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UAV multispectral remote sensing for the estimation of SPAD values at various growth stages of maize under different irrigation levels
No full textChlorophyll is crucial for photosynthesis in plants and the readings by a SPAD meter (Soil and Plant Analyzer Development) can be used to represent leaf chlorophyll content for monitoring crop growth status and predicting grain yield. Remote sensing technology has shown potential in non-destructive monitoring of SPAD values over large areas, but current SPAD inversion models are limited in their ability to incorporate multiple principal components besides spectral parameters, adapt to other variables such as water stress, and predict SPAD only throughout the entire growth period. This two-year study used crop parameters (plant height and leaf area index) and vegetation indices (VI) derived from unmanned aerial vehicle (UAV) multispectral images to develop SPAD prediction models for maize under different irrigation levels in the 2018 and 2019 growing seasons in Inner Mongolia, China. Two nonlinear machine learning models, random forest (RF) and support vector regression (SVR), and a multiple statistical regression method (partial least squares regression (PLSR)) were used to modeling SPAD. The results showed that the VIs with a high correlation with SPAD varied at each growth stage and the accuracy of SPAD estimation model can be improved significantly by dividing different growth stages (R2 increased by more than 104 %). PLSR performed better than RF and SVR for each growth period, especially at the reproductive R stage (R2 = 0.79, RMSE = 2.25). LAI and PH did not always improve prediction accuracy, but adding crop parameters did increase the correlation coefficient between predicted values and biomass by 8.3 %. This study provides valuable insights into the estimation of SPAD at different growth stages of maize under varying water stress levels using UAV data and crop parameters, offering guidance for farmland management and yield prediction
Preparation and Properties of Crosslinked Quaternized Chitosan-Based Hydrogel Films Ionically Bonded with Acetylsalicylic Acid for Biomedical Materials
No full textThe aim of the current study is to develop chitosan-based biomaterials which can sustainably release acetylsalicylic acid while presenting significant biological activity. Herein, an innovative ionic bonding strategy between hydroxypropyl trimethyl ammonium chloride chitosan (HACC) and acetylsalicylic acid (AA) was proposed, skillfully utilizing the electrostatic attraction of the ionic bond to achieve the controlled release of drugs. Based on this point, six crosslinked N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan acetylsalicylic acid salt (CHACAA) hydrogel films with varying acetylsalicylic acid contents were prepared by a crosslinking reaction. The results of 1H nuclear magnetic resonance spectroscopy (1H NMR) and scanning electron morphology (SEM) confirmed the crosslinked structure, while the obtained hydrogel films possessed favorable thermal stability, mechanical properties, and swelling ability. In addition, the drug release behavior of the hydrogel films was also investigated. As expected, the prepared hydrogel films demonstrated the capability for the sustainable release of acetylsalicylic acid due to ion pair attraction dynamics. Furthermore, the bioactivities of CHACAA-3 and CHACAA-4 hydrogel films with acetylsalicylic acid molar equivalents of 1.25 and 1.5 times those of HACC were particularly pronounced, which not only exhibited an excellent drug sustained-release ability and antibacterial effect, but also had a higher potential for binding and scavenging inflammatory factors, including NO and TNF-alpha. These findings suggest that CHACAA-3 and CHACAA-4 hydrogel films hold great potential for applications in wound dressing, tissue engineering scaffolds, and drug carriers
Spatial distribution of soil organic carbon across diverse vegetation types in a tidal wetland
No full textTidal wetlands are significant contributors to global "blue carbon" resources. The water and salt gradients in tidal wetlands shape vegetation distribution and store significant amounts of soil organic carbon (SOC). We selected four distinct regions within the intertidal zone comprising three distinct vegetation types: low-tide saltmarsh Suaeda salsa (LS), high-tide saltmarsh Suaeda salsa (HS), mid-high-tide Phragmites australis (P), and high-tide Tamarix chinensis (T). Through field sampling and indoor analysis, we found significant differences in SOC levels across various vegetation types along the land-sea gradient. Among these, LS exhibited the highest SOC levels, while P had the lowest. Additionally, there were vertical variations of SOC within a 1-m range among different vegetation types. Mantel analysis and SEM demonstrated that SWC influences SOC content by manipulating vegetation types, thereby regulating total soil carbon. Overall, our findings provide valuable insights for further investigating the effects of vegetation succession on soil carbon pool evolution
Monitoring and Evaluation of Coastal Ecological Carrying Capacity in the Context of Sustainable Development: A Case Study of Shandong Province
