Search Results (28)

While significant progress has been made in controlling point source pollution, agricultural non-point source pollution (AGNPSP) has emerged as a major contributor to global water pollution, posing a severe threat to ecological quality. According to China’s Second National Pollution Source Census, AGNPSP constitutes a substantial proportion of water pollution, making its mitigation a critical challenge. Identifying AGNPSP risk zones is essential for targeted management and effective intervention. This study focuses on Yongchuan District, a representative hilly–mountainous area in the Yangtze River Basin. Applying the landscape ecology “source–sink” theory, we selected seven natural factors influencing AGNPSP and constructed a minimum cumulative resistance model using remote sensing post-processing data. An attempt was made to classify the “source” and “sink” landscapes, and ultimately conduct a risk assessment of AGNPSP in Yongchuan District, identifying the key areas for AGNPSP control. Key findings include: 1. Vegetation coverage is the most significant natural factor affecting AGNPSP. 2. Extremely high- and high-risk zones cover 90% of Yongchuan, primarily concentrated in the central and southern regions, indicating severe AGNPSP pressure that demands urgent management. 3. The levels of ammonia nitrogen and total phosphorus in the typical sections are related to the risk levels of the corresponding sections. Consequently, the risk level of AGNPSP directly correlates with the pollutant concentrations measured in the sections. This study provides a robust scientific basis for AGNPSP risk assessment and targeted control strategies, offering valuable insights for pollution management in Yongchuan and similar regions. Full article

This paper investigates a backward stochastic linear quadratic control problem with an expected-type equality constraint on the initial state. By using the Lagrange multiplier method, the problem with a uniformly convex cost functional is first transformed into an equivalent unconstrained parameterized backward stochastic linear quadratic control problem. Then, under the surjectivity of the linear constraint, the equivalence between the original problem and the dual problem is proven by Lagrange duality theory. Subsequently, with the help of the maximum principle, an explicit solution of the optimal control for the unconstrained problem is obtained. This solution is feedback-based and determined by an adjoint stochastic differential equation, a Riccati-type ordinary differential equation, a backward stochastic differential equation, and an equality, thereby yielding the optimal control for the original problem. Finally, an optimal control for an investment portfolio problem with an expected-type equality constraint on the initial state is explicitly provided. Full article

Cinnamomum cassia has been extensively utilized in traditional medicine systems worldwide. The essential oil (EO) content and composition are influenced by various external and internal factors, such as climate and harvest season, making it vital to determine the optimal harvest period for high-quality EO production. This study is the first to evaluate the chemical profiles, as well as the antioxidant and antibacterial activities, of C. cassia leaf oil across the four seasons. GC–MS and FTIR analyses revealed significant seasonal variations in the components. Spring and autumn leaf oils contained the highest EO (2.20% and 1.95%, respectively) and trans-cinnamaldehyde (92.59% and 91.10%, respectively). Temperature and humidity primarily affected EO and trans-cinnamaldehyde accumulation. C. cassia leaf oil demonstrated the strongest antibacterial activity, with a minimum inhibitory concentration (MIC) of 0.25 mg/mL against S. aureus and L. monocytogenes for the spring oil. The MICs for the other three seasonal samples were 0.5 mg/mL for S. aureus, M. luteus, and L. monocytogenes, and 1.0 mg/mL for P. putida. The minimum bactericidal concentration (MBC) of the EOs across all seasons against S. aureus ranged from 0.5 to 1 mg/mL. Winter leaf oil exhibited high antioxidant activity, primarily due to the presence of cis-cinnamaldehyde, caryophyllene, humulene, alloaromadendrene, γ-muurolene, cis-bisabolene, o-methoxycinnamaldehyde, and phenolics. This study provides essential data and valuable references for optimizing resource utilization and determining the ideal harvest time for C. cassia leaves. Full article

Citric acid is an important organic acid with wide applications and diverse biological functionality. As the predominant organic acid in lemons, citric acid plays a crucial role in determining the flavor of citrus, especially in lemons. ATP citrate lyase (ACL, EC4.1.3.8) is the keg gene in citric acid metabolism. Several research studies on ACL only focused on high-sugar- and low-acid-content citrus varieties; however, the ACL mechanism in lemons with high acid and low sugar levels remains undetermined. In this study, a key candidate gene, ClACLB-1, for citrate cleavage was identified from the genome data of ‘Xiangshui’ lemon [Citrus limon (L.) Burm f.]. The putative protein coded by the gene ClACLB-1 is localized in the nuclear and cell membranes. The ClACLB-1 gene was expressed in all tissues, with the highest expression in male flowers and the lowest expression in mature fruits; the expression decreased during lemon fruit development. The overexpression of ClACLB-1 in transgenic tomatoes significantly increases the activity of citrate lyase, which subsequently reduces citric acid content. This study clarified the function of the ClACLB-1 gene in cleaving citric acid, provided new insights into the citric acid metabolism of citrus, and offered a theoretical reference for reducing acid and increasing sugar in citrus to improve fruit quality. It also helped to enhance the understanding of the metabolism and role of citrate in plants. Full article

