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Inspired by the transmission characteristics of the Coronavirus disease 2019 (COVID-19), an epidemic model with quarantine and standard incidence rate is first developed, then a novel analysis approach is proposed for finding the ultimate lower bound of the number of infected individuals, which means that the epidemic is uniformly persistent if the control reproduction number ℛ c > 1 . This approach can be applied to the related biomathematical models, and some existing works can be improved by using that. In addition, the infection-free equilibrium V0 of the model is locally asymptotically stable (LAS) if ℛ c < 1 and linearly stable if ℛ c = 1 ; while V0 is unstable if ℛ c > 1 . [ABSTRACT FROM AUTHOR]

China consumes 35% of the world's fertilizer every year; however, most of the nitrogen fertilizers, which are essential for rice cultivation, are not used effectively. In this study, factors affecting the nitrogen leaching loss rate were studied in typical soil and rice varieties in South China. The effects of various irrigation measures on rice growth and nitrogen leaching loss were investigated by conducting experiments with eight groups. These groups included traditional irrigation (TI) and shallow wet irrigation (SWI). The TI is a common irrigation method for farmers in South China, maintaining a water layer of 5-8 cm depth. For SWI, after establishing a shallow water layer usually maintaining at 1-2 cm, paddy is irrigated when the field water level falls to a certain depth, then this process is then repeat as necessary. The nitrogen distribution characteristics were determined using 15N isotope tracing. In addition, the effects of nitrification, denitrification, and microbial composition on soil nitrogen transformation at different depths were studied by microbial functional gene quantification and high-throughput sequencing. The results revealed that in the SWI groups, the total nitrogen leaching loss rate reduced by 0.3-0.8% and the nitrogen use efficiency (NUE) increased by 2.18-4.43% compared with those in the TI groups. After the 15N-labeled nitrogen fertilizer was applied, the main pathways of nitrogen were found to be related to plant absorption and nitrogen residues. Furthermore, paddy soil ammonia-oxidizing archaea were more effective than ammonia-oxidizing bacteria for soil ammonia oxidation by SWI groups. The SWI measures increased the relative abundance of Firmicutes in paddy soil, enhancing the ability of rice to fix nitrogen to produce ammonium nitrogen, thus reducing the dependence of rice on chemical fertilizers. Moreover, SWI enhanced the relative abundance of nirS and nosZ genes within surface soil bacteria, thereby promoting denitrification in the surface soil of paddy fields. SWI also promoted ammonia oxidation and denitrification by increasing the abundance and activity of Proteobacteria, Nitrospirae, and Bacteroidetes. Collectively, SWI effectively reduced the nitrogen leaching loss rate and increase NUE. [ABSTRACT FROM AUTHOR]

Q235b carbon steel, main material of early alkaline radioactive liquid waste tank, can be contaminated by 90Sr and 137Cs. In this work, batch contamination experiments were conducted to simulate contamination of steel. The results indicated that Fe3O4, main corrosion product, fell off to form sludges. Furthermore, Sr existed mainly in form of SrCO3 in oxide layer and sludge, and the corrosion made Sr enter into corrosion defects. While Cs was more limited to surface, mainly in form of CsNO3 on the surface of oxide layer and sludge. The findings of this work will facilitate the development of efficient decontamination techniques. [ABSTRACT FROM AUTHOR]

Background: Intracranial artery dissection (IAD) is a pathological dissection of the arterial wall. However, the morphological features and imaging characteristics of patients with intracranial artery dissection (IAD) remain poorly understood. Methods: The study reports on 70 IAD patients (30 culprit and 40 non-culprit). All participants underwent high-resolution magnetic resonance imaging (HR-MRI) scans. The morphological features and imaging characteristics of artery dissection were carefully investigated. Demographics and clinical characteristics of culprit and non-culprit patients were also collected. Apparent differences between the two groups, which could be used as biomarkers for ischemic event caused by the culprit dissection, were identified by receiver operating characteristic (ROC) curve analysis. Results: The IAD patients studied could be classified into five different types on the basis of morphological features: classical dissection (n = 31), fusiform aneurysm (n = 2), long dissected aneurysm (n = 9), dolichoectatic dissecting aneurysm (n = 6), and saccular aneurysm (n = 22). The direct sites of artery dissection (double lumen and intimal flap) can be seen in most IAD patients on HR-MRI. Additionally, the presence of hypertension, double lumen and intimal flap were associated with culprit lesions and might be considered biomarkers for the ischemic event caused by the culprit dissection. Conclusions: Analysis showed that HR-MRI allowed easy visualization of abnormal morphology of artery dissection lesions. This was of great significance for the diagnosis of IAD and gave a better understanding of its pathophysiological mechanism. [ABSTRACT FROM AUTHOR]

