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Fibre kinking is the most prevalent failure mode observed in UD composites. The accurate prediction of kinking failure is of paramount importance in industrial applications. To address this challenge, we develop a non-linear mean-field debonding model (NMFDM) based on our previous work, which efficiently captures the non-linear material behaviour of UD composites under longitudinal compression leading to kinking failure. Building upon the foundation of our earlier mean-field model, this enhanced NMFDM incorporates geometric non-linearity due to fibre rotation under longitudinal compression and the non-linear elasticity of fibres in the fibre direction. These additions address crucial aspects in kink band formation and the typically non-linear elastic behaviour of carbon fibres, which were not considered in our previous work. Additionally, we introduce a fibre kinking model (FKM) to predefine initial fibre misalignments in the geometries, allowing us to study the formation of kink bands. The FKM considers the effects of initial misalignments and fibre rotations during kinking by proposing a transformation law for off-axis cases. As a representative example, we investigate the initiation and evolution of kink band formation in an AS4/8552 UD composite by predefining various initial misalignments. The results demonstrate that our newly proposed NMFDM yields reliable predictions of kink band formation in UD composites, outperforming other existing models and even comparing favorably to micrograph observations of kink bands. Compared to our previous work, this enhanced model offers a more comprehensive understanding of kink band formation, particularly under large strains, by incorporating the non-linear elasticity of fibres in the fibre direction. This advancement opens up potential applications in designing composite structures with improved resistance to compressive failure, paving the way for broader applications in aerospace, automotive, and other industries where high-performance composite components are crucial. [ABSTRACT FROM AUTHOR]

Escherichia coli (E. coli) is a prevalent enteric bacterium and a necessary organism to monitor for food safety and environmental purposes. Developing efficient and specific methods is critical for detecting and monitoring viable E. coli due to its high prevalence. Conventional culture methods are often laborious and time-consuming, and they offer limited capability in detecting potentially harmful viable but non-culturable E. coli in the tested sample, which highlights the need for improved approaches. Hence, there is a growing demand for accurate and sensitive methods to determine the presence of viable E. coli. This paper scrutinizes various methods for detecting viable E. coli, including culture-based methods, molecular methods that target DNAs and RNAs, bacteriophage-based methods, biosensors, and other emerging technologies. The review serves as a guide for researchers seeking additional methodological options and aiding in the development of rapid and precise assays. Moving forward, it is anticipated that methods for detecting E. coli will become more stable and robust, ultimately contributing significantly to the improvement of food safety and public health. [ABSTRACT FROM AUTHOR]

Purpose: Exploring the different characteristics and influencing factors of sediment phosphorus (P) migration and transformation in lakes and reservoirs in different basins helps to identify the function of sediments in maintaining the steady state and key mechanism. Materials and methods: Two lakes (Lake Chaohu and Lake Qingling) within the Yangtze River basin and three reservoirs (Dongfeng Reservoir, Puding Reservoir, and Wujiangdu Reservoir) on Wujiang River were studied, and different P and nitrogen species in surficial and pore water, organic material and related exocellular enzyme, and sediment P fractions and iron, as well as P sorption in sediments, were analyzed. Results and discussion: In eutrophic lakes within the Yangtze River basin, the decomposition of organic matter in sediment can stimulate enzymatic hydrolysis release of organic P and the anaerobic desorption of iron binding P (Fe-P). In oligotrophic reservoirs on the Wujiang River, anaerobic desorption of Fe-P caused by mineralization of organic matter did not happen, but Fe-P was still the main P species released from sediment. Calcium-bound P (Ca-P) exhibited markedly different characteristics in these two types of water. Ca-P can be converted into bioavailable P by phosphorolytic bacteria in eutrophic lakes within the Yangtze River basin, but on account of high content of calcium ions in the reservoirs of Wujiang River, coprecipitate with phosphate and formation of Ca-P occurred. Although there was a higher potentiality of sediment P release in the reservoirs of Wujiang River, in terms of higher equilibrium P concentration, P in sediments was mainly static release driven by interstitial water concentration gradient due to larger water depth. Frequent wind and waves, especially in the open water area, in lakes within the Yangtze River basin, caused sediment resuspension, resulting in excessive P release from sediments. Conclusions: The different lake or reservoir morphology, physical and chemical environment, and organic matter properties codetermined the different sediment P migration and transformation characteristics in the studied lakes and reservoirs, which in turn maintained their own steady state. [ABSTRACT FROM AUTHOR]

The interfacial tension gradient forms tangential stress that drives fluid flow at a liquid–liquid interface, known as the Marangoni convection. In this study, we report on the electrocapillary-driven Marangoni flow at the polarizable interface between a gallium-based liquid metal droplet (LMD) and electrolytes, activated by the rotating electric field. When the electric field frequency exceeds 50 Hz , the amplitude of the oscillatory movement of LMD decays to zero, resulting in a stationary droplet. Utilizing micrometer-resolution particle image velocimetry (micro-PIV), we investigate the flow patterns around the LMD in detail. The visualized flow fields reveal two distinct flow patterns in the surrounding fluid at the central cross section of LMD, which vary with changes in frequency: normal flow (50 – 200 Hz) and tangential flow (300 – 1000 Hz). To reveal this flow mechanism, we first analyzed the fluid configuration in a linear electric field. Subsequently, we employ the stream functions to theoretically derive the slip velocity of the Marangoni flow in a rotating electric field. By combining this with the numerical simulations, we arrive at the following conclusions: At high frequencies (f ≥ 50 Hz), the time-averaged part of the interfacial tension gradient dominates the in-phase Marangoni flow, leading to normal flow; while the frequency increases (f ≥ 300 Hz), the electrorotation due to the out-of-phase charging accounts for the transformation of the flow pattern. Our work systematically studied the Marangoni flow under linear and rotating electric fields, which is vital in electrokinetic flows and of fundamental interest for the fluid dynamics society. [ABSTRACT FROM AUTHOR]

