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In this paper, we discuss the synergy of K–Ca in improving the removal efficiency of NO-NO2 by g-C3N4 in detail. The K–Ca modified g-C3N4 (GKXCY, GKC-Z) with varied K/Ca ratio and different dosage of K/Ca were prepared by a one-step thermal polymerization, and the pure g-C3N4 and K/Ca single modified g-C3N4 (GK-X, GC-Y) were taken as control index. The toxicity of NOX was adopt to evaluate the photocatalytic activity, and XRD, SEM, TEM, FT-IR, XPS, UV–Vis, PL and In-situ DRIFTS were taken to characterize the crystal phase, micromorphology, optical characteristics and NO degradation pathway. The results demonstrate that the by-product CaCO3 produced from calcium salt can improve the chemisorption ratio of g-C3N4 to NO-NO2. K–Ca co-doping can synergistically enhance the oxidation activity of g-C3N4 to NO-NO2. From the results, the sample GK0.1C0.4 was endowed with the best NOx degradation activity through K–Ca co-doping which can dramatically decrease the toxicity of NOX from 1 to 0.706 within 30 min. [ABSTRACT FROM AUTHOR]

In this paper, the mean-square asymptotic stability problem is investigated for the fractional-order nonlinear stochastic dynamic system in Hilbert space. First, a set of sufficient stability conditions based on the Mittag–Leffler function is established to achieve the mean-square asymptotic stability of the system under the Lipschitz condition and linear growth condition, respectively. Next, the convergence analysis of the closed-loop system is finished by directly utilizing the properties of the integral solution and Mittag–Leffler function. Furthermore, in Euclidean space, the mean-square asymptotic stability problem is addressed for the fractional-order nonlinear stochastic dynamic system, in which sufficient stability conditions are given based on the eigenvalues of the matrix operator. Finally, two numerical examples are performed to verify the correctness of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene and xylenes) are considered as hazardous air pollutants in urban environment. The aim of this study was to measure BTEX concentration, analyze the ozone and secondary organic aerosol formation potentials of BTEX and assess its health risks for the first time in the Guangzhong Plain (GZP). BTEX samples were collected continuously in five cities in GZP using the gas chromatography-hydrogen flame ionization/mass spectrometry analysis system, from September 2017 to January 2018. Results showed that the average BTEX level was higher in autumn (50.16 ± 31.84 µg m−3) than in winter (15.08 ± 19.49 µg m−3) in GZP. Diurnal variation of BTEX exhibited higher values in nighttime (20:00–7:00) than that in daytime (8:00–19:00). Vehicle emission was the predominant source of BTEX; biomass, biofuels and coal burning can affect BTEX concentration in winter. The total ozone formation potential (OFP) of BTEX was 219.19 ± 155.79 µg m−3 in autumn and 64.78 ± 91.73 µg m−3 in winter with maximum potential by toluene. Toluene and xylenes contributed 81.58% and 77.18% of the total secondary organic aerosol formation potentials (SOAFP) in autumn and in winter, respectively. The value of HQ at five urban sites was < 1 indicating the non-carcinogenic risk is negligible for people residing near these areas. The lifetime cancer risk (LTCR) value of benzene inhalation (1.54 × 10−5–3.05 × 10−5) in GZP in autumn was higher than 1.0 × 10−6, representing a probable cancer risk. Much effort is required to control regional BTEX levels and mitigate their impact on environment and human health. [ABSTRACT FROM AUTHOR]

The prediction and control of COVID-19 is critical for ending this pandemic. In this paper, a nonlocal SIHRDP (S-susceptible class, I-infective class (infected but not hospitalized), H-hospitalized class, R-recovered class, D-death class and P-isolated class) epidemic model with long memory is proposed to describe the multi-wave peaks for the spread of COVID-19. Based on the basic reproduction number R 0 , which is completely controlled by fractional order, the stability of the proposed system is studied. Furthermore, the numerical simulation is conducted to gauge the performance of the proposed model. The results on Hunan, China, reveal that R 0 < 1 suggests that the disease-free equilibrium point is globally asymptotically stable. Likewise, the situation of the multi-peak case in China is presented, and it is clear that the nonlocal epidemic system has a superior fitting effect than the classical model. Finally an adaptive impulsive vaccination is introduced based on the proposed system. Then employing the real data of France, India, the USA and Argentina, parameters identification and short-term forecasts are carried out to verify the effectiveness of the proposed model in describing the case of multiple peaks. Moreover, the implementation of vaccine control is expected once the hospitalized population exceeds 20 % of the total population. Numerical results of France, Indian, the USA and Argentina shed light on the varied effect of vaccine control in different countries. According to the vaccine control imposed on France, no obvious effect is observed even consider reducing human contact. As for India, although there will be a temporary increase in hospitalized admissions after execution of vaccination control, COVID-19 will eventually disappear. Results on the USA have seen most significant effect of vaccine control, the number of hospitalized individuals drops off and the disease is eventually eradicated. In contrast to the USA, vaccine control in Argentina has also been very effective, but COVID-19 cannot be completely eradicated. [ABSTRACT FROM AUTHOR]

