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Pasquier and Perrin discovered that the G2-horospherical manifold X of Picard number 1 can be realized as a smooth specialization of the rational homogeneous space parameterizing the lines on the 5-dimensional hyperquadric; in other words, it can be deformed nontrivially to the rational homogeneous space. We show that X is the only smooth projective variety with this property. This is obtained as a consequence of our main result that X can be recognized by its VMRT, namely, a Fano manifold of Picard number 1 is biregular to X if and only if its VMRT at a general point is projectively isomorphic to that of X. We employ the method the authors developed to solve the corresponding problem for symplectic Grassmannians, which constructs a flat Cartan connection in a neighborhood of a general minimal rational curve. In adapting this method to X, we need an intricate study of the positivity/negativity of vector bundles with respect to a family of rational curves, which is subtler than the case of symplectic Grassmannians because of the nature of the differential geometric structure on X arising from VMRT. [ABSTRACT FROM AUTHOR]

Behavior is one of the important factors reflecting the health status of dairy cows, and when dairy cows encounter health problems, they exhibit different behavioral characteristics. Therefore, identifying dairy cow behavior not only helps in assessing their physiological health and disease treatment but also improves cow welfare, which is very important for the development of animal husbandry. The method of relying on human eyes to observe the behavior of dairy cows has problems such as high labor costs, high labor intensity, and high fatigue rates. Therefore, it is necessary to explore more effective technical means to identify cow behaviors more quickly and accurately and improve the intelligence level of dairy cow farming. Automatic recognition of dairy cow behavior has become a key technology for diagnosing dairy cow diseases, improving farm economic benefits and reducing animal elimination rates. Recently, deep learning for automated dairy cow behavior identification has become a research focus. However, in complex farming environments, dairy cow behaviors are characterized by multiscale features due to large scenes and long data collection distances. Traditional behavior recognition models cannot accurately recognize similar behavior features of dairy cows, such as those with similar visual characteristics, i.e., standing and walking. The behavior recognition method based on 3D convolution solves the problem of small visual feature differences in behavior recognition. However, due to the large number of model parameters, long inference time, and simple data background, it cannot meet the demand for real-time recognition of dairy cow behaviors in complex breeding environments. To address this, we developed an effective yet lightweight model for fast and accurate dairy cow behavior feature learning from video data. We focused on four common behaviors: standing, walking, lying, and mounting. We recorded videos of dairy cow behaviors at a dairy farm containing over one hundred cows using surveillance cameras. A robust model was built using a complex background dataset. We proposed a two-pathway X3DFast model based on spatiotemporal behavior features. The X3D and fast pathways were laterally connected to integrate spatial and temporal features. The X3D pathway extracted spatial features. The fast pathway with R(2 + 1)D convolution decomposed spatiotemporal features and transferred effective spatial features to the X3D pathway. An action model further enhanced X3D spatial modeling. Experiments showed that X3DFast achieved 98.49% top-1 accuracy, outperforming similar methods in identifying the four behaviors. The method we proposed can effectively identify similar dairy cow behaviors while improving inference speed, providing technical support for subsequent dairy cow behavior recognition and daily behavior statistics. [ABSTRACT FROM AUTHOR]

To improve the detection speed of cow mounting behavior and the lightness of the model in dense scenes, this study proposes a lightweight rapid detection system for cow mounting behavior. Using the concept of EfficientNetV2, a lightweight backbone network is designed using an attention mechanism, inverted residual structure, and depth-wise separable convolution. Next, a feature enhancement module is designed using residual structure, efficient attention mechanism, and Ghost convolution. Finally, YOLOv5s, the lightweight backbone network, and the feature enhancement module are combined to construct a lightweight rapid recognition model for cow mounting behavior. Multiple cameras were installed in a barn with 200 cows to obtain 3343 images that formed the cow mounting behavior dataset. Based on the experimental results, the inference speed of the model put forward in this study is as high as 333.3 fps, the inference time per image is 4.1 ms, and the model mAP value is 87.7%. The mAP value of the proposed model is shown to be 2.1% higher than that of YOLOv5s, the inference speed is 0.47 times greater than that of YOLOv5s, and the model weight is 2.34 times less than that of YOLOv5s. According to the obtained results, the model proposed in the current work shows high accuracy and inference speed and acquires the automatic detection of cow mounting behavior in dense scenes, which would be beneficial for the all-weather real-time monitoring of multi-channel cameras in large cattle farms. [ABSTRACT FROM AUTHOR]

