Influence of defect locations and nitrogen doping configurations on the mechanical properties of armchair graphene nanoribbons

The effect of defect locations on the mechanical properties of armchair graphene nanoribbons (AGNRs) and the various configurations of nitrogen (N) doping on the mechanical properties of AGNRs were examined using molecular dynamics (MD) simulations. The variation of the Young’s modulus (YM) and the ultimate tensile strength (UTS) of pyridinic-N, graphitic-N, and pyrrolic-N by increasing the concentration of N doping was investigated. The results of MD simulations show that the defect location has a significant effect on the UTS and failure strain (FS) of AGNRs in both vertical and horizontal directions. In the horizontal direction, variations of the UTS and FS are lower than in the vertical direction. On the other hand, the variations of the YM is almost similar in vertical and horizontal directions. The results of this work indicate that the UTS and FS of AGNRs are more sensitive than the YM of AGNRs for different defect directions. Pyridinic-N improves the mechanical properties of the defective AGNR and performs better YM and UTS values than the graphitic-N. Substitution N atoms, which are located at the defective sites and/or at the edges of AGNRs, are mechanically more favorable. Pyrrolic-N configuration has the lowest mechanical properties among the other configurations. Furthermore, pyrrolic-N with Stone-Wales-1 (SW-1) type of defect has higher mechanical properties than pyrrolic-N with Stone-Wales-2 (SW-2) type of defect.     

Nitrogen‐Doping‐Induced Defects of a Carbon Coating Layer Facilitate Na‐Storage in Electrode Materials

A nitrogen‐doped, carbon‐coated Na₃V₂(PO₄)₃ cathode material is synthesized and the formation of doping type of nitrogen‐doped in carbon coating layer is systemically investigated. Three different carbon‐nitrogen species: pyridinic N, pyrrolic N, and quaternary N are identified. The most important finding is that different carbon‐nitrogen species in the carbon layer have different impacts on the improvement of the electrochemical properties of Na₃V₂(PO₄)₃. Pyridinic N and pyrrolic N significantly increase the electronic conductivity and create numerous extrinsic defects and active sites. Quaternary N only increases the electronic conductivity without creating extrinsic defects. Therefore, it is unexpectedly demonstrated that the Na₃V₂(PO₄)₃/C+N, in which with minimize content of quaternary N or exist most extrinsic defects, exhibits the best electrochemical performance, particularly the rate performance and cycling stability. For example, when the discharging rate increased from 0.2 C to 5 C, its capacity of 101.9 mAh g^?1 decays to 84.3 mAh g^?1 and an amazing capacity retention of 83% is achieved. Moreover, even at higher current density of 5 C, an excellent capacity retention of 93% is maintained even after 100 cycles.     

Selective Etching of Nitrogen‐Doped Carbon by Steam for Enhanced Electrochemical CO2 Reduction

Nitrogen‐doped carbon structures have recently been demonstrated as a promising candidate for electrocatalytic CO₂ reduction, while in the meantime the pyridinic and graphitic nitrogen atoms also present high activities for electroreduction of water. Here, an etching strategy that uses hot water steam to preferentially bind to pyridinic and graphitic nitrogen atoms and subsequently etch them in carbon frameworks is reported. As a result, pyrrolic nitrogen atoms with low water affinity are retained after the steam etching, with a much increased level of among all nitrogen species from 22.1 to 55.9%. The steam‐etched nitrogen‐doped carbon catalyst enables excellent electrocatalytic CO₂ reduction performance but low hydrogen evolution reaction activity, suggesting a new approach for tuning electrocatalyst activity.     

