Signatures of superconductivity near 80 K in a nickelate under high pressure.

Although high-transition-temperature (high-Tc) superconductivity in cuprates has been known for more than three decades, the underlying mechanism remains unknown1-4. Cuprates are the only unconventional superconductors that exhibit bulk superconductivity with Tc above the liquid-nitrogen boiling temperature of 77 K. Here we observe that high-pressure resistance and mutual inductive magnetic susceptibility measurements showed signatures of superconductivity in single crystals of La3Ni2O7 with maximum Tc of 80 K at pressures between 14.0 GPa and 43.5 GPa. The superconducting phase under high pressure has an orthorhombic structure of Fmmm space group with the [Formula: see text] and [Formula: see text] orbitals of Ni cations strongly mixing with oxygen 2p orbitals. Our density functional theory calculations indicate that the superconductivity emerges coincidently with the metallization of the σ-bonding bands under the Fermi level, consisting of the [Formula: see text] orbitals with the apical oxygen ions connecting the Ni-O bilayers. Thus, our discoveries provide not only important clues for the high-Tc superconductivity in this Ruddlesden-Popper double-layered perovskite nickelates but also a previously unknown family of compounds to investigate the high-Tc superconductivity mechanism.

Bioconversion of volatile fatty acids from organic wastes to produce high-value products by photosynthetic bacteria: A review.

Anaerobic fermentation of organic waste to produce volatile fatty acids (VFAs) production is a relatively mature technology. VFAs can be used as a cheap and readily available carbon source by photosynthetic bacteria (PSB) to produce high value-added products, which are widely used in various applications. To better enhance the VFAs obtained from organic wastes for PSB to produce high value-added products, a comprehensive review is needed, which is currently not available. This review systematically summarizes the current status of microbial proteins, H2, poly-ß-hydroxybutyrate (PHB), coenzyme Q10 (CoQ10), and 5-aminolevulinic acid (ALA) production by PSB utilizing VFAs as a carbon resource. Meanwhile, the metabolic pathways involved in the H2, PHB, CoQ10, and 5-ALA production by PSB were deeply explored. In addition, a systematic resource utilization pathway for PSB utilizing VFAs from anaerobic fermentation of organic wastes to produce high value-added products was proposed. Finally, the current challenges and priorities for future research were presented, such as the screening of efficient PSB strains, conducting large-scale experiments, high-value product separation, recovery, and purification, and the mining of metabolic pathways for the VFA utilization to generate high value-added products by PSB.

Effects of sludge retention time on sludge reduction by ultrasound treatment: Sludge characteristics, microbial community, and metabolism.

Both ultrasound and sludge retention time (SRT) enable the in-situ sludge reduction during wastewater treatment, but the influence of SRT on ultrasonic lysis - cryptic growth is unclear. This paper researched the influence of different SRTs on sludge lysis - cryptic growth using a sequential bio-reactor (SBR), then explained in details the changes of microorganisms in the SBR. The best SRT for sludge reduction was 30 d, and 47.29% reduction in sludge was achieved. The different SRTs changed the organic matter removal in the wastewater, and the removal rate decreased when SRT exceeded 60 d. The size of the sludge particles varied depending on the SRT, with the smallest size at SRT of 10d being 45.6 µm and the largest size at SRT of 90d being 110.0 µm. SEM showed that the sludge surface changed rough at longer SRT. FTIR and XPS showed notable effect in sludge functional group strength at SRT of 30 d. Extracellular polymeric substance (EPS) reduced the most at SRT of 30 d. The microbial communities of sludge varied with the SRT, and the unique main genus at SRT of 5, 15, 30 and 90 d were C10-SB1A, Lactococcus, Propioniciclava, Lactococcus, respectively. Furthermore, the SRT changed relative abundance of enzymes concerned with metabolism of carbon, nitrogen, and phosphorus. Similarly, SRT changed the metabolic rate, and the metabolic rate of carbon, nitrogen and phosphorus was best at SRT of 30 d.