In the multi-agent cooperative decision-making process, an agent needs to learn cooperatively with its neighbors to obtain the optimal strategy. The actions of agents can be classified into independent actions and interactive actions. The overall information and neighbor information obtained by the agent are different in guiding the selection of the two types of actions. Generally, real-time interaction between the representations of overall information and neighborhood information can facilitate the cooperative decision-making of agents. Therefore, this paper proposes a bidirectional real-time gain representation (BRGR) mechanism, which explicitly enables such real-time interactions. On the one hand, real-time effective neighborhood information representation is incorporated into the overall information representation via an attention module to achieve the gain of the overall information. The gains provide a better understanding and utilization of neighborhood information and guide the agents to make independent action selections. On the other hand, real-time overall information representation is integrated into the neighborhood information representation to achieve the gain of neighborhood information, which guarantees that the interactive actions are based on the current state of agent. The gains make the agents select proper interactive actions. Thus, the proposed BRGR mechanism enables the agents to effectively learn the optimal cooperative strategies. The BRGR is applied to state-of-the-art multi-agent reinforcement learning algorithms. The experimental results show that the BRGR significantly improves the performance of the base algorithms, and have more advantage in complex environments. [ABSTRACT FROM AUTHOR]

We study the question whether rational homogeneous spaces are rigid under Fano deformation. In other words, given any smooth connected family π : X → Z of Fano manifolds, if one fiber is biholomorphic to a rational homogeneous space S, is π an S-fibration? The cases of Picard number one were answered by Hwang and Mok. The manifold F (1 , Q 5) is the unique rational homogeneous space of Picard number one that is not rigid under Fano deformation, and a Fano degeneration of it is constructed by Pasquier and Perrin. For higher Picard number cases, one notices that the Picard number of a rational homogeneous space G/P satisfies ρ (G / P) ≤ rank (G) . Weber and Wiśniewski proved that the rational homogeneous spaces G/P with ρ (G / P) = rank (G) (i.e. complete flag manifolds) are rigid under Fano deformation. In this paper, we show that the rational homogeneous spaces G/P with ρ (G / P) = rank (G) - 1 are rigid under Fano deformation, provided that G is a simple algebraic group of type ADE, and G/P is not biholomorphic to F (1 , 2 , P 3) or F (1 , 2 , Q 6) . We also show that F (1 , 2 , P 3) has a unique Fano degeneration, which is explicitly constructed. Furthermore, the structure of possible Fano degenerations of F (1 , 2 , Q 6) is also described explicitly. Our main result is obtained by applying the theory of Cartan connections and symbol algebras. [ABSTRACT FROM AUTHOR]

1-Flat irreducible G-structures, equivalently, irreducible G-structures admitting torsion-free affine connections, have been studied extensively in differential geometry, especially in connection with the theory of affine holonomy groups. We propose to study them in a setting in algebraic geometry, where they arise from varieties of minimal rational tangents (VMRT) associated to families of minimal rational curves on uniruled projective manifolds. We prove that such a structure is locally symmetric when the dimension of the uniruled projective manifold is at least 5. By the classification result of Merkulov and Schwachhöfer on irreducible affine holonomy, the problem is reduced to the case when the VMRT at a general point of the uniruled projective manifold is isomorphic to a subadjoint variety. In the latter situation, we prove a stronger result that, without the assumption of 1-flatness, the structure arising from VMRT is always locally flat. The proof employs the method of Cartan connections. An interesting feature is that Cartan connections are considered not for the G-structures themselves, but for certain geometric structures on the spaces of minimal rational curves. [ABSTRACT FROM AUTHOR]