We have prepared NaYF4:Er3+/Yb3+/Ca2+ phosphors using the solvothermal method and discussed the influence of annealing on the crystal structure, morphology, and photoluminescence characteristics in this work. The results show that, with the increase of annealing temperature, the crystallization phase changes from a single cubic structure to a mixed phase of cubic and hexagonal phases and the morphology is also condensed from spherical particles to sheets. In particular, the PL intensity of the annealed phosphor becomes much stronger than that of the unannealed phosphor. An annealed NaYF4:Yb3+, Er3+/Ca2+ phosphor is selected as an example to investigate the performance of high temperature sensor based on the fluorescence intensity ratio between two green emissions. The measurement range and the maximum absolute sensitivity SA of the annealed sensor material are superior to the corresponding parameters of the same phosphor without annealing. The curve of relative sensitivity curve SR decreases as the ambient temperature increases, but that of the revolution δT presents an opposite trend. All the results show that the NaYF4:Er3+/Yb3+/Ca2+ phosphor is more suitable for application on the high temperature sensor after annealing. [ABSTRACT FROM AUTHOR]

Purpose: Sediment internal nutrient loading plays an important role in algal blooms. Thus, understanding the specific characteristics of nutrient (nitrogen (N) and phosphorus (P)) recycling from sediment is important for clarifying the processes and mechanisms of cyanobacterial growth and succession. Materials and methods: Sediments and water samples were collected monthly from five sampling sites in Lake Chaohu for 1 year. N and P concentrations in surface and interstitial water were determined, and fractions of sediment organic matter, P, and iron were quantified. P adsorption characteristics were modeled with adsorption isotherms. Results and discussion: Dolichospermum was the dominant bloom species in the western lake in April, followed by Microcystis from May to September in the whole lake. The impulsive regeneration and release mode from iron-bound P and ammonium (NH4+-N) regeneration from sediment in spring triggered the Dolichospermum bloom. In early summer, continuous P release potential as well as nitrate accumulation and NH4+-N deficiency due to NH4+-N prior assimilation by Dolichospermum jointly drove the transition from Dolichospermum to Microcystis due to the energy saving and competitive advantage of rapid uptake and storage of inorganic P as well as a wide range of N utilization forms for Microcystis. All these facts put the Dolichospermum towards common N and P stress. Furthermore, in summer, NH4+-N rapid regeneration from organic algal detritus remineralization due to the decline of Dolichospermum developed Microcystis blooms. Conclusions: The specific mode and pathway of N and P recycling from sediment determined the dominant algal species based on the particular N and P utilization strategies of the algae. Pulsed and a vast amount of P release facilitated the Dolichospermum growth, while continuous and a small quantity of P release was in favor of Microcystis growth. Organic N hydrolysis from Dolichospermum detritus further supported the development of a Microcystis bloom. [ABSTRACT FROM AUTHOR]

Located between the South and the East China Sea, the Taiwan Straits (TWS) are a marine shelf-channel area, with unique hydrological and geomorphological features affected by rivers inflow and with recent algal blooms with red tide events. This study aimed at assessing microbial distribution and function and their modulation in response to environmental gradients. Surface (0.5 m) water samples from 16 stations along five north to south transects were collected; total prokaryotic abundance by epifluorescence microscope and carbon substrate utilization patterns by Biolog Ecoplates were estimated. Spatially, a patchy microbial distribution was found, with the highest microbial metabolic levels and prokaryotic abundance in the TWS area between Minjiang River estuary and Pingtan Island, and progressive decreases towards offshore stations. Complex carbon sources and carbohydrates were preferentially metabolized. This study provides a snapshot of the microbial abundance and activity in TWS as a model site of aquatic ecosystems impacted from land inputs; obtained data highlights that microbial metabolism is more sensitive than abundance to environmental changes. [ABSTRACT FROM AUTHOR]

A novel high-order discretization method for the prediction of milling stability is proposed in this paper to increase the accuracy and efficiency considering the differential of directional cutting coefficient and vibration velocities. Same to the existing full-discretization method (FDM) and semi-discretization method (SDM), the milling system is expressed as a linear time-periodic equation and the time period is discretized into discrete time intervals to approximate the solution. In this algorithm, the cutting force coefficient matrix of the whole integrand is reconstructed to lay the foundation for the fast and accurate approximation. Then, the monodromy matrix (or the Floquet matrix) is calculated by the method used in the temporal finite element analysis (TFEA) instead of the multiple recursive algorithms which can improve the computational time. Finally, the computational efficiency is defined in a new way which gives quantitative comparisons for different discretization methods. It is shown that the proposed method can reduce the computational cost by 91–95% when the same errors are required. [ABSTRACT FROM AUTHOR]

In this work, without template and additives, sheet‐like mesoporous Cu3(PO4)2 ⋅ 3H2O was successfully used to create by a simple solvothermal method. XRD, FT‐IR, BET and SEM methods were used to characterize the structure and properties of the samples that were produced. The results revealed that the stacked mesoporous structure of the target sheet‐like product was well‐formed, and the pore diameter was centered at 3.17 nm. In addition, the sheet‐like mesoporous Cu3(PO4)2 ⋅ 3H2O shows excellent ability to improve the yield of styrene oxide by the research of solvents, catalyst dosage, molar ratio of styrene/TBHP, the reaction temperature and the reaction time in the reaction system. Thus, when the solvent was acetonitrile, the catalyst dosage was 10 mg, the molar ratio of styrene/TBHP was 1 : 4, the reaction temperature was 80 °C, and the reaction time was 8 h, the yield of styrene was 74.7 % and the conversion of styrene was 96.7 %, demonstrating that styrene oxide and benzaldehyde were the major products of the process. The cyclic stability of the catalyst was further assessed, and implied that the catalytic activity, selectivity, and the catalyst's properties fails to change significantly after five cycles, which further indicates the superior stability of the catalyst. [ABSTRACT FROM AUTHOR]

Dissolved inorganic phosphorus is an important form of directly bioavailable phosphorus for cyanobacteria in natural water. Dissolved organic phosphorus could be used by cyanobacteria via alkaline phosphatase, which is produced mainly by bacteria and also cyanobacteria itself. Herein, we review the current knowledge of extracellular phosphatase excreted by cyanobacteria, highlighting the development of detection method and its ecological roles in regulating phosphorus cycling in freshwater systems, which is based on reports for around 100 species of cyanobacteria. Recommendations are suggested concerning the extracellular phosphatase produced by bloom-forming cyanobacteria in terms of the ecological role, followed by a discussion of the future prospects for the study. [ABSTRACT FROM AUTHOR]

