•Quantify the interaction between urban ecological land and environmental factors.•Urban ecological land show spatiotemporal coupling with surface urban heat island.•The average explanatory power of ...patch dominance and richness was 19.95% and 16.03%.•Interaction of urban ecological land with topography rapidly increased in 2015–2020.•Interaction between urban ecological land and anthropogenic factors was dominant.
The surface urban heat island effect (SUHI) that occurs during rapid urbanization increases the health risks associated with high temperatures. Urban ecological land (UEL) has been shown to play an important role in improving urban heat stress, however, the impact of UEL interactions with the natural-anthropogenic environment on SUHI at the urban agglomeration-scale is less explored. In this study, the Google Earth Engine and GeoDetector were applied to characterize the spatiotemporal patterns of UEL and SUHI in the Guangdong-Hong Kong-Macao Greater Bay Area from 2000 to 2020 by extracting major built-up urban areas and quantifying the impacts of UEL and its interactions with the natural-anthropogenic factors on SUHI. The results show that the evolution of the UEL landscape structure exhibits clear spatiotemporal coupling with SUHI. Specifically, the UEL underwent a dispersion and degradation process in 2000–2015 and a convergence and restoration process in 2015–2020, the SUHI correspondingly transitioned from intensification and continuity to mitigation and contraction. The UEL landscape structure showed a notable impact on the SUHI reduction, and the dominance and richness of the patches explained an average of 19.95% and 16.03% of the SUHI, respectively. Moreover, the interaction between UEL and land urbanization rate and anthropogenic heat release had a dominant effect on SUHI, but this effect significantly declined from 2015 to 2020. With the implementation of ecological restoration projects, the interaction of UEL with topography rapidly increased and the SUHI gradually dominated by the joint interaction of UEL and natural-anthropogenic factors. A synthesis of the varying effects of several factors showed that the dynamic relationship between the development stages of the urban agglomeration’s regional system and SUHI may conform to the Environmental Kuznets Curve. SUHI reduction strategies should therefore comprehensively optimize the rational allocation of UEL landscape structures and natural-human elements to promote the well-being of residents.
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•The ESI was built to assess the ecological security level.•The SD model was constructed to forecast the future scenarios of ESI.•The historical situation and future scenarios in BTH ...were analyzed.•A relatively rational development mode for BTH was suggested.
Ecological security plays a crucial role in the sustainable development of urban agglomeration, where high population and economic density brings great pressure on eco-system. This paper selected six indicators to build an ecological security index (ESI), and constructed a system dynamics (SD) model to simulate and forecast its future scenarios. It aims at establishing the nexus among the socio-economic and ecological indicators, and identifying the key driving factors of ESI. Taking Beijing–Tianjin–Hebei urban agglomeration (BTH) as a case, this paper assessed the historical situation in 2000–2015 and forecasted the future scenarios in 2016–2030. The results show that, the ESI of BTH decreased from 0.665 in 2000 to 0.648 in 2015. It will decrease to 0.632 in 2030 if the existing development mode continues. Though it belonged to the higher security level all along, obvious disparities will exist in 13 cities in BTH according to the spatiotemporal variations of ESI and its six indicators. Low guarantee degree of eco-water use and fragile ecosystem will be the primary risks of BTH all along. As the existing development mode has considered the socio-economic benefits and ecological protection, it is rational to continue for the whole BTH. However, especially in the southeast cities, the ecological development mode should be strengthened. This paper provides a framework to assess the current conditions and forecast the future scenarios of ecological security for urban agglomerations. It also might help to explore the coupling mechanism between human and ecological system.
•An interesting hysteresis phenomenon was analyzed using entropy production theory.•A function was used to calculate the entropy production in the wall region.•Generation mechanism of the hump and ...hysteresis characteristics was obtained.
The hydraulic loss due to friction and unstable flow patterns in hydro-turbines causes a drop in their efficiency. The traditional method for analyzing the hydraulic loss is by evaluating the pressure drop, which has certain limitations and cannot determine the exact locations at which the high hydraulic loss occurs. In this study, entropy production theory was adopted to obtain a detailed distribution of the hydraulic loss in a pump-turbine in the pump mode. In the past, the wall effects of entropy production were not considered, which caused larger errors as compared with the method of pressure difference. First, a wall equation was proposed to calculate the hydraulic loss in the wall region. The comparison of hydraulic loss calculated by entropy production and pressure difference revealed a better result. Then, through the use of the entropy production theory, the performance characteristics were determined for a pump-turbine with 19mm guide vane opening, and the variation in the entropy production was obtained. Recently, an interesting phenomenon, i.e., a hysteresis characteristic, was observed in the hump region in pump-turbines. Research shows that the hysteresis characteristic is a result of the Euler momentum and hydraulic loss; the hydraulic loss accounts for a major portion of the hysteresis characteristic. Finally, the hysteresis characteristic in the hump region was analyzed in detail through the entropy production. The results showed that the hump characteristic and the accompanying hysteresis phenomenon are caused by backflow at the runner inlet and the presence of separation vortices close to the hub and the shroud in the stay/guide vanes, which is dependent on the direction of discharge.
