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Precise Orbit Determination (POD) of Satellite Laser Ranging (SLR)-tracked satellites is stepping towards millimeter-level precision, which requires further refinement of satellite perturbation models and consideration of more detailed perturbation force models that were not previously taken into accounted. Atmospheric drag is one of the main perturbative forces acting on a Low Earth Orbit (LEO) satellite, however, the atmospheric wind speed associated with atmospheric drag has not been considered in International Laser Ranging Service (ILRS) regular data processing. Therefore, in order to analyze the magnitude of atmospheric wind speed influence on POD of SLR satellites, this paper applies HWM14 (Horizontal Wind Model 14) atmospheric wind speed model to perform POD of LARES, Ajisai, Starlette, Stella, Larets satellites and analyses the results. The results show that after applying HWM14 atmospheric wind speed model, the SLR observation residual WRMS (Weighted Root Mean Square) value for LARES, Starlette, Stella, Larets satellites reach 1.04 cm, 2.13 cm, 1.73 cm, 3.36 cm, respectively, which are reduced by 0.10 cm, 0.30 cm, 0.00 cm, 0.05 cm, respectively. However, for Ajisai, one has an almost the same orbit residual WRMS value of 2.88 cm. The 3D (three-dimensional) orbit overlapping arcs error for LARES is 17.53 cm, which is reduced by 1.75 cm; for Starlette it is 19.12 cm, which is reduced by 0.96 cm; for Stella there is almost same orbit overlapping arcs error of 34.9 cm. The accuracy of orbit forecast for 1 day and 3 days for LARES reaches 147.57 cm and 163.96 cm, respectively, which is improved by 0.04 cm and 20.73 cm in the T (Tangential) direction, respectively. The accuracy of orbit forecast for 1 day and 3 days for Stella reaches 191.77 cm and 308.52 cm, respectively, which is improved by 1.95 cm and 6.74 cm in the T direction, respectively. The accuracy of orbit forecast for 1 day and 3 days for Larets reaches 6.18 m and 145.26 m, respectively, which is improved by 7.81 m and 473.61 m in the T direction, respectively. Above results display that considering HWM14 atmospheric wind speed model has a certain improvement for POD of LARES, Starlette, Stella and Larets. Therefore, the influence of atmospheric wind speed should be considered in the SLR POD and regular data processing. [ABSTRACT FROM AUTHOR]

This paper studies the unmanned aerial vehicle (UAV) based multiple intelligent reflecting surface (IRS) network, where the hovering UAV acts as a base station, and the IRS enhances signal transmission to across obstacle between users and UAV. To achieve the maximum sum rate of proposed communication scenario, a non-convex problem considering IRS association results, hovering altitude of UAV, and the phase shift design of multi-IRS is formulated. From the IRS association problem, we can find that the IRS association results are coupled to the decoding order of non-orthogonal multiple access (NOMA). To tackle this, a mathematical interference expansion scheme is developed to decouple it and transform it to convex by binary relaxation method. The non-convexity of hovering altitude optimization problem is solved by logarithm operation, approximation, and auxiliary matrices. For the phase shift optimization problem of multi-IRS, we propose a gradient approximation based initial scheme and develop a univariate optimization based approach on the basis to achieve the users sum rate improvement in multi-IRS. In the end, we compare the proposed scheme with baseline scheme to present the superiority of this work under various network settings. The internal reasons for the variation of simulation results are also analyzed. [ABSTRACT FROM AUTHOR]

Most background suppression algorithms are weakly robust due to the complexity and fluctuation of the star image's background. In this paper, a background suppression algorithm for stray lights in star images is proposed, which is named BSC-Net (Background Suppression Convolutional Network) and consist of two parts: "Background Suppression Part" and "Foreground Retention Part". The former part achieves background suppression by extracting features from various receptive fields, while the latter part achieves foreground retention by merging multi-scale features. Through this two-part design, BSC-Net can compensate for blurring and distortion of the foreground caused by background suppression, which is not achievable in other methods. At the same time, a blended loss function of smooth_L1&Structure Similarity Index Measure (SSIM) is introduced to hasten the network convergence and avoid image distortion. Based on the BSC-Net and the loss function, a dataset consisting of real images will be used for training and testing. Finally, experiments show that BSC-Net achieves the best results and the largest Signal-to-Noise Ratio (SNR) improvement in different backgrounds, which is fast, practical and efficient, and can tackle the shortcomings of existing methods. [ABSTRACT FROM AUTHOR]

Objective. To analyze the intervention effect of group counseling based on positive psychology on psychological crisis of college student. Method. SCL-90 mental health screening was performed on second-year students in a college by cluster stratification. Among the detected students, 210 were included into the group after brief interview and randomly assigned to the experimental group and the control group. The control group was given conventional intervention measures, and the experimental group was given group counseling according to the interview results. One week before the start, on the day of the end of the intervention and 3 months after the end of the intervention, the mental health level of all subjects was evaluated by symptom self-rating scale, general well-being scale, and adolescent mental resilience scale. Results. The scores of two groups were different at different time points during the intervention. With the extension of time, the score of the self-rating symptom scale in the experimental group decreased significantly, while the total score of the self-rating symptom scale in the control group increased, with statistical significance P < 0.05 . Before the intervention, there was no significant difference in general well-being between the two groups P > 0.05 . At 3 months after the end of intervention, the total score of the general well-being scale in the experimental group increased, while that in the control group decreased, with statistical significance P < 0.05 . Three months after the end of the intervention, the total score of adolescent mental resilience scale in the experimental group increased. Conclusion. Group counseling from the perspective of positive psychology can effectively improve the mental health status of medical students with psychological crisis and improve their mental resilience. [ABSTRACT FROM AUTHOR]

