科研成果

Bioaugmentation is an effective technology for treating wastewater containing recalcitrant organic pollutants. However, it is restricted by several technical problems, including the difficult colonization and survival of the inoculated bacteria, and the time-consuming start-up process. Considering the important roles of quorum sensing (QS) in regulating microbial behaviors, this study investigated the effects of N-acyl-homoserine lactones (AHLs)-based manipulation on the start-up of biofilm reactors bioaugmented with a pyridine-degrading strain Paracoccus sp. BW001. The results showed that, in the presence of two specific exogenous AHLs (C6-HSL and 3OC6-HSL), the biofilm formation process on carriers was significantly accelerated, producing thick and structured biofilms. The protein and polysaccharide contents of the extracellular polymeric substances (EPS) and soluble microbial products (SMP) in sludge were also elevated, possibly due to the increased abundance of several EPS-producing bacterial genera. Specifically, the stability and complexity of protein structures were improved. Besides the reactor running time, the AHL-manipulation was proved to be the main factor that drove the shift of bacterial community structures in the reactors. The addition of exogenous AHLs significantly increased the succession rate of bacterial communities and decreased the bacterial alpha diversity. Most importantly, the final proportions of the inoculated strain BW001 were elevated by nearly 100% in both sludge and biofilm communities via the AHL-manipulation. These findings strongly elucidated that AHL-based QS was deeply involved in biofilm formation, sludge characteristics, and microbial community construction in bioaugmented reactors, providing a promising start-up strategy for bioaugmentation technology.

Most previous studies treat regional transport of aerosols as a whole, without distinguishing the transport of secondary aerosols and that of their precursors. A new method of quantifying the transport forms of secondary inorganic aerosols (SIA) using the Nested Air Quality Prediction Modeling System was proposed. The contribution of nonlocal emissions to SIA in the receptor region was divided into three parts: (1) SIA chemically formed by nonlocal emissions in their source regions; (2) SIA chemically formed by nonlocal emissions during transport; and (3) SIA chemically formed by nonlocal emissions in the receptor region, representing transport of precursors. In the North China Plain, the transport of precursors and SIA produced during transport are the two main transport forms. Furthermore, the contribution from transport of precursors increased under polluted conditions in most cities. The results indicate that joint control of precursors is paramount for mitigating air pollution. ©2020. The Authors.

Radioactive wastewater containing high concentration of radionuclides poses severe threats to ecosystem and human health, so efficient removal of these toxic heavy metals is urgently needed. Titanate nanomaterials have been demonstrated good adsorbents for heavy metals due to ion exchange property. In this study, titanate nanorings (TNRs) were synthesized using the facile hydrothermal-cooling method. The TNRs were composed of sodium trititanate, with a chemical formula of Na0.66H1.34Ti3O7•0.27H2O and a Na content of 2.38 mmol/g. The TNRs demonstrated sufficient adsorption performance to radionuclides europium (Eu) and uranium (U) ions. Specifically, even at a high initial concentration of 50 mg/L, 86.5% and 92.6% of the two metal ions can be rapidly adsorbed by the TNRs within 5 min, and equilibrium was reached within 60 min at pH 5. The maximum adsorption capacity (Qmax) obtained by the Langmuir isotherm model was 115.3 mg/g for Eu(III) and 282.5 mg/g for uranium U(VI) at pH 5, respectively. The adsorption capacities of the two metals under various water chemical conditions were highly related to their species. Ion exchange between metal cations and Na+ in the TNR interlayers was the dominant adsorption mechanism, and adsorption of U(VI) was more complicated because of the co-existence of various uranyl (UO22+) and uranyl-hydroxyl species. The spent TNRs were effectively regenerated through an acid-base or ethylenediamine tetraacetic acid (EDTA) treatment and reused. Considering the large adsorption capacity and quick kinetic, TNRs are promising materials to remove radionuclides in environmental purification applications, especially emergent treatment of leaked radionuclides.