Ultralight ceramic aerogels with the property combination of recoverable compressibility and excellent high-temperature stability are attractive for use in harsh environments. However, conventional ...ceramic aerogels are usually constructed by oxide ceramic nanoparticles, and their practical applications have always been limited by the brittle nature of ceramics and volume shrinkage at high temperature. Silicon carbide (SiC) nanowire offers the integrated properties of elasticity and flexibility of one-dimensional (1D) nanomaterials and superior high-temperature thermal and chemical stability of SiC ceramics, which makes it a promising building block for compressible ceramic nanowire aerogels (NWAs). Here, we report the fabrication and properties of a highly porous three-dimensional (3D) SiC NWA assembled by a large number of interweaving 3C-SiC nanowires of 20–50 nm diameter and tens to hundreds of micrometers in length. The SiC NWA possesses ultralow density (∼5 mg cm–3), excellent mechanical properties of large recoverable compression strain (>70%) and fatigue resistance, refractory property, oxidation and high-temperature resistance, and thermal insulating property (0.026 W m–1 K–1 at room temperature in N2). When used as absorbents, the SiC NWAs exhibit an adsorption selectivity of low-viscosity organic solvents with high absorption capacity (130–237 g g–1). The successful fabrication of such an attractive material may provide promising perspectives to the design and fabrication of other compressible and multifunctional ceramic NWAs.
Lanthanum (La)-based materials have been recognized as promising adsorbents for aqueous phosphate removal. The incorporation of base metals into La (oxy)hydroxides represents an effective strategy ...to improve adsorption performance. Understanding how base metals affect phosphate adsorption is challenging but essential for the development of effective materials for phosphorus control. Herein, we demonstrated a high-performance LaFe (oxy)hydroxide and studied its mechanisms on phosphate adsorption. The P K edge X-ray absorption near edge structure (XANES) analysis showed that PO4 3– was preferentially bonded with La, and the lattice oxygen in LaFe (oxy)hydroxide was demonstrated to be the active site. The O K edge XANES suggested that Fe optimized the electron structure of La, and Fe/La metal orbital hybridization resulted in the shift of oxygen p character to unoccupied states, facilitating phosphate adsorption. Furthermore, surface analysis showed that the pore size and volume were increased due to the introduction of Fe, which enabled efficient utilization of the active sites and fast adsorption kinetics. The dual effects of Fe in LaFe (oxy)hydroxide greatly enhance the effectiveness of La and represent a new strategy for the development of future phosphorus-control materials.
Diabetes mellitus is a common disorder of endocrine and metabolic disorders. Long term hyperglycemia can lead to a variety of serious chronic complications, such as diabetic nephropathy, diabetic ...retinopathy, diabetes cardiovascular disease, and so on, threatening human life, health and safety. Scutellaria baicalensis Georgi is one of the most commonly used traditional Chinese medicine. Flavonoids are the main effective components of Scutellaria baicalensis Georgi. The flavonoids are mainly baicalin, baicalein, wogonoside and wogonin. The four have the effects of improving the renal function, insulin resistance and retinopathy of type 2 diabetic patients. The aim of this review is to summarize the pathogenesis and clinical research progress of baicalin, baicalein, wogonoside and wogonin in Scutellaria baicalensis Georgi in the treatment of type 2 diabetes mellitus and its complications.
High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements. Although in the infant ...stage, the emerging of this new family of materials has brought new opportunities for material design and property tailoring. Distinct from metals, the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering. Aside from strengthening, hardening, and low thermal conductivity that have already been found in high-entropy alloys, new properties like colossal dielectric constant, super ionic conductivity, severe anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, etc., have been discovered in HECs. As a response to the rapid development in this nascent field, this article gives a comprehensive review on the structure features, theoretical methods for stability and property prediction, processing routes, novel properties, and prospective applications of HECs. The challenges on processing, characterization, and property predictions are also emphasized. Finally, future directions for new material exploration, novel processing, fundamental understanding, in-depth characterization, and database assessments are given.