A Large Scalable and Low‐Cost Sulfur/Nitrogen Dual‐Doped Hard Carbon as the Negative Electrode Material for High‐Performance Potassium‐Ion Batteries

Among the negative electrode materials for potassium ion batteries, carbon is very promising because of its low cost and environmental benignity. However, the relatively low storage capacity and sluggish kinetics still hinder its practical application. Herein, a large scalable sulfur/nitrogen dual‐doped hard carbon is prepared via a facile pyrolysis process with low‐cost sulfur and polyacrylonitrile as precursors. The dual‐doped hard carbon exhibits hierarchical structure, abundant defects, and functional groups. The material delivers a high reversible potassium storage capacity and excellent rate performance. In particular, a high reversible capacity of 213.7 and 144.9 mA h g^?1 can be retained over 500 cycles at 0.1 A g^?1 and 1200 cycles at 3 A g^?1, respectively, demonstrating remarkable cycle stability at both low and high rates, superior to the other carbon materials reported for potassium storage, to the best of the authors' knowledge. Structure and kinetics studies suggest that the dual‐doping enhances the potassium diffusion and storage, profiting from the formation of a hierarchical structure, introduction of defects, and generation of increased graphitic and pyridinic N sites. This study demonstrates that a facile and scalable pyrolysis strategy is effective to realize hierarchical structure design and heteroatom doping of carbon, to achieve excellent potassium storage performance.     

Preclinical evaluation of the Aurora kinase inhibitors AMG 900, AZD1152-HQPA,and MK-5108 on SW-872 and 93T449 human liposarcoma cells

Liposarcoma is a malignant soft tissue tumor that originates from adipose tissue and is one of the most frequently diagnosed soft tissue sarcomas in humans. There is great interest in identifying novel chemotherapeutic options for treating liposarcoma based upon molecular alterations in the cancer cells. The Aurora kinases have been identified as promising chemotherapeutic targets based on their altered expression in many human cancers and cellular roles in mitosis and cytokinesis. In this study, we investigated the effects of an Aurora kinase A inhibitor (MK-5108), an Aurora kinase B inhibitor (AZD1152-HQPA), and a pan-Aurora kinase inhibitor (AMG 900) on undifferentiated SW-872 and well-differentiated 93T449 human liposarcoma cells. Treatment of the SW-872 and 93T449 cells with MK-5108 (0–1000 nM), AZD1152-HQPA (0–1000 nM), and AMG 900 (0–1000 nM) for 72 h resulted in a dose-dependent decrease in the total viable cell number. Based upon the EC₅₀ values, the potency of the three Aurora kinase inhibitors in the SW-872 cells was as follows: AMG 900 (EC₅₀ = 3.7 nM) > AZD1152-HQPA (EC₅₀ = 43.4 nM) > MK-5108 (EC₅₀ = 309.0 nM), while the potency in the 93T449 cells was as follows: AMG 900 (EC₅₀ = 6.5 nM) > AZD1152-HQPA (EC₅₀ = 74.5 nM) > MK-5108 (EC₅₀ = 283.6 nM). The percentage of polyploidy after 72 h of drug treatment (0–1000 nM) was determined by propidium iodide staining and flow cytometric analysis. AMG 900 caused a significant increase in polyploidy starting at 25 nM in the SW-872 and 93T449 cells, and AZD1152-HQPA caused a significant increase starting at 100 nM in the SW-872 cells and 250 nM in the 93T449 cells. The Aurora kinase A inhibitor MK-5108 did not significantly increase the percentage of polyploid cells at any of the doses tested in either cell line. The expression of Aurora kinase A and B was evaluated in the SW-872 cells versus differentiated adipocytes and human mesenchymal stem cells by real-time RT-PCR and Western blot analysis. Aurora kinase A and B mRNA expression was significantly increased in the SW-872 cells versus the differentiated adipocytes and human mesenchymal stem cells. Western blot analysis revealed a ~ 48 kDa immunoreactive band for Aurora kinase A that was not present in the differentiated adipocytes or the human mesenchymal stem cells. A ~ 39 kDa immunoreactive band for Aurora kinase B was detected in the SW-872 cells, differentiated adipocytes, and human mesenchymal stem cells. A smaller immunoreactive band for Aurora kinase B was detected in the SW-872 cells but not in the differentiated adipocytes and human mesenchymal stem cells, and this may reflect the expression of a truncated splice variant of Aurora kinase B that has been associated with poor patient prognosis. The 93T449 cells demonstrated decreased expression of Aurora kinase A and B mRNA and protein compared to the SW-872 cells, and also expressed the truncated form of Aurora kinase B. The results of these in vitro studies indicate that Aurora kinase inhibitors should be further investigated as possible chemotherapeutic agents for human liposarcoma.     