Purpose: Zaozigou gold mine is located in the Qinghai-Tibet Plateau, and it is one of the largest gold (Au) mines in China. Agricultural soil pollution of toxic trace elements (TTEs) in Au mining area has become an increasingly common issue and potentially harms the environment and human health. In this paper, 78 samples were collected from a typical Au mining area to evaluate pollution degree of TTEs in the soils and assess related human health risk. Materials and methods: In this study, a total of 78 samples including 36 agricultural soil, 21 sediment, and 21 river samples were collected from the Au mining area. The soil chemical properties of soil samples were analysed. The geo-accumulation (Igeo), contamination factor (CF), and pollution loading index (PLI) were used to analyse the degree of contamination by TTEs. In addition, potential ecological and health risks to local residents via different three exposure routes were revealed using potential ecological risk index and US-EPA health risk assessment models. Pearson correlations between soil chemical properties and toxic elements concentration were calculated. Results and discussion: Results showed that the mean concentrations of As, Cd, Zn, Pb, Cr, and Hg in soils were 27.02, 4.22, 1.57, 1.46, 1.17, and 4.88 times higher than the background values, respectively. The Igeo index and CF values indicated that As pollution was the most severe and Hg and Cd pollution was moderate. Additionally, PLI indicated that soil As and Hg posed extremely high risks. The average potential ecological risk value of all TTEs was 602.34, and As had a higher contribution rate than the other elements, suggesting that the study area was under very high risk, mainly posed by soil As. The hazard index values for Pb, Cr, Cd, Hg, and Zn were below safe value of 1. However, the hazard index values of As for local adults and children were 1.66 and 10.25, respectively. Meanwhile, As presented the unacceptable carcinogenic risks for local residents. The presence of As was related to mining activities, based on the Pearson correlation (between soil chemical properties and TTE contents) and As levels in rivers and sediments near the mining area. Conclusions: As pollution from Au mining activities has posed potential ecological risks to the ecosystem and caused human health risk in the Au mining area. Therefore, more efficient policies to control As contamination in the soils should be implemented as soon as possible. [ABSTRACT FROM AUTHOR]

Though gold mines provide significant economic benefits to local governments, mining causes soil pollution by potentially toxic trace elements (PTEs) in mining areas, especially in the Qinghai-Tibet Plateau. Screening of native plant species from mining areas is now an effective, inexpensive, and eco-friendly method for the remediation of PTEs in situ. In the present study, we conducted experiments to assess the accumulation of As, Cd, Pb, and Zn in 12 native plant species growing on a typical gold mining area in the Qinghai-Tibet Plateau. Our results showed that rhizosphere soils have high soil organic matter content, high levels of As, and moderate levels of Cd. Geranium pylzowianum accumulated relatively higher As in its shoots and exhibited translocation factor (TF) higher than 1 for As (4.65), Cd (1.87), and Pb (1.36). Potentilla saundersiana had bioconcentration factor of shoot (BCF-S) higher than 1 for Cd (4.52) and Pb (1.70), whereas its TF was higher than 1 for As, Cd, Pb, and Zn. These plant species exhibit strong tolerance to these PTEs. Furthermore, Elymus nutans accumulated low levels of As, Cd, Pb, and Zn in their shoots and exhibited TF values lower than 1 for the four PTEs. Therefore, G. pylzowianum is a promising candidate for the in situ phytoextraction of As, and P. saundersiana can be used as an effective plant for Cd and Pb phytoextraction. E. nutans is better suited for the phytostabilisation of multiple PTEs. This work is of significant importance for screening native plant species that can provide a reference for phytoremediation of PTE-contaminated soils in this area or other place with similar climate, and has a good potential for developing PTE phytoremediation strategies at mining sites. [ABSTRACT FROM AUTHOR]

Scheduling optimization of maintenance, repair and operations (MRO) service resources of complex product can help an enterprise improve customer service satisfaction, build value-added products, and enhance the enterprise's market competitiveness. This paper studies a scheduling optimization method for the MRO service resources of complex product. First, the scheduling problem in service resources is analyzed, a mathematical model for the service scheduling problem is given, and three objective functions to be optimized are proposed, which are to reduce customer waiting time, reduce excessive human resources, and maximize the cost performance index of the resources. Then, three separate objectives for optimizing service resource scheduling are analyzed based on three proposed methods which are improved genetic algorithm method, combined weight coefficient optimization method, and multi-objective optimization method based on the nondominated sorting genetic algorithm II (NSGA-II). Finally, we use the three methods to carry out scheduling optimization of MRO service resources in the case of a large vertical mill. According to the analysis and comparison of results, the multi-objective optimization method based on the NSGA-II algorithm has an advantage in the scheduling optimization of complex product MRO service resources. In the engineering application, the service scheduling of complex products for managers provides theoretical basis, and can reduce the loss caused by subjective judgment. [ABSTRACT FROM AUTHOR]