To efficiently remove nitrogen from the biofiltration system, the effect of different electron donors and C/N (dissolved organic carbon [DOC]/nitrate) on dissimilatory nitrate reduction to ammonium (DNRA), and denitrification was studied. Electron donor addition significantly increased the gene abundance (nirS and nrfA) and denitrification rate, resulting in higher NO3−-N removal efficiency (over 70%) in refractory organic carbon (bagasse and rice straw) groups. Easily degradable organic carbon (sucrose) caused rapid DOC accumulation, fueling the DNRA process, and NH4+-N accumulation. Inorganic electron donors (ferrous sulfate and sodium sulfide) were unsuitable due to poor denitrification gene abundance, low rate, as well as low NO3−-N removal efficiency. The decrease in C/N was beneficial to denitrification but restricted the occurrence of DNRA, finally reducing N retention capacity. Therefore, the regulation of C/N can play a significant contributory role in the switching of denitrification and DNRA process. [ABSTRACT FROM AUTHOR]

A finite element model of steel frame joints is established using finite element analysis software ANSYS/LS-DYNA. The ideal triangular impact load is used to numerically analyze the dynamic response of steel frame welded joints under blast loading, the main factors affecting this response, and the failure modes of three types of joints, so as to provide reference for the antiexplosive design of steel frame joints. The results show that steel frame joints vibrate violently in the explosive blast direction. Due to the strain rate effect, the strength of steel increases, the material enters the plastic strengthening stage, and there is a certain residual displacement. In addition, displacement and stress caused by blast action in the joint area are large, and the flange shear failure of the beam and column is prone to occur in the joint. Increasing the flange width of the beam and the column cannot improve the antiexplosive performance of the joints, while increasing their thickness can. Furthermore, bolted and welded joints have the highest stiffness and best antiexplosion performance, followed by welded joints, while the antiexplosion performance of bolted joints was the worst. [ABSTRACT FROM AUTHOR]

Gallium-based liquid metals (LMs) are a new type of intelligent material, and their ability to move under the action of an electric field provides new opportunities for the design of small flexible vehicles. However, due to the extremely high fluidity of LMs and the poor automatic control ability of LM vehicles, it's still a huge challenge to control the movement of LMs flexibly and accurately. Therefore, in this paper, a small traction vehicle is designed by putting the flexible LM in rigid armor to make the movement more controllable. Moreover, a desktop-level small automatic guided vehicle (sAGV) system is built by using an external control circuit to follow a predetermined trajectory. Firstly, the basic characteristics of the vehicles driven by a LM droplet are simulated and analyzed. Then the effects of different factors on the movement velocity of the vehicles are measured by experiment. Finally, as a preliminary application test, the sAGV system is used to control the vehicles following a specific trajectory and realize the targeted transportation of cargos. The sAGV system designed in this paper can realize the automatic and precise control of the movement of the small vehicle. The current findings will inspire the further construction of complex small operating systems and the realization of accurate control. [ABSTRACT FROM AUTHOR]

Purpose: Dissimilatory nitrate (NO3−) reduction to ammonium (DNRA) is a significant nitrogen (N) transformation process in estuarine ecosystem. The objectives of this study were to clarify the key biotic and abiotic factors influencing DNRA potential rates in Xiamen Bay. Methods: We characterized DNRA, anammox, and denitrification rates through 15 N isotope tracer experiments. Then quantitative real-time PCR and high-throughput sequencing analysis were conducted to analyze the abundance and community of DNRA bacteria. Spearman correlation analysis was used to understand the relationships of DNRA rate, nrfA abundance, and community with environmental characteristics. Results: Denitrification was dominated in dissimilatory NO3− reduction processes in sediments of Xiamen Bay. Bacteroidetes and Proteobacteria were the main phyla of DNRA bacteria and Pelobacter was the dominant genus. Spearman correlation analysis showed that DNRA rate was significantly positively correlated with nitrite (NO2−) and NO3− in interstitial water, total organic carbon (TOC), acid volatile sulfide (AVS), and total nitrogen (TN) in sediment. Besides, nrfA abundance showed positive correlations with DNRA rate, NO2−, TOC, AVS, and TN. Furthermore, AVS and nrfA abundance were positively correlated with Pelobacter. Conclusion: DNRA rates were limited by sulfide, organic carbon, abundances of nrfA gene, and DNRA bacteria. Sulfide and organic carbon shaped DNRA bacterial community thereby controlled DNRA rate. Heterotrophic sulfide-producing genus (Pelobacter) prevailed among DNRA bacteria, which might support autotrophic DNRA bacteria. In this way, heterotrophic and autotrophic DNRA bacteria were connected through sulfide-producing genus and acted as a whole functional community. [ABSTRACT FROM AUTHOR]

Purpose: Nitrogen (N) and phosphorus (P) are the key elements leading to eutrophication, and it is important to jointly control N and P release from sediments into the water column. Methods: Different mixed materials including P sorbent, natural organic carbon (C), and an oxidizing agent were applied in a 1-year pilot-scale experiment. Results: The addition of iron-rich (IR) clay and Phoslock agent promoted the formation of iron bound P (Fe(OOH)~P) and calcium bound P (CaCO3~P) in sediments, respectively. IR clay offered more advantages in immobilization of phosphorus as refractory P, and the Phoslock agent more effectively reduced the risk of P release into water, which was expressed as a low equilibrium P concentration (EPC0). Mixtures of sugarcane (SU) detritus and IR clay exhibited high carbohydrate (CHO) contents, which further fuelled both denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This indicated that the SU dosage should be controlled to avoid DNRA over denitrification. Attention should be given to the fact that SU introduction significantly promoted the generation of an anaerobic state, leading to the desorption and release of Fe(OOH)~P, which could be alleviated by using Oxone. Multienzyme activity analysis showed that P and N transformation shifted from P desorption to organic P hydrolysis and from ammonification to denitrification and DNRA, respectively. Conclusion: We recommend the use of P sorbent and organic C combined with oxidizing agents as effective mixed materials for sediment remediation, which could enhance P adsorption and provide electron donors for denitrification, while also avoiding the generation of anoxia. [ABSTRACT FROM AUTHOR]