Cs(2)AgBiBr(6 )having a double perovskite structure is expected to be used in nonlead and stable optoelectronic devices and has received wide attention recently. At this stage, structures of optoelectronic devices using double perovskite and hybrid perovskite are the same. And the energy band structures of double perovskite and hybrid perovskite are different, which will cause energy-level mismatch in the device with double perovskite, which in turn will seriously restrict further improvement of the device performance. A strategy to solve this problem by constructing energy-level gradients with poly(3-hexylthiophene) (P3HT)/MoO3/poly[bis(4-phenyl)(2,4,6-trimethylphenyo-amine] (PTAA) was reported for the first time. The construction of energy-level gradient is mainly achieved by P3HT and PTAA. MoO3 plays a role in protecting the substrate (P3HT) and does not hinder hole transport because it is itself a p-type semiconductor. The champion power conversion efficiency of devices with P3HT/MoO3/PTAA is improved by more than a quarter compared to the standard devices. Moreover, in the champion device, the power conversion efficiency achieved 1.94% with a short-circuit current of 2.80 mA/cm(2).

Conventional ultrafiltration (UF) technology suffers from membrane fouling and limited separation performance. This work demonstrates a novel electrical tuning strategy to improve the separation efficiency of the UF process. An electrically enhanced UF (EUF) system with two sets of oppositely placed membrane–electrode modules was set up. A series of multicycle treatment experiments were conducted to reveal the performance and tuning mechanism of the EUF system. The applied electrical tuning operation brought about an up to 68% reduction of average transmembrane pressure increasing rate (Rp), indicating a strong capability in inhibiting membrane fouling. This fouling reduction can be mainly ascribed to the applied electrophoretic force, changes in solution chemistry, and generation of peroxide, which repulses foulants away from the membrane, hampers foulant adsorption owing to enhanced electrostatic repulsion, and degrades foulants, respectively. The 1.2 V voltage was identified as an effective voltage for stably inhibiting membrane fouling. Besides, the electrical tuning operation led to an up to ∼32% increase in foulant retention rate (φ) owing to both non-Faradaic effects (including electrosorption and electrophoretic repulsion) and Faradaic oxidative degradation. Moreover, the electrical tuning operation allowed a remarkable desalination capability with a significantly higher desalination rate and an up to ∼43% greater salt adsorption capacity as compared with a conventional capacitive deionization process. Additionally, the EUF system achieved a good performance in removing heavy metals (Ag, Cu, Pb, Se, and Sb). The overall enhanced EUF performance suggests promising prospects for practical applications.

To investigate the regional secondary organic aerosol (SOA) formation at Yangtze River Delta (YRD) region, China, the chemical composition of fine particles and their gaseous precursors were simultaneously measured at a regional site, Taizhou, during EXPeriment on the eLucidation of the atmospheric Oxidation capacity, aerosol foRmation and their Effects in Yangtze River Delta (EXPLORE-YRD) intensive field campaign from May to June 2018. Secondary organic carbon (SOC) was estimated by both bottom-up and top-down method, i.e. the yield method from volatile organic compounds (VOCs) oxidation, and the elemental carbon (EC) tracer method. Our result showed that the oxidation of alkanes and aromatics measured by GC-MS/FID based on the yield method could only explain 25.3% of the SOC derived from the EC tracer method, in which aromatics were the dominant contributors (23.9%). This percentage increased to 39.5% while two semi-volatile organic compounds (SVOCs), i.e. naphthalene, and methylnaphthalene, were used in the calculation, suggesting the importance of SVOCs on SOA formation. The SOA formation pathways were further explored. The good correlation of SOC and odd oxygen (Ox) indicated the important role of photochemical reactions on SOA formation in the summer of YRD. Our findings evaluated the contributions of VOCs to SOA formation in Taizhou, revealed the importance of SVOCs to SOA formation and highlighted an urgent need for more exploration of SVOCs in the future. © 2020 The Authors

Hidden Markov models (HMMs) underpin the solution to many problems in computational neuroscience. However, it is still unclear how to implement inference of HMMs with a network of neurons in the brain. The existing methods suffer from the problem of being nonspiking and inaccurate. Here, we build a precise equivalence between the inference equation of HMMs with time-invariant hidden variables and the dynamics of spiking winner-take-all (WTA) neural networks. We show that the membrane potential of each spiking neuron in the WTA circuit encodes the logarithm of the posterior probability of the hidden variable in each state, and the firing rate of each neuron is proportional to the posterior probability of the HMMs. We prove that the time course of the neural firing rate can implement posterior inference of HMMs. Theoretical analysis and experimental results show that the proposed WTA circuit can get accurate inference results of HMMs.