• Three sequential processes occur, including coalescence, spreading, retraction. • Spreading diameter and time are normalized by impact and stationary droplets. • Effects of Weber number, droplet volume ratio, surface wettability are clarified. • Maximum spreading coefficient elevates at larger Weber number or drop volume ratio. • An accurate theoretical model of the maximum spreading diameter is proposed. In numerous applications related to droplet impact, impacting droplets often interact with solid surfaces with adhesive droplets rather than dry surfaces, but the former is significantly less studied than the latter. Here, for the fundamental process of droplet impact on a stationary droplet on the surface, we investigate droplet dynamics and maximum spreading under various conditions. The spreading diameter and time are reasonably nondimensionalized as the spreading coefficient and dimensionless time by considering both the impacting and stationary droplets, and the complex influence of diameters of two droplets is reduced to the effect of a single droplet volume ratio. The proposed dimensionless framework provides a method to simplify influencing factors and facilitates the study of droplet dynamics under different Weber numbers, surface wettabilities, and droplet volume ratios. The maximum spreading coefficient increases with the increase of the Weber number or the droplet volume ratio, while it is nearly independent of surface wettability. A theoretical model of the maximum spreading diameter is established through energy analysis. By considering the coupled effects of various factors and modifying the viscous dissipation, the model has the merits of high prediction accuracy and broad applicability. Our findings can not only advance the basic understanding of the ubiquitous droplet impact phenomena, but also provide useful guidance for applications such as spraying cooling and inkjet printing. [Display omitted] [ABSTRACT FROM AUTHOR]

The study is aimed at observing the influence of microribonucleic acid- (miRNA-) 30a-50p on the pulmonary fibrosis in mice with Streptococcus pneumoniae infection through the regulation of autophagy by Beclin-1. Specific pathogen-free mice were instilled with Streptococcus pneumoniae through the trachea to establish the pulmonary fibrosis model. Then, they were divided into the miRNA-30a-50p mimics group (mimics group, n = 10) and miRNA-30a-5p inhibitors group (inhibitors group, n = 10), with the control group (n = 10) also set. Pulmonary tissue wet weight/dry weight (W/D) was detected. The content of tumor necrosis factor-α (TNF-α), interleukin- (IL-) 6, and myeloperoxidase (MPO) was determined using enzyme-linked immunosorbent assay (ELISA). Besides, the changes in the pulmonary function index dynamic lung compliance (Cdyn), plateau pressure (Pplat), and peak airway pressure (Ppeak) were monitored, and the gene and protein expression levels were measured via quantitative PCR (qPCR) and Western blotting. The expression level of miRNA-30a-5p was substantially raised in the mimics group (p < 0.05), but extremely low in the inhibitors group (p < 0.05). The mimics group had obviously raised levels of serum aminotransferase (AST), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP), and pulmonary tissue W/D (p < 0.05). Additionally, the expression levels of TNF-α, IL-6, and MPO were notably elevated in the mimics group, while their expression levels showed the opposite conditions in the inhibitors group (p < 0.05). According to the HE staining results, the inhibitors group had arranged orderly cells, while the mimics group exhibited lung injury, pulmonary edema, severe inflammatory response, and alveolar congestion. In the inhibitors group, Cdyn was remarkably elevated, but Pplat and Ppeak declined considerably (p < 0.05). Besides, the inhibitors group exhibited elevated messenger RNA (mRNA) levels of Beclin-1 and LC3, lowered mRNA levels of α-SMA and p62, a raised protein level of Beclin-1, and a markedly decreased protein level of p62 (p < 0.05). Silencing miRNA-30a-5p expression can promote the expression of Beclin-1 to accelerate the occurrence of autophagy, thereby treating pulmonary fibrosis in mice with Streptococcus pneumoniae infection. [ABSTRACT FROM AUTHOR]

The algorithm proposed in this paper aims at solving the problem of star map matching in high-limiting-magnitude astronomical images, which is inspired by geometric voting star identification techniques. It is a two-step star map matching algorithm relying only on angular features, and adopts a reasonable matching strategy to overcome the problem of poor real-time performance of the geometric voting algorithm when the number of stars is large. The algorithm focuses on application scenarios where there are a large number of dense stars (limiting magnitude greater than 13, average number of stars per square degree greater than 185) in the image, which is different from the sparse star identification problem of the star tracker, which is more challenging for the robustness and real-time performance of the algorithm. The proposed algorithm can be adapted to application scenarios such as unreliable brightness information, centroid positioning error, visual axis pointing deviation, and a large number of false stars, with high accuracy, robustness, and good real-time performance. [ABSTRACT FROM AUTHOR]

Non-toxic tin (Sn)-based perovskite is one of the most promising substitutes for toxic lead (Pb)-based perovskite. However, it is difficult to prepare well due to its instability and self-oxidation. In this study, co-adding suitable inorganic tin (II) fluoride (SnF 2) and organic poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] in the Sn-based precursor solution was applied for the first time to obtain the high-quality methylammonium tin bromide (MASnBr 3) perovskite film. The structural, morphological, and optical analyses discussed in this article indicate that simply adding inorganic SnF 2 is insufficient to obtain MASnBr 3 perovskite films with high crystallinity, uniform surface, and good optical properties. However, the SnF 2 and P(VDF-TrFE) co-additives help to cause a significant decrease in morphological defects, an increase in absorption, and an enhancement in photoluminescence (PL). The X-ray diffraction (XRD) peak positions do not differ regardless of the type of additives, but the peak intensities are changed depending on the amount of the additives. It is exciting that the device fabricated using the co-added MASnBr 3 perovskite films has an increased current density and a lower turn-on voltage. • The ferroelectric copolymer, P(VDF-TrFE), was first applied to improve the fabrication of the Sn-based perovskite film. • The MASnBr 3 film with SnF 2 and P(VDF-TrFE) had optimized morphology, structure, optical property, and stability. • The simple device based on improved MASnBr 3 exhibited better properties of high current density and lower turn-on voltage. [ABSTRACT FROM AUTHOR]