Life cycle assessment of n-caproic acid production via chain elongation from food waste: Comparison of shunting and staged technology.

n-Caproic acid is a widely used biochemical that can be produced from organic waste through chain elongation technology. This study aims to evaluate the environmental impacts of n-caproic acid production through chain elongation by two processes (i.e., shunting and staged technology). The Open-life cycle assessment (LCA) model was used to calculate the environmental impacts of both technologies based on experimental data. Results showed that the shunting technology had higher environmental impacts than the staged technology. Water and electricity made bigger contribution to the environmental impacts of both technologies. Reusing chain elongation effluent substituting for water and using electricity produced by wind power could reduce the environmental impacts of water and electricity effectively. Using ethanol from food waste had higher global warming potential than fossil ethanol, which suggested that a cradle-to-grave LCA is needed to be carried out for specific raw materials and chain elongation products in the future.

Age and sex differences in the association between Dietary Inflammatory Index and severe headache or migraine: a nationwide cross-sectional study.

BACKGROUND: Migraine and severe headaches are extremely prevalent neurological disorders that plague humans and society. Prior research has revealed that DII may affect the occurrence of migraines, but there are too few relevant studies and more are required. This study aimed to determine the association between severe headache or migraine and the Dietary Inflammatory Index (DII), with particular attention to age and gender differences. METHODS: Using data from the National Health and Nutrition Examination Survey (NHANES), we performed a cross-sectional study. In addition, we investigated the association between DII and severe headache or migraine using weighted multivariate logistic regression models, and restricted cubic splines models were plotted to explore their linear correlation. RESULTS: There were a total of 13,439 people participating in the study, and of those, 2745 experienced a severe headache or migraine within the previous three months. The DII was linearly and positively correlated with severe headache or migraine (odds ratio [OR] = 1.05, 95% confidence interval [CI] = 1.01-1.08, p = 0.0051). Stratified analysis showed that this relationship persisted among women and those aged < 60 years, with ORs of 1.08 (95% CI = 1.04-1.13, p = 0.0004) and 1.05 (95% CI = 1.01-1.09, p = 0.0071), respectively. CONCLUSIONS: We found that greater levels of DII were significantly related to an increased likelihood of migraine onset, especially among women and young and middle-aged populations. Further research is required to validate and expand upon our results.

Sulfur-manganese carbonate composite autotrophic denitrification: nitrogen removal performance and biochemistry mechanism.

A novel composite sulfur-manganese carbonate autotrophic denitrification (SMAD) system was developed to reduce sulfate production and provide pH buffer function while improving denitrification efficiency without external organics. The average removal efficiency of total nitrogen (TN) was 98.09% and 96.29%, and that of NO3--N was 99.53% and 97.77%, respectively, in the SMAD system with a hydraulic retention time (HRT) of 6 h and 3 h. They were significantly higher than that in the controls (quartz sand, manganese carbonate ore, and sulfur systems). The H+ produced by the sulfur autotrophic denitrification (SAD) process promoted the release of Mn2+ in the SMAD system. And this system had a stable pH with no accumulation of NO2--N. The decrease of sulfate and formation of Mn oxides through Mn2+ electron donation confirmed the presence of the manganese autotrophic denitrification (MAD) process in the SMAD system. Dominant functional bacteria in the SMAD system were Thiobacillus, Chlorobium, and Sulfurimonas, which were linked to nitrogen, sulfur, and manganese conversion and promoted denitrification. Meanwhile, Flavobacterium participating in Mn2+ oxidation was found only in the SMAD system. The SMAD system provided a new strategy for advanced tailwater treatment.

Structure and composition of dissolved organic matters in sludge by ultrasonic treatment.