No full textThe research on coastal ecological carrying capacity holds great significance for the sustainable development of coastal areas and is a focal point of the United Nations Sustainable Development Goals (SDGs). This study coupled multi-source data and ecological analysis models to construct a multi-level evaluation system and analysis method for the coastal ecological carrying capacity of Shandong Province so as to realize the dynamic monitoring and evaluation of the coastal ecological carrying capacity of Shandong Province from 2010 to 2020. The results indicated: (1) The ecological carrying capacity of the coastal zone in Shandong Province showed a "U"-shaped development trend, with 2016 being a turning point. (2) The economic development-social support system gradually became the main force driving the overall improvement of coastal ecological carrying capacity. (3) The system coupling coordination degree of ecological carrying capacity in the coastal areas of Shandong Province showed a trend of first decreasing and then increasing, with a high level of internal coupling coordination of carrying capacity. (4) Per capita GDP, environmental protection investment, per capita water resources, and other indicators were the main factors driving the changes in the ecological carrying capacity of the coastal zone. This study aims to provide methodological reference and data support for coastal ecosystem monitoring, assessment, and climate change response
Surface-Enhanced Raman Scattering-Based Lateral Flow Assay Strips Using Highly Symmetric Gold Nanostars
No full textThe applications for lateral flow assay (LFA) strips in point-of-care testing have been significantly constrained by their insufficient sensitivity and reproducibility. To address these inherent issues, we developed surface-enhanced Raman scattering (SERS)-based LFA strips, in which highly symmetric Au nanostars (Sym-AuNS) were employed as the sensing element. Due to the uniform tip-sharp nanostructure and a certain number of branches on the surface of Sym-AuNS, it generates a uniform hotspot distribution, thus producing a strong and stable SERS signal. As a proof of concept, human IgG was chosen as the target to evaluate the performance of the proposed SERS-LFA strips. In human serum spiked samples, the limit of detection for human IgG detection was achieved as low as 38 ng/mL, which exhibited a 2-fold, 3-fold, and 13-fold sensitivity improvement compared with the SERS-LFA strips using conventional gold nanostars (AuNS), enzyme-linked immunosorbent assays (ELISA), and the conventional LFA strips, respectively. Furthermore, the SERS-LFA strips demonstrated high assay reproducibility, with a relative standard deviation of 7.75% for five repeated tests, much lower than those of SERS-LFA strips using AuNS (24.6%), ELISA (12.42%), and conventional LFA strips (31.32%). These results demonstrate that the construction of sensitive and reproducible SERS-LFA strips was obtained, and this platform using Sym-AuNS as SERS nanoparticles paves the way for a promising approach in immunoassay technology
Adsorption and desorption of nonylphenol on the biodegradable microplastics in seawater
No full textBiodegradable plastics have been widely used and their interaction with endocrine disrupting chemicals in the environment is worth exploring. This study selected poly (butylene adipate-co-terephthalate), poly (butylene succinate), polylactic acid (PLA) and a non-biodegradable microplastics (PE) as control to explore the adsorptiondesorption behavior of nonylphenol (NP) on the biodegradable microplastics in seawater. The adsorption capacity of NP on PLA (60.78 mu g g- 1) was approximately 50% lower than that on PE (116.53 mu g g- 1) which was the non-biodegradable microplastic control. Almost all biodegradable microplastics showed negligible desorption capacity compared to PE, indicating a lower environmental risk of biodegradable microplastics. The pH could influence the interaction between the NP and biodegradable microplastics through the formation of hydrogen bonds. The adsorption-desorption capacity of microplastics might increase at the condition of the high salinity and seawater erosion. Physical adsorption was the major adsorption processes based on the Gibbs free energy changes that calculated. The adsorption mechanism of microplastics was determined by calculating the crystallinity of microplastics, simulating the surface electrostatic potential of microplastics and conducting hydrophilicity tests of microplastics. The adsorption and desorption capacities of NP on biodegradable microplastics were mainly influenced by various mechanisms, including the crystallinity of the microplastics, hydrogen bonding and hydrophobic effects. These results will offer new perspectives on the interaction between biodegradable microplastics and NP in the ocean
Improving the Stability and Anti-Infective Activity of Sea Turtle AMPs Using Multiple Structural Modification Strategies
No full textAntimicrobial peptides (AMPs) are regarded as promising candidates for combating antimicrobial resistance. Previously we identified an AMP named Cm-CATH2 from the green sea turtle, which exhibited potent antibacterial activity and attractive potential in application. However, natural AMPs including Cm-CATH2 frequently suffer from structural instability and sensitivity to physiological conditions, limiting their effectiveness. Herein, we explored various strategies to enhance the efficacy and stability of Cm-CATH2, including peptide truncation, non-natural amino acid substitutions, disulfide bond-based cyclization, and stapled peptide techniques. The results demonstrated that the truncated NCM4 significantly improved the antimicrobial capability of Cm-CATH2 while also enhancing its anti-inflammatory and antibiofilm activities with minimal cytotoxicity. Further ornithine-substituted peptide oNCM markedly enhanced the stability of NCM4 without compromising its antimicrobial efficacy. This study successfully designed a lead peptide oNCM with significant development potential, while providing valuable insights into the advantages and limitations associated with diverse strategies for enhancing the stability of AMPs
