Nanning Normal University

To improve the computational accuracy of numerical solutions for second kind Fredholm integral equations, this paper proposes a numerical solution method based on SSA (Singular Spectrum Analysis). Firstly, power series are chosen as the approximate analytical expression of the unknown function. Then, the composite Simpson quadrature formula is used for the definite integral part. Subsequently, the equation group is transformed into a function optimization problem. Finally, the best coefficients of the power series are solved using the SSA algorithm. Through 6 numerical experiments, the results show that compared with existing methods in literature, the proposed method has improved the calculation accuracy by 1–10 orders of magnitude, which verifies its feasibility and superiority. Moreover, this method provides a new approach for numerical solutions of second kind Fredholm integral equations.

Exploring the regional territorial spatial equilibrium state (TSES) has emerged as a key goal of “Two Mountains” planning and decision‐making, as well as territorial spatial governance. However, there is still a shortage of perspectives that consider the ecosystem service value (ESV) to reveal and predict TSES. To this end, this study develops a framework for analyzing the interaction between ESV and socio‐economic value (SEV), investigates the pattern, process, and mechanism of their interaction employing spatial equilibrium model, and couples the MOP‐PLUS model to predict the interaction between the two under different scenarios, in order to fill in the gaps of the current research. The results show that: (1) From 1980 to 2020, the ESV (decreasing trend) and SEV (increasing trend) in the Southwest Guangxi Karst‐Beibu Gulf (SGK‐BG) show opposite trends and distribution patterns. Under all three simulated projection scenarios, the projected ESV of SGK‐BG in 2030 shows different degrees of decreases, with economic development leading to the greatest fluctuations in the rate of decrease; the implementation of an ecological protection strategy leads to a small decrease in the SEV, and vice versa. (2) The TSE for coordinated equilibrium state (CES) districts and counties are mainly clustered in the GSK region, with the number in 2020 increasing by 30% compared to 1980; the ecological imbalance state (EIS) areas are mainly located in the central part of the study area and some districts along the coast of the Beibu Gulf, and the developmental imbalance state (DIS) areas are located in the northwestern part of the study area. The above three TSES have the highest number of distributions in the business as usual scenario (BAUS), the economic development first scenario (EDFS), and the ecological conservation first scenario (ECFS), respectively. The above differences in different spatial equilibriums reveal a serious developmental imbalance between economic development and ecological conservation. This study emphasizes the pathways evolution of different equilibrium subregions under the realization of ESV, and the evaluation results are not only a useful supplement to the research on the “Two Mountains” theory, but also can help policymakers to provide scientific decisions in promoting the synergistic, equilibrium and orderly development of the region.

Cancer is one of the most significant diseases that afflict human beings. The pursuit of high efficacy and low-toxicity anticancer drugs has always been a paramount research objective for scientists. In the present study, we incorporated two selenocyano pharmacophores into the 2-site and 17-branch chain of the steroid nucleus in various manners, utilizing estradiol as the fundamental framework. Consequently, several estradiol bisselenocyanate compounds with a 2-selenocyano-17-selenocyanoester structure were synthesized. When compared to the positive control steroidal anti-tumor drug 2-methoxyestradiol, certain derivatives exhibited superior inhibitory activity against tumor cells in vitro, surpassing their monoselenocyanate precursors. The representative compound 4b induced programmed apoptosis in HeLa cells in a concentration-dependent manner during apoptosis and cell cycle experiments, while causing G2 phase arrest predominantly in the cell cycle. Moreover, compound 4b exhibited significant inhibitory effects on cell migration and demonstrated remarkable inhibitory activity against HeLa xenograft tumors in zebrafish models. These findings suggest that these compounds hold potential as promising candidates for anti-tumor drugs and warrant further investigation.