The leaching of dissolved organic matter (DOM) from the sludge into the liquid phase is induced by ultrasound. However, there is limited investigation into the structure and molecular composition of sludge DOM in this process. The molecular structure and composition of sludge DOM in ultrasonic treatment were comprehensively elucidated in this study. The sludge dissolved organic carbon (DOC) and three-dimensional fluorescence spectroscopy (3D-EEM) image had most significant change at 15-min ultrasonic time and 1.2 W/mL ultrasonic density, respectively. Gas Chromatography-Mass Spectrometry (GC-MS) analysis indicated that ultrasonic treatment of sludge reduced the macromolecules to small molecules in DOM. Then, electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) analysis revealed that lignin, tannins, and carbohydrates were the main components of sludge DOMs after ultrasound treatment. analysis revealed that lignin, tannins, and carbohydrates were the main components of sludge DOMs after ultrasound treatment. Furthermore, through the Van Krevelen analysis, the major components were CHO (48.50%) and CHOS (23.20%) in the DOM of ultrasonicated sludge. This research provides the basis for the practical application of ultrasonic treatment of sludge and provides basic information for DOM components.

Whole-cell FRET monitoring of transcription factor activities enables functional annotation of signal transduction systems in living bacteria.

Bacteria adapt to their constantly changing environments largely by transcriptional regulation through the activities of various transcription factors (TFs). However, techniques that monitor TF-promoter interactions in situ in living bacteria are lacking. Herein, we developed a whole-cell TF-promoter binding assay based on the intermolecular FRET between an unnatural amino acid, l-(7-hydroxycoumarin-4-yl) ethylglycine, which labels TFs with bright fluorescence through genetic encoding (donor fluorophore) and the live cell nucleic acid stain SYTO 9 (acceptor fluorophore). We show that this new FRET pair monitors the intricate TF-promoter interactions elicited by various types of signal transduction systems, including one-component (CueR) and two-component systems (BasSR and PhoPQ), in bacteria with high specificity and sensitivity. We demonstrate that robust CouA incorporation and FRET occurrence is achieved in all these regulatory systems based on either the crystal structures of TFs or their simulated structures, if 3D structures of the TFs were unavailable. Furthermore, using CueR and PhoPQ systems as models, we demonstrate that the whole-cell FRET assay is applicable for the identification and validation of complex regulatory circuit and novel modulators of regulatory systems of interest. Finally, we show that the FRET system is applicable for single-cell analysis and monitoring TF activities in Escherichia coli colonizing a Caenorhabditis elegans host. In conclusion, we established a tractable and sensitive TF-promoter binding assay, which not only complements currently available approaches for DNA-protein interactions but also provides novel opportunities for functional annotation of bacterial signal transduction systems and studies of the bacteria-host interface.

A new perspective on hippocampal synaptic plasticity and post-stroke depression.

Post-stroke depression, a common complication after stroke, severely affects the recovery and quality of life of patients with stroke. Owing to its complex mechanisms, post-stroke depression treatment remains highly challenging. Hippocampal synaptic plasticity is one of the key factors leading to post-stroke depression; however, the precise molecular mechanisms remain unclear. Numerous studies have found that neurotrophic factors, protein kinases and neurotransmitters influence depressive behaviour by modulating hippocampal synaptic plasticity. This review further elaborates on the role of hippocampal synaptic plasticity in post-stroke depression by summarizing recent research and analysing possible molecular mechanisms. Evidence for the correlation between hippocampal mechanisms and post-stroke depression helps to better understand the pathological process of post-stroke depression and improve its treatment.

Comparison of Efficacy and Safety of Laparoscopic Holmium laser Lithotripsy and Laparoscopic Bile Duct Exploration for Bile Duct Stones: A Systematic Review and Meta-Analysis.