Size, morphology, and composition of airborne particles strongly affect human health and visibility, precipitation, and the kinetic characteristics of particles. In this study, the morphology and chemical composition of particles emitted from conventional (diesel and gasoline) and alternative (CNG and methanol) fuel vehicles were characterized through scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The SEM images revealed that the size of primary particles (without agglomeration) was approximately 10 nm in the exhaust from all the tested vehicles. The particles emitted from gasoline vehicle (GV), CNG vehicle (CNGV), and methanol vehicle (MV) had the same median diameter, 62 nm, which was smaller than those from heavy diesel vehicle (HDV) and light diesel vehicle (LDV). Soot was observed in the HDV, LDV, and GV samples but not in the CNGV and MV. The fractal dimension, which was used to quantify the degree of irregularity of soot, was 1.752 ± 0.014, 1.789 ± 0.076, and 1.769 ± 0.006 in the exhaust from HDV, LDV, and GV samples, respectively. The particles discharged by all tested vehicles contained the elements C, O, Fe, and Na. The main element in the samples of HDV, LDV, and GV was C, while O was the main element in the samples of alternative fuel vehicles. The profiles of minor elements were more complex in the emissions of alternative fuel vehicles than those in the emissions of conventional fuel vehicles. The results improved our understanding of the morphology and elemental composition of particles emitted from vehicles powered by diesel, gasoline, CNG, and methanol. [ABSTRACT FROM AUTHOR]

Alternative-fueled vehicles have been introduced to solve the problem of the energy crisis and address air pollution. However, typical pollutants (e.g., methane and methanol) are emitted through combustion of the alternative fuel. In this study, the concentrations of regulated pollutants (CO, NO) and unregulated pollutants (CH4, methanol, formaldehyde, and 8 NMHC species) in the exhaust from methanol, CNG, and gasoline-fueled vehicles (MV, NGV, and GV) were measured systematically on a chassis dynamometer during an in-use vehicle driving cycle. The emission factors of these gaseous pollutants were calculated, and the ozone formation potential (OFP) of each ozone precursor measured in this work was evaluated with the MIR scale. The results showed that NO and NMHC species exhausted from the MV and NGV decreased significantly than that from the GV. However, the unburned pollutants exhausted from MV and NGV warrant attention. For the OFPs, CO was the largest contributor for all tested vehicles. Formaldehyde was ranked the second for the MV and NGV. Among the tested vehicles, the OFPs of NGV were the lowest. The results are helpful in quantitating analysis of the vehicle emissions and evaluating the impacts of alternative-fueled vehicles on atmospheric environment. [ABSTRACT FROM AUTHOR]

In this paper, a generalized fractional-order SEIR model is proposed, denoted by SEIQRP model, which divided the population into susceptible, exposed, infectious, quarantined, recovered and insusceptible individuals and has a basic guiding significance for the prediction of the possible outbreak of infectious diseases like the coronavirus disease in 2019 (COVID-19) and other insect diseases in the future. Firstly, some qualitative properties of the model are analyzed. The basic reproduction number R 0 is derived. When R 0 < 1 , the disease-free equilibrium point is unique and locally asymptotically stable. When R 0 > 1 , the endemic equilibrium point is also unique. Furthermore, some conditions are established to ensure the local asymptotic stability of disease-free and endemic equilibrium points. The trend of COVID-19 spread in the USA is predicted. Considering the influence of the individual behavior and government mitigation measurement, a modified SEIQRP model is proposed, defined as SEIQRPD model, which is divided the population into susceptible, exposed, infectious, quarantined, recovered, insusceptible and dead individuals. According to the real data of the USA, it is found that our improved model has a better prediction ability for the epidemic trend in the next two weeks. Hence, the epidemic trend of the USA in the next two weeks is investigated, and the peak of isolated cases is predicted. The modified SEIQRP model successfully capture the development process of COVID-19, which provides an important reference for understanding the trend of the outbreak. [ABSTRACT FROM AUTHOR]