Developing efficient and robust free‐standing electrocatalysts for overall water splitting is a promising but challenging task. Herein, the N‐incorporated Ni nanosheets non‐fully encapsulated by N‐doped carbon (NC) layer are fabricated (N─Ni©NC). The introduction of N not only regulates the size of nanosheets in N─Ni©NC but also promotes the electrochemical activity of metal Ni. Experimental and theoretical results reveal that strong bonding of the lattice N activates the inert metal Ni by promoting charge transfer between Ni and N. In addition, the upward shift of the d‐band center induced by lattice N enhances the adsorption of intermediates, thereby making Ni as a new OER active site together with C. This strategy of generating Ni and C dual active sites by introducing lattice N greatly accelerates oxygen evolution reaction (OER) kinetics, resulting in excellent electrocatalytic performance of N─Ni©NC. At the current density of 10 mA cm⁻², the overpotentials of hydrogen evolution reaction (HER) and OER are 27 and 206 mV, respectively, and the cell voltage for overall water splitting only needs 1.47 V. This work offers a unique heteroatom activation approach for designing free‐standing electrodes with high activity.

State‐of‐the‐art model‐based predictive control techniques for AC motor drives are reviewed in this paper. A plethora of MPC algorithms with vast number of complex ideas has emerged in the last decade and this work makes an attempt to present those concepts in an intuitive, comprehensive and hierarchical manner. More emphasis is laid on finite control set model predictive control (FCS‐MPC) methods, especially predictive torque control (PTC) and predictive current control (PCC) because of their emergence as the prime focus of ongoing research in energy efficient drive control. The main focus of this review is to analyse the most recent work, signpost the future research directions, identify the core challenges and consolidate the ideas into a coherent and concise reference. A comprehensive classification based on actuation signals is presented and reviewed in detail. Then, the important challenges in MPC implementation, such as computational complexity reduction and delay compensation, weighting factor selection for multi‐objective cost functions, steady state performance and ripple reduction, parameter variations/model mismatching and achieving extended prediction horizons, are surveyed and most relevant solutions are reviewed. A detailed analysis of the last five years related work is given at the end and it is concluded that the future course seems to be diverting towards voltage vector selection with optimised phase, magnitude and duty ratios. Computational burden is still one of the main hurdle towards MPC proliferation and adaptation in AC drive control at the industrial level. However, with advent of high speed and cheaper signal processors and development of efficient algorithms, MPC is rapidly becoming the control method of choice for energy‐efficient drive control.

This paper constructs the volatility network of stock price indices in 49 countries, taking the COVID-19 event as an external shock to examine the impact of major emergencies on the volatility network of stock indices, the risk transmission mechanism across borders and the characteristics of key nodes. We further analyze the centrality of the network theory and empirical mechanism of the optimal portfolio weighting under the “mean–variance” framework while extending the results to portfolio risk management scenarios. The key findings are the impact of COVID-19 has led to a significant increase in convergence in the behavioral patterns of main countries stock indexes, changes in volatility network nodes and significant differences in topological structure characteristics. Compared with markets of emerging countries, the stock indexes in developed markets show the highest correlation before and after the epidemic. The main countries stock indexes volatility network based on geographic distribution reflects the characteristics of clustering and homogeneity. The stock indexes of few countries, such as Singapore, France, Germany, and the Netherlands, are the key market and source of market risk during the outbreak. Under the “mean–variance” framework, theoretical and empirical analysis shows that the optimal portfolio is more inclined to allocate more weight to stock indexes with low centrality, low volatility, and high Sharpe ratio. Because the marginal asset portfolio with less centrality is more conducive to reducing the overall risk of the asset portfolio. The main research objective of this paper is to provide financial regulators and financial practitioners with relevant ideas and strategies for inter-country portfolio risk management under major emergencies, and to provide important insights for them to understand the correlation structure and risk transfer characteristics of the global stock indexes of main countries under the impact of major emergencies, and for market participants to optimize their portfolio structure and manage portfolio risks.

A machine learning-based financial statement quality assessment model is proposed, which aims to provide a reliable reference for the value assessment of new energy enterprises and guide the decision-making of the market and investors. The model improves the free cash flow model and applies the gray time series combination model to predict the future operating income of the enterprise. The study shows that the accuracy of the gray time series combination model in predicting the future income of the enterprise is better than that of a single model, effectively integrates the information and data of multiple models, and enriches the system of enterprise value assessment methods.

