Microbial community shift via black carbon: Insight into biological nitrogen removal from microbial assemblage and functional patterns.

Understanding the ecological relationship of microbial community under external stimulation is crucial for environmental restoration. Black carbon (e.g., biochar) have been widely deemed as a strategy to enhance pollutants removal because of its structure and redox-active property. However, the underlying ecological mechanism of microbial community under black carbon addition is poorly understood. The major purposes of this study were to determine the microbial assemblage and functional patterns via null model test, network analysis, and function prediction. The results showed that the nitrate removal efficiency of modified black carbon system achieved 46.44%. Both deterministic and stochastic processes were significant for mediating the microbial assemblage and the deterministic process dominated (>95%) the assemblage of community. Keystone taxa in the black carbon systems, involving Sulfuricella, Allorhizobium, and Nitrospira, stimulated the shift of community composition regarding the nitrogen removal. The existence of black carbon and the biotic interactions increased biological nitrate utilization and promoted nitrogen removal. Overall, this study presents the mechanism of bacterial community assembly and provides insight into biological nitrogen removal from microbial ecological perspective.

A space-confined strategy toward large-area two-dimensional crystals of ionic liquid.

Understanding and manipulating nano-confined ionic liquids (ILs) has tremendous implications in nanotechnology and chemical engineering. Here, a peculiar growth phenomenon of a nano-confined [Bmim][NTFI] ionic liquid is revealed by utilizing two-dimensional channels in mica. The intercalated ILs underwent liquid-solid transition and self-assembled into a self-similar two-dimensional crystal in an epitaxial relation with the confining material. The terraced IL crystals, ranging from monolayer to bilayer to several dozen layers, are characterized by unexpectedly large areas extending to µm-scale and enhanced thermal stability with a melting temperature 73 K higher than that of the corresponding bulk IL. The notable asymmetric feature of the layered crystals hints at anisotropic growth under confinement, which produces a well-defined hexagonal geometric shape. Finally, a molecular scale growth mechanism of ordered ILs is qualitatively interpreted by a birth-and-spread model. Our findings have enabled new research on nanoconfined ILs and opened up an avenue to tailoring the structure of ILs for their applications under confinement.

Height-driven structure and thermodynamic properties of confined ionic liquids inside carbon nanochannels from molecular dynamics study.

Understanding the structural transition of ionic liquids (ILs) confined in a nanospace is imperative for the application of ILs in energy storage, gas separation, and other chemical engineering techniques. In this work, the quantitative relations between the properties and height of the nanochannel (H) for the ([Emim]+[TF2N]-) IL are explored through molecular dynamics simulations. Interestingly, the entropy of the confined IL exhibits a nonmonotonic behavior as H increases: initially increasing for H < 1.0 nm and then decreasing for 1.0 < H < 1.1 nm, followed by increasing again for H > 1.1 nm; it finally approaches that of liquid bulk ILs. The vibrational spectrum of the confined IL is analyzed to investigate the nature of nonmonotonic entropy, showing that the liquidity and partial solidity will be respectively attenuated and enhanced as H decreases from 5.0 to 0.75 nm. Moreover, the hydrogen bond (HB) network and external force are also calculated, showing similar nonmonotonic behaviors when compared with the thermodynamic properties. The entropy gain of the confined IL originates from the reduced HB interactions, weaker external force, and partial solid nature, where more phase space sampling for ILs inside a bilayer graphene nanochannel (BLGC) can be achieved. All the above relations demonstrate that there exists a critical height of the nanochannel (HCR = 1.0 nm) at which the confined IL possesses weaker HB interaction, higher entropy, and better stability. The critical height of the nanochannel is also identified in the analysis of the local structures of cation head groups and anions, indicating that the confined IL could have a faster in-plane diffusive ability. These factors can serve as key indicators in quantitatively characterizing the mechanism for the structural transition of ILs inside a nanochannel and facilitate the rational design of nanopores and nanochannels to regulate the properties and structures of ILs in practical application scenarios.

NHC-catalyzed regiodivergent syntheses of difunctionalized 3-pyrazolidinones from α-bromoenal and monosubstituted hydrazine.

A formal [3 + 2] annulation of α-bromoenal with monosubstituted hydrazine could give 1,5 or 2,5-difunctionalized 3-pyrazolidinone regiodivergently by tuning the structure of the N-Heterocyclic Carbene (NHC) catalyst. Moderate to high yields, mild reaction conditions, good regioselectivity and potential biological significance of the final product have made this protocol attractive for the assembly of 3-pyrazolidinone.

Relation disentanglement, the potential risk assessment, and source identification of heavy metals in the sediment of the Changzhao Reservoir, Zhejiang Province.