We consider non-autonomous ordinary differential equations in two cases. One is the one-dimensional case that admits a condition of hyperbolicity, and the other one is the higher-dimensional case that admits an exponential dichotomy. For differential equations of this kind, we give a rigorous treatment of the Harmonic Balance Method to look for almost periodic solutions. [ABSTRACT FROM AUTHOR]

Unhealthy diet, in particular high-fat diet (HFD) intake, can cause the development of several metabolic disorders, including obesity, hyperlipidemia, type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), and metabolic syndrome (MetS). These popular metabolic diseases reduce the quality of life, and induce premature death worldwide. Evidence is accumulating that the gut microbiota is inextricably associated with HFD-induced metabolic disorders, and dietary intervention of gut microbiota is an effective therapeutic strategy for these metabolic dysfunctions. Polysaccharides are polymeric carbohydrate macromolecules and sources of fermentable dietary fiber that exhibit biological activities in the prevention and treatment of HFD-induced metabolic diseases. Of note, natural polysaccharides are among the most potent modulators of the gut microbiota composition. However, the prebiotics-like effects of polysaccharides in treating HFD-induced metabolic diseases remain elusive. In this review, we introduce the critical role of gut microbiota human health and HFD-induced metabolic disorders. Importantly, we review current knowledge about the role of natural polysaccharides in improving HFD-induced metabolic diseases by regulating gut microbiota. [ABSTRACT FROM AUTHOR]

Herein, we report the H2O2‐mediated synthesis of 1,2,4‐thiadiazole derivatives under metal‐free conditions at room temperature with ethanol as the sole solvent. Various substrates could undergo the reaction smoothly, providing the expected yields of the desired products. Moreover, the target products were obtained by filtration or extraction instead of column chromatography, which requires a large amount of organic solution and silica gel during purification. The developed synthetic method can be potentially applied in the large‐scale preparation of 1,2,4‐thiadiazole derivatives as agrochemicals, pharmaceuticals, and functional materials. [ABSTRACT FROM AUTHOR]

In this paper, for a discontinuous skew-product transformation with the integrable observation function, we obtain uniform ergodic theorem and semi-uniform ergodic theorem. The main assumptions are that discontinuity sets of transformation and observation function are ignorable in some measure-theoretical sense. The theorems extend the classical results which have been established for continuous transformations and continuous observation functions. [ABSTRACT FROM AUTHOR]

The change of fatty acid composition has been regarded as an indicator of altered lipid metabolism during human tumourigenesis, but the details are still unclear. We have previously demonstrated a monounsaturated fatty acid (MUFA) named oleic acid (OA) was involved in renal cell carcinoma (RCC) cell growth, as an extracellular signaling molecule to regulate 786-O cell proliferation via the integrin-linked kinase (ILK) pathway. In this study, we further observe the effects of OA on cell invasion of RCC and the potential mechanism by which OA worked was determined. The transwell invasion assay showed OA increased cell invasion of RCC in a dose-dependent manner. Western blotting results indicated ILK, COX-2, and MMP-9 proteins were involved for their high expressions and these effects were reversed when down-regulating the expression of ILK by special siRNA. The MMPs inhibitor GM6001 could weaken the abilities of OA on RCC cells invasion. These results suggested MUFA indeed affected cell invasion of RCC, which was depended by the regulation of ILK pathway. [ABSTRACT FROM AUTHOR]

Under the condition that the damping factor is between zero and one, chaotic dynamics is proved to exist in one-dimensional transiently chaotic neural networks by Li-Misiurewicz theorem. This result extends the previous result which is done under the condition that the damping factor is zero. Because the value of damping factor affects the speed of dynamical process of transiently chaotic neural networks, this result provides more complete theoretical basis for applications. Finally, two examples by numerical simulation are given to reinforce and illustrate this result. [ABSTRACT FROM AUTHOR]

The structural behavior during the first reservoir-filling phase is significant for evaluating a super high arch dam's safety. This paper presents an in situ monitoring network of the Xiluodu Dam in Yunnan, China, including a deformation monitoring system using geodetic and nongeodetic monitoring. The system also includes a refined thermal monitoring system based on a slab-level active cooling system. The thermal--structural decoupling numerical analysis method for a dam--water--foundation system is presented in this study with considerations of viscoelasticity material properties and internal/external thermal loads. The structural behavior of the Xiluodu Dam during the first reservoir-filling phase is analyzed using the smart monitoring system with combination of the in situ monitoring technique and the numerical simulation method. The in situ monitoring result can provide intuitional instructions of the structural behavior, showing a positive correlation between the dam deformation and the reservoir water level. The monitoring results are also used as the verification reference of the numerical model. The distribution characteristics of the displacement and stress of the dam subjected to load cases such as nonimpounding, impounding process, and the normal operating water level are discussed and predicted. [ABSTRACT FROM AUTHOR]