BACKGROUND: Laparoscopic holmium laser lithotripsy (LHLL) has been used to treat bile duct stones with unclear outcomes. A meta-analysis was conducted to investigate the LHLL and laparoscopic bile duct exploration (LBDE) efficacy and safety in treating bile duct stones. METHODS: The correlational studies were searched databases, such as PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang, and VIP, to identify eligible studies from inception to July 2022. The dichotomous and continuous outcomes were evaluated using odds ratio (OR), risk difference (RD) and weighted mean difference (WMD) with 95% confidence intervals (CIs). Stata 15.0 and Review Manager 5.3 software helped in data analyses. RESULTS: A total of 23 studies with 1,890 patients, primarily from China, were included. The results indicated that operation time (WMD = - 26.94; 95% CI:(- 34.30, - 19.58); P < 0.00001), estimated blood loss (WMD = - 17.97; 95% CI: (- 22.94, - 13.00); P = 0.002), rate of residual stone (OR = 0.15, 95%CI: (0.10, 0.23); P < 0.00001), length of hospital stay (WMD = - 2.88; 95% CI:(- 3.80, - 1.96); P < 0.00001) and time to bowel function recovery (WMD = - 0.59; 95% CI: (- 0.76, - 0.41); P < 0.00001) had statistically significant differences between the two groups. In postoperative complications, biliary leakage (RD = -0.03; 95% CI: (- 0.05, -0.00); P = 0.02), infection (RD = - 0.06; 95% CI: (- 0.09,- 0.03); P < 0.00001) and Hepatic injury (RD = - 0.06; 95% CI: (- 0.11, - 0.01); P = 0.02) revealed statistically significant differences. However, no significant differences were observed in biliary damage (RD = - 0.03; 95% CI: (- 0.06, 0.00); P = 0.06) and hemobilia (RD = - 0.03; 95% CI: (- 0.06, 0.00); P = 0.08). CONCLUSION: The current meta-analysis indicated that LHLL could be more effective and safer than LBDC. However, these results should be confirmed with a larger sample size and rigorously designed randomized controlled trials.

A transferrable and integrative type I-F Cascade for heterologous genome editing and transcription modulation.

The Class 1 type I CRISPR-Cas systems represent the most abundant and diverse CRISPR systems in nature. However, their applications for generic genome editing have been hindered due to difficulties of introducing the class-specific, multi-component effectors (Cascade) in heterologous hosts for functioning. Here we established a transferrable Cascade system that enables stable integration and expression of a highly active type I-F Cascade in heterologous bacterial hosts for various genetic exploitations. Using the genetically recalcitrant Pseudomonas species as a paradigm, we show that the transferred Cascade displayed substantially higher DNA interference activity and greater editing capacity than both the integrative and plasmid-borne Cas9 systems, and enabled deletion of large fragments such as the 21-kb integrated cassette with efficiency and simplicity. An advanced I-F-λred system was further developed to enable editing in genotypes with poor homologous recombination capacity, clinical isolates lacking sequence information, and cells containing anti-CRISPR elements Acrs. Lastly, an 'all-in-one' I-F Cascade-mediated CRISPRi platform was developed for transcription modulation by simultaneous introduction of the Cascade and the programmed mini-CRISPR array in one-step. This study provides a framework for expanding the diverse type I Cascades for widespread, heterologous genome editing and establishment of editing techniques in 'non-model' bacterial species.

Machine learning algorithms to predict intraoperative hemorrhage in surgical patients: a modeling study of real-world data in Shanghai, China.

BACKGROUND: Prediction tools for various intraoperative bleeding events remain scarce. We aim to develop machine learning-based models and identify the most important predictors by real-world data from electronic medical records (EMRs). METHODS: An established database of surgical inpatients in Shanghai was utilized for analysis. A total of 51,173 inpatients were assessed for eligibility. 48,543 inpatients were obtained in the dataset and patients were divided into haemorrhage (N = 9728) and without-haemorrhage (N = 38,815) groups according to their bleeding during the procedure. Candidate predictors were selected from 27 variables, including sex (N = 48,543), age (N = 48,543), BMI (N = 48,543), renal disease (N = 26), heart disease (N = 1309), hypertension (N = 9579), diabetes (N = 4165), coagulopathy (N = 47), and other features. The models were constructed by 7 machine learning algorithms, i.e., light gradient boosting (LGB), extreme gradient boosting (XGB), cathepsin B (CatB), Ada-boosting of decision tree (AdaB), logistic regression (LR), long short-term memory (LSTM), and multilayer perception (MLP). An area under the receiver operating characteristic curve (AUC) was used to evaluate the model performance. RESULTS: The mean age of the inpatients was 53 ± 17 years, and 57.5% were male. LGB showed the best predictive performance for intraoperative bleeding combining multiple indicators (AUC = 0.933, sensitivity = 0.87, specificity = 0.85, accuracy = 0.87) compared with XGB, CatB, AdaB, LR, MLP and LSTM. The three most important predictors identified by LGB were operative time, D-dimer (DD), and age. CONCLUSIONS: We proposed LGB as the best Gradient Boosting Decision Tree (GBDT) algorithm for the evaluation of intraoperative bleeding. It is considered a simple and useful tool for predicting intraoperative bleeding in clinical settings. Operative time, DD, and age should receive attention.

