for coordination control of unmanned ground vehicle-manipulator systems (UGVMs). Through a null-space-based behavioral control (NSBC) framework, the multi-objective coordination control is transformed into a single-objective tracking control at the mission layer. Since cost functions and control constraints are simplified at control layer, the complexity of controller design is reduced. Then, an identifier-actor-critic reinforcement learning algorithm framework is introduced to learn the optimal control policy by balancing the control performance and consumption. Simulation results show that control costs are reduced around 13.5% per sampling period compared to existing multiple objective control methods. Finally, the BADP method is experimentally validated using four real UGVMs. [ABSTRACT FROM AUTHOR]

Partitioning of americium from lanthanides (Ln) present in used nuclear fuel plays a key role in the sustainable development of nuclear energy1–3. This task is extremely challenging because thermodynamically stable Am(III) and Ln(III) ions have nearly identical ionic radii and coordination chemistry. Oxidization of Am(III) to Am(VI) produces AmO22+ ions distinct with Ln(III) ions, which has the potential to facilitate separations in principle. However, the rapid reduction of Am(VI) back to Am(III) by radiolysis products and organic reagents required for the traditional separation protocols including solvent and solid extractions hampers practical redox-based separations. Herein, we report a nanoscale polyoxometalate (POM) cluster with a vacancy site compatible with the selective coordination of hexavalent actinides (238U, 237Np, 242Pu and 243Am) over trivalent lanthanides in nitric acid media. To our knowledge, this cluster is the most stable Am(VI) species in aqueous media observed so far. Ultrafiltration-based separation of nanoscale Am(VI)-POM clusters from hydrated lanthanide ions by commercially available, fine-pored membranes enables the development of a once-through americium/lanthanide separation strategy that is highly efficient and rapid, does not involve any organic components and requires minimal energy input.A new strategy to separate radioactive americium from lanthanides based on complexation with polyoxometalates and ultrafiltration technique is highly efficient and rapid, does not involve any organic components and requires minimal energy input. [ABSTRACT FROM AUTHOR]

Air-borne GNSS can provide vertical tropospheric information on different heights compared to the traditional ground permanent stations. However, the decorrelation of heights and tropospheric parameters for GNSS high-kinematic observation remains a challenge. The general stochastic process noise is set to constant for a certain time duration, inducing obvious errors for air-borne GNSS data processing. We proposed a new GNSS zenith total delay (ZTD) estimation method suitable for high-kinematic air-borne observation, in which process noise considers both the temporal and spatial atmosphere state variation assisted by numerical weather models. An unmanned aerial vehicle (UAV) experiment was designed using both traditional models and the proposed dynamic model. For assessments of ZTD, ERA5-ZTD was used as the reference to evaluate external accuracy, and a closed-loop test was proposed to evaluate inner accuracy. The results show that the proposed method outperforms the traditional estimation method, significantly improving the convergence and the accuracy of ZTD results. It achieved an inner accuracy of 4 mm, with an improvement of at least 55.5% over the traditional method. The proposed method can satisfy the demand for real-time data processing and potentially benefit high-precision meteorological applications. [ABSTRACT FROM AUTHOR]

Copyright of Frontiers of Information Technology & Electronic Engineering is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The accuracy of the tropospheric mapping functions is greatly influenced by the mapping function modeling methods. In the past decades, the 'fast' method rather than the rigorous least-squares methods was dominantly used for the development of mapping functions, such as Vienna Mapping Functions 1 (VMF1), considering the convergence issue and computation efficiency. In this study, we reconsider the suitability of the rigorous least-squares methods in operational mapping function development and present a new mapping function modeling method where the number of to-be-estimated coefficients in the mapping function continued fraction is adaptively determined according to the convergence in the least-squares fitting. The modeling accuracy of the new method is evaluated during 40 days spanning four seasons in 2020 at globally distributed 905 Global Navigation Satellite Systems (GNSS) stations. Significant improvement of the new method to the 'fast' method is found, with hydrostatic and wet mapping function modeling mean absolute errors (MAEs) of 1.6 and 1.3 mm for the new method and of 3.6 and 3.0 mm for the 'fast' method, respectively. Multi-GNSS Precise Point Positioning (PPP) of the new method is conducted at 107 International GNSS Service (IGS) Multi-GNSS Experiment (MGEX) stations. Effectiveness of the new method is also found for the PPP station height and zenith total delay estimation. [ABSTRACT FROM AUTHOR]