Brassinazole-resistant (BZR) transcription factors have important roles in the brassinosteroid (BR) signalling pathway and are widely involved in plant growth and abiotic stress processes. However, there are few studies on the functions and regulatory mechanisms of BZR TFs in birch. In this study, 5 BZR genes were identified from birch. The qRT-PCR results showed that the expression levels of most BpBZRs were significantly downregulated and/or upregulated in at least one organ following NaCl and PEG stress or ABA, GA 3 and JA treatments. In particular, BpBZR1 expression was changed in all three organs after exposure to NaCl stress at all time points, indicating that this gene may be involved in salt stress. The BpBZR1 transcription factor was shown to have transcriptional activation activity in a yeast two-hybrid assay. Through a transient transformation system, we found that overexpression of BpBZR1 in birch resulted in lower H 2 O 2 and MDA accumulation, higher SOD and POD activities and maintained a higher photosynthetic intensity and a lower chlorophyll degradation rate than those of the control plants under salt stress. These results preliminarily showed that overexpression of the BpBZR1 gene increased the tolerance of birch to salt stress. • BpBZR genes can respond to three abiotic stresses (salt and drought) and three hormone treatments (ABA, GA 3 and JA). • BpBZR1 has transactivation activity. • BpBZR1 overexpression increased ROS-scavenging capability and antioxidant enzymes activities. • BpBZR1 could effectively enhance the tolerance of transgenic birch to salt stress. [ABSTRACT FROM AUTHOR]

Due to their advantages in rapid deployment and miniaturization, UAVs have been widely used in various fields, especially for disaster scenarios which require emergency communications. This article considers a fog UAV wireless network and focuses on improving energy efficiency through subchannel assignment and power allocation. Specifically, in order to make better use of limited spectrum resources, this article considers integrating NOMA which is widely recognized as an emerging transmission technology into UAV wireless networks. On the basis of the proposed UAV network architecture, a two-sided matching and swapping algorithm is proposed to optimize subchannel assignment. We provide a power allocation method to maximize energy efficiency. Simulation results show that the proposed UAV system architecture, as well as the resource allocation method, can prominently improve the energy efficiency of fog UAV wireless networks. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries hold broad prospects as the low-cost and high-energy storage system. However, the practical application is limited by the intrinsic insulating nature of sulfur and severe shuttle effect of soluble polysulfide intermediates. Herein, we demonstrate a convenient self-assembly strategy for encapsulating carbon nanotubes in nitrogen-doped hollow carbon shells, to construct a nitrogen-doped tube-in-tube carbon nanostructure (NTTC) as a host material of sulfur. In this peculiar structure, the highly conductive carbon nanotube cores facilitate the electron transfer while the hollow porous structure is capable of accommodating high sulfur content of 70 wt% in the composites. Moreover, the nitrogen doping helps to alleviate the shuttle effect owing to enhanced chemisorption towards polysulfides. Benefiting from these merits, the NTTC/S composite with the high areal mass loading of ~2.5 mg cm−2 presents a high reversible capacity (1346.9 mAh g−1 at 0.05 C) and excellent rate capability (533.5 mAh g−1 at 3C). More impressively, NTTC/S electrode exhibits good cycling stability at a high rate of 2 C corresponding to slight capacity decay of 0.055% per cycle over 500 discharge/charge cycles. [ABSTRACT FROM AUTHOR]

A green and simple 'one-pot' electrochemical off–on approach to synthesize pyrimidin-2(1H)-ones was realized without any catalyst, oxidant and toxic reagent. The desired products were obtained in moderate to good yields after the stepwise 'one-pot' reaction. The results of control experiments and cyclic voltammetry indicated that the electrooxidation of DHPMs might proceed via two steps process losing two-electrons and two-protons by absorption control with radical intermediates. [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) could reduce surface runoff and provide essential ecosystem service (ES) in flood management. More frequent flooding necessitated GI intervention to promote flood regulation and mitigation service. This study presented the Supply-Demand-Intervention framework of ES for flood mitigation in Nanjing, and aimed to explore flood interventions of GI that improve ES supply and satisfy ES demand from the perspective of landscape pattern. This study quantified ES supply by runoff reduction capacity and assessed ES demand by flood risk index, respectively. Stepwise regression analysis revealed the association between landscape pattern and ES supply and demand. We found the mismatch between ES supply and demand in Nanjing, as well as the spatial heterogeneity between ES supply and demand during various design storms. Urban central areas showed the low ES supply, high ES demand and high priority rank of intervention. Current GI conditions had the difficulty in dealing with more severe floods in Nanjing. And landscape elongation, shape, fragmentation, and segmentation were found to have significant effect on ES supply and demand. More elongated and segmented landscape, with less continuity and connectedness, could promote ES supply, while less fragmentated landscape, with complex shape, could reduce ES demand. Different intervention strategies were proposed to adapt to different areas for promoting ES delivered by GI. In Gulou and Qinhuai district, it was suggested to apply well-shaped elongated cropland and water areas to segment and disperse the built-up land. These findings could provide critical implications for reasonable GI planning and management in flood mitigation and adaption. [Display omitted] • This study proposed Supply-Demand-Intervention framework of ecosystem service. • Ecosystem service supply and demand showed spatial heterogeneity and unmatched relationship. • Green infrastructure with more irregular shape promoted ecosystem service supply and satisfy demand. • More segmented and less fragmented landscape was more than essential. [ABSTRACT FROM AUTHOR]

Highlights • Petroleum ether extracted residue of coal tar was stepwise separated using four solvents by CC. • A same set of fractions and residue were analyzed by GPC, TG-FTIR, PY-GC/MS and FTIR. • The order of the final thermal weight loss rates is: TS > PCT > EAS > THFS > MAS. • Pyrolysis products of TS, EAS, MAS and IS all contain more oxygen compounds. • The pyrolysis volatiles of THFS mainly contain aliphatic and their average content is 82.39 wt%. Abstract The petroleum ether extracted residue (PCT) of the low temperature coal tar were separated and analyzed in this study. PCT was stepwise separated into toluene eluent (TS), ethanol eluent (EAS), methanol eluent (MAS), tetrahydrofuran eluent (THFS) and residue (IS) by chromatography column (CC) with Al 2 O 3. Their composition and structure feature were confirmed by gel permeation chromatography (GPC), Uv-fluorescence, thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR), pyrolysis gas chromatography-mass spectrometer (PY-GC/MS) and Fourier transformed infrared (FTIR). The results show that the yields of TS, EAS, MAS, THFS are 1.70 wt%, 33.22 wt%, 18.97 wt% and 1.41 wt%, respectively. The order of their molecular weights from small to large is as follows: MAS < PCT < TS < EAS < THFS. The compound types of pyrolysis volatiles from TS, EAS, MAS and IS change completely with the temperature rising. TS pyrolysis volatiles mainly contain oxygen compounds and nitrogen compounds. EAS pyrolysis volatiles mainly contain aromatic hydrocarbons and oxygen compounds·THFS pyrolysis volatiles mainly contain aliphatic hydrocarbons (C33-C43 alkanes), and their average content is 82.39 wt%. The pyrolysis temperature from 500 °C to 600 °C is the cut-off point, at which light aromatic hydrocarbons and low boiling phenols are detected, and they may connected by bridge bonds. [ABSTRACT FROM AUTHOR]

