Search

River discharge plays an indispensable role in maintaining the stability of the hydrosphere system and eco-environment. Previous methods that utilize satellite imagery to estimate discharge over poorly gauged basins are generally tailored for large rivers and heavily reliant on ground-based measurements. Consequently, uncertainties often escalate when these methods are applied to medium-sized rivers. Based on Landsat 5 Thematic Mapper (TM) and unmanned aerial vehicle (UAV) images, this study proposed a framework for estimating the discharge of large and medium rivers with limited ground observations. It comprises (1) a modified C/M method, which considers the spatial heterogeneity of rivers using single-site observation data, and (2) a newly developed method for estimating river bathymetry with zero discharge measurements (RIBA-zero). Results show that, utilizing the modified C / M method, rivers wider than three times the satellite resolution (i.e., 90 m) exhibit a relative root mean square error (rRMSE) of 0.23 in the velocity estimation. Narrower rivers display a slight increase in the rRMSE (0.41), which is still within an encouraging range. For both types of river widths, the accuracy of flow velocity estimation is higher during high-flow periods compared with the low-flow counterparts. In terms of the flow area estimation, the RIBA-zero method is much more suited for parabola-shaped cross-sections (rRMSE = 0.22) and flood seasons (rRMSE = 0.35). Additionally, when replacing 30-m Landsat 5 TM with 10 m-resolution Sentinel-2 imageries, the approaches make a significant improvement in velocity estimation for rivers narrower than 90 m across all periods, exhibiting great potential to estimate discharge in medium rivers with finer resolution satellite imageries. The framework requires a few ground observations for discharge estimates with the Nash–Sutcliffe efficiency coefficient (NSE) reaching ∼0.9, thereby greatly facilitating hydrology-related studies with profound implications for sustainable water resources management worldwide. • A modified C/M method for flow velocity estimation was proposed. • A mathematical modelling method was developed to estimate river bathymetry. • Estimating discharge over poorly gauged basins using data from one gauged station. [ABSTRACT FROM AUTHOR]

In this study, a novel predictor–corrector guidance law based on the all-coefficient adaptive control theory is proposed for the approach and landing phase of an unpowered reusable launch vehicle (RLV). The flight phase includes two portions: the initial gliding flight phase and the final exponential flare one. The equilibrium glide condition and an exponential function of altitude are used to parameterize the guidance commands of two portions and generate the guidance sequence. Based on the first order characteristic model which has the advantages of less characteristic parameters and easy analysis, the all-coefficient adaptive predictor–corrector guidance method is presented. The guidance law has the ability of generating new trajectories online according to the current states and the final conditions of the landing point. Then, the stability and finite-time convergence of the guidance law are analyzed. Considering the process constraints, the fusion guidance law is obtained. Finally, simulation results demonstrate the effectiveness and robustness of the proposed guidance law, with respect to the large initial states errors and parameter uncertainties. The simulations also show that the system under the proposed guidance law converges to a small neighborhood of zero after limited steps. [ABSTRACT FROM AUTHOR]

• We presented a framework for accurate NPS estimation by coupling satellite and UAVs. • It introduced five high-resolution parameters greatly improving estimation accuracy. • It presented a new NPS "observation" simulation method to verify NPS modeling. • It can solve the problem of global NPS modeling verification in large-scale areas. Quantitatively and accurately analyzing nonpoint-source (NPS) pollution is essential for efficiently preventing the input of NPS loads into inland waters. However, the accuracy of previous NPS pollution models is limited by the accuracy of ground parameter data. In addition, there are few effective methods that thoroughly verify modeling results at large scales. This paper presents a framework for accurate NPS pollution estimation by coupling satellite and unmanned aerial vehicle (UAV) monitoring data, and the results are verified by both field sampling and a newly developed inlet NPS pollution "observation" simulation method. Fractional vegetation coverage (FVC) data obtained by satellite were used to improve the accuracy of the runoff module of the framework. Satellite and UAV data were coupled to acquire livestock data, determine inlets, and identify reservoir buffer zones and vegetation types. These new data were then used to improve the accuracy of the livestock and runoff modules in the framework. The results show that the estimation accuracy of total nitrogen, total phosphorus, ammonia nitrogen, and chemical oxygen demand with FVC were improved by 39.96%, 69.29%, 54.05% and 47.22% (in relative error), respectively. The high-resolution livestock data acquisition improved the estimation accuracy of the NPS pollution load by 7–53%. The high-resolution inlet extraction improved the accuracy by 3–24%. The high-resolution buffer zone identification improved the accuracy with the estimated NPS pollutant concentration into reservoir decreasing by 60–99%. Finally, the high-resolution vegetation type identification improved the accuracy by 10–72%. The framework performs satisfactorily, which was verified based on the simulated NPS observations with an average relative error of 11.54–24.31%. We found that the FVC, livestock number, and inlet number are key parameters for NPS pollution modeling; the introduction of monthly variation in the FVC makes the modeled NPS pollution load much higher in areas with mature complex forested ecosystems or densely distributed vegetation but much lower in areas with sparsely distributed vegetation. The above methods provide a scientific reference for high-efficiency NPS pollution prevention in inland waters, laying a solid basis for decision-making regarding water quality management in data-scarce regions around the world. [Display omitted] [ABSTRACT FROM AUTHOR]