Despite fungi playing an important role in nutrient decomposition in aquatic ecosystems and being considered as vital actors in the ecological processes, they received limited attention regarding the community in aquaculture pond sediments which are extremely important and typically disturbed habitats. Using an ITS1 region of fungal rDNA, this study aimed to investigate sediment fungal communities in fish, crab, and crayfish ponds for decades of farming practices at representative aquaculture regions in the middle Yangtze River basin, China. We then aimed to explore the community patterns associated with species-based farming practices in the ponds at 18 farms. The results showed that the pond sediments harbored more than 9,000 operational taxonomic units. The sediments had significantly higher alpha diversity in crab ponds compared to that in fish and crayfish ponds. The fungal phyla largely belonged to Ascomycota and Chytridiomycota , and the dominance of Rozellomycota over Basidiomycota and Aphelidiomycota was observed. The majority of sediment fungal members were ascribed to unclassified fungi, with higher proportions in fish ponds than crab and crayfish ponds. Further, the fungal communities were markedly distinct among the three types of ponds, suggesting divergent patterns of fungal community assemblages caused by farming practices in aquaculture ponds. The community diversity and structure were closely correlated to sediment properties, especially sediment carbon content and pH. Thus, the distribution and pattern of fungal communities in the sediments appear to primarily depend on species-based farming practices responsible for the resulting sediment carbon content and pH in aquaculture ponds. This study provides a detailed snapshot and extension of understanding fungal community structure and variability in pond ecosystems, highlighting the impacts of farming practices on the assembly and succession of sediment fungal communities in aquaculture ponds. [ABSTRACT FROM AUTHOR]

The shift of mutualistic nutrient relationship among algae, free-living and attached bacteria as well as the effects on algal growth were conducted in experimental mesocosm in which three nutrient addition treatments, including excessive phosphorus (P), excessive carbon (C) and nitrogen (N) to P as 16:1, were designed. The algal community composition did not change greatly in all treatments. The mutualism between algae and its attached bacteria was confirmed in treatments with excessive P and N:P as 16:1, in terms of the significantly higher dissolved organic nutrients derived from algae, extracellular enzyme activities produced by attached bacteria with high abundance and production. Interestingly, compared to treatment with excessive P, this mutualism was even more pronounced in treatment with N:P as 16:1, and resulted in stronger ecological function expressed as higher chlorophyll a content, indicating the importance of nutrient addition with stoichiometric equilibrium. On the contrary, excessive organic C input led to the nutrients competition between algae and free-living bacteria due to the latter's growth in biomass and luxury uptake of inorganic nutrients, which finally limited algal growth. Our results indicated that mutualistic relationship among algae, free-living and attached bacteria could be shifted by nutrient equilibrium (N:P ratio) and dissolved organic C availability. [ABSTRACT FROM AUTHOR]

[Objective] The paper was to study the improvement of poplar bark extract on intestinal Lactococcus lactis of white feather broilers. [Method] Totally 450 Ross 308 white-feather broilers were randomly divided into five groups: control group, low dose group, medium dose group, high dose group, and antibiotic group (oxytetracycline hydrochloride). The feeding duration was 45 d. The probiotics were screened and isolated through homology, and the physiological and biochemical characteristics of chicken intestinal bacteria in different groups were compared to determine the properties of bacterial strain. The drug resistance, antibacterial ability, proliferation ability, acid resistance and bile salt resistance of isolated strain were tested, and a strain of L. lactis was obtained. [Result] The isolated L. lactis was sensitive to other drugs except natural tetracyclines, and there was no significant difference among the four groups except oxytetracycline group; as the concentration of extract increased, the inhibition of L. lactis against Salmonella sp. increased; the medium dose extract had the largest increase in the ability to tolerate the proliferation of L. lactis. [Conclusion] Feeding poplar bark extract will produce positive effects on the physiological characters of intestinal L. lactis in broiler chicken, which will provide potential probiotic strain for chicken production. [ABSTRACT FROM AUTHOR]

A novel method is proposed to pump room‐temperature ionic liquids (ILs) by making use of liquid‐metal‐enabled electrocapillary flow driven by a DC‐biased AC forcing. The effectiveness of this pump strategy is demonstrated by both numerical simulation and experimental observation considering multiple frequency electrochemical polarization. The device can work practically in a wide range of different parameters, such as DC bias, AC voltage amplitude, the shape of the waveform, as well as the electrode separation. Though liquid metal (LM) has already been reported to help deliver the traditional sample of high‐conductivity aqueous electrolytes, its adaptability to drive ILs has apparent advantages, such as quicker pump flow rate due to greater initial interfacial ion adsorption, and much longer operating life due to its nonvolatile feature. The results prove invaluable for the elaborate construction of flexible electrokinetic platforms taking high‐speed ILs as the working fluid. [ABSTRACT FROM AUTHOR]

Background: Achieving nitrogen (N) and phosphorus (P) control in sediment remediation projects by adding natural materials is receiving increasing attention. In this study, different natural materials, including iron-rich clay minerals, calcite, kaoline, sugarcane bagasse and Phragmites detritus, were applied to test their effects on N and P in a mesocosm experiment. Results: Iron-rich clay minerals and Phragmites detritus had obvious advantages for P control; they resulted in almost undetectable levels of soluble reactive phosphorus (SRP) in the water column throughout the experiment. This finding can be explained by their strong P adsorption ability. The high level of available organic carbon in the sediment and water column after sugarcane bagasse addition provided enough electron donors for denitrification and dissimilatory nitrate reduction to ammonium (DNRA), which caused nitrate (NO3−-N) deficiency and ammonium (NH4+-N) accumulation in the water column. Additionally, this resulted in anaerobic conditions, further fuelling the release of P from iron-bound P induced by anoxia. Thus, the amount of sugarcane bagasse applied should be considered carefully in order to balance denitrification and DNRA as well as P releases. Calcite and Phragmites detritus are recommended as remediation materials for N removal based on their significant promotion of denitrification and limitation of DNRA, which resulted in low NO3−-N and NH4+-N levels. These results can be explained by the shifts in the functional microbial community composition and abundance after the addition of natural materials. Conclusions: Iron-rich clay minerals and Phragmites detritus are promising sediment remediation materials for P immobilization due to their strong P adsorption ability. Taken together, the selection of sediment remediation materials should consider the N and P coupling relationship, to prevent NO3−-N removal from causing P leaching or NH4+-N accumulation. [ABSTRACT FROM AUTHOR]