Woody plant encroachment impacts on soil carbon and microbial processes: results from a hierarchical Bayesian analysis of soil incubation data

Quantitative methods were used to examine soil properties and their spatial heterogeneity in a 0-year fenced mobile dune (MD0), an 11-year fenced mobile dune (MD11) and a 20-year fenced mobile dune (MD20) in Horqin Sandy Land, Northern China. The objective of the study was to assess the effect of vegetation restoration on heterogeneity of soil properties in sand dunes and to provide a concept model to describe the relationship between vegetation succession and spatial heterogeneity variation of soil properties in the dunes. The results showed that the average values of vegetation cover, species number and diversity, soil organic carbon (C), total nitrogen (N), and electrical conductivity (EC) increased with the increase in fenced age of mobile dunes, while soil water content (0–20 cm) showed the reverse trend. Geostatistical analysis revealed that the spatial heterogeneity of soil organic C, total N, EC, very fine sand content, and soil water content (0–20 cm) increased from MD0 to MD11 with succession from sand pioneer plant to shrub species then decreased from MD11 to MD20 due to continuous development of herbaceous plants. Canonical correspondence analysis (CCA) showed that there was a relatively high correspondence between vegetation and soil factors, suggesting that the major gradients relating soil organic C, total N, EC, pH, slope, very fine sand content, and soil water content are the main factors for the distribution of dune plants and account for 68.1% of the species-environment relationship among the three sites. In addition, the distribution of the sand pioneer plant was positively related to the relative height of the sampling site and soil water content, and that of most herbaceous plants were determined by soil organic C, total N, EC, pH, and very fine sand content in mobile dunes. The conceptual model of relationship between vegetation succession and spatial heterogeneity of soil properties in mobile dunes suggests spatial patterns of soil properties are most strongly related to plant-induced heterogeneity in dune ecosystems prone to wind erosion, and conversely, the magnitude and degree of spatial heterogeneity in soil properties can influence the plant distribution pattern and vegetation succession of mobile dunes.     

Architecting Nitrogen Functionalities on Graphene Oxide Photocatalysts for Boosting Hydrogen Production in Water Decomposition Process

This study elucidates how nitrogen functionalities influence the transition and transfer of photogenerated electrons in graphene‐based materials. Graphene oxide dots (GODs) and Nitrogen‐doped GODs (NGODs) are synthesized by thermally treating graphene oxide (GO) sheets in argon and ammonia, respectively, and then ultrasonically exfoliating the sheets in nitric acid. The nitrogen functionalities of NGODs are mainly quaternary/pyridinic/pyrrolic, and the nitrogen atoms in these functionalities are planar to the GO sheets and repair the vacancy defects on the sheets. Hydrothermal treatment of NGODs in ammonia yields ammonia‐treated NGODs (A‐NGODs), with some pyridinic/pyrrolic groups being converted to amino/amide groups. The nitrogen atoms in the amino/amide groups are not planar to the GO sheets and are prone to donate their lone pair electrons to resonantly conjugate with the aromatic π electrons. The promoted conjugation facilitates the relaxation of photogenerated electrons to the triplet states and prolongs the electron lifetime. When deposited with Pt as the co‐catalyst, the samples catalyze H₂ production from an aqueous triethanolamine solution under 420 nm monochromatic irradiation at quantum yields of 7.3% (GODs), 9.7% (NGODs), and 21% (A‐NGODs). The high activity of A‐NGODs demonstrates that architecting nitrogen functionalities effectively mediate charge motion in carbon‐based materials for application to photoenergy conversion.     

