Electron-hole pairing can occur in a dilute semimetal, transforming the system into an excitonic insulator state in which a gap spontaneously appears at the Fermi surface, analogous to a ...Bardeen-Cooper-Schrieffer (BCS) superconductor. Here, we report optical spectroscopic and electronic transport evidence for the formation of an excitonic insulator gap in an inverted InAs/GaSb quantum-well system at low temperatures and low electron-hole densities. Terahertz transmission spectra exhibit two absorption lines that are quantitatively consistent with predictions from the pair-breaking excitation dispersion calculated based on the BCS gap equation. Low-temperature electronic transport measurements reveal a gap of ~2 meV (or ~25 K) with a critical temperature of ~10 K in the bulk, together with quantized edge conductance, suggesting the occurrence of a topological excitonic insulator phase.
The properties of anyons — two-dimensional particles that are neither fermions nor bosons — have been directly measured in a quantum Hall interferometer.
•Novel approach for high-strength pharmaceutical wastewater by PD/A was confirmed.•PD/A biofilm was developed rapidly and had high tolerance to real wastewater.•Higher LB-EPS was produced with ...protein 3-turn helices structure was obtained.•Relatively stable TN removal efficiency of 81.2% was achieved with increasing load.•Thauera was highly enriched and dominated for partial NO3− reduction to NO2−.
Biological nitrogen removal from pharmaceutical wastewater has drawn increasing attention due to biotoxicity and inhibition. In this study, for the first time, a novel approach integrating partial-denitrification with anaerobic ammonia oxidation (PD/A) in a sequencing biofilm batch reactor (SBBR) was proposed and demonstrated to be efficient to treat the bismuth nitrate and bismuth potassium citrate manufacturing wastewater, containing ammonia (NH4+-N) and nitrate (NO3−-N) of 6300±50 mg L − 1 and 15,300±50 mg L − 1. The maximum anammox activity was found at the shock effect of influent total nitrogen (TN) of 100 mg L − 1 with NO3−-N/NH4+-N of 1.0. Long-term operation demonstrated that the PD/A biofilm was developed rapidly after 30 days using synthetic influent, with TN removal efficiency increasing from 40.9% to 80.8%. Significantly, the key bacteria for PD/A had high tolerance and adapted rapidly to pharmaceutical wastewater, achieving a relatively stable TN removal efficiency of 81.2% with influent NH4+-N and NO3−-N was 77.9 ± 2.6 and 104.1 ± 4.4 mg L − 1 at a relatively low COD/NO3−-N of 2.6. Anammox pathway contributed to TN removal reached 83.6%. Significant increase of loosely-bound extracellular polymeric substances was obtained with increasing protein of 3-turn helices structure as response to the inhibitory condition. High-throughput sequencing analysis revealed that the functional genus Thauera was highly enriched in both biofilms (9.5%→43.6%) and suspended biomass (15.5%→57.5%), which played a key role in high NO2−-N accumulation. While the anammox bacteria decreasing from 7.8% to 1.6% in biofilm, and from 1.8% decreased to 0.1% in the suspended sludge. Overall, this study provides a new method of high-strength pharmaceutical wastewater treatment with low energy consumption and operation cost, as well as a satisfactory efficiency.
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Correlation and frustration play essential roles in physics, giving rise to novel quantum phases
. A typical frustrated system is correlated bosons on moat bands, which could host topological orders ...with long-range quantum entanglement
. However, the realization of moat-band physics is still challenging. Here, we explore moat-band phenomena in shallowly inverted InAs/GaSb quantum wells, where we observe an unconventional time-reversal-symmetry breaking excitonic ground state under imbalanced electron and hole densities. We find that a large bulk gap exists, encompassing a broad range of density imbalances at zero magnetic field (B), accompanied by edge channels that resemble helical transport. Under an increasing perpendicular B, the bulk gap persists, and an anomalous plateau of Hall signals appears, which demonstrates an evolution from helical-like to chiral-like edge transport with a Hall conductance approximately equal to e
/h at 35 tesla, where e is the elementary charge and h is Planck's constant. Theoretically, we show that strong frustration from density imbalance leads to a moat band for excitons, resulting in a time-reversal-symmetry breaking excitonic topological order, which explains all our experimental observations. Our work opens up a new direction for research on topological and correlated bosonic systems in solid states beyond the framework of symmetry-protected topological phases, including but not limited to the bosonic fractional quantum Hall effect.