• Endo-β-1,3-glucanase (ENG) could restore mature basal stipe wall extensibility. • ENG-pretreated basal stipe walls could be induced to extend by chitinase. • ENG released more glucose from the basal stipe walls than the apical stipe walls. • Products released from basal stipe by ENG were consistent with that of β-1,3/1,6-glucan. • β-1,3/1,6-Glucan more accumulated and cross-linked in basal stipe than apical stipe The mature basal stipe of mushroom Coprinopsis cinerea loses wall extensibility. We found that an endo-β-1,3-glucanase ENG from C. cinerea could restore mature basal stipe wall extensibility via pretreatment such that the ENG-pretreated basal stipe walls could be induced to extend by chitinase ChiIII. ENG pretreatment released glucose, laminaribiose, and 3-O-D-gentiobiose-D-glucose from the basal stipe walls, consistent with ENG-digested products of β-1,6-branched β-1,3-glucan. Different effects of endo-β-1,3-glucanase ENG and exo-β-1,3-glucanase EXG pretreatment on the structure, amount and ratio (β-1,3-glucoside bonds to β-1,6-glucoside bonds) of products from the basal stipe and the apical stipe cell walls, respectively, and on the cell wall extensibility and the cell wall ultra-architecture of the basal stipes were analyzed. All results demonstrate that the more accumulation and cross-linkage of β-1,6-branched β-1,3-glucan with wall maturation lead to loss of wall extensibility of the basal stipe regions compared to the apical stipe cell walls. [ABSTRACT FROM AUTHOR]

• Changes of coastal sub-watershed characteristics during 18 years were analyzed. • It's the first study to discuss the impact of landscape pattern on sediment DOM. • The fragmentation degree of the landscape has negative effects on sediment DOM. • Cropland and forest have positive effects on humic-like components of DOM. • Sub-watershed features have stronger effects on DOM quality than on its content. Dissolved organic matter (DOM), which is influenced by watershed characteristics, plays an important role in carbon (C) budgets and reflects human impacts on the river ecosystem. This study aims to analyze the changes of land use and landscape patterns in three sub-watersheds and the effects of these sub-watershed characteristics on the content and quality characteristics of DOM. We collected sediment samples of different depth from exits of three sub-watersheds. Samples were analyzed for content and quality of DOM based on absorbance and fluorescence properties using ultraviolet–visible spectroscopy (UV–vis) absorbance and fluorescence spectroscopy. Results show that the land use types of the three sub-watersheds are mainly cropland and construction land. And the construction land area of three sub-watersheds increase from 2000 to 2018, while the area of cropland decrease. In addition, we find that forestland and cropland negatively influence sediment DOC contents and positively influence the proportion of humic fluorescence. And the water area has positive effect on protein-like DOM compounds. Moreover, the degree of fragmentation of the landscape has negative effects on sediment DOC contents. The connectivity of the landscape and the agglomeration of the patch have positive effects on humic-like components in sediment DOM at the exit of the sub-watershed. In general, sub-watershed characteristics have stronger effects on DOM quality than on its content. This study provides new insights on the importance of watershed characteristics on the content and quality of sediment DOM in river and supplies the support for river ecosystem management. [ABSTRACT FROM AUTHOR]