Controls on Litter Decomposition of Emergent Macrophyte in Dongting Lake Wetlands

Both litter composition and site environment are important factors influencing litter decomposition, but their relative roles in driving spatial variation in litter decomposition among wetlands remain unclear. The responses of mass loss and nutrient dynamics to site environment and litter source were investigated in Carex brevicuspis leaves from the Dongting Lake wetlands, China, using reciprocal transplants of litterbags. Litters originating from lower elevation (24–25 m; flooded for 180–200 days every year) and higher elevation (27–28 m; flooded for 60–90 days every year) sites were incubated simultaneously at lower and higher sites at three locations for 1 year. The remaining litter mass, N, P, and lignin contents were analyzed during decomposition. Initial N and P contents were richer in litters from lower sites than those from higher ones. The decomposition rate was higher for the litters originating from lower sites (0.0030 day^?1) than those from higher ones (0.0025 day^?1) and higher at lower sites (0.0031 day^?1) than at higher sites (0.0024 day^?1). Litters from lower sites displayed greater N and P mineralization than those from higher sites, whereas only P dynamics were affected by site elevation. The variation in litter decomposition rate among the different litter source groups was twice that among the different site elevation groups. These data indicate that, in wetlands ecosystems, litter composition plays a more important role in the speed of litter decomposition than site environment (here represented by site elevation).     

Effect of nitrogen and phosphorus fertilization on the composition of rhizobacterial communities of two Chilean Andisol pastures

The effect of nitrogen (N) and phosphorus (P) fertilization on composition of rhizobacterial communities of volcanic soils (Andisols) from southern Chile at molecular level is poorly understood. This paper investigates the composition of rhizobacterial communities of two Andisols under pasture after 1- and 6-year applications of N (urea) and P (triple superphosphate). Soil samples were collected from two previously established sites and the composition of rhizobacterial communities was determined by denaturing gradient gel electrophoresis (PCR–DGGE). The difference in the composition and diversity between rhizobacterial communities was assessed by nonmetric multidimensional scaling (MDS) analysis and the Shannon–Wiener index. In Site 1 (fertilized for 1 year), PCR–DGGE targeting 16S rRNA genes and MDS analysis showed that moderate N application (270 kg N ha^?1 year^?1) without P significantly changed the composition of rhizobacterial communities. However, no significant community changes were observed with P (240 kg P ha^?1 year^?1) and N–P application (270 kg N ha^?1 year^?1 plus 240 kg P ha^?1 year^?1). In Site 2 (fertilized for 6 years with P; 400 kg P ha^?1 year^?1), PCR–DGGE targeting rpoB, nifH, amoA and alkaline phosphatase genes and MDS analysis showed changes in rhizobacterial communities only at the highest rate of N application (600 kg N ha^?1 year^?1). Quantitative PCR targeting 16S rRNA genes also showed higher abundance of bacteria at higher N application. In samples from both sites, the Shannon–Wiener index did not show significant difference in the diversity of rhizobacterial communities. The changes observed in rhizobacterial communities coincide in N fertilized pastures with lower soil pH and higher pasture yields. This study indicates that N–P application affects the soil bacterial populations at molecular level and needs to be considered when developing fertilizer practices for Chilean pastoral Andisols.     

Correlation Between Atomic Structure and Electrochemical Performance of Anodes Made from Electrospun Carbon Nanofiber Films

A systematic study is made of the effect of the nitrogen species on the performance of Li‐ion storage and the capacities of carbon‐based anodes in Li‐ion batteries (LIBs). Electrospun carbon nanofiber (CNF) films are fabricated for use as binder‐free electrodes using a polyacrylonitrile precursor. When the CNF films are subjected to carbonization, transformation occurs from an amorphous to a graphitic structure with associated reduction of nitrogen‐containing functional groups. The structural change strongly affects where the Li ions are stored in the CNF electrodes. It is revealed that Li ions can be stored not only between the graphene layers, but also at the defect sites created by nitrogen functionalization. The latter is mainly responsible for the widely reported improved electrochemical performance of LIBs due to N‐doping of carbon materials. An optimized carbonization temperature of 550 °C is identified, which gives rise to a sufficiently high nitrogen content and thus a high capacity of the electrode.     