A convergent paired electrolysis method for the synthesis of 1‐pyrazolyl‐substituted tetrahydroisoquinolines has been developed. The reaction proceeded without any transition metal catalyst and chemical oxidant. The desired products could be isolated in high yields (80–99%) in 60–80 minutes. The Faradaic efficiency was 108% and gram‐scale synthesis (84%) could be carried out. Mechanistic studies revealed that the C−N bond formation process might mainly involve a nucleophilic addition reaction. [ABSTRACT FROM AUTHOR]

An approximate analytical model was established in this study to predict the transient mass flux and ignition time of solid combustibles exposed to time-dependent exponentially increasing heat flux. Critical mass flux was employed as the ignition criterion in the developed model. A new approximation strategy was used to simplify the complicated exact solution and to derive explicit correlations between ignition time and heat flux. Linear and quadratic heat fluxes were focused and the conclusions under other heat fluxes can be extended through analogy. An equivalent ignition temperature, involving critical mass flux, thermodynamics and chemical kinetics, was found in this study. The negative square root of ignition time is linearly proportional to the heat flux at ignition time. Under linear and quadratic heat fluxes, the ignition heat flux increases with a 1/3 and a 1/5 ( a is a constant in the heat flux expression), respectively, whereas the total heat absorbed by the solid before ignition is proportional to a −1/3 and a −1/5 , respectively. The capability of the proposed model was validated by another analytical model, numerical simulations and experimental data of black PMMA (Polymethyl Methacrylate) and pine wood. Furthermore, the effect of surface heat loss on the predictions of the proposed model was estimated and parametric study based on critical mass flux was implemented. [ABSTRACT FROM AUTHOR]

Most studies, employing ignition temperature as the ignition criterion, utilized surface absorption of radiant incident heat flux in analytical models when investigating the ignition mechanism of solid combustibles. However, in-depth absorption exerts its influence on ignition time significantly for translucent solid, especially at high radiant heat flux. In this work, we extend the previous researches from surface absorption to in-depth absorption to develop an approximate analytical ignition model using critical mass flux instead of critical temperature. An approximation methodology is proposed during derivation to study the in-depth absorption scenario. The comparison among this model, available experimental data of black PMMA in the literature and previous numerical simulations indicates that the proposed model provides relatively high accuracy in predicting ignition time. Furthermore, the pure surface absorption circumstance is also reexamined and compared with the classical ignition theory. The results show that surface absorption hypothesis accelerates the total mass flux, which consequently shortens the ignition time. However, in-depth absorption assumption eliminates the heat accumulation on surface and results in good prediction for ignition time at high heat flux. For in-depth absorption, the absorption coefficient affects the heat penetration depth and temperature distribution in this layer which consequently affects the thermal degradation reaction rate, mass flux and finally ignition time. Meanwhile, the ignition time considering both surface and in-depth absorption is discussed, and the relationship with pure surface and in-depth absorption conditions is obtained. [ABSTRACT FROM AUTHOR]

Focuses on a study which discussed radiative and nonradiative transitions in GaAs:Er. Method used for the analysis of the growth of erbium doped GaAs; Estimation of the nonradiative Auger-type process based on a simple model for the excitation dependence of the emission; Factor dominant in temperature induced quenching of the emission.

Vector orthogonal frequency-division multiplexing (V-OFDM) for single-transmit-antenna systems is a generalization of OFDM where single-carrier frequency-domain equalization and OFDM are just two special cases. Phase noise in a V-OFDM system leads to a common vector block phase error (CVBPE) and an intervector block carrier interference effect. Severe performance degradation may occur if these two effects are not estimated and compensated well. In this paper, blind and semiblind phase noise estimation and compensation in a V-OFDM system is investigated by using the expectation-maximization (EM) algorithm. This is motivated by the fact that the conventional frequency-domain phase noise suppression schemes based on pilot-aided common phase error (CPE) or CVBPE estimation and compensation are not spectrally efficient as the vector block size is increased. Two novel schemes are proposed: One estimates the CVBPE only, and the other estimates the entire phase noise sequence in the time domain. General closed-form formulas for the maximization step of the EM algorithm for the two schemes are derived, and their computational complexity values are analyzed. The performances of the two schemes are investigated by using linear-minimum-mean-square-error (LMMSE) receivers. Simulations show that the two proposed schemes are very effective in estimating and compensating for phase noise in V-OFDM systems. It turns out that the second proposed scheme not only outperforms the traditional CPE or CVBPE schemes but is computationally efficient as well when applied to V-OFDM systems. [ABSTRACT FROM PUBLISHER]

The monitoring of space debris is important for spacecraft such as satellites operating in orbit, but the background in star images taken by ground-based telescopes is relatively complex, including stray light caused by diffuse reflections from celestial bodies such as the Earth or Moon, interference from clouds in the atmosphere, etc. This has a serious impact on the monitoring of dim and small space debris targets. In order to solve the interference problem posed by a complex background, and improve the signal-to-noise ratio between the target and the background, in this paper, we propose a novel star image enhancement algorithm, MBS-Net, based on background suppression. Specifically, the network contains three parts, namely the background information estimation stage, multi-level U-Net cascade module, and recursive feature fusion stage. In addition, we propose a new multi-scale convolutional block, which can laterally fuse multi-scale perceptual field information, which has fewer parameters and fitting capability compared to ordinary convolution. For training, we combine simulation and real data, and use parameters obtained on the simulation data as pre-training parameters by way of parameter migration. Experiments show that the algorithm proposed in this paper achieves competitive performance in all evaluation metrics on multiple real ground-based datasets. [ABSTRACT FROM AUTHOR]