With a 10% reversible compressive strain in more than 10 deformation cycles, the shape memory polymer composites (SMPCs) could be used for deployable structure and releasing mechanism. In this paper, without traditional electro-explosive devices or motors/controllers, the deployable SMPC flexible solar array system (SMPC-FSAS) is studied, developed, ground-based tested, and finally on-orbit validated. The epoxy-based SMPC is used for the rolling-out variable-stiffness beams as a structural frame as well as an actuator for the flexible blanket solar array. The releasing mechanism is primarily made of the cyanate-based SMPC, which has a high locking stiffness to withstand 50 g gravitational acceleration and a large unlocking displacement of 10 mm. The systematical mechanical and thermal qualification tests of the SMPC-FSAS flight hardware were performed, including sinusoidal sweeping vibration, shocking, acceleration, thermal equilibrium, thermal vacuum cycling, and thermal cycling test. The locking function of the SMPC releasing mechanisms was in normal when launching aboard the SJ20 Geostationary Satellite on 27 Dec., 2019. The SMPC-FSAS flight hardware successfully unlocked and deployed on 5 Jan., 2020 on geostationary orbit. The triggering signal of limit switches returned to ground at the 139 s upon heating, which indicated the successful unlocking function of SMPC releasing mechanisms. A pair of epoxy-based SMPC rolled variable-stiffness tubes, which clapped the flexible blanket solar array, slowly deployed and finally approached an approximate 100% shape recovery ratio within 60 s upon heating. The study and on-orbit successful validation of the SMPC-FSAS flight hardware could accelerate the related study and associated productions to be used for the next-generation releasing mechanisms as well as space deployable structures, such as new releasing mechanisms with low-shocking, testability and reusability, and ultra-large space deployable solar arrays. [ABSTRACT FROM AUTHOR]

Isophorone diisocyanate-loaded microcapsules were synthesized with controllable size for self-healing of structural polymer materials. The obtained microcapsules showed good compatibility with polymer resins, e.g., one-component epoxy and multi-component polyurethane/water glass structural materials. During the processing of composite self-healing materials, the highly cross-linked composite capsule wall ensured the integrity of microcapsules and prevented the leakage and degradation of reactive liquid isocyanates effectively. A relatively larger amount of self-healing agent could be released to the local cracks with the increasing size and content of microcapsules in polymer matrix which improved the self-healing efficiency of the composites. Based on the microcapsules with a diameter of ~96 μm, the healing efficiency of epoxy composites containing 15 wt% of capsules and polyurethane/water glass composites containing 20 wt% of capsules could reach to 105 and 101% recovery of fracture toughness, respectively. The crack-healing effect was further verified by scanning electron microscopy. Meanwhile, a possible self-healing mechanism of microcapsules to the cracks of composite polymer materials was proposed. [ABSTRACT FROM AUTHOR]

Because of the unstable hydrodynamic conditions in the wild, the endangered aquatic plant should be cultivated first in constructed wetlands for the protection and expansion of germplasm resources. Ottelia acuminata (Gagnep.) Dandy has become extinct in Erhai Lake, Yunnan province, China. In order to optimize substrates for this species to artificial cultivation, the native substrate (sandy soils) and the other three representative ones (red paddy soils, alluvial paddy soils, and purple paddy soils) collected from Erhai lakeside were applied to cultivate O. acuminata for 50 days. Multi indicators, such as antioxidant enzymes activity, malondialdehyde and chlorophyll-α concentration, and relative growth rate of O. acuminata, were discussed and statistically analyzed to classify the substrates. The results suggested that even disregarding the physiology significance of these indicators, hierarchical clustering analysis had high efficiency on optimizing substrates. Although various single indexes suggested different optimal substrates for macrophyte growth, red paddy soil was never excluded out the optimal substrate classes. Further study is needed to assess the substrates optimization functionalities of these indicators. This study offers amounts of physiology data and an effective method to optimize substrates of O. acuminata. It is helpful for environmental scientists and ecological engineers to conduct the similar study on endangered species. [ABSTRACT FROM AUTHOR]