Effects of lysed sludge reflux point on ultrasound lysis-cryptic growth in anaerobic/aerobic (A/O) wastewater treatment: Sludge reduction, microbial community, and metabolism.

Ultrasonication allows sludge reduction to be performed in situ during wastewater treatment, and the reflux point of the lysed sludge affects this performance. This study investigated the effects of reflux point (anaerobic stage, carbon/nitrogen (C/N) lowest stage, and aerobic stage) on sludge lysis-cryptic growth in an anaerobic/aerobic reactor and variations in the sludge and microbial community. The best reflux point occurred at the lowest C/N ratio stage, and a 50.96% reduction in excess sludge was achieved. The reflux of the lysed sludge to the aerobic stage reduced nitrogen and phosphorus removal. The reflux of the lysed sludge decreased the average sludge size, reaching 29.2 µm when reflux to the aerobic stage. Scanning electron microscopy showed that the sludge surface was unaffected by the reflux point. The Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy results showed that the most prominent variation in the intensity of the sludge functional groups occurred when the reflux was at the lowest C/N stage. The amount of extracellular polymeric substances decreased the most during reflux to the anaerobic stage. The sludge microbial communities varied with the reflux point, and the dominant phyla during reflux to the anaerobic, lowest C/N, and aerobic stages were Bacteroidetes, Firmicutes, and Bacteroidetes, respectively. Furthermore, the reflux point did not alter the metabolic pathway of sludge microorganisms but increased the number of enzymes in metabolic pathways.

Dystrophic Calcification of the Lower Leg in a Patient with Chronic Lower Extremity Venous Insufficiency and Diabetes Mellitus: A Case Report and Literature Review.

ABSTRACT: Chronic lower extremity venous insufficiency can cause local dystrophy, and some patients will develop calf dystrophic calcification. In this case report, the authors describe a patient with varicose veins of both lower extremities, venous insufficiency of the lower extremities, recurring ulcers on the left leg for more than 20 years, and diabetes mellitus with dystrophic calcification of the calf. The patient's left leg ulcer showed extensive chronic inflammation, pathological calcification, and necrosis of the subcutaneous tissue with a thickness of approximately 0.5 to 1 cm. The computed tomography, X-ray, and hematoxylin-eosin staining results confirmed calcification; the leg skin thickened because of inflammatory irritation. After 11 months of treatment, the calcified and necrotic calcification and necrotic tissue were removed, and the wound healed.

Spatial and temporal dynamics of microbial community composition and factors influencing the surface water and sediments of urban rivers.