An efficient and practical bis(alkoxo)palladium complex Cat.I catalyzed C–H arylation of heterocycles with heteroaryl chlorides has been developed. With 1 mol % of Cat.I , the direct arylation of a series of heterocycles with various heteroaryl chlorides could proceed smoothly affording desired products in moderate to excellent yields. The catalytic system allows one-pot synthesis of 2,5-diheteroaryled thiophenes via twofold direct C–H arylation. [ABSTRACT FROM AUTHOR]

Baiyin city, which is located upstream of the Yellow River and in the central part of Gansu province, China, is severely contaminated by heavy metals such as chromium. A Gram-positive bacterium BYCr-1 capable of reducing hexavalent chromium (Cr(VI)) to trivalent (Cr(III)) aerobically was isolated from a rare-earth ore in Baiyin, Gansu, China. 16S rRNA analysis revealed that it was closely related to Bacillus subtilis. It can reduce 0.2 mM Cr(VI) to Cr(III) in M9 medium after 48 h incubation. Transmission electron microscopy (TEM) image showed that Cr(III) precipitates were located both inside and outside the cells. An nfrA gene was upregulated by 5.3 folds upon Cr(VI) treatment. Furthermore, E. coli-NfrA demonstrated elevated chromate-reducing ability. Our results indicate that BYCr-1 is able to resist and reduce high concentrations of Cr(VI), which makes it a potentially suitable candidate for bioremediation of Cr(VI) contamination. This study also reveals that nfrA confers Cr(VI)-reducing ability in Bacillus subtilis. [ABSTRACT FROM AUTHOR]

Vector orthogonal frequency division multiplexing (V-OFDM) for single transmit antenna systems is a generalization of OFDM where single-carrier frequency domain equalization (SC-FDE) and OFDM are just two special cases. It has been shown to be able to collect multipath diversity and thus generally outperforms OFDM. The performance of OFDM under phase noise has been extensively studied in the literature. These effects can be summarized as introducing a common phase error (CPE) and inter carrier interference (ICI) resulting in poor performance. The performance of V-OFDM under phase noise still remains uninvestigated and in this paper it is shown that phase noise in V-OFDM systems leads to a common vector block phase error (CVBPE) as well as an inter vector block carrier interference (IVBCI) effect. An expression for the signal plus interference noise ratio (SINR) for a V-OFDM system is derived and found to agree closely with simulation results. A pilot vector CVBPE based phase noise estimation technique is derived, and then combined with the maximum likelihood (ML) and the linear minimum mean square error (LMMSE) estimators to estimate the phase noise. It turns out that compared with OFDM, V-OFDM systems can perform phase noise estimation with lower complexity. The decorrelation and cancellation techniques are then used to compensate for the phase noise impairment. Numerical results for both coded and uncoded systems with perfect and practical channel estimation are provided to validate the analysis and effectiveness of the proposed phase noise estimation and compensation methods. [ABSTRACT FROM AUTHOR]

• We analyzed flood risk propagation based on modified Susceptible Infected Recovered model. • Flood depth-damage curve could be established by flood depth and economic losses in Nanjing. • Built-up land and cropland were more sensitive to flood change during flood events. • Differences of flood risk appeared in districts of Nanjing and Jianye District showed high risk. Increasing urban flood posed serious threat to urban safety and sustainable development, and resulted in great loss and damage. It was significant and indispensable to master the potential change of urban flood for flood risk mitigation and adaption. Floods not merely caused the physical losses, but also led to potential damage and harm during flood risk propagation. Studies have mainly focused on the physical features of flood risk and post-disaster reconstruction, while few have discussed the potential risk consequence considering flood risk propagation. Therefore, this study analyzed flood risk propagation based on modified Susceptible Infected Recovered (SIR) model. We performed flood simulation and modelling, mapped urban flood risk in consideration of flood risk propagation, and estimated flood losses in Nanjing with flood return periods of 5, 10, 20, 50, and 100 years. Results indicated that inundated area occupied 517.19, 654.11, 657.92, 834.49 and 1045.80 km2 with return periods from 5 to 100 years respectively. Jianye District showed high flood risk and it was suggested to protect people's lives and assets to reduce susceptibility and vulnerability, and enhance urban drainage capacity for recovery improvement. Moreover, total economic losses reached $27.85, $30.89, $32.91, $35.50 and $38.55 billion and led to the 14.38%, 15.94%, 15.94%, 18.32% and 19.90% GDP loss rate respectively. This study could support the effective flood risk mitigation practice for adaptive urban development. [ABSTRACT FROM AUTHOR]

In this paper, a multiple-input–multiple-output (MIMO) system with finite-bit feedback first proposed by Love–Heath is considered, where a transmitted signal consists of a precode followed by an orthogonal space–time block code (OSTBC), such as Alamouti code. A new design criterion and a corresponding design method of precoders are proposed. Simulations show that the precoders obtained by our proposed criterion and method perform better than the existing ones. Furthermore, since our proposed precoders have a layered structure, their designs can be implemented in the simplest Grassmannian manifold. Moreover, a fast encoding algorithm can be applied, which can greatly reduce the complexity of codeword selection. In this paper, we also propose non-unitary precoders and their design criterion and method based on the performance analysis and the special property of an OSTBC. Interestingly, non-unitary precoders can significantly improve performance over unitary precoders. [ABSTRACT FROM PUBLISHER]

Abstract: A novel palladium complex based on N,O-ligand was synthesized, which shows a high catalytic activity in the Suzuki cross-coupling reaction without using any phosphine ligand. More importantly, no significant loss of the catalytic activity was observed after six recycles. We suggest that this catalyst has commercial and industrial potential in the future. [Copyright &y& Elsevier]