In this paper, the problem of preview optimal control for second-order nonlinear systems for marine vessels is discussed on a fully actuated dynamic model. First, starting from a kinematic and dynamic model of a three-degrees-of-freedom (DOF) marine vessel, we derive a fully actuated second-order dynamic model that involves only the ship’s position and yaw angle. Subsequently, through the higher-order systems methodology, the nonlinear terms in the system were eliminated, transforming the system into a one-order parameterized linear system. Next, we designed an internal model compensator for the reference signal and constructed a new augmented error system based on this compensator. Then, using optimal control theory, we designed the optimal preview controller for the parameterized linear system and the corresponding feedback parameter matrices, which led to the preview controller for the original second-order nonlinear system. Finally, a numerical simulation indicates that the controller designed in this paper is highly effective. Full article

Industrial solid waste is characterized by complex mineral phases and various components. Low-carbon cementitious materials can be prepared through precise regulation based on the material composition and properties of various industrial solid wastes. In this study, electrolytic manganese residue (EMR), carbide slag (CS), and granulated blast-furnace slag (GBFS) were used as alternatives to cement to prepare multicomponent solid waste cementitious materials. The effects of the proportions of EMR and CS on the cementitious activity of GBFS and the activation mechanism of alkali and sulfur were studied. The results showed that with increasing EMR content, the strength first increased and then decreased. At a GBFS content of 20%, CS content of 2%, and EMR content of 8%, the compressive strength was highest, reaching 45.5 MPa after 28 days of curing, mainly because the OH⁻ in CS and SO₄²⁻ in EMR synergistically stimulated the active components in GBFS. Hydrated products such as ettringite and hydrated calcium silicate (C–S–H gel) were generated and interlaced with each other to improve the densification of the mortar. Overall, the proposed system provides an avenue to reduce or replace the production of cement clinker and achieve the high-value-added utilization of industrial solid waste. Full article

Understanding the mechanism of mode-locking in a laser with high-order transverse mode is important for achieving an ultrashort pulses train under more complicated conditions. So far, mode-locking with high-order transverse mode has not been reported in other lasers except the multimode fiber laser. This paper demonstrates robust mode-locking with high-order transverse mode in a Kerr-lens mode-locked vertical-external-cavity surface-emitting laser for the first time, to the best of our knowledge. While the longitudinal modes are locked, continuous mode-locking accompanied by high-order transverse mode up to TEM₄₀ is observed. The threshold of the mode-locking is only a little bigger than that of the lasing. After the laser oscillation is built up, the mode-locked pulse train can be obtained almost immediately and maintained until the thermal rollover of the laser. Output powers of 717 mW under fundamental mode and 666 mW under high-order transverse mode are achieved with a 4.3 ps pulse duration and 1.1 GHz pulses repetition rate, and some phenomenological explanations to the related characteristics of the mode-locked operation of high-order transverse mode in the vertical-external-cavity surface-emitting laser are proposed. Full article

Advanced light sources in the blue-green band are crucial for underwater wireless optical communication (UWOC) systems. Vertical-external-cavity surface-emitting lasers (VECSELs) can produce high output power and good beam quality, making them suitable for UWOC. This paper presents a 108 m distance UWOC based on a 100 mW 490 nm blue VECSEL and an acousto-optic modulator (AOM). The high-quality beam, which is near diffraction-limited, undergoes relatively small optical attenuation when using a conventional avalanche photodiode (APD) as the detector and employing 64-pulse position modulation (PPM). At the time-slot frequency of 50 MHz, the bit error rate (BER) of the UWOC was 2.7 × 10⁻⁵. This is the first reported AOM-based UWOC system with a transmission distance over 100 m. The estimated maximum transmission distance may be improved to about 180 m by fully utilizing the detection accuracy of the APD according to the measured attenuation coefficient of the blue VECSEL used. This type of UWOC system, composed of a high-beam-quality light source and a conventional detector, make it more closely suited to practical applications. Full article