Heavy metal contamination in the water body is a distinctly important issue for the water security of the reservoir. 114 sediment samples of Changzhao Reservoir were collected to investigate the spatial (horizontal and vertical) distribution characteristics, risk assessment, and source identification of heavy metals. The concentrations of heavy metals at the surface layer of sediment were slightly higher compared with that at the middle and bottom layer sediment in the most sampling sites. The concentration of Zn and Cd was significantly different in the different depths of sediment (P ≤ 0.01, Tukey HSD test). pH and Cd were identified as the key factors for TOC in the sediment by the Boruta algorithm. The proportion of "uncontaminated to moderately contaminated" for Cd, Zn, and As in the surface layer was 84.21%, 47.37%, and 34.21%, which indicated that the quality of sediment was mostly impacted by Cd, Zn, and As. The agricultural non-point source pollution is dominant according to the source identification method of APCS-MLR. Overall, this paper presents the distribution and conversion trends of heavy metals and provides the insights of the reservoir protection in the future work.

Electron Density Learning of Z-Bonds in Ionic Liquids and Its Application.

Ionic liquids (ILs) exhibit fascinating properties due to special Z-bonds and have been widely used in electrochemical systems. The local Z-bond networks potentially cause a discrepancy in electrochemical properties. Understanding the correlations between the Z-bond energy (EZ-bond) and the electrochemical properties is helpful to identify appropriate ILs. It is difficult to estimate the correlations from single density functional theory calculations or molecular dynamic simulations. In this work, a machine learning model targeting the electronic density (ρBCP) of Z-bonds has been trained successfully, as expected for use in systems above the nanoscale size. The connection between the EZ-bond and the electrochemical potential window in ILs@TiO2, as well as that between the EZ-bond and the charge carrier mobility in ILs-PEDOT:Tos@SiO2, was separately investigated. This study highlights an efficient model for predicting ρBCP in nanoscale systems and anticipates exploring the connection between Z-bonds and the electrochemical properties of IL-based systems.

Water-Controlled Structural Transition and Charge Transfer of Interfacial Ionic Liquids.

Clarification of the water-induced structural transitions and electron transfer between ionic liquids (ILs) and a solid surface allows for establishing a unified view of the electrical properties of interfacial ILs via a hitherto unexplored pathway. Here, we propose a simple and effective method to quantitatively identify and extract the transferred electrons between ILs and a solid surface, while demonstrating the critical structural transition of interfacial ILs from ordered stripe structures to disordered aggregation structures. The formation of hydrated anions, rooted in the hydrogen bonds of O-H···O between the anion and water, lies at the tipping point where electron transfer ends and aggregation structure begins. In addition, it is discovered to what extent the hydrophilicity of substrates can affect electron transfer, and a regulation method based on the electric field is explored. These experimental findings may refresh our knowledge of interfacial ILs and provide an effective method for evaluating the intrinsic electrical features of the ILs-solid surface.

Insights into Ionic Liquids: From Z-Bonds to Quasi-Liquids.

Ionic liquids (ILs) hold great promise in the fields of green chemistry, environmental science, and sustainable technology due to their unique properties, such as a tailorable structure, the various types available, and their environmentally friendly features. On the basis of multiscale simulations and experimental characterizations, two unique features of ILs are as follows: (1) strong coupling interactions between the electrostatic forces and hydrogen bonds, namely in the Z-bond, and (2) the unique semiordered structure and properties of ultrathin films, specifically regarding the quasi-liquid. In accordance with the aforementioned theoretical findings, many cutting-edge applications have been proposed: for example, CO2 capture and conversion, biomass conversion and utilization, and energy storage materials. Although substantial progress has been made recently in the field of ILs, considerable challenges remain in understanding the nature of and devising applications for ILs, especially in terms of e.g. in situ/real-time observation and highly precise multiscale simulations of the Z-bond and quasi-liquid. In this Perspective, we review recent developments and challenges for the IL research community and provide insights into the nature and function of ILs, which will facilitate future applications.

Ultralow Friction and High Robustness of Monolayer Ionic Liquids.

Ultralow friction between interacting surfaces in relative motion is of vital importance in many pure and applied sciences. We found that surfaces bearing ordered monolayer ionic liquids (ILs) can have friction coefficient µ values as low as 0.001 at pressures up to 78 MPa and exhibit good structure recoverability. This extreme lubrication is attributed primarily to the ordered striped structure driven by the "atomic-locking" effect between carbon atoms on the alkyl chain of ILs and graphite. The longer alkyl chain has lower µ values, and the stripe periodicity is decisive in reducing energy dissipation during the sliding process. In combination with simulation, the alternate atomic-scale ordered and disordered ionic regions were recognized, whose ratio fundamentally determines the µ values and lubrication mechanism. This finding is an important step toward the practical utilization of ILs with negligible vapor pressure as superlubricating materials in future technological applications operating under extreme conditions.