Signal-space diversity is a power- and bandwidth-efficient diversity technique. To exploit the signal-space diversity, joint maximum-likelihood (ML) detection at the receiver is usually needed, where the complexity grows exponentially with the dimension of the lattice. In this letter, we propose a serial concatenated scheme and two simple iterative methods to exploit the signal-space diversity. The simple iterative methods are based on the idea of soft interference cancellation. The first iterative method is based on a vector Gaussian approximation, while the second one is based on a scalar Gaussian approximation. The complexity of the first iterative method grows cubically with the dimension of the lattice, and the simulations show that its performance approaches that of the optimal maximum a posteriori detection method. The complexity of the second Iterative method grows linearly with the dimension of the lattice, and the simulations show that when the dimension of the lattice N = 32, at bit-error rate = -5, the performance gap between the Rayleigh fading channel and the Gaussian channel is only 0.3 dB. [ABSTRACT FROM AUTHOR]

The movement of landslide-debris flows is strongly affected by entrainment and runout-path terrain. Herein, mobility alteration was explored from an energy perspective via the discrete element method, using the Shaziba geohazard. The dynamics of the Shaziba geohazard were investigated based on field investigations and numerical simulations. The multiple energy evolutions, conversions, and dissipations of different initiation areas and distinct landslide processes, including kinetic, potential, frictional, and collisional energy, were quantitatively and systematically investigated. The simulation results provide a clear presentation of the inter-particle interactions and energy transfer behavior. Friction caused the most significant energy dissipation, yet collisions dominated the mobility reduction during the entrainment process and interactions with the runout-path terrain. The entrained area possessed higher mobility due to entrainment-induced energy transfer, with distinct forms of energy supplement at different depths. Moreover, the deflection and arching effects of runout-path terrains altered the velocity and direction of landslides and could be used to explain the dissipation of landslide energy as well as reduced mobility. At the cliff, the high-velocity and near-vertical impact on the sediment resulted in the rapid dissipation of landslide energy in collisions. The results provide a reference for analyzing and predicting the movement and mitigating threats of similar geohazards. [ABSTRACT FROM AUTHOR]

Three π-conjugated small molecules DPBT , DEPBT and DEPBPy , based on bithiazole or bipyridine were designed and synthesized. In DEPBT and DEPBPy , the central core and terminal phenyl groups are connected by C C double bonds, whereas in DPBT , they are combined through C–C single bonds. The effects of the molecular structural changes on their crystal structures, optoelectronic properties and thin film morphologies were comparatively studied. In addition, their resistive memory performance was primarily investigated for the first time. Both DEPBT - and DEPBPy -based devices exhibit typical binary memory behavior, while DPBT -based device presents no memory property. The experimental results confirm that the introduction of C C bridged bonds into molecules could enhance the molecular interaction, which plays an important role in the molecular arrangement on the thin film, and has a significant contribution to charge transport in memory devices. This work demonstrates that aryl vinyl terminated bithiazoles and bipyridines both are good promising candidates for organic memory storage. Image 1 • Three π-conjugated heteroaromatic molecules based on bithiazole or bipyridine were designed and synthesized. • The effect of molecular structural changes on the crystal structure, optoelectronic property and film morphology were studied. • The results confirm that C C bridged bond extends conjugated backbone and enhances intermolecular interaction. • The introduction of C C bridged bond is beneficial to improve molecular film quality and electrical memory performance. • This work demonstrates that aryl vinyl terminated bithiazoles and bipyridines both are good promising candidates for OMDs. [ABSTRACT FROM AUTHOR]

• Three aryl vinyl terminated fluorenone-based molecules were synthesized for resistive memory device applications. • The optoelectronic properties and film-forming ability of the fluorenone-core molecules were comparatively studied. • The memory behavior of fluorenone-based devices can be tuned from Flash to WORM by adjusting molecular aryl end groups. Three aryl vinyl terminated 9-fluorenone compounds ( p Me-DEPFO, DEPFO and F5-DEPFO) were designed and synthesized. The single crystal structure of p Me-DEPFO shows that the molecule has a good planarity and packs orderly, which is crucial for the charge transport. The optical and electrochemical properties indicate that aryl end groups with different electron push-pull effect can adjust the molecular HOMO and LUMO energy levels (E HOMO : -5.14∼-5.53 eV; E LUMO : -2.91∼-3.13 eV), which lead to different energy gaps (E g opt: 2.23∼2.40 eV). The "Al/fluorenone/ITO" devices of p Me-DEPFO and DEPFO both exhibit excellent non-volatile flash memory property with high ON/OFF ratios (∼104 and 106). In contrast, F5-DEPFO -based device displays WORM memory behavior with high ON/OFF ratio (∼105). The experimental and theoretical calculation results confirm that the adjustment of molecular end groups leads to the different of film-forming ability, which tuned the resistive memory behavior. [ABSTRACT FROM AUTHOR]

• Coal tar was separated into n-hexane insoluble-hot benzene solubles and insolubles. • The separation products were analyzed by FTIR, XPS, 1H/13C NMR, TG and PY-GC/MS. • The ring number of the aromatic structure in HIBI is larger than that in HIBS. • HIBS has more thiophenic sulfur. HIBI has more shorter alkyl side chains and COO–. • HIBS and HIBI are mainly composed of aromatics, phenolic and heteroatomic compounds. The composition and structure analysis of coal tar is a very important basic issue. In the process of preparing asphaltenes (insoluble in C5-C7 n -alkanes but soluble in hot benzene, HIBS) according to the definition, it was found that hot benzene insoluble (HIBI) components still exist in the coal tar. It is necessary to carry out in-depth analysis and identification of their compositions and structures, in order to obtain detailed information, which provides a certain guiding significance for the deep processing of coal tar. Their compositions and structures were studied by means of physical and thermo-chemical analysis, including Fourier transform infrared spectroscopy (FTIR), Uv-fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), 1H magic angle spinning nuclear magnetic resonance spectroscopy (1H-MAS-NMR), 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy (13C-CP/MAS-NMR), thermogravimetric analysis (TG) and pyrolysis gas chromatography-mass spectroscopy (PY-GC/MS). The results show that: HIBS and HIBI are mainly composed of aromatic compounds, phenolic compounds and heteroatomic compounds, but the forms of these compounds are different. The ring number of the aromatic structure in HIBI is larger than that in HIBS. The main bonding ways of oxygen in HIBS and HIBI include C O, C–O, C–OH, C–O–C and COO–, but the peak positions of those functional groups are slightly offset. There are more COO– in the structure of the latter. Compared with HIBS, HIBI contains more carboxyl hydrogen and more oxygen-bonded hydrogen, thus inferring that HIBI contains more oxygenated compounds. In addition, HIBI has more shorter alkyl side chains. [ABSTRACT FROM AUTHOR]