According to Bronfenbrenner’s ecological theory, the interaction between micro- and macro-factors improves human development. Previous studies suggest that community social capital, which refers to the interaction between residents and communities, promotes the subjective well-being of residents in residential communities. However, little is known about the mechanisms underlying this relationship. This study explored the link between community social capital and life satisfaction among urban residents and examined the mediating role of psychological flourishing and moderating effect of educational level. Data were obtained from a cross-community survey of 816 urban residents in China aged 20–60 years. The results indicated that psychological flourishing mediated the link between community social capital and life satisfaction among urban residents after controlling for gender, age, marital status, dwelling time, and monthly income. Furthermore, educational attainment moderated the association between community social capital and psychological flourishing. The mediating effect of psychological flourishing was stronger among residents with low educational attainment than those with high educational attainment, indicating that the benefits of community social capital were greater among the former group. This study extends our knowledge of the effect of community social capital on urban residents’ subjective well-being, including its role in reducing educational inequality in human well-being. Full article

The inherent characteristics of cellulose-derived aerogels, such as their natural abundance and environmental friendliness, make them highly interesting. However, its significant shrinkage before and after the supercritical drying procedure and low mechanical strength limit its potential application. Here, we propose a strategy to prepare cellulose diacetate aerogels (CDAAs) with low drying shrinkage, exceptional thermal insulation, and superior mechanical strength. The low drying shrinkage (radial drying shrinkage of 1.4%) of CDAAs is attributed to their relative strong networking skeletons, which are greatly formed by tert-butanol solvent exchange in exerting the interaction of reducing the surface tension force. In this case, CDAAs are eventually endowed with the low bulk density of 0.069 g cm⁻³ as well. Additionally, as-prepared CDAAs possess an abundant three-dimensional networking structure whose pore size is concentrated in the diameter range of ~50 nm, and the result above is beneficial for improving the thermal insulation performance (thermal conductivity of 0.021 W m⁻¹ K⁻¹ at ambient environmental and pressure conditions). On the other hand, the optimal compressive stresses of CDAAs at 3% and 5% strain are 0.22 and 0.27 MPa respectively, indicating a mechanically well robustness. The above evidence demonstrates indeed the exceptional thermal insulation and superior compressive properties of CDAAs. This work may provide a new solution for developing a kind of high-performance cellulose-derived aerogel in the future. Full article

Amantadine (AMD) is an antiviral drug that is prohibited for use in livestock and poultry. In this study, carboxyl-modified magnetic nanoparticles (MNPs) were synthesized using the solvothermal method in one step with harmless and inexpensive regents, and they were used to label monoclonal antibodies (mAbs) of AMD in microwells with electrostatic adsorption. Then, a magnetic immunochromatography assay (MICA) method was successfully established. Under optimal conditions, the MICA showed a good performance, with a linear range of 0.2~10.0 µg/L. The limit of detection (LOD) was 0.068 µg/L with the instrument, and the visual LOD (vLOD) was 0.5 µg/L. There was no cross-reaction with rimantadine and ribavirin. The vLOD in real samples was 1.0 µg/kg. The developed MICA has the advantages of convenience, speed, and sensitivity, which make it suitable for the on-site rapid detection of AMD residues in chicken tissues and eggs. Full article

A structural landform is defined by its surface morphology, controlled by tectonics, lithology (arrangement and resistance), and folded structures, and demonstrated by the characteristics and relationships between geological and geomorphic elements. It is very important to use geographic information system (GIS) technology to accurately describe and express elements of structural landforms and their relationships. In this study, a GIS approach for expressing structural landforms, based on “forms–elements–relationships”, was developed. The contributions of this paper are as follows: (1) Combined with the surface morphological characteristics, the structural landforms were abstracted into geological and geomorphic elements, and the characteristics and relationships of these elements were analyzed. (2) The elements of structural landforms and their relationships were abstracted into spatial objects and topological relationships. The spatial objects of the structural landform were designed based on the types and characteristics of structural landform elements. The topological relationships were developed based on the definition of the structural landform morphotype. (3) The structural landform markup language (SLML) method of “forms–elements–relationships” was created. (4) Two typical structural landforms, namely, Qixia Mountain and Gaoli Mountain, were used as examples to verify the feasibility and effectiveness of the GIS approach for expressing structural landforms. This paper describes and expresses the “forms–elements–relationships” of structural landforms from the perspective of GIS, which is expected to promote the joint development of structural geomorphology and GIS. Full article