Effects of black carbon-based thin-layer capping for nitrogen-overloaded sediment remediation on microbial community assembly.

Black carbon is considered as a promising material for thin-layer capping for sediment remediation. However, the effects of black carbon-based thin-layer capping on microbial communities have not been thoroughly studied. Here, the preparation conditions of capping material were optimized, and the interaction and assembly mechanisms of the microbial community in sediment under black carbon capping were studied. The results showed that concentration of NH4+-N in the overlying water was stably lower than 0.5 mg/L after capping. The abundance of key genes related to nitrogen transformation in the sediment was increased. Denitrification was the dominant nitrogen removal pathway under coarse granule capping, while aromatic compound degradation was dominant under fine granule capping and dissimilatory N reduction to ammonium was regarded as the dominant nitrogen removal pathway. Community assembly was mainly driven by deterministic processes (≥ 80%). Interactions between rare and common operational taxonomic units were most frequent. The functional zoning of nitrogen transformation in the vertical aerobic, hypoxic, and anaerobic zones of the sediment was strengthened because of black carbon capping. Overall, these results expand our current understanding of the ecological significance of black carbon capping for remediating contaminated sediment.

Topological engineering of two-dimensional ionic liquid islands for high structural stability and CO2 adsorption selectivity.

Ionic liquids (ILs) as green solvents and catalysts are highly attractive in the field of chemistry and chemical engineering. Their interfacial assembly structure and function are still far less well understood. Herein, we use coupling first-principles and molecular dynamics simulations to resolve the structure, properties, and function of ILs deposited on the graphite surface. Four different subunits driven by hydrogen bonds are identified first, and can assemble into close-packed and sparsely arranged annular 2D IL islands (2DIIs). Meanwhile, we found that the formation energy and HOMO-LUMO gap decrease exponentially as the island size increases via simulating a series of 2DIIs with different topological features. However, once the size is beyond the critical value, both the structural stability and electrical structure converge. Furthermore, the island edges are found to be dominant adsorption sites for CO2 and better than other pure metal surfaces, showing an ultrahigh adsorption selectivity (up to 99.7%) for CO2 compared with CH4, CO, or N2. Such quantitative structure-function relations of 2DIIs are meaningful for engineering ILs to efficiently promote their applications, such as the capture and conversion of CO2.

A novel hydroxofluorographene-coated melamine foam for efficient and repeatable oil removal from water.

With the frequent occurrence of oil spill accidents and the continuous discharge of oily water during oil production and transportation, effective oil removal from environmental water by adsorption still faces severe challenges. Here, a novel absorbent hydroxofluorographene-coated melamine foam, namely G(OH)F@MF, with high affinity to oils was fabricated via stepwise assembly. The G(OH)F@MF absorbent achieved effective removal of various oils within 1 min with relatively high adsorption capacities for petrol (89.34 g/g), lubricating oil (89.60 g/g), and peanut oil (104.79 g/g). Furthermore, it could be regenerated by simply squeezing and reused for more than 10 times with an adsorption capacity exceeding 37.12 g/g. In addition, the results indicated that the G(OH)F@MF absorbent was suitable for oil cleanup at a wide range of pH values (4-12) and temperatures (5-45 °C). The adsorption performance of the material was stable in the presence of natural organic matter and even in different water environments. This study can provide a novel sorbent and method for the green, rapid, recyclable, and stable removal of oils from environmental water.

Enhanced biological nitrogen removal from sediment by graphene derivative-mediated community assembly.

Understanding the underlying mechanism that drives the microbial community mediated by graphene derivative is crucial for achieving the enhancement of biological nitrogen removal by external stimulation. The main objectives of this study were to identify the bacterial community assembly mechanism via null model test and molecular ecological network analysis in the sediment culture system. Results showed graphene derivative increased biological nitrogen removal efficiency by 125%. The high electron transfer efficiency and denitrifying enzyme activities were achieved. Deterministic assembly is dominate (>90%) in all the community assembly while the stochastic assembly process only existed in graphene derivative system (6.67%). The nitrogen removal was enhanced due to the intensification of the interaction on the microbial community between stochastic assembly and deterministic assembly. Keystone taxa in the graphene derivative systems, including Sulfuricella, Rhodobacter, and Comamonadaceae, drove the alteration of community structure relating to the nitrogen removal.

Response of nitrite accumulation and microbial characteristics to low-intensity static magnetic field during partial nitrification.