Knowledge of the concrete temperature of a dam is necessary for the implementation of improved construction methodologies. A monitoring-mining-modeling system is proposed in this article to study the thermal state of a super high arch dam in China. The monitoring-mining-modeling system includes an in situ monitoring network setup, data mining methods, and numerical finite element analysis. Two engineering cases are surveyed in detail using monitoring-mining-modeling system. The first case is the long-term temperature rise phenomenon, whose cause is determined from the data mining result, and the numerical modeling of the external boundary condition is improved using the result. The modeling result then shows that the effect of the TRP is also a dangerous factor for the deformation and stress state of the dam. The second case is the performance of cooling pipes. The energy absorption capability of the cooling pipes is revealed by the data mining result, as well as the performance difference between high-density polyethylene and iron pipes. The numerical modeling result shows good agreement with the monitored result, which demonstrates the closed-loop validity of the monitoring-mining-modeling system. [ABSTRACT FROM AUTHOR]

This paper analyzes a mathematical model of the photosynthetic carbon metabolism, which incorporates not only the Calvin-Benson cycle, but also another two important metabolic pathways: starch synthesis and photorespiratory pathway. Theoretically, the paper shows the existence of steady states, stability and instability of the steady states, the effects of CO concentration on steady states. Especially, a critical point is found, the system has only one steady state with CO concentration in the left neighborhood of the critical point, but has two with CO concentration in the right neighborhood. In addition, the paper also explores the influence of CO concentration on the efficiency of photosynthesis. These theoretical results not only provide insight to the kinetic behaviors of the photosynthetic carbon metabolism, but also can be used to help improving the efficiency of photosynthesis in plants. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850-900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes. [ABSTRACT FROM AUTHOR]

Van der Waals materials have received a great deal of attention for their exceptional layered structures and exotic properties, which can open up various device applications in nanoelectronics. However, in situ epitaxial growth of dissimilar van der Waals materials remains challenging. Here we demonstrate a solution for fabricating van der Waals heterostructures. Graphene/hexagonal boron nitride (h-BN) heterostructures were synthesized on cobalt substrates by using molecular beam epitaxy. Various characterizations were carried out to evaluate the heterostructures. Wafer-scale heterostructures consisting of single-layer/bilayer graphene and multilayer h-BN were achieved. The mismatch angle between graphene and h-BN is below 1°. [ABSTRACT FROM AUTHOR]

Nitrogen-doped Mg0.12Zn0.88O nanocrystalline thin film was grown on c-plane sapphire substrate. Asymmetric Ni/Au and Ti/Au Schottky contacts and symmetric Ni/Au contacts were deposited on the thin film to form metal-semiconductor-metal (MSM) laser devices. Current-voltage, photocurrent, and electroluminescence characterizations were performed. Evident random lasing with a threshold current of ~36mA is demonstrated only from the asymmetric MSM device. Random lasing peaks are mostly distributed between 340 and 360 nm and an output power of 15nW is measured at 43mA injection current. The electron affinity difference between the contact metal and Mg0.12Zn0.88O:N layer plays an important role for electron and hole injection and subsequent stimulated random lasing. [ABSTRACT FROM AUTHOR]

This paper investigates the methodologies for locating and identifying components on a printed circuit board (PCB) used for surface mount device inspection. It's the foundation of other inspections, such as solder joint inspection, component type recognization and so on. The proposed scheme consists of two stages: solder joint extraction and protective coating extraction. This work uses automatic multilevel thresholding approach for detecting specular areas which contain solder joints. Some invalid specular areas, such as markings and via-holes are recognized and removed by comparing the colour distribution features of the target objects and the reference objects. A novel approach based on connection graph and the segmented gray-scale PCB images is developed to classify all recognized solder joints as several clusters. And then, the protective coating is extracted by the positions of the clustered solder joints. Experimental results show that the proposed method can recognize most of components effectively. [ABSTRACT FROM AUTHOR]

In this paper, we discuss a simplified model of mitosis in frog eggs proposed by M. T. Borisuk and J. J. Tyson in [1]. By using rigorous qualitative analysis, we prove the existence of the periodic solutions on a large scale and present the space region of the periodic solutions and the parameter region coresponding to the periodic solution. We also present the space region and the parameter region where there are no periodic solutions. The results are in accordance with the numerical results in [1] up to the qualitative property. [ABSTRACT FROM AUTHOR]

An electrically pumped nitrogen doped p-type ZnO nanowires/undoped n-type ZnO thin film homojunction random laser with a 10-period SiO2/SiNx distributed Bragg reflector is demonstrated. The formation of p-n homojunction is confirmed by the current-voltage and photocurrent characteristics. The random lasing behaviors with a low threshold of around 3mA are observed. The output power is measured to be 220 nW at a drive current of 16 mA. [ABSTRACT FROM AUTHOR]