Background: The N2-fixing cyanobacterium, Aphanizomenon flos-aquae is a globally distributed bloom causing species that degrades water quality of fresh and marine water bodies. Overcoming phosphorus (P) deficiency is one of the ecological advantages for bloom-forming cyanobacteria. It remains unclear to what extent can A. flos-aquae alleviate P deficiency by regulating P using strategies. Results: Based on in situ observations of extracellular alkaline phosphatase (APase) in A. flos-aquae via enzyme-labeled fluorescence in freshwater bodies in China, Poland and Czechia, we further investigated responses of isolated A. flos-aquae to different P supplies (dissolved inorganic P (Pi) as +DIP, dissolved organic α-glycerophosphate and β-glycerophosphate as +DOPα and +DOPβ, P-free condition as P-depleted). The significantly negative relationships between percentage of APase producing cells and soluble reactive P concentration in both fields and cultures suggested that the excretion of APase in cyanobacterium was regulated by ambient Pi supply. Suffering from P deficiency in the P-depleted treatments, A. flos-aquae showed the highest APase activity but a vigorous growth at the early culture stage, which might also benefit from the formation of polyphosphate body (PPB) and the decrease of cell P quota. In the +DOP treatments, the coordination of dissolved DOP mineralization and continuous prompt utilization of PPB might contribute to a maintenance but not reproduction of A. flos-aquae when relying on DOP, since the specific growth rate kept around 0 cells L−1 day−1 at the second half culture period and the highest cell density reached only 13.38% of that in +DIP treatments while photochemical efficiency was comparable during the whole experiment. Luxury uptake of phosphate as PPB in the +DIP treatments was consistent to the canonical view of polyphosphate as P storage. Conclusion: Aphanizomenon flos-aquae could achieve an instantaneous growth in response to P deficiency with the coordination of P utilization strategies, while it maintained a long-term sustainable growth but not reproduction under sole DOP supply. Persistent and active reproduction could only be achieved in high Pi supply, which implying that an effective consequence can be expected for combating the bloom of A. flos-aquae when controlling P supply. [ABSTRACT FROM AUTHOR]

Purpose: The construction of riparian buffer strips has become increasingly important due to the effective phosphorus (P) retention of the strips, thus preventing eutrophication in freshwater ecosystems. The key mechanism is P sorption in soils. To provide some suggestions for increasing the sorption ability of P, the relationships between P sorption behavior and both land use patterns and distance from the shoreline were determined. Materials and methods: In April, July, and October 2013, field investigations were carried out along the shoreline of Lake Chaohu. Eleven sections, including 36 sampling sites at different distances from the shoreline, were chosen, and these sections contained different types of riparian buffer strips, such as grassland, farmland, forest, wetland, and forest/grassland. The P species, sorption parameters, and dominant vegetation species were analyzed. Results and discussion: The total P (TP) and P sorption maximum (Qmax) showed no recognizable seasonal variation and were closely correlated with the distance from the shoreline. The further the distance from the shoreline, the higher the TP and Qmax values, suggesting that soil traits could determine the P sorption extent. However, the Olsen-P content and equilibrium P concentration (EPC0) fluctuated greatly, with the peak occurring in spring and the minimum occurring in summer in the majority of the sampling sites. In addition, positive relationships existed between the TP content and the Qmax value as well as the Olsen-P content and the EPC0 value. Canonical correlation analysis (CCA) further showed that the Olsen-P content and EPC0 values were closely related to the dominant vegetation species, indicating that land use patterns played a decisive role in regulating the P sorption strength and the level of available P. Conclusions: To effectively adsorb P (increase Qmax) and prevent P leaching (reduce the EPC0), we recommend changing the land use patterns (more constructed wetlands and forests with grass) in riparian buffers. [ABSTRACT FROM AUTHOR]

Nitrogen (N) removal efficiency through denitrification is usually not ideal and stable in biofilter systems due to the deficiency of organic carbon supply and difficulty of formation of anaerobic status, which could be enhanced by regulating the inflow carbon/nitrogen ratio (C/N), outflow water level, retention time, and addition of plant detritus through the pilot-scale stormwater biofilter study. Removal efficiency of ammonium (NH4+-N), soluble reactive phosphorus (SRP), and total phosphorus (34–90%) was significantly higher than that of nitrate (NO3−-N), dissolved total nitrogen (DTN), and total nitrogen (TN) (9–25%) in the biofilter systems. The addition of plant detritus (especially herbaceous plant) in biofilter systems can enhance the nitrogen (N) and phosphorus (P) removal efficiency by >24%. Through further regulation of inflow C/N, retention time, and outflow water level to promote denitrification, removal efficiency of NO3−-N, DTN, and TN was significantly enhanced and reached up to 83%, 68%, and 73% on average, respectively. However, P leaching increased due to SRP release from iron-bound P caused by anoxia. In the overall consideration of N and P removal, optimized inflow C/N, retention time, and outflow water level are estimated as 10–30, 1–2 h, and 20–40 cm, respectively, which makes a crucial contribution to simultaneous N and P removal. [ABSTRACT FROM AUTHOR]

Several Italian and Chinese temperate lakes with soluble reactive phosphorus concentrations < 0.015 mg L−1 were studied to estimate nitrogen and phosphorus regeneration mediated by microbial decomposition and possible different mechanisms driven by prevailing oligo- or eutrophic conditions. Leucine aminopeptidase (LAP), beta-glucosidase (GLU) and alkaline phosphatase (AP), algal, and bacterial biomass were related to trophic and environmental variables. In the eutrophic lakes, high algal and particulate organic carbon concentrations stimulated bacterial respiration (> 20 μg C L−1 h−1) and could favor the release of inorganic phosphorus. High extracellular enzyme activities and phosphorus solubilizing bacteria abundance in sediments accelerated nutrient regeneration. In these conditions, the positive GLU-AP relationship suggested the coupling of carbon and phosphorus regeneration; an efficient phosphorus regeneration and high nitrogen levels (up to 0.067 and 0.059 mg L−1 NH4 and NO3 in Italy; 0.631 and 1.496 mg L−1 NH4 and NO3 in China) led to chlorophyll a peaks of 14.9 and 258.4 μg L−1 in Italy and China, respectively, and a typical algal composition. Conversely, in the oligo-mesotrophic lakes, very low nitrogen levels (in Italy, 0.001 and 0.005 mg L−1 NH4 and NO3, respectively, versus 0.053 and 0.371 mg L−1 in China) induced high LAP, while low phosphorus (33.6 and 46.3 μg L−1 total P in Italy and China, respectively) led to high AP. In these lakes, nitrogen and phosphorus regeneration were coupled, as shown by positive LAP-AP relationship; however, the nutrient demand could not be completely met without the supply from sediments, due to low enzymatic activity and phosphorus solubilizing bacteria found in this compartment. [ABSTRACT FROM AUTHOR]