In this research, we realized the conversion of visible light to electrical energy and C–H activation by the synergistic catalytic effect of visible-light and photoelectric current. An atom-economical and environment-friendly self-biasing interfacial photo-electrocatalytic method for cascade C–H activation/cyclization is provided to construct N-containing fused ring compounds using an m-BiVO4 film as a photoanode. There are obvious advantages of this transformation due to no external bias and a small overpotential, saving electrical energy and avoiding excessive oxidation of malononitrile to achieve better chemical reactivity and selectivity. Meanwhile, the recovered photoanode could be used more than ten times. [ABSTRACT FROM AUTHOR]

An optical frequency-response analysis (OFRA) method is proposed to detect the winding deformation in a power transformer. Compared to existing frequency-response analysis (FRA) systems, the proposed system has several unique merits, such as high immunity to electromagnetic interference, direct display of winding deformation, no influence of connected power equipment, and long reliability in harsh environments. First, the principle of optical frequency-response detection and noise elimination is introduced. Then, the algorithm used to acquire the winding deformation matrix is discussed in detail. Next, winding deformation experiments are carried out to investigate the diagnostic ability of the proposed OFRA method. The experimental results indicate that the OFRA can locate the deformation disc and determine the deformation level correctly. [ABSTRACT FROM AUTHOR]

A direct electrooxidative cross-dehydrogenative-coupling (CDC) reaction between N-aryl-tetrahydroisoquinolines and 4-hydroxycoumarins has been realized. This protocol provides a green, mild and fast method to construct 3-tetrahydroisoquinoline substituted coumarins in the absence of any catalysts and exogenous oxidants. A variety of N-aryl-tetrahydroisoquinolines and 4-hydroxycoumarins are compatible with this transformation to give the corresponding products in moderate to excellent yields. Moreover, the results of control experiments, cyclic voltammetry experiments, and density functional theory (DFT) calculations indicated that the electrooxidative CDC reaction might involve both radical addition and nucleophilic addition processes. [ABSTRACT FROM AUTHOR]

Star image registration is the most important step in the application of astronomical image differencing, stacking, and mosaicking, which requires high robustness, accuracy, and real-time capability on the part of the algorithm. At present, there are no high-performance registration algorithms available in this field. In the present paper, we propose a star image registration algorithm that relies only on radial module features (RMF) and rotation angle features (RAF) while providing excellent robustness, high accuracy, and good real-time performance. The test results on a large amount of simulated and real data show that the comprehensive performance of the proposed algorithm is significantly better than the four classical baseline algorithms as judged by the presence of rotation, insufficient overlapping area, false stars, position deviation, magnitude deviation, and complex sky background, making it a more ideal star image registration algorithm than current alternatives. [ABSTRACT FROM AUTHOR]

In this letter, the mathematical equivalence between the vector OFDM proposed by Xia in 2001 and the quadrature OFDMA proposed by Zhang et. al. in 2009 is shown. Having the mathematical equivalence, all the discussed aspects of the one can be applied to the other in a straightforward manner. [ABSTRACT FROM PUBLISHER]

A catalytic system comprised of a bis(alkoxo)palladium complex and Xantphos is tested in the heteroarylation of 2-methylthiophene (I) and heteroarenes (VI). [ABSTRACT FROM AUTHOR]

Many large landslides in reservoir areas have been recognized as the presence of multi-sliding zones owing to the distinctive deformation characteristics. Due to water-level fluctuations, the deformation mechanism of the multi-sliding zones landslide is poorly understood. Herein, a simplified model of a multi-sliding zones landslide subjected to the operation reservoir was conducted to reproduce the deformation process and obtain the deformation characteristics, pore water pressure, and earth pressure to investigate the deformation mechanism. The results suggest that the deformation exhibited by the multi-sliding zones landslide subjected to the operated reservoir take on a regional deformation characteristic with the multi-sliding zones as the boundary and correspond to the abrupt change in earth pressure and pore water pressure. According to the effective stress principle, the deformation mechanism is investigated by relying on the response relationship between effective stress and deformation. It shows that the softening effect caused by initial water infiltration, outward seepage force caused by initial water-level drawdown and the driving force are the external factors triggering the regional deformation of the multi-sliding zones landslide, while the immediate cause of the regional deformation is the rapid change in effective stress, which combined with the decreasing trend before the rapid effective stress release, is crucial for accurately assess whether the multi-sliding zones landslide is about to deform. This research provides improved insight into the deformation mechanism of the multi-sliding zones landslide. [ABSTRACT FROM AUTHOR]

For the first time, MIDA boronates (II) are used in C-H arylation reactions of heterocycles. [ABSTRACT FROM AUTHOR]

A number of aryl-phenyl, hetaryl-phenyl and hetaryl-hetaryl cross-coupling products is obtained using two different tolyliminoethylferrocene-derived palladacycle catalyst-solvent systems (PFP-EtOH/H2O preferentially for bromides and PFD/XPhos-H2O preferentially for chlorides). [ABSTRACT FROM AUTHOR]

An efficient and regioselective phosphine-free arylation of thiophenes, benzothiophene, benzofuran and pyrrole derivatives is presented. [ABSTRACT FROM AUTHOR]

A facile and one-step strategy has been developed for the preparation of highly fluorescent nitrogen and phosphor co-doped carbon quantum dots (NP-CQDs) through the thermal treatment of the mixture of citric acid and O -phosphorylethanolamine. The as-prepared NP-CQDs emit strong blue-green light under irradiation of 365 nm light and show emission maxima at 475 nm in aqueous solution. And these NP-CQDs exhibit great stability in high-salt conditions, excellent photostability and a high quantum yield of about 8.45%. Interestingly, the NP-CQDs have been successfully utilized for the sensitive and selective fluorometric detection of Fe 3+ without interference from other ions in aqueous solution. Moreover, we have found that the NP-CQDs can enhance the photocatalytic activity of TiO 2 for the degradation of dyes under simulated sunlight irradiation. [ABSTRACT FROM AUTHOR]