In the end of 2019, a new type of coronavirus first appeared in Wuhan. Through the real-data of COVID-19 from January 23 to March 18, 2020, this paper proposes a fractional SEIHDR model based on the coupling effect of inter-city networks. At the same time, the proposed model considers the mortality rates (exposure, infection and hospitalization) and the infectivity of individuals during the incubation period. By applying the least squares method and prediction-correction method, the proposed system is fitted and predicted based on the real-data from January 23 to March 18 - m where m represents predict days. Compared with the integer system, the non-network fractional model has been verified and can better fit the data of Beijing, Shanghai, Wuhan and Huanggang. Compared with the no-network case, results show that the proposed system with inter-city network may not be able to better describe the spread of disease in China due to the lock and isolation measures, but this may have a significant impact on countries that has no closure measures. Meanwhile, the proposed model is more suitable for the data of Japan, the USA from January 22 and February 1 to April 16 and Italy from February 24 to March 31. Then, the proposed fractional model can also predict the peak of diagnosis. Furthermore, the existence, uniqueness and boundedness of a nonnegative solution are considered in the proposed system. Afterward, the disease-free equilibrium point is locally asymptotically stable when the basic reproduction number R 0 ≤ 1 , which provide a theoretical basis for the future control of COVID-19. [ABSTRACT FROM AUTHOR]

To investigate the genetic diversity, spatiotemporal dynamics, and transmission networks of HIV-1 CRF55_01B epidemic in China. A total of 209 partial pol gene sequences of HIV-1 CRF55_01B were sampled during 2007–2015 from 7 provinces of China. Phylogenetic analyses and trait diffusion process of these sequences were performed using Bayesian methods. Distance-based molecular network analyses were performed to infer putative relationships. Characteristics of genetically linked individuals were analyzed. Our study identified that HIV-1 CRF55_01B likely originated among men who have sex with men (MSM) in Guangdong province in January 2003 (April 2000–April 2005), and that Guangdong province and MSM are major hubs for the spread of the HIV-1 CRF55_01B epidemic in China. A Bayesian Skygrid plot revealed that the effective population size of HIV-1 CRF55_01B experienced increased phase followed by a plateau. All sequences from persons of unknown risk clustered within groups who reported MSM risk. This could be because Chinese MSM may not report such risk due to HIV/AIDS-related stigmatization and discrimination. This study inferred the transmission dynamics of the HIV-1 CRF55_01B epidemic in China at high resolution. The methods developed in this study may be critical for designing effective HIV prevention strategies in China and beyond. [ABSTRACT FROM AUTHOR]

The methionine adenosyltransferase 2β gene (Mat2b) encodes for the regulatory subunit of methionine adenosyltransferase (MAT), which catalyzes the biosynthesis of S-adenosylmethionine. MAT2B interacts with G protein-coupled receptor kinase interacting ArfGAP1 to increase the activity of extracellular signal-regulated kinases (ERKs) for the regulation of cell growth, metabolism, and differentiation. ERK activity is also essential for oocyte meiosis in mice. However, the regulatory role of MAT2B in mouse oocyte meiosis remains unclear. Accordingly, this study investigated the effect of MAT2B on mouse oocyte maturation. Immunostaining showed that MAT2B localized predominantly in the nucleus of fully grown germinal vesicle (GV) oocytes. After germinal vesicle breakdown (GVBD), MAT2B homogeneously localized in the cytoplasm. A low oocyte maturation rate was observed in Mat2b siRNA-treated oocytes. Furthermore, Mat2b knockdown repressed the phosphorylation of ERK1/2 and consequently blocked MAPK. Denuded oocytes treated with 20 μM U0126 mainly blocked MAPK phosphorylation and affected oocyte maturation. The oocytes arrested at GVBD and metaphase I (MI) by Mat2b silencing or U0126 treatment had several types of abnormal microtubule assembly. Furthermore, Mat2b knockdown or U0126 treatment resulted in the aberrant expression of six maternal transcripts, namely, Fgf8, Cdc2, Gdf9, Padi6, Polr2d, and Tecb2. To the best of our knowledge, this study is the first to demonstrate that Mat2bs play an important role in mouse oocyte maturation though MAPK signaling. [ABSTRACT FROM AUTHOR]