The temporal and spatial characteristics of urban river bacterial communities help us understand the feedback mechanism of bacteria to changes in the aquatic environment. The Fuhe River plays an important role in determining the water ecological environment of Baiyangdian Lake. 16S rRNA gene sequencing was used to study the microbial distribution characteristics in the Fuhe River in different seasons. The results showed that some environmental factors of the surface water (ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP)) were different on the spatial and temporal scales. Moreover, there were no seasonal differences in the contents of TN, TP, total organic carbon (TOC), or heavy metals in the sediments. The distributions of Cyanobacteria, Actinomycetes and Firmicutes in the water and Actinomycetes and Planctomycetes in the sediments differed significantly among seasons (P < 0.05). There were significant spatial differences in bacteria in the surface water, with the highest abundance of Proteobacteria recorded in the river along with the highest nutrient concentration, while the abundance of Bacteroidetes was higher in the upstream than the downstream. Microbial communities in the water were most sensitive to temperature (T) and the TP concentration (P < 0.01). Moreover, differences in the bacterial community were better explained by the content of heavy metals in the sediments than by the chemical characteristics. A PICRUSt metabolic inference analysis showed that the effect of high summer temperatures on the enzyme action led to an increase in the abundances of the metabolic-related genes of the river microorganisms.

Bulk Passivation Enables Hundredfold-Enhanced Electroluminescence of Monophosphine Cu4 I4 Cubes.

Electroluminescent (EL) clusters emerged rapidly, owing to their organic-inorganic hybrid character useful for comprehensive performance integration and the potential for large-scale display and lighting applications. However, despite their good photoluminescent (PL) properties, until present, no efficient EL monodentate ligand-based clusters were reported due to structural variation during processing and excitation and exciton confinement on cluster-centered quenching states. Here we demonstrate an effective bulky passivation strategy for efficient cluster light-emitting diodes with a monophosphine Cu4 I4 cube named [TMeOPP]4 Cu4 I4 . With terminal pyridine groups, an active matrix named TmPyPB supports an effective host-cluster interplay for configuration fixation, structural stabilization, and exciton-confinement optimization. Compared to common inactive hosts, the passivation effects of TmPyPB markedly reduce trap-state densities by 24-40 % to suppress nonradiative decay, resulting in state-of-the-art PL and EL quantum yields reaching 99 % and 15.6 %, respectively, which are significantly improved by about 7-fold. TmPyPB simultaneously increases EL luminance to 104 nits, which is ≈100-fold that of the non-doped analogue.

Phase Coherence of Pairs of Cooper Pairs as Quasi-Long-Range Order of Half-Vortex Pairs in a Two-Dimensional Bilayer System.

It is known that the loss of phase coherence of Cooper pairs in two-dimensional superconductivity corresponds to the unbinding of vortex-antivortex pairs with the quasi-long-range order in the order-parameter phase field, described by the Berezinskii-Kosterlizt-Thouless (BKT) transition of a 2D XY model. Here we show that the second-order Josephson coupling can induce an exotic superconducting phase in a bilayer system. By using tensor-network methods, the partition function of the 2D classical model is expressed as a product of 1D quantum transfer operator, whose eigenequation can be solved by an algorithm of matrix product states rigorously. From the singularity shown by the entanglement entropy of the 1D quantum analog, various phase transitions can be accurately determined. Below the BKT phase transition, an interlayer Ising long-range order is established at T_{Ising}, and the phase coherence of both intralayers and interlayers is locked together. For two identical layers, the Ising transition coincides with the BKT transition at a multicritical point. For two inequivalent layers, however, there emerges an intermediate quasi-long-range order phase (T_{Ising}

Impact of Left Atrial Appendage Closure Combined with Catheter Ablation on Endocrine and Mechanical Cardiac Function in Patients with Atrial Fibrillation.