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•Effluent TN as low as 4.0 mg N/L was achieved via PD-Anammox process.•Anammox was stable and accounted for 78.2% on nitrogen removal.•Low nitrous oxide (N2O) was produced in ...PD-Anammox process.•Oxygen consumption, COD demand and sludge production would be largely reduced.•PD-Anammox process can be easily retrofitted from existing plants.
High nitrate (NO3−-N) concentration in the effluent of wastewater treatment plants (WWTPs), cannot meet the increasing stringent discharge limits. Hence, the tertiary treatment is necessary to lower the total nitrogen concentration. In this study, an innovative partial denitrification (PD)-Anammox process was applied to remove the nitrate nitrogen (20–40 mg N/L) from secondary effluent. The nitrate wastewater were firstly fed to PD sequencing batch reactor (SBR, 10 L) to produce nitrite along with the low carbon/nitrogen ratio (C/N) municipal sewage (NH4+ of 57.8 mg N/L, COD of 175.8 mg/L), then the effluent from SBR was pumped to the anaerobic sludge blanket (UASB, 3.2 L) performing anammox for further nitrogen removal. The integrated process was operated for 224 days with the secondary effluent to municipal sewage volume ratio of 2.9–6. The results suggested that an excellent nitrate removal efficiency of 97.9% was achieved, and the mean removal efficiency of NH4+-N and COD from municipal sewage were 95.2% and 81.6%, respectively, leading to the total nitrogen and COD concentration in the final effluent as low as 4.0 mg N/L and 30.1 mg/L, respectively. Anammox was the main nitrogen removal pathway with a mean proportion of 78.2%, and Candidatus_Brocadia was identified as the dominating genus. Furthermore, it was found that a minor nitrous oxide (N2O) was produced in the integrated process. The PD-Anammox process was verified to be economically and environmentally feasible for retrofitting of existing plants.
Anaerobic ammonium oxidation (anammox) has been extensively investigated for cost-efficient nitrogen removal from wastewater. However, the major issues of nitrate (NO3−-N) residue and instability in ...the current combination of nitritation and anammox process necessitates being addressed efficiently. The recently proposed partial-denitrification (PD), terminating NO3−-N reduction to nitrite (NO2−-N), has been regarded as a promising alternative of NO2−-N supplying for anammox bacteria. Given the engineering practices, the steadily high NO2−-N production, alleviating organic inhibition, and reducing greenhouse gas of PD process offers a viable and efficient approach for anammox implementation. Moreover, it allows for the extending applications of anammox process due to the NO3−-N removal availability. Here we comprehensively review the important new outcomes and discuss the emerging applications of PD-based anammox including the process development, mechanism understanding, and future trends. Significant greater stability and enhanced nitrogen removal efficiency have been demonstrated in the novel integrations of PD and anammox process, indicating a broad perspective in dealing with the mainstream municipal sewage, ammonia-rich streams, and industrial NO3−-N contained wastewater. Furthermore, researches are still needed for the predictable and controllable strategies, along with the detailed microbiological information in future study. Overall, the achievement of PD process provides unique opportunity catalyzing the engineering applications of energy-efficient and environmental-friendly wastewater treatment via anammox technology.
•Partial-Denitrification provides a stable and efficient alternative for nitrite supply.•PD process offers extending application of anammox treating nitrate wastewater.•PD/A holds potential in improved efficiency for mainstreams and sidestreams treatment.•Emerging opportunities are given for wastewater treatment engineering by PD/A.•Predictable controlling strategies and penetrating microbial mechanism are needed.