In this study, considering the various terminal constraints, and strong coupling between different flight states, a novel segmented and weighted adaptive predictor-corrector guidance method is proposed for the ascent phase of hypersonic aircraft. Firstly, by means of the analysis of whole ascent phase, it can be found that the magnitudes of different states vary greatly during the ascent phase. In order to reduce the impact of the difference, a dimensionless policy is adopted for the dynamic equations. And then, based on the all-coefficient adaptive control theory, the time-varying dynamic factors which will be used in the guidance law are calculated. Analyzing the dynamic factors and the whole flight characteristics of ascent phase, it can be concluded that the change of attack angle has great and monotonous influence on the terminal flight path angle and altitude, and the flight path angle at the later period of ascent phase has little impact on the guidance channel of altitude. Consequently, the whole flight phase is divided into the first flight subphase whose guidance object is eliminating the terminal altitude and velocity errors with the weighted guidance law, and the second flight subphase when the terminal flight path angle and velocity errors are used to correct the guidance command. What's more, the selection principle of guidance parameters is analyzed, and it is very important for the terminal guidance accuracy of various states. Finally, the effectiveness and robustness of the proposed guidance law are demonstrated by the Monte-Carlo simulations. The comparison simulation also shows that the effectiveness of the dimensionless scheme and weighted policy which can both improve the guidance accuracy. [ABSTRACT FROM AUTHOR]

Highlights • Q-TOF-MS/MS analysis reveals a novel mode of Eng16A action on barley β-glucan. • Eng16A can cleave (1 → 4)-β-linkages adjacent to two sides of the (1 → 3)-β-linkage. • Insertion of a (1 → 3)-β-linkage makes (1 → 4)-β-linkages prone to cleavage by Eng16A. Abstract We previously reported that an endo-β-1,3(4)- d -glucanase, Eng16A, from C. cinerea shows a higher degradation activity toward barley β-glucan than laminarin. HPAEC-PAD and Q-TOF-MS/MS analyses show that Eng16A-digestion products of barley β-glucan not only contain some oligosaccharides with (1 → 3)-β-linkage adjacent to the reducing end, which is consistent with β-1,3(4)-glucanase-digestion products, but also include some oligosaccharides containing (1 → 4)-β-linkage adjacent to the reducing end which is consistent with cellulase-digestion products. Thus, Eng16A possesses both cellulase and β-1,3(4)-glucanase activities. Because Eng16A does not degrade cellulose, we propose that the insertion of a (1 → 3)-β-linkage among the groups of (1 → 4)-β-linkages may make these (1 → 4)-β-linkages prone to cleavage by Eng16A. Furthermore, Eng16A also possesses transglycosylation activity which leads to some products containing one or a few consecutive (1 → 3)-β-linkages adjacent to the non-reducing end. Therefore, HPAEC-PAD and Q-TOF-MS/MS analyses provide an efficient approach to reveal complicated modes of action of some endo-β-1,3(4)- d -glucanases on barley β-glucan. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizers significantly increase crop yield; however, the negative impact of excessive nitrogen use on the environment and soil requires urgent attention. Improving crop nitrogen use efficiency (NUE) is crucial to increase yields and protect the environment. Foxtail millet (Setaria italica L.), a gramineous crop with significant tolerance to barren croplands, is an ideal model crop for studying abiotic stress resistance in gramineous crops. However, knowledge of the regulatory network for NUE in foxtail millet is fragmentary. Herein, we identified an R2R3-like MYB transcription factor in foxtail millet, SiMYB30 , which belongs to MYB subfamily 17. The expression of SiMYB30 is responsive to low nitrogen (LN) concentration. Compared with wildtype Kitaake, seedlings of rice lines overexpressing SiMYB30 showed significantly increased shoot fresh and dry weights, plant height, and root area under LN treatment indoors. Consistently, overexpression of SiMYB30 in field experiments significantly increased grain and stem nitrogen contents, grain yield per plant, and stem weight in rice. Furthermore, qRT-PCR revealed that SiMYB30 effectively activated the expression of nitrogen uptake-related genes— OsNRT1 , OsNRT1.1B , and OsNPF2.4 —and nitrogen assimilation-related genes— OsGOGAT1 , OsGOGAT2 , and OsNIA2. Notably, SiMYB30 directly bound to the promoter of OsGOGAT2 and regulated its expression. These results highlight the novel and pivotal role of SiMYB30 in improving crop NUE. • SiMYB30 transcription factor expression responds to LN and ABA treatments. • SiMYB30 could increase shoot biomass at the seedling stage. • SiMYB30 enhances the yield and grain nitrogen content at maturity. • SiMYB30 activates OsNRT1 , OsNIA2 , OsNRT1.1B , OsGOGAT1, and OsGOGAT2 expression. • SiMYB30 from foxtail millet confers tolerance to low nitrogen to transgenic rice. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wetland types have significant impacts on the distribution of SIC, DIC and PIC. • The sequestration of CO 2 during the formation of PIC was mainly biological source. • High soil pH and SOC were conducive to the fixation of CO 2 during PIC formation. • The PIC should not be ignored in estimating the carbon budget of blue carbon. As an important area for the exchange of matter between land and sea, the storage, source and fixation of soil inorganic carbon in coastal wetlands are of great significance for the sequestration of CO 2. To clarify the source and carbon sequestration mechanism of soil insoluble inorganic carbon in coastal wetlands, this study selected four representative wetlands in Jiaozhou Bay, including mudflat wetland, aquaculture pond wetland, Suaeda salsa wetland and Phragmites australis wetland, and used stable carbon isotope technology to measure the δ13C values of soil insoluble inorganic carbon (SIC), soil organic carbon (SOC) and soil CO 2. The results showed that the contents of SIC, dissolved inorganic carbon (DIC) and pedogenic carbonate (PIC) were 3.17–12.27 g∙kg−1, 0.05–0.09 g∙kg−1, 0.19–5.22 g∙kg−1, respectively, and there were significant differences in the content of different forms of soil inorganic carbon in soil of different wetland types. The main component of SIC in coastal wetland soils was PIC (59.7 %–86.5 %) (except for the aquaculture pond wetland). The CO 2 fixed in the process of PIC formation was mainly from biogenic CO 2 , with atmospheric CO 2 as a supplement, and the restoration of coastal wetland vegetation can promote the production of biogenic CO 2 and the formation of PIC. High soil pH and SOC were conducive to the fixation of CO 2 during PIC formation. Ca2+ and SWC had a positive effect on the inorganic sequestration of atmospheric CO 2 , but a negative effect on the inorganic sequestration of biogenic CO 2 in coastal wetlands. The content of PIC was equivalent to or even higher than the SOC, and the conversion process of SOC to PIC promoted the conversion of short-term to long-term geological carbon cycling. Therefore, the role of PIC should not be ignored in estimating the carbon budget of the 'blue carbon' habitat in coastal wetlands in the future. [ABSTRACT FROM AUTHOR]