Background: The combined procedure of left atrial appendage closure (LAAC) and catheter ablation (CA) is a safe and feasible therapy to treat patients with atrial fibrillation (AF). However, the effect of the combined procedure on cardiac function remains unclear. This study aimed to investigate the changes in endocrine and mechanical function of the heart following the combined procedure. Methods: This retrospective study included 62 consecutive patients who underwent the combined procedure of AF ablation and WATCHMAN LAAC and 62 sex and age-matched patients who only received AF ablation. During follow-up, patients were examined for brain natriuretic peptide (BNP) levels to represent endocrine cardiac function. Mechanical cardiac function was assessed during echocardiographic examination by means of the LA ejection fraction, LA strain (Ƹ), and LA strain rate (SR). Results: (1) The BNP levels decreased acutely after the procedure, rose at day 3 postoperation, but trended downwards at 3 months postoperation in both groups. No significant difference was observed between the two groups. (2) LA ejection fraction, LA Ƹ, and SR exhibited a continuous upward trend over a 3-month follow-up in both groups. There was no significant difference in LA ejection fractions, SRe (the parameter of LA conduit function), and SRa (the parameter of LA booster pump function) between the two groups. However, the Ƹ and SRs (the parameters of LA reservoir function) improved in patients treated with CA alone. Conclusions: The combined procedure of LAAC and CA significantly improved the endocrine and mechanical function of the heart. Compared to simple CA, based on CA with LAAC intervention, it does not significantly change LA endocrine function but may lead to a decline in the LA reservoir function.

Study on performance and mechanism of enhanced low-concentration ammonia nitrogen removal from low-temperature wastewater by iron-loaded biological activated carbon filter.

In order to strengthen the treatment of low-concentration ammonia nitrogen wastewater at low temperature, iron-loaded activated carbon (Fe-AC) with ultrasonic impregnation method was used as the filter material of biofilter process. The performance and mechanism of ammonia nitrogen removal from simulated secondary wastewater by iron-loaded biological activated carbon filter (Fe-BACF) were studied at 10 °C. The characterization results showed that iron was loaded on the surface of AC in the form of Fe2O3, and the specific surface area, total pore volume, pore size and alkaline functional group content of Fe-AC were obviously increased. After the formation of biofilm on the surface of filter media, the average removal rate of ammonia nitrogen by Fe-BACF (97.9%) was significantly higher than that of conventional BACF (87.8%). The improved surface properties increased the number and metabolic activity of microorganisms, and promoted the secretion of EPS on the surface of Fe-BAC. The results of high-throughput sequencing showed that the existence of Fe optimized the bacterial community structure on the surface of Fe-BAC, with the increase of the abundances of psychrophilic bacteria and ammonia nitrogen removal bacteria. The mechanism of enhanced ammonia nitrogen removal by Fe-BACF was the joint action of many factors, among which the main causal relationship was that modification of iron could optimize the number and category of microorganisms on Fe-BAC surface by improving the surface properties, thus improving the biological nitrogen removal ability. Results of this study provided a practical way for the treatment of low ammonia nitrogen wastewater in cold regions.

Fe-N complex biochar as a superior partner of sodium sulfide for methyl orange decolorization by combination of adsorption and reduction.

To enhance the decolorization of methyl orange (MO), Fe-N complex biochar (Fe-N-BC) was developed as an accelerator in the sodium sulfide (Na2S) reduction system. The decolorization effect and mechanism of MO in the Fe-N-BC/Na2S composite system were studied. Surface pore analysis, Raman spectroscopy, FT-IR, XPS, and electrochemical analysis were used to characterize Fe-N-BC and unmodified biochar (BC). These results demonstrated that Fe-N-BC had better adsorption performance (specific surface area 463.46 m2 g-1) and electron transfer capacity than BC. By adding Fe-N-BC to the Na2S reduction system for MO, it was found that the decolorization of MO was greatly improved (increased by 93%). Besides, the effects of critical factors such as the initial concentration of Na2S, the dosage of Fe-N-BC, pH value, and temperature on the decolorization rate of MO were evaluated. Through the analysis of the action mechanism, the cooperation mode of Fe-N-BC and Na2S was to form an infinite cycle of adsorption-reduction-regeneration, so as to realize the rapid decolorization of MO. On the one hand, Fe-N-BC could adsorb MO and Na2S on its surface to increase the contact opportunity; on the other hand, it could act as a redox mediator to accelerate the electron transfer of the reduction reaction. In addition, the degradation of MO by Na2S was also an in-situ regeneration of Fe-N-BC. These findings may provide a feasible method to decolorize azo dyes quickly by cooperating with chemical reducing agents from a new perspective.