Mo-doped BiVO4 microcrystals with tetragonal structures were prepared by a hydrothermal method. The phase transformation from monoclinic to tetragonal was observed as the concentration of molybdenum ions increased up to 10 mol%. Accordingly, the morphology of the as-preparation samples evolved from plate-shaped (molybdenum-free BiVO4) to pie-like (BiVO4:Mo). The photocatalytic activity of BiVO4:Mo with a tetragonal structure was much higher than that of the pure BiVO4 host with a monoclinic phase by using RhB as the simulated pollutants under sun-like irradiation. The degradation rate of RhB was increased from 40% with molybdenum-free BiVO4 to 97.8% with the Mo-doped BiVO4 materials. [ABSTRACT FROM AUTHOR]

Engineering semiconductor-based homo- (hetero-) junctions in hierarchical nanostructures is a promising way to achieve the high performance and recyclable photocatalysts toward pollutants degradation in water. Herein, we develop a kind of hierarchical p-n heterojunctions photocatalysts through controllable decoration of ultrathin p-BiOBr nanosheets onto n-TiO2 electrospun nanofibers by using a traditional solvothermal method. Structural characterization results indicate that the BiOBr nanosheets are assembled uniformly onto the TiO2 nanofibers. This well-designed hierarchical p-n heterojunctions in the p-BiOBr/n-TiO2 nanofibers photocatalyst lead to not only the improved generation/separation of photoinduced charges-carriers, but also the increased amount of redox sites. Benefiting to these advantages, the optimal p-BiOBr/n-TiO2 nanofibers exhibited the apparent rate constant of 0.1 and 0.15 min−1 for photocatalytic RhB and MO degradation under UV-light irradiation, which is twice and three times higher than that of mechanically mixtured BiOBr nanosheets and TiO2 nanofibers, respectively. Control experiments demonstrate that both the photoinduced electrons and the oxygen free radicals play the major roles on the enhancement of photocatalytic activity. Moreover, the p-BiOBr/n-TiO2 nanofibers photocatalysts with the unique nonwoven structure can be easily recycled without secondary pollution, in particular, still maintaining almost the initial photocatalytic activity during the wastewater treatment. [ABSTRACT FROM AUTHOR]

Short-chain chlorinated paraffins are industrial contaminants of great concern due to their persistent and toxic characteristics. The predicted distribution of short-chain chlorinated paraffins in air, water, soils and sediments is unclear because their physiochemical properties are poorly known. Here, we calculated the coefficients that control the partitioning behaviors of 16 short-chain chlorinated paraffins. The results show an increase in partitioning coefficients with chlorine number for short-chain chlorinated paraffins with carbon chain length of 10. Mono-chlorinated short-chain chlorinated paraffins show an increase in partitioning coefficients with carbon number. Short-chain chlorinated paraffins with chlorines at both ends of the carbon chain have relatively lower values of logKow and logKoa. Results from the fugacity model show that mono-chlorinated short-chain chlorinated paraffins are likely to partition into water, whereas multi-chlorinated short-chain chlorinated paraffins are likely to partition into soil. [ABSTRACT FROM AUTHOR]

Aim: A-nine month of field trail was conducted to investigate the accumulation capacity of cadmium and zinc by Arabidopsis halleri spp. germmifera. Methods: An experimental site moderately contaminated with Zn and Cd was chosen to evaluate the field traits of seed sowing and seedling transplantation. The exchangeable fraction and total Cd and Zn in the soil and the concentration in harvested plants were determined by inductively coupled plasma mass spectrometer. Results: The shoot biomass of A. halleri ssp. germmifera increased after more than 8 months of cultivation, and it was approximately 2.13 t ha in the seedling transplantation group, which was more than three times higher than in the seed sowing group. The lower ratio of Zn/Cd concentration in plants than in the soil and the higher bioaccumulation factor indicated that A. halleri ssp. germmifera has a higher uptake efficiency for Cd than for Zn. In total, A. halleri ssp. germmifera removed 18.20 kg Cd ha and 27.38 kg Zn ha from the soil. After nine months of growth, A. halleri ssp. germmifera extracted (22.87 ± 9.21) % of total Cd concentration and (2.99 ± 0.94) % of total Zn concentration from the soil. However, no significant decrease of exchangeable concentration was shown in soil Cd and Zn, which revealed that the uptake of Cd and Zn by A. halleri ssp. germmifera not only came from exchangeable forms but also from non-exchangeable fractions. Conclusions: The results of present study indicated that A. halleri ssp. germmifera can be used to efficiently remove different forms of Cd from contaminated land. [ABSTRACT FROM AUTHOR]