China has been the largest producer and emitter of perfluorooctanoic acid and its salts (PFOA/PFO). However, the flows of PFOA/PFO from manufacture and application to the environment are indistinct, especially flows from waste treatment sites to the environment. Here, a life cycle analysis of PFOA/PFO is conducted in which all major flows of PFOA/PFO have been characterized for 2012. Processes related to uses and possible releases of PFOA/PFO include manufacture and use, waste management, and environmental storage. During manufacture and use, emission from application was the most important (117.0 t), regardless of whether it flowed first to waste treatment facilities or was directly released to the environment, followed by manufacture of PFOA/PFO (3.9 t), while flows from the service life and end of life of consumer products were the lowest (1.2 t). Among five waste treatment routes, flows through wastewater treatment plants (WWTPs) were the highest (10.6 t), which resulted in 12.8 t of PFOA/PFO being emitted into the environment. Masses of PFOA/PFO emission were estimated to be 96.3 t to the hydrosphere, 25.6 t to the atmosphere, and 3.2 t to soils. Therefore, control over reduction of PFOA/PFO should focus on application of reliable alternatives and emission reduction from WWTPs using effective treatment techniques. [ABSTRACT FROM AUTHOR]

We show that nef cycle classes on smooth complete spherical varieties are effective, and the products of nef cycle classes are also nef. Let $$X$$ be a smooth projective spherical variety such that its effective cycle classes of codimension $$k$$ are nef, where $$1\le k\le \text {dim}(X)-1$$ . We study the properties of $$X$$ . In particular if $$X$$ is a toric variety, then $$X$$ is isomorphic to the product of some projective spaces; if $$X$$ is toroidal, then $$X$$ is isomorphic to a rational homogeneous space; if $$X$$ is horospherical, $$\text {dim}(X)\ge 3$$ and $$k=2$$ , then effective divisors on $$X$$ are nef; if $$X$$ is horospherical and effective divisors on $$X$$ are nef, then there is a morphism from $$X$$ to a rational homogeneous space such that each fiber is isomorphic to the product of some horospherical varieties of Picard number one. [ABSTRACT FROM AUTHOR]

After global commercialization of short-chain perfluoroalkyl acids (PFAAs) as substitutes to conventional long-chain PFAAs by the major manufacturers, two fluorine industry parks for production of short-chain PFAAs located in the Daling River Basin of northern China have developed rapidly in the last few years. This study provides a systematic assessment of sources, emissions, transportation, and potential risks of the PFAAs in this area. The C4 perfluorobutane sulfonic acid (PFBS) and perfluorobutanoic acid (PFBA) were the predominant short-chain PFAAs in river water, with maximum concentrations of 2.90 and 1.35 μg/L, respectively. Park 1 equipped with a telomerization process was identified to be the source of linear and branched mixtures of PFBS, PFBA, and perfluorooctanoic acid (PFOA), while park 2 with an electrochemical fluorination process (ECF) was identified to be the source of linear and branched mixtures of PFBS and PFOA. Partition coefficients between water and sediment were consistent for C4-C8 perfluoroalkyl carboxylic acids (PFCAs) but directly proportional to C9-C11 PFCAs and perfluoroalkyl sulfonic acids (PFSAs). Analysis on the health risk of PFBS and PFBA suggested that they were not without risk since short chain PFAAs are known to be recalcitrant during water treatment. [ABSTRACT FROM AUTHOR]