The impacts of nutrient amendment termination on the growth strategies of algae and bacteria were conducted in experimentally designed mesocosm in which two different phosphorus (P) dosages were treated. The algal community composition did not change greatly in Group A (low phosphorus) and Group B (high phosphorus). In Group A, the secretion of bacterial alkaline phosphatase (AP) after nutrient termination stimulated bacterial phosphorus acquisition, which caused the decrease in algal phosphorus levels, in terms of the increase of bacterial abundance and bacterial production, as well as the decrease in chlorophyllaand particulate organic carbon. The algal collapse resulted in dissolved organic carbon secretion, further fuelling bacterial growth. In Group B, excess phosphorus input urged algae to store phosphorus as poly-phosphate. When phosphorus input ceased, in order to maintain their used high phosphorus demand, algae strengthened to gain phosphorus through the hydrolysis of dissolved organic phosphorus in water column and ploy-phosphate inside the cells by AP, evidenced by high algal alkaline phosphatase activity, algal growth continuation, and bacterial growth decline. These facts indicated that phosphorus content should reduce to a lower level than expected, so that algal bloom can be effectively controlled in eutrophic water bodies. [ABSTRACT FROM AUTHOR]

Phosphorus (P) fractionation and sorption behavior as well as the abundance and community composition of phosphorus-solubilizing bacteria (PSB) in sediments, including inorganic phosphate-solubilizing bacteria (IPB) and organic phosphate-mineralizing bacteria (OPB), were investigated in 27 sampling sites of five sections in the Three Gorges Reservoir (TGR) in December 2012. The calcium-bound phosphorus (CaCO∼P) accounted for the largest part for P fractions in the sediment of TGR, which was paralleled with IPB outnumbering OPB. Furthermore, some PSB isolates, such as Micromonospora sp., Aminobacter sp., and Arthrobacter sp., were shared by the IPB and OPB. Thus, some IPB species functioned as OPB and vise versa, which could be further reflected by a negative and significant relationship between PSB (IPB + OPB) number and content of CaCO∼P together with acid-soluble organic phosphorus (ASOP). Spatially, the highest ASOP content in the section Mudong and the highest CaCO∼P plus iron-bound phosphorus (Fe(OOH)∼P) as well as equilibrium phosphorus concentration (EPC) in the sections of Yunyang and Zigui due to sediment sequestration by the dam, as well as the positive relationship between EPC and the ratios of different phosphorus species and phosphorus sorption maximum ( Q ), jointly indicated pathway diversification and potential risk of phosphorus release mediated by PSB in TGR. [ABSTRACT FROM AUTHOR]

Purpose: Nitrogen (N) application in excess of assimilatory capacity for aquaculture ponds can lead to water-quality deterioration through ammonia accumulation with toxicity to fish. Ammonia-oxidizing archaea (AOA) and bacteria (AOB) potentially process extra ammonium, so their abundance and diversity are of great ecological significance. This study aimed to reveal variations in communities of AOA and AOB as affected by aquaculture activities. Materials and methods: From June to September 2012, water and sediments were sampled monthly in three ponds feeding Mandarin fish in a suburb of Wuhan City, China. Molecular methods based on ammonia monooxygenase ( amoA) gene were used to determine abundance and diversity of AOA and AOB in the sediments. Results and discussion: The pond with the highest fish stock had the highest nutrient loadings in terms of different forms of N and carbon (C) in both sediment and water. The abundance and diversity of AOB were significantly higher than those of AOA in the sediment. The AOB abundance showed a significantly positive relationship to concentration of soluble reactive phosphorus (SRP) in interstitial water, and both abundance and diversity of AOA were significantly negative to concentration of ammonium in interstitial water. Furthermore, AOA species affiliated to Nitrososphaera-like and Nitrosophaera Cluster was distinguishable from those observed in other aquaculture environments. Conclusions: Nutrients in sediment were enriched by intensive aquaculture activity, among which organic N and C, together with ammonium and SRP, shaped the communities of ammonia oxidizers, with AOB dominating over AOA in terms of abundance and diversity. [ABSTRACT FROM AUTHOR]

Sediment phosphorus (P) release accelerates lake eutrophication, while retention capacity and release potential of different P fractions, calcium-bound P (CaCO3∼P) in particular, still remains unclear. Fractionation and sorption behaviors of phosphorus were studied in sediment of a Chinese shallow lake (Lake Wabu) and two inflowing rivers from December 2011 to December 2012. Abundance of P releasing bacteria was analyzed, and their main species were isolated using a culture-dependent method and identified by their 16S rDNA sequences. CaCO3∼P release abilities of these bacteria were also tested. In sediments of both the lake and rivers studied, the rank order of the different P extracts was CaCO3∼P > iron-bound P > acid-soluble organic P > hot NaOH-extractable organic P. At the same time, CaCO3∼P content and equilibrium P concentration (EPC0) values in river sediments were significantly higher than those in the lake. Additionally, EPC0changes non-monotonically with increasing CaCO3∼P content, forming a V-shaped curve, with the lowest EPC0at an intermediate CaCO3∼P content (around 180 mg kg−1). Below this threshold, CaCO3∼P was a component strengthening P retention; moreover, CaCO3∼P became an active species responsible for P release. Noticeably, between the two parts divided by this threshold, the differences in abundance of inorganic phosphorus solubilizing bacteria (IPB) and organic phosphorus mineralizing bacteria (OPB) were insignificant and the dominant IPB species clustered together. By contrast, OPB was distinguished from each other, whose dominant species isolated from the part with higher CaCO3∼P content, namelyNovosphingobium sp., exhibited a stronger ability to solubilize CaCO3∼P. Shortly, with lower content, CaCO3∼P tends to stabilize P in sediment; while with higher content or under eutrophic condition, it shifted into P source, with some OPB species becoming the main factors to drive its release. [ABSTRACT FROM AUTHOR]