The objective of this paper was to investigate a petroleum-contaminated groundwater site in northeast China. Based on the monitoring and analysis of environmental characteristics of groundwater slightly contaminated with petroleum, microbes were added into the petroleum-contaminated groundwater via single-well and multiple-well models to enhance bioremediation. The effect of enhanced bioremediation was monitored and analyzed, and variations in the environmental characteristics of groundwater containing total petroleum hydrocarbons (TPH) were identified to provide a scientific basis for controlling and remediating petroleum-contaminated groundwater. Findings confirmed that this site was slightly contaminated and TPH levels exhibited a slight decreasing trend. After enhanced remediation, the microbial degradation effect was large, and the TPH concentration significantly reduced. In particular, near the wells treated by bioremediation, the amounts of electron acceptors, such as NO , Fe, and SO , markedly decreased. The product of the microbial degradation process, HCO , gradually increased in the treated wells. Activities of the enzyme catechol 1, 2-dioxygenase decreased, while those of catalase increased. Reductions in pH, from 7.4 to 6.1, were recorded, and the groundwater environment became further deoxidized. [ABSTRACT FROM AUTHOR]

The particle formation and growth events observed at a semirural background site in Denmark were analyzed based on particle number size distribution data collected during the period from February 2005 to December 2010. The new particle formation (NPF) events have been classified visually in detail according to 3D daily plots in combination with an automatic routine. A clear seasonal variation was found in the way that events occurred more frequently during the warm season from May to September and especially in June. The mean values of the apparent 6 nm particle formation rates, the growth rate and the condensation sink were about 0.36 cm s, 2.6 nm h, 4.3 × 10 s, respectively. A positive relationship of oxidation capacity (O = O + NO) of the atmosphere and the appearance of NPF events was found indicating that the oxidation of the atmosphere was linked to the formation of new particles. An analysis of a 3-day backward trajectories revealed that NW air masses from the North Sea were giving the highest probability of NPF events, namely between 20 and 40 %. [ABSTRACT FROM AUTHOR]

This report shows an increase of PAH-related microbial functional genes with PAH concentration in soils. Adaptation of microbial communities to organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) is a crucial issue. However, there is little knowledge on mechanisms ruling microbial community selection. Here, we studied microbial functional genes in soils contaminated by PAHs. We used GeoChip, an advanced functional gene array for gene analysis. Soil PAH concentrations were measured and microbial functional genes were categorized. PAH-related microbial functional genes, bph, nah, nidA, phd, dfb, and qor, were quantitatively expressed. Total microbial functional genes and PAH-related microbial functional genes were compared with PAH concentration by cluster analysis and curve-fitting analysis. We found that the average abundance of PAH-related microbial functional genes increased from 0.13 to 0.33, whereas that of total microbial functional genes decreased from 0.22 to 0.10 when PAHs concentration increased from 1.01 to 164.28 mg kg. It was also found that the classification of microbial community structure characteristics based on PAH-related microbial functional genes was closely similar to the classification based on PAHs concentration. Findings reveal that PAH stress promotes the dominance of PAH-related microbial communities. [ABSTRACT FROM AUTHOR]

