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Nitrification is believed to be one of the primary processes of N2O emission in the agroecological system, which is controlled by soil microbes and mainly regulated by soil pH, oxygen content and NH4+ availability. Previous studies have proved that the relative contributions of ammonia oxidizing bacteria (AOB) and archaea (AOA) to N2O production were varied with soil pH, however, there is still no consensus on the regulating mechanism of nitrification-derived N2O production by soil pH. In this study, 1-octyne (a selective inhibitor of AOB) and acetylene (an inhibitor of AOB and AOA) were used in a microcosm incubation experiment to differentiate the relative contribution of AOA and AOB to N2O emissions in a neutral (pH = 6.75) and an alkaline (pH = 8.35) soils. We found that the amendment of ammonium (NH4+) observably stimulated the production of both AOA and AOB-related N2O and increased the ammonia monooxygenase (AMO) gene abundances of AOA and AOB in the two test soils. Among which, AOB dominated the process of ammonia oxidation in the alkaline soil, contributing 70.8% of N2O production derived from nitrification. By contrast, the contribution of AOA and AOB accounted for about one-third of nitrification-related N2O in acidic soil, respectively. The results indicated that pH was a key factor to change abundance and activity of AOA and AOB, which led to the differentiation of derivation of N2O production in purple soils. We speculate that both NH4+ content and soil pH mediated specialization of ammonia-oxidizing microorganisms together; and both specialization results and N2O yield led to the different N2O emission characteristics in purple soils. These results may help inform the development of N2O reduction strategies in the future. [ABSTRACT FROM AUTHOR]

• A novel potential energy regeneration method with simple structure is proposed. • A hydraulic cylinder and an accumulator are used to reuse the huge potential energy. • The energy conversion chain with the proposed method is short. • The energy efficiency of the boom system can be further improved. • The system can significantly improve the fuel engine working performance. Hydraulic excavators are essential excavation machines, with more than 3.8 million sets in use in the mining, and engineering and architectural engineering construction fields. However, during the working process, a large amount of gravitational potential energy is wasted, causing low energy efficiency and poor emissions. Taking a large-scale excavator as an example, during a certain 90° excavation process, the gravitational potential energy wastage of the working device is approximately 975.1 kJ, which amounts to at least 20% of the energy consumption of the entire machine, causing significant energy waste and serious pollution. And, during the boom lowering process, the changing rate of potential energy is about 406.4 kW. In order to improve the energy efficiency of hydraulic excavators, the recovery of this huge energy that changes rapidly with low cost and high efficiency is a big problem that must be solved. This paper proposes a gravitational potential energy recovery scheme with an energy conversion cylinder and a hydraulic accumulator. Using this scheme, the gravitational potential energy of the working device can be stored and reused directly, without increasing the cost and install power of the machine largely. In the study, first, the system parameters are designed, following which the multidisciplinary dynamic model of the hydraulic excavator is established. The influence of the accumulator parameters on the energy recovery ratio is studied based on the model. The results demonstrate that with the newly designed system more than 75.9% of the gravitational potential energy can be stored in the accumulator during the lowering process. Moreover, during a certain lifting process, the input energy to the pump can be reduced by 52%. On this basis, a 76 t hydraulic excavator test system is constructed using the above principle. The experimental results match strongly with the co-simulation results. The energy consumption can be reduced to approximately 238 kJ during a certain 90° excavation cycle, and the system can reduce the carbon dioxide emissions by 28088.4 kg per year. The energy-saving and emission-reduction effects are remarkable; furthermore, this principle can directly be applied to other lifting machines. [ABSTRACT FROM AUTHOR]

Abstract The conventional design methods for tracked walking systems of large hydraulic excavators based on empirical formulas, does not take into account the dynamic load of the track. As such, a safety margin factor has to be adopted to ensure adequate working strength. However, the machine weight will be increased, and the hydraulic system will be overmatched. To address this design issue, an electromechanical–hydraulic design approach based on co-simulation is proposed in this study. The proposed design approach consists of four parts, namely, 1) a terramechanics model of the track that considers the pressure–sinkage relationship and soil shear stress of the individual tracked plate, 2) a tracked multibody dynamics (MBD) model that considers the intermittent transmission between the sprocket and the tracks, 3) the hydraulic systems model, and 4) the data communication interface. To demonstrate the proposed approach, it was used to design a large hydraulic excavator with a bucket capacity of 15 m3. Experimental results from the prototype showed that the proposed design principle can accurately reflect the impact load and periodic torque fluctuations on the track. The maximum error between the simulated and experimental results is 5.4% in forward walking and 12.7% in backward walking, thus demonstrating the effectiveness and accuracy of the proposed design approach. Graphical abstract Unlabelled Image Highlights • A co-simulation design method for ultra-large tracked walking systems is proposed. • Dynamic intermittent transmission pair and terramechanics are considered. • Interactions among track, excavator structure and hydraulic system are considered. • Dynamic load and periodical fluctuation are reflected accurately in the method. • The test verifies the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