Dongxiang common wild rice (Oryza rufipogon Griff.) is believed to have the northernmost distribution of any wild rice species. Many favorable genes were lost during rice domestication, and Dongxiang common wild rice is a potential source of many genes related to biological and abiotic stress resistance and high grain yield. Despite its importance, japonica rice has not yet been used as a background material for the construction of introgression lines carrying Dongxiang common wild rice chromosome segments. In this study, we used Dongxiang common wild rice as the donor parent and Nipponbare (Oryza sativa L), a reference-sequence japonica cultivar, as the recurrent parent to develop a set of 104 chromosome segment substitution lines (CSSLs) through crossing and backcrossing with marker-assisted selection based on 203 polymorphic molecular markers evenly distributed across 12 chromosomes. The 104 CSSLs covered 87.94% of the genome of Dongxiang common wild rice. Each CSSL contained an average of four introgressed segments, and the average segment length was 3.3 Mb. Quantitative trait locus (QTL) analysis of the panicle-related traits of the CSSLs at two sites (Beijing and Nanchang, Jiangxi Province) revealed 18 QTLs for eight traits. Among these 18 QTLs were two known grain length- and width-related genes and four novel QTLs. In addition, two QTLs were verified, and two novel QTLs were identified, for panicle neck length, a domestication-related trait. The developed CSSLs potentially represent a valuable population for detecting favorable genes in common wild rice and creating germplasm resources for japonica rice breeding. • A set of 104 chromosome segment substitution lines was developed. • The 104 chromosome segment substitution lines covered 87.94% of the genome sequence of Dongxiang common wild rice. • QTL analysis was performed for panicle-related traits at two sites, and 4 novel grain length and width QTLs were observed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carbon stable isotopes and fluorescence components were identified. • Source contributions were evaluated by isotope and fluorescence respectively. • First study to quantitatively identify terrestrial DOM sources in Jiaozhou estuary. • Characterize the spatial variability of source apportionment of DOM sources. Abstract Identification of allochthonous sources of dissolved organic matter (DOM) plays a significant role in biogeochemical cycles and regional management in estuarine areas. In this study, samples of sediments and potential sources including farmland, forest, aquaculture, industrial and rural area were collected. Carbon stable isotope (combing δ13C DOM and C/N ratios) and fluorescence spectroscopy were applied to calculate the relative contribution of each DOM source in Dagu estuary. Furthermore, their capabilities for the source apportionment were compared. Results suggested that the input sources of DOM obtained with isotope ratios contained most of the land uses in Dagu estuary. And farmland, aquaculture and industry were the dominant sources. By contrast, the source obtained with fluorescence spectroscopy was mainly aquaculture. Furthermore, we discussed the spatial variability of source contributions in different locations along the river (from internal to seaward areas) based on isotope ratio analysis. These results indicated that: (1) In general, the allochthonous input of DOM derived from multiple sources. In different sediment sites, the contributions of land use were different. (2) Among the potential sources, aquaculture and industrial areas were the dominated sources. And the contributions derived from aquaculture pond showed a seaward increase characteristic (3.4%–66.1%) expect for G22 areas (91.7%). This study provides a useful insight for carbon cycling and the interaction of terrestrial and marine biogeochemical processes. [ABSTRACT FROM AUTHOR]