The novel catalyst is insoluble in various organic solvents. [ABSTRACT FROM AUTHOR]

• The VHC fretting fatigue strength of railway axles was systematically investigated. • Fretting fatigue damage of railway axles was evaluated by the MWCM coupled with TCD. • The reasons why the VHC fretting fatigue occurs in railway axles are clarified. • Fretting fatigue test cycle for railway axles is suggested to be beyond 107. Fretting fatigue cracks at the press-fitted part of railway axles are commonly observed in the very high cycle (VHC) regime. However, most studies concerning the fretting fatigue behaviour of railway axles have been limited to the high cycle (HC) regime, which cannot provide sufficient knowledge to ensure the safe operation of railway axles over a service life of 30 years. In this study, fretting fatigue experiments for scaled railway axles were extended from the HC regime to the VHC regime. The fretting wear and fretting fatigue damage were observed and measured. Finally, based on the finite element simulation, an evaluation method coupled with the Modified Wöhler Curve Method (MWCM) and the theory of critical distance (TCD) was developed to investigate the fretting fatigue damage. The experimental investigation found that the fretting fatigue strength of railway axles in the VHC regime decreased with an increase in the number of test cycles, which can be described by the Basquin equation. This suggests that the fretting fatigue strength in the VHC regime can be predicted to provide data for the design of safer railway axles. The numerical study showed that the developed evaluation method can provide a reasonable estimation of the occurrence of fretting crack initiation in the VHC regime, and that the fretting fatigue damage can be described by the MWCM equivalent stress. The stress concentration at the press-fitted part gradually increased due to the continuous fretting wear, which resulted in the disappearance of the fretting fatigue limit of the press-fitted railway axles in the HC regime, and VHC fretting fatigue occurred. [ABSTRACT FROM AUTHOR]

Space debris detection is vital to space missions and space situation awareness. Convolutional neural networks are introduced to detect space debris due to their excellent performance. However, noisy labels, caused by false alarms, exist in space debris detection, and cause ambiguous targets for the training of networks, leading to networks overfitting the noisy labels and losing the ability to detect space debris. To remedy this challenge, we introduce label-noise learning to space debris detection and propose a novel label-noise learning paradigm, termed Co-correcting, to overcome the effects of noisy labels. Co-correcting comprises two identical networks, and the predictions of these networks serve as auxiliary supervised information to mutually correct the noisy labels of their peer networks. In this manner, the effect of noisy labels can be mitigated by the mutual rectification of the two networks. Empirical experiments show that Co-correcting outperforms other state-of-the-art methods of label-noise learning, such as Co-teaching and JoCoR, in space debris detection. Even with a high label noise rate, the network trained via Co-correcting can detect space debris with high detection probability. [ABSTRACT FROM AUTHOR]

Abstract: Mercury (Hg) contaminants are widespread in Lanzhou and cause environmental pollution. Mercury pollution is harmful to environments and human health. Microbes are able to reduce Hg (II) to less toxic form elemental Hg which could be a potential alternative for mercury remediation. We've isolated a strain named Lzu-02 from sediments of the Lanzhou Reach of the Yellow River which is able to resist Hg (II). It was also able to reduce Hg (II) to elemental Hg aerobically when incubated in M9 medium with 40 μM HgCl2. The optimum condition of resisting and reducing Hg (II) for Lzu-02 was pH 6 and 37 °C. Lzu-02 was identified to be most similar to Staphylococcus epidermidis by 16S sequencing analysis and Vitek phenotype identification. We also found that Lzu-02 had a mer operon consisting of SmerR, SmerC, SmerT and SmerA genes. The relative expressions of three genes (SmerC, SmerT and SmerA) were upregulated when Lzu-02 was cultivated in M9 medium with 40 μM HgCl2. These results suggested that strain Lzu-02 could be useful for the bioremediation of Hg (II) in Lanzhou reach of the Yellow River. [Copyright &y& Elsevier]

Abstract: A series of derivatives based on annelated β-oligothiophenes were synthesized and characterized as active layer in organic field-effect transistors (OFETs). Highest field-effect mobility of 0.52V−1 s−1 for 2,5-dibiphenyl-dithieno[2,3-b:3′,2′-d]thiophene (DBP-DTT), 2.2cm2 V−1 s−1 for 2,5-distyryl-dithieno[2,3-b:3′,2′-d]thiophene (DEP-DTT), and 0.16cm2 V−1 s−1 for 1,4-di[2-dithieno[2,3-b:3′,2′-d] thiophen-2-yl-vinyl]benzene (DDTT-EP) were obtained, while 2,5-diphenyl-dithieno [2,3-b:3′,2′-d]thiophene (DP-DTT) presents no field-effect behaviors. Their thermal, optical and electrochemical properties, topographical and X-ray diffraction patterns of films, and the single crystal structures were also investigated. With the end-capping groups changing in these materials, the intermolecular interactions could transform from S–S in DP-DTT to S–C in DBP-DTT, to S–π in DEP-DTT, and to the coexisting of S–S and S–π in DDTT-EP. According to the device performances and the results of transfer integral calculations, it was revealed that S–π intermolecular interaction benefits not only improving the mobility but also reducing the threshold voltage (VT ), while S–S intermolecular interaction is not favorable for promoting the mobility. [Copyright &y& Elsevier]

A mild and efficient visible-light-induced synthesis of C-3 dicarbonyl coumarins from 3-arylacetylene coumarins without a photocatalyst was reported. This iodide-mediated method exhibited broad substrate scope and good functional group tolerance, and a series of C-3 dicarbonyl coumarins were obtained in moderate to excellent yields. Based on the control experimental results, it was found that the visible-light-induced oxidation might be via both radical and ionic processes. Moreover, some synthesized compounds displayed high sensitivity to hydrogen peroxide (H2O2) with a low detection limit (DL, down to 0.149 μM). [ABSTRACT FROM AUTHOR]