Static magnetic field (SMF) with the intensity of 15 mT was applied during partial nitrification (PN) process to evaluate the impacts on nitrogen transformation and microbial characteristics. Results showed that the startup period of PN process at ambient temperature was markedly shortened by SMF, and the nitrite accumulation increased by 18% due to SMF exposure. The ammonia oxidizing bacteria (AOB) amoA gene copy numbers in the reactor with SMF exposure were 40% higher than that without SMF exposure, indicating the AOB abundance was enriched by SMF exposure. The characteristics of extracellular polymeric substances (EPS) changed accordingly. The extracellular protein increased by 30% due to SMF exposure, and it favored the aggregation of sludge flocs. The activated sludge with SMF exposure had a more compact structure, which was in favor of partial nitrification.

[The effects of dentists'performance on the clinical effects of root canal preparation].

PURPOSE: To evaluate the effects of dentists'performance on the clinical efficacies of root canal preparation. METHODS: 164 teeth, including 66 vital teeth and 98 necrotic pulp teeth , were divided into two groups in random. All the root canals were prepared using ProTaper nickel-titanium rotary by two dentists with junior senior qualification. The incidence of instruments fracture, endodontic interappointment pain (EIP) and successful rates of root canal filling of the two groups were compared by X(2) test with SAS 6.2 software package. RESULTS: Between the two groups, the difference of the incidence of instruments fracture in molar was significant (P<0.05). The incidence of EIP between the two groups had high significant difference (P<0.01); The difference of vital teeth and necrotic pulp teeth was significant (P<0.05) in junior dentist group. The successful rates of root canal filling had significant differences (P<0.05), especially in necrotic pulp molar teeth. CONCLUSION: Skilled and accurate operation can improve the clinical efficacies of root canal preparation.

[A study on the accuracy of electronic root canal length measurement and its influential factors].

PURPOSE: To study the accuracy of JUSTY-II electronic apex locator and the influential factors on the accuracy of root canal working length measurement. METHODS: 148 teeth, including 71 teeth with pulpitis, 46 with necrotic pulp and 31 with apical periodontitis, were divided into two groups in random. The accuracy of electronic root canal working length measurement group was compared with that of the manual measurement group by Chi(2) test. The influence of clinical types, root canal in dry or moisture conditions and root canal preparation on the accuracy of root canal working length measurement was analyzed. RESULTS: The accuracy of electronic apex locator was 87.84%, while it was 43.24% in manual measurement, the difference was significant (P<0.01). The accuracy in the group of apical periodontitis was significantly lower than that of the other groups (P<0.05). Root canal in dry or moisture conditions had no effect on the accuracy of root canal length measurement, but root canal preparation could decrease the accuracy of measurement (P<0.05). CONCLUSION: Electronic apex locator is an accurate and convenient device in measurement of root canal working length. Apical periodontitis and root canal preparation can decrease the accuracy of measurement.

[Clinical study of the effect of preventing dentine hypersensitiveness by using Fluor Protector and Green Or on the prepared vital pulp abutment teeth].

PURPOSE: To study and evaluate the effect preventing dentine hypersensitiveness by using Fluor Protector or Green Or on the prepared vital pulp abutment teeth of PFM bridges. METHODS: 118 cases, 246 prepared vital pulp abutment teeth, were randomly divided into three groups: Experimental Group A--treated with the Fluor Protector and temporary crown; Experimental Group B--treated with the Green Or and temporary crown, and Control Group--only using temporary crown. The results of desensitization in 3 groups were evaluated. F test was used for analysis (DSPV6.01). RESULTS: Significant differences were found between experimental Group A, B and the control group after 1 week (when cementing the PFM bridges); and also after 1 month (P<0.05). But no significant difference was found between experimental Group A and B (P>0.05). CONCLUSIONS: The effect of preventing dental hypersensitiveness by using Fluor Protector or Green Or on the prepared vital pulp abutment teeth of PFM bridges is ideal. It is easy to use and worth being widely applied.

[A comparison of the effect between Vitapex paste and antibiotic paste in apexification.].

PURPOSE: To study the effects of two root canal filling material in the apexification. METHODS: 172 juvenile permanent teeth,including 62 teeth with pulpitis, 32 teeth with necrotic pulp and 78 teeth with periapical periodontitis, were divided into two groups.The root canal was filled with Vitapex paste and antibiotic paste.Every patient was examined once three months.The treatment lasted 6-30 months.The outcome of treatment was investigated for three years following treatment. RESULTS: The effective rate in the group of Vitapex paste and antibiotic paste group were 86.0% and 91.9% (P>0.05).In periapical periodontitis group,the effective rate of antibiotic paste group was significantly higher than the other (P<0.05). CONCLUSION: Both Vitapex paste and antibiotics paste were good filling materials in apexification. Antibiotic paste was better than the other in periapical periodontitis group.