Molecular dynamics simulations of void defects in the energetic material HMX

A molecular dynamics (MD) simulation was carried out to characterize the dynamic evolution of void defects in crystalline octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX). Different models were constructed with the same concentration of vacancies (10 %) to discuss the size effects of void. Energetic ground state properties were determined by annealing simulations. The void formation energy per molecule removed was found to be 55–63 kcal/mol^?1, and the average binding energy per molecule was between 32 and 34 kcal/mol^?1 according to the change in void size. Voids with larger size had lower formation energy. Local binding energies for molecules directly on the void surface decreased greatly compared to those in defect-free lattice, and then gradually increased until the distance away from the void surface was around 10 Å. Analysis of 1 ns MD simulations revealed that the larger the void size, the easier is void collapse. Mean square displacements (MSDs) showed that HMX molecules that had collapsed into void present liquid structure characteristics. Four unique low-energy conformers were found for HMX molecules in void: two whose conformational geometries corresponded closely to those found in HMX polymorphs and two, additional, lower energy conformers that were not seen in the crystalline phases. The ratio of different conformers changed with the simulated temperature, in that the ratio of α conformer increased with the increase in temperature.     

CYP1A1 MspI polymorphism is associated with prostate cancer susceptibility: evidence from a meta-analysis

Cytochrome P450 1A1 (CYP1A1), an important phase I xenobiotic metabolizing enzyme, is responsible for metabolizing numerous carcinogens, particularly polycyclic aromatic hydrocarbons. The genetic polymorphism of CYP1A1 at the site of MspI (CYP1A1 MspI) has been implicated in prostate cancer risk, but the results of individual studies remain conflicting and inconclusive. The aim of this meta-analysis was to investigate the association of CYP1A1 MspI polymorphism with prostate cancer risk more precisely. We performed a comprehensive search of the PubMed, Embase, Web of Science, and China National Knowledge Infrastructure databases from their inception up to September 20, 2012 for relevant publications. The pooled odds ratios with the corresponding 95 % confidence intervals (95 % CIs) were calculated to assess the association of CYP1A1 MspI polymorphism with prostate cancer risk. In addition, stratified analyses by ethnicity and sensitivity analyses were conducted for further estimation. Sixteen eligible publications with 6,411 subjects were finally included into the meta-analysis after checking the retrieved papers. Overall, meta-analysis of total studies suggested that individuals carrying the TC genotype and a combined C genotype (CC + TC) were more susceptible to prostate cancer (OR_{TC vs. TT} = 1.33, 95 % CI 1.10–1.61, P _OR = 0.004; OR_{CC+TC vs. TT} = 1.27, 95 % CI 1.05–1.55, P _OR = 0.016). Stratified analysis of high quality studies also confirmed the significant association (OR_{TC vs. TT} = 1.32, 95 % CI 1.04–1.67, P _OR = 0.024; OR_{CC+TC vs. TT} = 1.30, 95 % CI 1.02–1.66, P _OR = 0.035). In subgroup analyses by ethnicity, a significant association between the CYP1A1 MspI polymorphism and risk of prostate cancer was found among Asians (OR_{TC vs. TT} = 1.44, 95 % CI 1.20–1.72, P _OR < 0.001; OR_{CC+TC vs. TT} = 1.33, 95 % CI 1.12–1.58, P _OR = 0.001), but not in Caucasians or mixed populations. The meta-analysis suggests an important role of the CYP1A1 MspI polymorphism in the risk of developing prostate cancer, especially in Asians.     