Bacteria and fungi are primary constituents of airborne microbes in fine particulate matter (PM2.5) and significantly impact human health. However, hitherto, seasonal variation and effect of air ...pollution on microbial community composition and structure are poorly understood. This study analyzed the bacterial and fungal composition of PM2.5 under different air pollution levels during different seasons in Beijing. We altogether collected 75PM2.5 samples during four seasons from April 2014 to January 2015, under different air pollution levels and employed high-throughput sequencing methods to analyze microbial composition. The results showed that air pollution decreased species richness and community diversity of bacteria in PM2.5. The variation in bacterial and fungal community composition and structure was significantly related to the season but there was no correlation between their abundance and pollution levels. Pathogenic bacteria and fungi were more abundant in winter than other seasons. To best of our knowledge, this is the first study that demonstrates seasonal variation characteristics of bacteria and fungi in PM2.5 in heavy haze contaminated areas and highlights the effects of air pollution on the atmospheric microbial community. This study would be useful to other bioaerosol studies focusing on the role of the atmospheric particulate matter on human health.
Principal coordinate analysis of the samples using Weighted-UniFrac distance matrix, and classified as Bacteria (a) and fungi (b). Display omitted
•Seasonal variations of inhalable microbial communities in PM2.5 were investigated.•Impact of air pollution level on bioaerosol was discussed.•High-throughput sequencing method was used to identified bacteria and fungi.•The bioaerosol in PM2.5 showed significant seasonal variations.
Elimination of nitrogen pollution from wastewater containing high-strength nitrate (NO3−-N) is a significant issue to prevent deterioration of water quality and eutrophication of receiving water ...body. Traditional denitrification process faces several challenges including the huge organic carbon demand, intermediate products accumulation, and long acclimatization period. In this study, an efficient solution was given by a novel two-stage Partial Denitrification (PD)-Anammox process. High NO3−-N (1000 mg N/L) wastewater and municipal sewage (COD: 182.5 mg/L, ammonia (NH4+-N): 58.3 mg/L) were simultaneously introduced to the PD reactor for NO3−-N converting to NO2−-N. The NH4+-N and NO2−-N in effluent of PD were removed in subsequent anammox reactor. Results showed that a satisfactory nitrogen removal was achieved by optimizing the volume ratios of influent NO3−-N and municipal sewage, as well as the external organic matter dosage. The NO3−-N removal efficiency reached up to 95.8% without accommodation period, along with the NH4+-N removal achieving 92.8%. Anammox contributed to 78.9% of TN removal despite the high COD (76.5–98.6 mg/L) in PD effluent was introduced, indicating the significant stability of the integrated process. The microbial analysis suggested that the Candidatus Brocadia, identified as anammox bacteria, cooperated stable with denitrifying bacteria in 215-day operation. The PD-Anammox process offers an economically and technically attractive approach in the high NO3−-N wastewater treatment since it has great advantages of much low carbon demand, minimal sludge production, enabling simultaneous treatment of municipal sewage, and avoiding the common issues in traditional denitrification process.
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•Simultaneous treatment of high-strength nitrate and municipal sewage was demonstrated.•Nitrate removal efficiency reached up to 95.8% at influent nitrate of 1000 mg/L.•Municipal sewage was treated with nitrogen removal efficiency of 92.8%.•Anammox and denitrifying bacteria cooperated for advanced nitrogen removal.•Partial-denitrification combining with anammox is an economic and efficient option.
We observe the magnetic oscillation of electric conductance in the two-dimensional InAs/GaSb quantum spin Hall insulator. Its insulating bulk origin is unambiguously demonstrated by the antiphase ...oscillations of the conductance and the resistance. Characteristically, the in-gap oscillation frequency is higher than the Shubnikov–de Haas oscillation close to the conduction band edge in the metallic regime. The temperature dependence shows both thermal activation and smearing effects, which cannot be described by the Lifshitz-Kosevich theory. A two-band Bernevig-Hughes-Zhang model with a large quasiparticle self-energy in the insulating regime is proposed to capture the main properties of the in-gap oscillations.
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