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•Cellulose-rich grass clipping showed great potentials for biofuel production.•Ultrasound-Ca(OH)2 was the most effective pretreatment method.•Pretreatment removed lignin and ...hemicellulose, and increased crystallinity index.•Reducing sugar yield of grass clipping reached 414mg/g after pretreatment.
Grass clipping, a cellulose-rich raw material, has great potential to produce biofuels, but must be firstly hydrolyzed to liberate fermentable sugars. In this study, grass clipping was pretreated with ultrasound (US), Ca(OH)2, NaOH, US-Ca(OH)2 and US-NaOH at relatively low temperature to enhance its enzymatic hydrolysis. The solubilization of hemicellulose and lignin, and crystallinity index of cellulose increased after US-alkaline pretreatment, leading to a significant increase of enzyme accessibility to cellulose. Compared with another four pretreatments, US-Ca(OH)2 pretreatment of grass clipping showed the best improvement for reducing sugar yield. X-ray diffraction (XRD) determination and scanning electron microscope (SEM) observation showed that the crystallinity index of grass clipping increased and the grass clipping surface suffered from serious erosion after US-Ca(OH)2 pretreatment. Then, the operating conditions of US-Ca(OH)2 pretreatment and enzymatic hydrolysis were systematically optimized, and the suitable operating conditions were as follows: US power density of 0.65W/ml, US pretreatment time of 30min, Ca(OH)2 concentration of 0.75%, pretreatment temperature of 75°C, enzyme loading of 125FPU/g, and hydrolysis time of 72h. The reducing sugar yield of grass clipping pretreated by US-Ca(OH)2 reached 414mg/g, increasing by 3.5 times compared with that of raw grass clipping. The US-Ca(OH)2 pretreatment of grass clipping at low temperature significantly enhanced the potential of grass clipping as a promising raw material to produce biofuels.
Oxidation and sorption mechanism could well explain the higher Sb(III) uptake by FMBO than FeOOH and MnO
2.
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► FMBO is an effective novel adsorbent to remove Sb(III) and exhibits much ...higher removal capacity than FeOOH and MnO
2. ► Oxidation and sorption mechanism could well explain the higher Sb(III) uptake by FMBO than MnO
2 and FeOOH. ► The manganese oxide within FMBO dominates the oxidation of Sb(III) to Sb(V), whereas the iron oxide acts as the adsorption sites.
Antimony is a regulated pollutant to be well controlled. This study compared the removal capability and mechanisms involved in the removal of Sb(III) by Fe–Mn Binary Oxide (FMBO), ferric hydroxide (FeOOH), and manganese dioxide (MnO
2). FMBO shows a maximum Sb removal capacity of 1.76
mmol/g and was much higher than that of both FeOOH (0.83
mmol/g) and MnO
2 (0.81
mmol/g). Characterization techniques of FTIR and XPS indicated the different variation trends of functional groups, surface elemental composition, and chemical valence of Fe, Mn, and Sb after the adsorption of Sb(III) on these three adsorbents. As for FMBO, results indicated that the manganese oxide dominated in oxidation of Sb(III) to Sb(V) whereas the iron oxide adsorbed the Sb(III) and Sb(V). The oxidation and sorption mechanism was proposed to involve in the removal of Sb(III) by FMBO. FMBO may be promisingly used to remove Sb from drinking water and wastewater.
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•Electrochemical mechanism is the core for enhanced performance of CWL-MFCs.•Abundance and gene-expression patterns of EAB affect operational efficiency.•Oxygen and rhizosphere ...secretion from plants boost operation.•Carbon-based, multi-electrodes and porous substrates contribute to operation.
Constructed wetland-microbial fuel cells (CWL-MFCs) are eco-friendly and sustainable technology, simultaneously implementing contaminant removal and electricity production. According to intensive research over the last five years, this review on the operation mechanism was conducted for in-depth understanding and application guidance of CWL-MFCs. The electrochemical mechanism based on anodic oxidation and cathodic reduction is the core for improved treatment in CWL-MFCs compared to CWLs. As the dominant bacterial community, the abundance and gene-expression patterns of electro-active bacteria responds to electrode potentials and contaminant loadings, further affecting operational efficiency of CWL-MFCs. Plants benefit COD and N removal by supplying oxygen for aerobic degradation and rhizosphere secretions for microorganisms. Multi-electrode configuration, carbon-based electrodes and rich porous substrates affect transfer resistance and bacterial communities. The possibilities of CWL-MFCs targeting at recalcitrant contaminants like flame retardants and interchain interactions among effect components need systematic research.
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