The existing combustion kinetic modeling method which aims at developing phenomenological combustion mechanisms characterized by multiple reactions confronts several challenges, including the conflicts between computing resources and mechanism scales during numerical simulation, etc. In order to address these issues, the minimized reaction network method for complex combustion system modeling based on the principle of simultaneous chemical equilibrium is proposed, which is aimed to develop combustion mechanisms with minimal reaction steps under a limited number of species. The concept of mechanism resolution is proposed in this method, and the reaction network with minimal reaction steps under a given mechanism resolution is constructed so that the scale of mechanisms is compressed greatly. Meanwhile, distinguishing from other mechanisms, the reversible form of elementary reactions is adopted and the classical two-parameter (A, E_a) Arrhenius equation fits the rate constants. Typical n-alkanes including n-butane, n-heptane, n-octane, n-decane, n-dodecane and n-hexadecane were taken as examples to indicate the development process of mechanisms and systematic kinetic validations were carried out. Results show that this method leads to very compact mechanisms with satisfactory accuracy, and it eliminates the process of mechanism reduction and is beneficial for mechanism optimization. This method and the derived kinetic mechanisms are hoped to contribute to combustion engineering applications. Full article

In the 1980s, China began to recognize the gravity of the problem of non-point agricultural source pollution and conduct research on it. Agricultural non-point source pollution in China, on the other hand, differs from foreign agricultural non-point source pollution and industrial point source pollution. Because the features of agricultural non-point source pollution are complicated, it is critical to investigate a whole-chain management policy system appropriate for China’s agricultural pattern. Based on the current situation of agricultural non-point source pollution in China, this study summarizes the four stages of agricultural non-point source pollution prevention and control policies, namely the discovery stage with macro policies as the main focus, the exploration stage with single research indicators, the initial systematic strengthening stage, and the focused stage with targeted characteristics. Simultaneously, it examined the technological approaches that are suitable for China’s national circumstances and have been investigated by relying on international experience in present-day Chinese management. However, there are still some problems and challenges in agricultural non-point source pollution management policies, such as a lack of non-point source information support, a lack of coordination between different departments, a lack of support in measurement and retroactive calculation and treatment, a lack of an in-depth concept of zoning and classification, a lack of policy, an institutional system, and insufficient capital investment. Based on these problems and combining them with Green Agriculture, Beautiful China, and other goals, this paper puts forward suggestions to strengthen the policy data support of the agricultural non-point source pollution management system, enhance the research and development of the law of pollutant migration and transformation, encourage the innovation of low-cost and high-benefit treatment technology, improve the construction of the management system, strengthen the collaboration of departments, increase the investment of funds, and make other suggestions so as to promote the treatment of agricultural non-point source pollution with high quality and efficiency. Full article

Obesity is a recognized epidemic worldwide, and the accumulation of excess free saturated fatty acids (SFAs) in cells induces cellular lipotoxic damage and increases the risk of a wide spectrum of metabolic diseases including type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD). Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) have been reported to combat SFA-induced cellular damage. However, the comparative studies of the two types of unsaturated fatty acids (UFAs) are still limited. We investigated the effects of different MUFAs and PUFAs in the human hepatocyte line L-02 cells in vitro, and in high-fat-diet (HFD)-induced obese C57BL/6 mice in vivo. The results of the in vitro study showed that SFAs induced significant cellular lipotoxic damage, but the combination of MUFAs/PUFAs with SFAs significantly improved the impaired cell viability. Particularly, oleic acid (OA) was superior to eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and arachidonic acid (AA) in terms of its anti-apoptotic effect and inhibition of endoplasmic reticulum (ER) stress. In vivo, both olive-oil-enriched (HFD + OO) and fish-oil-enriched high-fat diets (HFD + FO) reduced hepatic steatosis and improved insulin sensitivity in obese mice. However, FO induced an abnormal increase in serum aspartate aminotransferase (AST) and an increase in the oxidative stress indicator Malondialdehyde (MDA). Liver-targeted lipidomic analysis showed that liver lipid metabolites under the two types of UFA dietary interventions differed from the HFD group, modulating the abundance of some lipid metabolites such as triglycerides (TGs) and glycerophospholipids. Furthermore, the FO diet significantly increased the abundance of the associated FA 20:5 long-chain lipid metabolites, whereas the OO diet regulated the unsaturation of all fatty acids in general and increased the abundance of FA 18:1 in the overall lipid metabolites, especially TGs, which may primarily contribute to the FO, and OO drove protection in NAFLD. Full article