Tunnel construction in watershed area of urban lakes would accelerate eutrophication by inputting nutrients into them, while mechanisms underlying the internal phosphorus cycling as affected by construction events are scarcely studied. Focusing on two main pathways of phosphorus releasing from sediment (enzymatic mineralization and anaerobic desorption), spatial and temporal variations in phosphorus fractionation, and activities of extracellular enzymes (alkaline phosphatase, β-1,4-glucosidase, leucine aminopeptidase, dehydrogenase, lipase) in sediment were examined, together with relevant parameters in interstitial and surface waters in a Chinese urban lake (Lake Donghu) where a subaqueous tunnel was constructed across it from October 2013 to July 2014. Higher alkaline phosphatase activity (APA) indicated phosphorus deficiency for phytoplankton, as illustrated by a significantly negative relationship between APA and concentration of dissolved total phosphorus (DTP). Noticeably, in the construction area, APAs in both sediment and surface water were significantly lower than those in other relevant basins, suggesting a phosphorus supply from some sources in this area. In parallel, its sediment gave the significantly lower iron-bound phosphorus (Fe(OOH)∼P) content, coupled with significantly higher ratio of iron (II) to total iron content (Fe/TFe) and dehydrogenase activities (DHA). Contrastingly, difference in the activities of sediment hydrolases was not significant between the construction area and other basins studied. Thus, in the construction area, subsidy of bioavailable phosphorus from sediment to surface water was attributable to the anaerobic desorption of Fe(OOH)∼P rather than enzymatic mineralization. Finally, there existed a significantly positive relationship between chlorophyll a concentration in surface water and Fe(OOH)∼P content in sediment. In short, construction activities within lakes may interrupt cycling patterns of phosphorus across sediment-water interface by enhancing release of redox-sensitive phosphate, and thereby facilitating phytoplankton growth in water column. [ABSTRACT FROM AUTHOR]

Anabaena and Microcystis are common dominant cyanobacterial genera and frequently form blooms in large shallow eutrophic lakes in China. There is usually a quick succession between these two cyanobacterial blooms in early summer; however, there is currently no solid evidence based on photosynthesis and population competition to explain this phenomenon. This study compared the photosynthetic parameters and the indirectly measured thylakoid membrane fluidity characteristics between Anabaena and Microcystis. The results showed that the growth rate, the maximum photochemical efficiency of PSII ( F/ F), and the maximum relative electron transport rate ( r ETR) of Microcystis cultured at 25 °C were significantly lower than those from cells grown at 15 °C, indirectly suggesting a marked limitation of thylakoid membrane fluidity at low temperatures. Chlorophyll fluorescence dynamics also indicated inhibition of NPQ formation and membrane fluidity when Microcystis was cultured at low temperatures; however, this inhibition was not significant for Anabaena. Fourier transition infrared (FT-IR) spectrometry indicated that the thylakoid membrane of Anabaena can maintain homeostasis fluidity through the upregulation of unsaturated fatty acids when exposed to chilling stress. Increasing the temperature significantly promoted the growth rate of Microcystis, while it had little effect on Anabaena. Moreover, photoinhibition of Anabaena was more easily induced by high light, thus accelerating the bloom succession from Anabaena to Microcystis during warm seasons. An activation-energy model was used to deduce that the threshold temperature of bloom succession was 15.4 °C, which would increase to 16.2 °C and decrease to 14.9 °C under conditions of N-limitation and P-limitation. [ABSTRACT FROM AUTHOR]

Lake sediment substantially accumulates nutrients, while little is known regarding the conditions under which it tends to be a sink or source of phosphorus. It is postulated that the above functions were largely dependent on trophic state. To test this hypothesis, composition, abundance, and size-spectrum of phytoplankton were studied in a Chinese shallow lake (Lake Donghu), together with concentrations and sorption behaviors of phosphorus in water column and sediment. Relationships among these variables were also examined by structural equation model. In the basins with the lowest phosphorus concentration, sediment was a phosphorus source as judged by equilibrium phosphorus concentration, directly affecting the abundance of phytoplankton with smaller size. Contrastingly, in the basins with the highest phosphorus concentration, sediment tended to uptake phosphorus, companied by the lowest ratio of nitrogen to phosphorus, diversity, and evenness of phytoplankton with the smaller size one dominating. Oscillatoria sp. was directly affected by ammonia and phosphorus. Moreover, with a balanced exchange of phosphorus between sediment and water column, phytoplankton increased markedly with the highest diversity and evenness in the basins having intermediate phosphorus concentration. Overall, trophic state modulated sediment functions to supply nutrient and was in turn greatly affected by the sediment in shallow lakes. [ABSTRACT FROM AUTHOR]

The research of the relationships among free-living bacteria, attached bacteria and different algal species can provide valuable evidence for understanding the reason of algal bloom development under nutrient limitations. Significantly positive relationships between chlorophyll a and attached bacteria in Microcystis-bloom ponds and between chlorophyll a and free-living bacteria in other algal bloom ponds were observed. Microcosm experiments further confirmed the synchronized growth of Microcystis and attached bacteria as well as Pediastrum and free-living bacteria. Carbon and bacteria stimulation experiments suggested that extracellular organic carbon from Microcystis was more complex, inducing specific attached bacterial communities and markedly high extracellular enzymes, which can strongly fuelled Microcystis development. On the contrary, dissolved organic carbon from Pediastrum was simple and suitable for free-living bacteria, which can made a distinct effect on Pediastrum growth depending on the degree of nutrients uptake by free-living bacteria. Based on the above results, it can be proposed that the reason of Microcystis bloom breakout in Chinese shallow lakes should be attributed to the close nutrient complementary relationship between Microcystis and specific attached bacteria mediated by dissolved organic carbon and extracellular enzymes at the development of bloom, which might provide scientific support for the research of Microcystis bloom control. [ABSTRACT FROM AUTHOR]