Evaluating the bone regeneration in calvarial defect using osteoblasts differentiated from adipose-derived mesenchymal stem cells on three different scaffolds: an animal study

The aim of this study was to investigate the effect of three different scaffolds on the viability and differentiation of adipose-derived mesenchymal stem cells (ADMSCs) to osteoblast for bone regeneration of calvarial defect in rabbit model. Adipose was harvested from the nape of 12 rabbits by direct surgery or hollow-tip cannula. Two standardized circular calvarial defects (case and control), 8 mm in diameter each, were created in all the animals. The animals were divided into 3 different groups. In group 1 (G1), the defect was filled with polyamide + ADMSC. In group 2, poly lactic-co-glycolic acid + ADMSC was used. In group 3, decellularized amniotic membrane + ADMSC was applied. In the control defect, the non-seeded scaffolds were applied for filling the defect. Decellularized pericardial scaffolds were used as a membrane on the scaffolds. The animals were euthanized 2, 4, and 8 weeks of operation and new bone formation was assessed by different analyses. Immunohistochemical (IHC) staining with osteopontin and osteocalcin antibodies was also performed. After 2 weeks of wound healing, minimal bone regeneration was detected in all groups. Almost complete defect closure was observed in all experimental groups after 8 weeks of operation, with the greatest defect closure in the animals treated with polyamide scaffolds as compared to biopsies obtained from control defects and other experimental groups. The maximal tensile load was higher in G1, 4 and 8 weeks postoperatively, suggesting the usefulness of polyamide + ADMSC for bone regeneration in calvarial defects. Results of the IHC staining demonstrated a significant difference between seeded and non-seeded scaffold in both short- and long-term follow-ups (P < 0.05). In addition, a significant difference was observed in enhancement of IHC staining of both markers in polyamide group (seeded or non-seeded) 4 and 8 weeks postoperatively in comparison with other scaffolds. It was concluded that bone regeneration in critical calvarial defect was more successful in seeded polyamide.     

Litter- and soil carbohydrate-carbon stocks in 2-, 4- and 10-year-old improved fallows in eastern Zambia

This study evaluated the effects of tree species and sites on soil carbohydrates, litterfall, and litter chemistry in 2-, 4- and 10-year-old improved fallows at three sites in eastern Zambia. Between April 2002 and August 2003, litter was collected in 2-year-old tree fallows at Kalichero, Kalunga and Msekera for chemical analyses. Soil samples collected at 0–30 cm from all experiments were analysed for total soil organic carbon (SOC), but only those from 4- and 10-year-old fallows were analysed for carbohydrates. Soil arabinose- and mannose-C stocks, and carbohydrate-C percentages of SOC (7.7–20.6 %) significantly (P < 0.05) differed across tree species in 10-year-old coppicing fallows at Msekera. Converting M + F to improved fallows resulted in a decline in monosaccharide-C, carbohydrate-C stocks and carbohydrate-C percentage of SOC. There were significant (P < 0.05) variations in litterfall (0.7–2.3 t ha^?1 year^?1) and litter C contents (0.3–1.1 t ha^?1 year^?1) across 2-year-old coppicing tree fallows at Msekera. Litter production and C contents were significantly greater on sandy soils at Kalunga than on fine-textured soils at Msekera. Litter chemical contents (C, N, AUR and polyphenols) and ratios (C:N, P:N, AUR:N, and (AUR + P):N) for litter in fallows differed significantly (P < 0.05) across species and sites. In this study, the role of litter in carbon cycling in improved fallows depended on tree species and site conditions.     