Purpose: This paper presents a novel approach to interpret ground-level O with the measured atmospheric stability index (ASI). Methods: O concentrations were monitored by automatic analysers at three types of stations: traffic site, residential site and regional background site in 2005, and the ASI was simultaneously measured by observing radon and its short-lived decay products. Results: The observed results showed a clear annual variation of O concentrations with a maximum in spring, relatively high at the regional background site over 120 ppb, and lower at the residential and traffic sites at about 70 ppb. ASI gives information about the dilution properties of the lower boundary layer and allows to highlight the relevant role of the dilution factor in determining atmospheric pollution events. We demonstrated the analysis of O night peak episodes with vertical wind and ASI. Conclusions: With the advantage of ASI and vertical wind profiles, it was possible to isolate particular photochemical pollution phenomena of O peaks from the free troposphere reservoir or formed by local reactions. This shows that the index constitutes a powerful and valuable tool for describing O night-peak episodes at background station. [ABSTRACT FROM AUTHOR]

Adenomatous polyposis coli (APC) regulates cell-cell adhesion and cell migration through activating the APC-stimulated guanine nucleotide-exchange factor (GEF; Asef), which is usually autoinhibited through the binding between its Src homology 3 (SH3) and Dbl homology (DH) domains. The APC-activated Asef stimulates the small GTPase Cdc42, which leads to decreased cell-cell adherence and enhanced cell migration. In colorectal cancers, truncated APC constitutively activates Asef and promotes cancer cell migration and angiogenesis. Here, we report crystal structures of the human APC/Asef complex. We find that the armadillo repeat domain of APC uses a highly conserved surface groove to recognize the APC-binding region (ABR) of Asef, conformation of which changes dramatically upon binding to APC. Key residues on APC and Asef for the complex formation were mutated and their importance was demonstrated by binding and activity assays. Structural superimposition of the APC/Asef complex with autoinhibited Asef suggests that the binding between APC and Asef might create a steric clash between Asef-DH domain and APC, which possibly leads to a conformational change in Asef that stimulates its GEF activity. Our structures thus elucidate the molecular mechanism of Asef recognition by APC, as well as provide a potential target for pharmaceutical intervention against cancers. [ABSTRACT FROM AUTHOR]

The principle involved in the phenanthrene degradation is regarded as the key to unlock the mechanisms governing the pathway of other polycyclic aromatic hydrocarbons. Past studies have made some pathway proposals via metabolite analysis. In this study, two dominating species ( phn01 and phn02) were isolated from oil contaminated soil and were used in lab-scale experiment of phenanthrene degradation. The GC/MS results revealed the metabolites of pyruvate, phthalate, 1-hydroxy-2-naphthaldehyde and 9-phenanthrol at retention time of 12.01, 15.34, 16.82 and 18.16 min, respectively. A new proposal of pathway was derived. Selective degradation indicated the relationship of coordination between these two species, one of which was mainly responsible for pyruvate production and the other for pyruvate consumption. Pyruvate played a role of microbial demarcation which might be closely associated with invoking signal for microbial community during biodegradation. [ABSTRACT FROM AUTHOR]

The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl- β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500). The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium. A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient k (1.234, 0.726 and 0.448 L·g) and the degradation rate k (0 mmol·L: 0.055, 0.094, and 0.112; 20 mmol·L: 0.126, 0.141, and 0.156; 40 mmol·L: 0.141, 0.156 and 0.184 d) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L: 15.16, 40.01, and 145.5; 40 mmol·L: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation. [ABSTRACT FROM AUTHOR]

There have been very few reports on protein domains that specifically recognize sulfur. Here we present the crystal structure of the sulfur-binding domain (SBD) from the DNA phosphorothioation (PT)-dependent restriction endonuclease ScoMcrA. SBD contains a hydrophobic surface cavity that is formed by the aromatic ring of Y164, the pyrolidine ring of P165, and the non-polar side chains of four other residues that serve as lid, base, and wall of the cavity. The SBD and PT-DNA undergo conformational changes upon binding. The S187RGRR191 loop inserts into the DNA major groove to make contacts with the bases of the GPSGCC core sequence. Mutating key residues of SBD impairs PT-DNA association. More than 1000 sequenced microbial species from fourteen phyla contain SBD homologs. We show that three of these homologs bind PT-DNA in vitro and restrict PT-DNA gene transfer in vivo. These results show that SBD-like PT-DNA readers exist widely in prokaryotes. [ABSTRACT FROM AUTHOR]