With the progression of regional connectivity, attaining the ‘dual-carbon target’ is no longer the narrative of a single city. To achieve synergistic governance among cities in the basin economic zone, it is essential to establish a multidimensional ecological compensation mechanism. This research amended the conventional carbon accounting model by utilising carbon emissions and economic data from 59 cities in China’s Yellow River Basin, covering the period from 2004 to 2021, after the timeframe of significant alterations in the administrative divisions of cities was removed. It additionally compares and analyses the clustering patterns and trajectories of centre-of-gravity shifts in regional ecocompensation credits while investigating the impact processes through geo-probes. The findings indicate that the amended carbon account has a more decentralised distribution when interregional disparities are considered. Second, ecocompensation credits are characterised mostly by low-high and low-low agglomeration; nevertheless, their regional distribution is uneven. Moreover, the rankings of the top five cities in terms of ecocompensation exhibited minimal variation each year. The degree of green technology is the primary determinant of the spatiotemporal evolution of ecological compensation. The conclusions of this study can serve as a valuable reference for the execution of medium- and long-term ecocompensation policies and aid in attaining the ‘dual-carbon’ aim.

As the misuse of antibiotics increases bacterial resistance, the treatment of infected wounds caused by bacteria encounters significant challenges. Conventional antimicrobial dressings often fall short in their ability to inhibit bacterial infections while simultaneously promoting wound healing. To address this issue, a polysaccharide self‐healing hydrogel (CPP@PDA/Que3) wound dressing is successfully developed by incorporating quercetin and polydopamine nanoparticles into a carboxymethyl chitosan matrix. The dressing can be easily injected locally to create a protective barrier over the wound, effectively stopping bleeding and rapidly inhibiting inflammation. Furthermore, the CPP@PDA/Que3 hydrogel exhibits remarkable antioxidant and antibacterial properties, stemming from the combination of quercetin and near‐infrared (NIR) photothermal therapy. It demonstrates the ability to eliminate 99.52% of Staphylococcus aureus and 99.39% of Escherichia coli in in vitro antibacterial experiments. Additionally, the in vivo wound healing experiment shows a healing rate of ≈97%. The experimental results indicate that under NIR laser (808 nm) irradiation, the polysaccharide‐based hydrogel dressing significantly inhibits bacterial growth, reduces oxidative stress, expedites angiogenesis, and thereby accelerates the transition from inflammation to wound healing. In summary, the CPP@PDA/Que3 hydrogel exhibits significant potential as a wound dressing, providing a novel approach for clinically advancing the treatment of bacterial wounds.

Potassium sodium niobate-based ferroelectric materials are potential alternatives to Pb-based perovskites due to their outstanding ferroelectric and piezoelectric properties. In our previous work, (Na0.5K0.5)1-xAgxNb1-xTaxO3 was constructed with a coexistence of orthorhombic and tetragonal phases at room temperature, successfully regulating various polarization properties. However, despite the x = 0.075 sample's excellent piezoelectric and ferroelectric characteristics, the significant coercive field it exhibits poses a challenge for polarization. Further investigation is needed to address this issue. This study introduces SrTiO3 as a second phase into (Na0.5K0.5)0.925Ag0.075Nb0.925Ta0.075O3, effectively regulating the microstructure and disorder. Moreover, leveraging the synergistic effect of phase boundary and disorder engineering, the ferroelectric properties are well modulated at room temperature. These results provide valuable methods and guidance for regulating ferroelectric properties in lead-free ferroelectrics.

The dinoflagellate genus Heterocapsa includes several widely distributed and potentially toxic species associated with Harmful Algal Blooms (HABs), particularly affecting the Western Pacific Ocean. To reveal the biodiversity of Heterocapsa in Beibu Gulf, six strains were morphologically characterized using light and scanning electron microscopy, while large subunit rDNA (LSU rDNA) and internal transcribed spacer (ITS) were sequenced for phylogenetic analysis through maximum likelihood and Bayesian inferences. Two strains (BGERL169, BGERL170) were identified as Heterocapsa philippinensis ribotype I, three (BGERL171-BGERL173) as a new Heterocapsa philippinensis ribotype II, and one strain (BGERL174) as Heterocapsa pseudotriquetra. Cells of H. philippinensis were ovoid to spherical, yellowish-brown, with reticulate chloroplasts, and had a sausage-shaped nucleus positioned longitudinally along the dorsal side of the cell, and the theca was arranged in Po, cp, X, 5′, 3a, 7″, 6c, 5s, 5‴, 2⁗. Additionally, BGERL169 and BGERL171 showed no hemolytic toxicity in rabbit erythrocyte lysis assays. To the best of our knowledge, this research provides the first morphological and phylogenetic analysis of H. philippinensis, including the identification of a new ribotype, as well as the discovery of H. pseudotriquetra in Chinese waters. The findings contribute to the understanding of Heterocapsa species biogeography and toxicity in Chinese waters, offering valuable data for future HAB monitoring in Beibu Gulf.