In the present study, we investigated concentrations and composition profiles of perfluoroalkyl substances (PFASs) in surface water from the Daling River in different seasons. The highest concentration of ΣPFASs (9540 ng L) and dominant homologues were found in surface water collected in summer. Perfluorobutanoic acid (PFBA), perfluorobutane sulfonate (PFBS), and perfluorooctanoic acid (PFOA) were the dominant PFASs in four seasons with a total contribution of over 90 %. The discharge of two fluorine chemical industry parks was predicted to be the main contamination source of PFASs in the study area. The daily and annual mass flows were calculated according to data of detected PFAS concentrations and water discharge, and the annual mass loading of PFASs into the Bohai Sea from the Daling River reached to 461 kg year. Hazard assessment indicated that concentrations of PFASs in study area had little risk to aquatic organisms and wildlife. However, the multiple health risk would be relatively high if the water was served as drinking water in the study area. [ABSTRACT FROM AUTHOR]

Let X ⊊ ℙ be an n-dimensional nondegenerate smooth projective variety containing an m-dimensional subvariety Y. Assume that either m > $\frac{n} {2} $ and X is a complete intersection or that m ⩾ $\frac{N} {2} $. We show deg( X) | deg( Y) and codim Y ⩾ codim X, where 〈 Y〉 is the linear span of Y. These bounds are sharp. As an application, we classify smooth projective n-dimensional quadratic varieties swept out by m ⩾ $\left[ {\frac{n} {2}} \right] $ + 1 dimensional quadrics passing through one point. [ABSTRACT FROM AUTHOR]

The pollution level and source of perfluoroalkyl substances (PFASs) in mainstream and tributary of Daling River in northeast China were investigated in present study. Concentrations of PFASs in surface water and sediment ranged from 4.6 to 3,410 ng/L and from 0.08 to 2.6 ng/g dry weight, respectively. The lowest levels of PFASs were found in vicinity of a drinking water source located in upstream of Daling River. Xihe tributary, which is adjacent to two local fluorine industrial parks, contained the highest level of PFASs. Short-chain PFASs, including perfluorobutanoic acid and perfluorobutane sulfonate, were of higher levels due to their emerging as alternative products for perfluorooctane sulfonate. High level of perfluorooctanoic acid was also found in Daling River. Based on these results, it can be concluded that the relatively severe pollutions of Xihe tributary were caused by long-term development of the two local fluorine industry parks. [ABSTRACT FROM AUTHOR]

Purpose: Hypothermia therapy shows its unique potential for reducing mortality in animal study and improving neurologic outcome in patients with traumatic brain injury. However, therapeutic hypothermia for pediatric traumatic brain injury remains a controversial issue. To determine the effectiveness and safety of hypothermia treatment for pediatric traumatic brain injury patients, we conducted this meta-analysis. Patients and methods: We analyzed the data from MEDLINE, Pubmed, EMBASE, and Cochrane Library by electronic searching. No limitation of language was selected for analysis. We extracted the mortality and adverse events from the published trials. Results: Six clinical trials and 366 pediatric patients met our inclusion criteria. Pediatric patients with traumatic brain injury treated with hypothermia had more unfavorable outcome than those in the normothermia group (RR 1.73, 95 % CI 1.06 to 2.84), and this increased risk is statistically significant. Patients with therapeutic hypothermia are slightly likely to be induced by cardiac arrhythmia, and the likelihood is also significant (RR 2.57, 95 % CI 1.01 to 6.54). Risk of pneumonia has no statistical difference between normothermia and hypothermia arms (RR 0.90, 95 % CI 0.73 to 1.12). Two of the included trials have reported their detail randomization assignment. Conclusions: Hypothermia may slightly increase the risk of mortality in children with traumatic brain injury and the ratio of cardiac arrhythmia after this hypothermia therapy is slightly higher than that in normothermia groups. In the future, more randomized controlled trials and multicenter studies on the mechanism of therapeutic hypothermia are required. [ABSTRACT FROM AUTHOR]

Methyl N-phenyl carbamate (MPC) was synthesized from aniline, urea and methanol. The effects of catalysts, loading amounts, preparation condition of catalyst and reaction condition on the synthesis of MPC were investigated. It was shown that KNO3 modified zeolite HY gave the best performance to MPC formation among the evaluated catalysts, over which 93.1% aniline conversion and 82.6% MPC selectivity were obtained under the optimum reaction condition. Additionally, a possible catalytic mechanism to the formation of MPC in this reaction was proposed. [ABSTRACT FROM AUTHOR]