In view of the serious adhering failure of cemented carbide inserts during the heavy-duty cutting of water chamber head, the adhering failure mechanism of inserts and the element diffusion model of the adhering process were investigated. First, based on cutting simulations, the cutting force was found to be as high as 45.2 kN while the maximum cutting temperature was 930 °C. Under the combined action of mechanical and thermal loads, element diffusion occurred between insert and workpiece and formed an adhering layer, resulting in the adhering failure of inserts. After that, the element diffusion dynamics equation of the adhering process was proposed according to Fick's law. Based on the semi-infinite long-bar diffusion model and its initial conditions and boundary conditions, the dynamics equation was solved, with the element diffusion concentration model obtained. In the end, the experimental scheme of element diffusion was put forward, and the element diffusion between the cemented carbide insert and workpiece at elevated temperatures was experimentally investigated. The diffusion distance of Co in 508III steel was measured as 8 μm. The element diffusion concentration within the diffusion distance was compared with the value predicted by the model, with the effectiveness of the element diffusion model validated. The concentration distribution of diffusing elements in the diffusion cross section was characterized through experiments and compared with the theoretical concentration distribution. The research results can provide a basis for the in-depth study of the formation mechanism of insert-chip adhering layers and their influence on the cutting performance and service life of inserts. [ABSTRACT FROM AUTHOR]

We report a facile approach for the fabrication of a new class of graphene oxide (GO)-based nanoassemblies by layer-by-layer (LbL) technique. The single-layer thickness and intrinsic negatively charged carboxyl groups of GO nanosheets provide a natural platform for LbL assembly of polyelectrolyte nanofilms by electrostatic forces at mild and aqueous conditions. The general applicability of our approach is demonstrated by the preparation of GO nanoassemblies with sizes of 100-200 nm using various charged polyelectrolytes, including synthetic polymers, polypeptides, and DNA oligonucleotides. Systemic assessment of cytotoxicity and acute stress response show that no discernable signs of cytotoxicity are associated with exposure of GO and its nanoassemblies [GO/PLL (poly ( l-lysine)), GO/PLL/PSS (poly(sodium-4-styrenesulfonate)), GO/PLL-PEG (PEGlayted PLL), GO/PLL/PLGA-PEG (PEGlayted poly ( l-glutamic acid))] up to 1 μg/mL. Studies on cellular uptake and subcellular localization show that a representative nanoassembly, GO/PLL-PEG, can effectively cross cell membranes and localize mainly in lysosomal compartments, without induction of noticeable harmful effects as confirmed by detection of mitochondrial depolarization and lysosomal pH. [ABSTRACT FROM AUTHOR]

We have modified a glassy carbon electrode by single-step electrodeposition of graphene (GR), gold nanoparticles (AgNPs), and chitosan (CS) directly from a solution containing graphene oxide, tetrachloroauric acid, and chitosan. The surface and electrochemical properties of the film-modified electrode were investigated by SEM and TEM images. The AuNPs have a diameter of about 20 nm and are uniformly dispersed in the matrix. Combining the advantages of GR (i.e., high surface area and conductivity), of AuNPs (excellent electrical conductivity) and CS (excellent film-forming ability and good water permeability), the hybrid film effectively enhances electron-transfer and promotes the response to lead(II) ion. Under the optimum conditions, a linear relationship exists between electrical current and the concentration of lead (II) ion in the range between 0.5 to 100 μg L-1, with a detection limit of 1 ng L-1 (at an SNR of 3). The electrode was successfully applied to the detection of lead(II) in spiked samples of river water. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have electrodeposited a composite film consisting of graphene oxide, chitosan and glucose oxidase directly on a glassy carbon electrode (GCE) through electrochemical reduction of a solution of the 3 components under controlled direct electrical potential. The procedure takes only several minutes, and the thickness of the resulting film is uniform and controllable. The GOx has uncompromised bioactivity and exhibits reversible 2-proton and 2-electron transfer in presence of glucose. It therefore can be used amperometric sensing of glucose. The biosensor has a fast response (<3 s), a detection limit of 0.4 μM (which is 50-fold lower compared to the biosensor prepared by drop-casting solutions of the same materials onto an GCE), and a linear response in the 0.4 μM to 2 mM concentration range (which again is much better than that of the biosensor prepared by the drop-casting method). Other features include high reproducibility, long-time storage stability, and satisfactory selectivity. We presume that the direct single-step electrodeposition of this nanocomposite offers a promising approach towards novel types of highly sensitive and stable electrochemical biosensors. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]