Highlights • ChiEn3 was an exochitinase with a processive mode of action. • ChiEn3 hydrolyzed only soluble chitin (not insoluble chitin substrates). • ChiEn3 showed hyperhydrolytic activity toward 85% deacetylated chitosan. • ChiEn3-digested products of 85% deacetylated chitosan had high antioxidant activity. • ChiEn3 showed remarkable thermophilicity. Abstract ChiEn3 from Coprinopsis cinerea was characterized as an exo-acting chitinase with a processivity. ChiEn3 hydrolyzed only soluble chitin and exhibited a hyperhydrolytic activity toward 85% deacetylated chitosan which was 33.6-fold higher than its hydrolytic activity toward glycol chitin. Its maximum hydrolytic activity was observed at 60 °C and retained 66.2% of hydrolytic activity after 60 min incubation at 60 °C. Commercial 85% deacetylated chitosan was degraded by ChiEn3 to a series of COSs with a DP of 2–20 in which COSs with a DP of 3–6 were dominant, whereas, lab-prepared chitosan (F A = 0.65) was degraded by ChiEn3 to COSs with a DP of 2–10 in which the AA dimer was dominant. DPPH-radical-scavenging activity of ChiEn3-digested products of 85% deacetylated chitosan was 3.32-fold higher than that of undigested 85% deacetylated chitosan. Therefore, ChiEn3 shows a valuable advantage for application to the preparation of COSs from commercial 85% deacetylated chitosan. [ABSTRACT FROM AUTHOR]

• A coaxial gravity heat pipe with internal fins in evaporator section is proposed. • The thermal resistance of CGHP is decreased by 13.43% maximally with internal fins compared to without fins. • The flow pattern and temperature distribution of CGHP obtained from CFD method are analyzed and studied. • The heat transfer performance with down fins n df = 3 is superior than that of other cases. Heat pipe has great potential in the field of building and industrial energy exploitation due to high-efficiency heat transfer capability. In order to enhance the thermo-hydrodynamic performance of a coaxial gravity heat pipe (CGHP), the thermal transport behaviors of CGHP have been fully analyzed. In present research, firstly, the theoretical model and experiment tests of the internal flow and heat transfer of a CGHP is established when it is in a thermo-hydraulically stable operation mode. Subsequently, a coaxial gravity heat pipe was fully investigated to test its effects of thermal transport performance, including input powers, flow velocity, and the number of fins. The results show that mean reductions of overall thermal resistance achieved about 4.93% and 13.43% for fins n f = 4 and n f = 12, respectively. Moreover, the influence of internal fins of evaporator section on the liquid-vapor flow has been comprehensively obtained, including the steam disturbance, generation of bubbles and nucleate boiling. The CFD results reveal that the down fins number n df = 0 causes bubbles to adhere to the evaporator surface, thereby reducing the heat transfer capability, whereas a n df = 3 case causes bubbles to easily depart the evaporator surface, enhancing heat transfer capability. Current theoretical and CFD results agreed well with experimental data within mean error being no more than 10%. [ABSTRACT FROM AUTHOR]

• Coal Ignition is affected by its volatile content and fragmentation. • The flame fronts of different coal have different fluctuation periodicities. • Fragmentation may enhance the combustion efficiency of pulverized coal. • The surface functional groups of char affects the characteristics of emissions. In this paper, an experimental system of pulverized coal carrying flow combustion based on a flat-flame diffusion flame burner was built. The coal combustion characteristics including ignition process, coal fragmentation and surface morphology were investigated, and the CO and CO 2 emission characteristics of pulverized coal during combustion, and the changing pattern of functional groups on the surface of coal char. As indicated by the experimental results, the flame front of the pulverized coal combustion fluctuates periodically, and the fluctuation frequency exerts an influence on the stability of the temperature field around the pulverized coal particles. While increasing the specific surface area of the pulverized coal, fragmentation during combustion reduces the particle size of the pulverized coal. Pulverized coal with fragmentation characteristics shows a higher combustion efficiency in blast furnace injection. The content of functional groups on the surface of coal particles has an effect on the production of CO and CO 2 , and the increase in the oxygen-containing functional groups on the surface of coal char promotes the generation of CO. [ABSTRACT FROM AUTHOR]