Base-driven dehydrohalogenation coupled with catalytic hydrodehalogenation as a novel strategy for rapid dehalogenation of halogenated organic compounds containing aliphatic C-X bonds
No full textThe type of C-X bonds had a considerable effect on catalytic dehalogenation of halogenated organic compounds (HOCs). DDT and its metabolites (DDD and DDE) contain aliphatic C-Cl bonds, aromatic C-Cl bonds, and vinylic C-Cl bonds in their molecules, and thus catalytic dehalogenation of DDT, DDD, and DDE over Pd/C was investigated in this study. It was found that the halogen atom removal rates of DDT and DDD over Pd/C were significantly lower than that of DDE. Moreover, the hydrodehalogenation (HDH) of aromatic C-Cl bonds and vinylic C-Cl bonds were found to be more favorable compared with that of aliphatic C-Cl bonds. The mechanism of this phenomenon was studied with the aid of the hybrid B3LYP/6-311 + +G* * method. Theoretical calculations indicated that the Egap between LUMO and HOMO was the major cause for the sluggish HDH of DDT and DDD over Pd/C. Furthermore, alkali metal hydroxides with stronger basicity had more advantageous in converting aliphatic C-Cl bonds in DDT into vinylic C-Cl bonds in DDE via the dehydrohalogenation (DHX) reaction in n-butanol. Based on these studies, base-driven DHX coupled with Pd/C-catalyzed HDH was developed for the rapid dehalogenation of DDT and DDD. Firstly, DDT and DDD in n-butanol were converted into DDE and DDMU via the NaOH-driven DHX reaction within 20 min and 40 min. Subsequently, DDE and DDMU in n-butanol-water (1:1, V/V) were completely hydrodehalogenated into DPE catalyzed by Pd/C (25 mg) within 30 min and 25 min. This provided vital guidance for efficient dehalogenation of HOCs containing aliphatic C-X bonds
Subsoiling with straw return promotes soil nitrogen supply and increase maize yield in saline-alkaline farmland of the Yellow River Delta
No full textThe distinct soil physicochemical properties of saline-alkali farmland often lead to nutrient deficiencies, particularly in nitrogen. Both straw return and tillage are essential practices for modifying saline-alkali soils, however, their combined effects on soil properties, nitrogen(N) transformation and absorption, as well the crop yield remain inadequately understood. A field experiment was conducted to assess the cumulative impacts of straw return and tillage (rotary tillage, deep tillage and subsoiling) on soil salinity, nitrogen transformation and maize yield. The results revealed that the soil pH and electrical conductivity (EC) significantly decreased from the 0-20 cm layer to the 20-40 cm layer, indicating that deep tillage was less effective on salt accumulation in the surface soil. The return of straw return and tillage practices significantly influenced the fractions of soil organic nitrogen (SON) and the distribution percentage in total nitrogen. Additionally, these practices notably interacted to increase soil acid insoluble-N, active SON and stable SON. The combination of straw return and rotary tillage resulted in a higher content of stable SON in the 0-20 cm soil layer. Conversely, the combination of straw return and subsoiling proved to be more effective on soil available N and active SON supplying, as well as maintaining stable nitrogen levels. Furthermore, straw return combined with subsoiling achieved the highest plant nitrogen uptake and yield, with increases of 21.7% and 38.2%, respectively, compared to the rotary without straw. Principal component analysis (PCA) revealed that stable SON was the primary contributor influencing maize yield, while inorganic N in the 0-20 cm layer and hydrolysable ammonium nitrogen (NH4+-N) in the 20-40 cm were also the closely related factors. These results provide a new insight for implementing straw return measures to enhance soil quality and increase crop production in saline-alkali farmland
Stratification in central Bohai Sea and how it has shaped hypoxic events in summer
No full textIn the last 10 years (2012-2021), five hypoxic events have been observed in summer in the central Bohai Sea (CBS). Frequent and persistent hypoxia will have an impact on the ecosystem of the CBS. In this paper, historical sea temperature (ST), salinity (SAL), density (Den), and dissolved oxygen (DO) concentration data from three stations in the CBS are analyzed via the linear regression method, and the correlations between the stratification factors (ST, SAL, and Den) and DO concentration are determined. The thresholds of the stratification factors at the three stations in June in the year in which hypoxia occurred were determined and applied to survey data from 29 stations in late May to early June in 2022 in the CBS; this assessment found that the data from 19 stations indicated that hypoxia was about to occur. In August, the survey data showed that 14 out of the 29 stations indicated hypoxic conditions, of which 12 were from the predicted 19 stations, meaning that the estimation accuracy reached 63%. The same approach was applied to data from June 2023. The data for August from a bottom-type online monitoring system in the CBS verified the occurrence of hypoxic events around Sta. M2. The results show that the strength of the seawater stratification plays a leading role in hypoxic events in the summer in the CBS, and the thresholds of the stratification factors can be used to predict the occurrence of hypoxic events