The ecological function of land use is the basis for developing an ecological civilization and realizing sustainable development. This paper may help guide the coordination of economic development and ecological development in China’s coastal border areas. Based on theoretical analysis, this paper studies the spatiotemporal evolution of the functional spaces and the ecological function transitions of land use in the Beibu Gulf Economic Zone (BGEZ) by analyzing patterns, processes, and factors by applying eco-environmental quality index, grid subdivision, kriging interpolation, barycenter model, and Geodetector. This paper constructs a theoretical framework of ecological function transitions of land use based on the research idea of “system-pattern-process-factor”, and carries out empirical research. Some conclusions can be drawn as follows: (1) The ecological space in the BGEZ has continuously decreased, converting mainly into agricultural production space and industrial-mining production space. The production space has expanded slowly. The area of living space in the BGEZ has increased rapidly. (2) The ecological function of land use in the BGEZ has continued to weaken, especially in the southern part of the BGEZ. The “high - sub-high” quality zones of ecological function are retreating to the north. (3) There were more deterioration transition areas than optimization transition areas of ecological function in the BGEZ. The former were mostly located in the central and southern urbanized areas of the BGEZ, whereas the latter were mostly located in the edge zones of district and county units. (4) As for the driving factors of the deterioration transitions of land use ecological function in the BGEZ, the significant trend of “de-ecologization” of the land cover/land use structure was the dominant driving factor; the interactions among the “natural-socioeconomic-managerial” systems were the main recessive factor. The natural system played a fundamental role, and the driving force of natural factors was the strongest. The industrialization, urbanization, and GDP increment in the socioeconomic system and the policy positioning of development intensity in the managerial system played a significant role. The interactions among natural factors, road construction, and industrial non-agricultural transformation had a “fuze” effect on stimulating driving forces.

Citrus maxima ‘Shatian Yu’ displays varying nutritional profiles influenced by its production area. This study evaluated pomelo fruits from four primary and one developing ‘Shatian Yu’ production area. Notably, ‘Shatian Yu’ from the Guilin area exhibited higher sugar and alcohol content, suggesting enhanced taste. Principal component analysis and OPLS-DA revealed significant metabolite differences among production areas. In Guilin, variations were observed in a few substances, including sugars, alcohols, and phenolic acids. When compared with Rong City, Guilin showed a decrease in four phenolic acids and an increase in three organic acids, eighteen amino acids, eighteen lipids, and one vitamin. This comprehensive analysis provides valuable insights for the development of ‘Shatian Yu’ cultivation, highlighting the impact of production areas on fruit quality.

Chemical genetics is a multidisciplinary research method. In this study, it is used to screen compounds that promote aluminum-induced malate secretion in Arabidopsis thaliana. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK; LY2228820) significantly increased the transcription of Arabidopsis thaliana aluminum-activated malate transporter 1 (AtALMT1) and sensitive to proton rhizotoxicity 1 (STOP1)-regulated genes, multidrug and toxic compound extrusion and aluminum sensitive 3, but not AtSTOP1 and the Al-biomarker genes At3g28510, At5g13320, suggesting that LY2228820 increased the early expression of STOP1-regulated genes without affecting AtSTOP1 expression. Inhibition of p38 MAPK (LY2228820) and Aurora A (MLN8237) increased aluminum-activated malate transport via AtALMT1, suggesting that both MLN8237 and LY2228820 interfere with AtALMT1 activity. An increase in root elongation was also observed in Arabidopsis after applying compounds LY2228820 and MLN8237. Thus, both LY2228820 and MLN8237 may play important roles in alleviating the inhibitory effects of aluminum on roots.