The development of induced pluripotent stem cells (iPSCs) has enabled study of the mechanisms underlying cellular reprogramming. Here, we have studied the dynamic distribution of H2A.Z during induced reprogramming with chromatin immunoprecipitation deep sequencing (ChIP-Seq). We found that H2A.Z tended to accumulate around transcription start site (TSS) and incorporate in genes with a high transcriptional activity. GO analysis with H2A.Z incorporated genes indicated that most genes are involved in chromatin assembly or disassembly and chromatin modification both in MEF and Day 7 samples, not in iPSCs. Furthermore, we detected the highest level of incorporation of H2A.Z around TSS in Day 7 samples compared to MEFs and iPSCs. GO analysis with only incorporated genes in Day 7 also displayed the function of chromatin remodeling. So, we speculate H2A.Z may be responsible for chromatin remodeling to enhance the access of transcription factors to genes important for pluripotency. This study therefore provides a deeper understanding of the mechanisms underlying induced reprogramming. [ABSTRACT FROM AUTHOR]

The development of induced pluripotent stem cells (iPSCs) has enabled study of the mechanisms underlying cellular reprogramming. Here, we have studied the dynamic distribution of H2A.Z during induced reprogramming with chromatin immunoprecipitation deep sequencing (ChIP-Seq). We found that H2A.Z tended to accumulate around transcription start site (TSS) and incorporate in genes with a high transcriptional activity. GO analysis with H2A.Z incorporated genes indicated that most genes are involved in chromatin assembly or disassembly and chromatin modification both in MEF and Day 7 samples, not in iPSCs. Furthermore, we detected the highest level of incorporation of H2A.Z around TSS in Day 7 samples compared to MEFs and iPSCs. GO analysis with only incorporated genes in Day 7 also displayed the function of chromatin remodeling. So, we speculate H2A.Z may be responsible for chromatin remodeling to enhance the access of transcription factors to genes important for pluripotency. This study therefore provides a deeper understanding of the mechanisms underlying induced reprogramming. [ABSTRACT FROM AUTHOR]

The development of induced pluripotent stem cells (iPSCs) has enabled study of the mechanisms underlying cellular reprogramming. Here, we have studied the dynamic distribution of H2A.Z during induced reprogramming with chromatin immunoprecipitation deep sequencing (ChIP-Seq). We found that H2A.Z tended to accumulate around transcription start site (TSS) and incorporate in genes with a high transcriptional activity. GO analysis with H2A.Z incorporated genes indicated that most genes are involved in chromatin assembly or disassembly and chromatin modification both in MEF and Day 7 samples, not in iPSCs. Furthermore, we detected the highest level of incorporation of H2A.Z around TSS in Day 7 samples compared to MEFs and iPSCs. GO analysis with only incorporated genes in Day 7 also displayed the function of chromatin remodeling. So, we speculate H2A.Z may be responsible for chromatin remodeling to enhance the access of transcription factors to genes important for pluripotency. This study therefore provides a deeper understanding of the mechanisms underlying induced reprogramming. [ABSTRACT FROM AUTHOR]

Nutrient (N and P) fluxes via excretion by macrozoobenthos were estimated in a Chinese large shallow lake (Lake Taihu). The spatial variation in nutrient fluxes and the differences of specific excretion rate among six dominant species were quantified. The distribution of dominant species varied significantly among different trophic lake areas. The maximum biomass of macrozoobenthos was calculated in phytoplankton-dominated lake areas, while the minimum occurred in macrophyte-dominated lake areas. Mass-specific excretion rate among six dominant species was significantly different. Our results indicated that nutrient flux through benthic invertebrate varied spatially, which was affected by dominant benthic species composition and biomass.Limnodrilus hoffmeisteri,Corbicula flumineaandBellamya aeruginosamade the greatest contribution to the total nutrient fluxes in Lake Taihu. N and P fluxes excreted by macrozoobenthos were greatest in phytoplankton-dominated lake areas (1037.7 μmol N m−2d−1and 111.74 μmol P m−2d−1), which were almost 20 times greater than in the other lake areas. Since N and P excreted by macrozoobenthos could be rapidly absorbed by algae, macrozoobenthos might be a significant nutrient source contributing to frequent algal blooms in Lake Taihu. [ABSTRACT FROM AUTHOR]

Bacterial and phytoplankton communities are known to be in close relationships, but how natural and anthropogenic stressors can affect their dynamics is not fully understood. To study the response of microbial communities to environmental and human-induced perturbations, phytoplankton and bacterial communities were seasonally monitored in a Mediterranean coastal ecosystem, Syracuse Bay, where multiple conflicts co-exist. Quali-quantitative, seasonal surveys of the phytoplankton communities (diatoms, dinoflagellates and other taxa), the potential microbial enzymatic activity rates (leucine aminopeptidase, beta-glucosidase and alkaline phosphatase) and heterotrophic culturable bacterial abundance, together with the thermohaline structure and trophic status in terms of nutrient concentrations, phytoplankton biomass (as Chlorophyll-a), and total suspended and particulate organic matter, were carried out. The aim was to integrate microbial community dynamics in the context of the environmental characterization and disentangle microbial patterns related to natural changes from those driven by the anthropic impact on this ecosystem. In spite of the complex relationships between the habitat characteristics, microbial community abundance and metabolic potential, in Syracuse Bay, the availability of organic substrates differently originated by the local conditions appeared to drive the distribution and activity of microbial assemblage. A seasonal pattern of microbial abundances was observed, with the highest concentrations of phytoplankton in spring and low values in winter, whereas heterotrophic bacteria were more abundant during the autumn period. The autumn peaks of the rates of enzymatic activities suggested that not only phytoplankton-derived but also allochthonous organic polymers strongly stimulated microbial metabolism. Increased microbial response in terms of abundance and metabolic activities was detected especially at the sites directly affected by organic matter inputs related to agriculture or aquaculture activities. Nitrogen salts such as nitrate, rather than orthophosphate, were primary drivers of phytoplankton growth. This study also provides insights on the different seasonal scenarios of water quality in Syracuse Bay, which could be helpful for management plans of this Mediterranean coastal environment. [ABSTRACT FROM AUTHOR]