Non-equilibrium molecular dynamics study of nanoscale thermal contact resistance

Interfaces play an important role in microscale and nanoscale heat transfer processes with molecular dynamics (MD) simulations often used to study these interfacial phenomena. In this study, two models were used to simulate thermal conduction across micro contact points and the thermal contact resistance using non-equilibrium molecular dynamics simulations with consideration of the near field radiation. When the ratio of the length of the micro contact to the length of the conduction region is less than 0.125, the influence of the near field radiation should be considered; but when the ratio is larger than 0.2, it can be neglected. When the computational domain sizes are 8.50 × 10.62 × 8.50 nm and 10.62 × 10.62 × 10.62 nm, the MD results show that the thermal contact resistance exponentially increases with decreasing area of the micro contact point and increases with increasing micro contact layer thickness. The MD thermal contact resistances in nanoscale are much larger than that of the classical thermal analysis since the material thermal conductivity reduction is ignored in the classical model. The results also show that material defects increase the thermal resistance.     

Adsorption and decomposition mechanism of hexogen (RDX) on Al(111) surface by periodic DFT calculations

The adsorption of hexogen (RDX) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and aluminum atoms induce the N?O and N?N bond breaking of the RDX. Subsequently, the dissociated oxygen atoms, NO₂ group and radical fragment of RDX oxidize the Al surface. The largest adsorption energy is ?835.7 kJ mol^–1. We also investigated the adsorption and decomposition mechanism of RDX molecule on the Al(111) surface. The activation energy for the dissociation steps of V4 configuration is as large as 353.1 kJ mol^–1, while activation energies of other configurations are much smaller, in the range of 70.5–202.9 kJ mol^–1. The N?O is even easier than the N?NO₂ bond to decompose on the Al(111) surface.     

Characterisation of the effect of electrostatic interaction on the structure of Trp-cage using molecular dynamics simulation

A mutated variant of 20 amino acid miniprotein Trp-cage (TC5b), called TC5c (Asp9 replaced by Asn9), was designed to demonstrate the effect of a salt bridge. As a result of strong electrostatic interaction, the distance distribution between Asp9 and Arg16 exhibited a larger probability in the range of the salt bridge for TC5b compared to TC5c. The probability of α-helix formation for residues 3–8, as well as for residues 11–14, was high for TC5b. The salt bridge formation between Asp9 and Arg16 in TC5b was indicated by (a) a strong correlation of their distance of separation with the subtended angle with the centre and (b) a step decrease in the distance between Gly11O and Arg16H at 12 ns. Replica exchange molecular dynamics simulation at different temperatures in the range of 270–590 K indicated that the average distance between Asp9 and Arg16, end-to-end distance, root mean square deviation with respect to a reference NMR structure of TC5b did not change significantly with temperature below 370 K for TC5b and increased at higher temperatures. These values were higher for TC5c for the whole temperature range, with their rate of increase with temperature being higher below 370 K.     

3D Macroporous Nitrogen‐Enriched Graphitic Carbon Scaffold for Efficient Bioelectricity Generation in Microbial Fuel Cells

Microbial fuel cell (MFC) can generate electricity based on oxidation of organic compounds by exoelectogens, giving rise to a promising potential for recovering electrical energy from organic wastewater. The structure and property of anode materials have inherent impact to extracellular electron transfer (EET), an interfacial process that greatly limits bioelectricity production of MFC. Herein, a three dimensional (3D) macroporous nitrogen‐enriched graphitic carbon (NGC) scaffold is fabricated from commercially available melamine foam using facile pyrolysis method. The NGC electrode is demonstrated to promote EET ef?ciently, achieving a power density of 750 mW m^?2 based on pure cultured Shewanella oneidensis MR‐1 in acetate‐feeding MFC. The unique 3D open‐cell structure not only offers habitats for colonization of electroactive bio?lm up to a maximal density but also provides macroporous architecture for internal mass transfer without concern of bio‐blocking and bio‐fouling. Additionally, nitrogen incorporation also plays a signi?cant role in enhancing EET, where pyrrolic nitrogen is much more active than graphitic and pyridinic nitrogen as indicated by density functional theory calculation. This work provides a proof‐of‐concept demonstration of a high‐ef?ciency, cost‐effective, easily scaling‐up, and environmentally friendly anode material of bioelectrochemical systems for electricity generation, hydrogen production, and pollutant degradation.