ABSTRACT: A series of novel ultralow dielectric porous polyimide (PI) films containing adamantane groups was prepared via the thermolysis of polyethylene glycol (PEG) oligomers mixed into PI matrix. Scanning electron microscopy results indicated that the porous PI films showed closed pores with an average diameter of 120 ± 10 nm. Good thermal properties with 5% weight loss temperature of 499 °C in air atmosphere and glass transition temperature in excess of 310 °C were shown for porous PI films. Notably, the ultralow dielectric constant of porous PI films with 1.85 at 1 MHz was obtained and revealed via broadband dielectric spectroscopy. The effects of the chemical structure of the PI matrix and PEG content on the decomposition behavior of PEG and the performance of porous films were investigated. Wide‐angle X‐ray diffraction results indicated that the PI matrix with large d‐spacing generated weaker interactions between the PEG and PI backbone than those of PI matrix with small d‐spacing. As a result, the PEG for the PI matrix with large d‐spacing was completely decomposed. As indicated by the broadband dielectric spectroscopy results, lower dielectric porous PI films were prepared when the PEG contents in the PI matrix increased from 0 to 20 wt %. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 549–559 [ABSTRACT FROM AUTHOR]

Carbon‐based anodes are the key limiting factor in increasing the volumetric capacity of lithium‐ion batteries. Tin‐based composites are one alternative approach. Nanosized Sn–Fe–C anode materials are mechanochemically synthesized by reducing SnO with Ti in the presence of carbon. The optimum synthesis conditions are found to be 1:0.25:10 for initial ratio of SnO, Ti, and graphite with a total grinding time of 8 h. This optimized composite shows excellent extended cycling at the C/10 rate, delivering a first charge capacity as high as 740 mAh g−1 and 60% of which still remained after 170 cycles. The calculated volumetric capacity significantly exceeds that of carbon. It also exhibits excellent rate capability, delivering volumetric capacity higher than 1.6 Ah cc−1 over 140 cycles at the 1 C rate. [ABSTRACT FROM AUTHOR]

Complexity of large structure of hydraulic shovel system drives the guideline development for designing a swing unit of the shovel. Some of the issues are how to achieve smooth swing motion, save energy, and easily adjust its swing velocity. In this paper, we proposed a dual-closed-hydraulic-circuit (DCHC) accordingly to meet the design requirement. In the DCHC system, instead of manual adjustment, the displacement of hydraulic axial piston pump is controlled by programmed software algorithm through electronic control device, which significantly simplifies the current circuit design. The DCHC system also enables controllable recuperation of kinetic energy of swing motion for use by other actuators. Accordingly, the new system will achieve smoother motion compared with existing system and more efficient operation. We demonstrate the advantages of our DCHC design through simulation and verify through developing a hydraulic shovel prototype with bucket capacity of 15 cubic meters and operational weight of 270 tons. Both simulation and experimental results indicate that the DCHC system is feasible and works as intended. [ABSTRACT FROM AUTHOR]

Novel thermoresponsive copolymers of zwitterionic sulfobetaine methacrylate (SBMA)- and N,N-dimethylaminoethyl methacrylate (DMAEMA)-grafted silica nanoparticles are prepared via surface-initiated atom transfer radical polymerization. The phase behavior of these nanoparticles is investigated. The hybrid nanoparticles exhibit tunable phase transition temperature between the upper critical solution temperature (UCST) and the lower critical solution temperature (LCST) in aqueous solution. A high PSBMA content in P(SBMA- co-DMAEMA) copolymer in the hybrid nanoparticles leads to aggregation at low temperatures because of dominant electrostatic interactions of ionic pairs, whereas a relatively low PSBMA content in the hybrid nanoparticles results in a phase transition at high temperatures as a result of predominant hydrophobic interactions of the PDMAEMA. Interestingly, hybrid nanoparticles with a suitable molar ratio of SBMA/DMAEMA exhibit both UCST and LCST in aqueous solution, where the water-insoluble microdomains of hybrid nanoparticles are generated by the PSBMA or PDMAEMA region depending on the temperature. The above dual-thermoresponsive phase transition is also controllable in salt solution. A facile change in the molar content of copolymer grafted on silica nanoparticles will tune the UCST and LCST readily. [ABSTRACT FROM AUTHOR]

Soil fauna play a crucial role in sustaining agro-ecosystem functions. Crop straw is recommended for application to agricultural fields to improve soil quality. However, the effects of crop straw combined with different synthetic fertilizers on the soil faunal community remain unclear, and knowledge regarding purple soil is limited. Using the conserved cytochrome c oxidase I (COI) gene as markers, we examined the responses of the soil faunal community to different fertilization in upland purple soil of southwestern China. The accuracy of the morphological and molecular methods in characterizing soil nematodes was compared. Our results showed that different fertilization treatments significantly changed the soil faunal community structure (Adonis test, R2 = 0.43, P = 0.011). Sixteen biomarkers were identified according to LEfSe (linear discriminant analysis effect size). The diversity and species number of soil fauna were closely related to soil organic matter (SOM) and total phosphorus (TP) (P < 0.05). This study indicates that crop straw return can improve the soil fertility and diversity of soil fauna in purple soil. Additionally, the morphological approach and molecular method based on the COI gene can be considered as complementary approaches in characterizing soil nematode community. [ABSTRACT FROM AUTHOR]

Soil fauna play a crucial role in sustaining agro-ecosystem functions. Crop straw is recommended for application to agricultural fields to improve soil quality. However, the effects of crop straw combined with different synthetic fertilizers on the soil faunal community remain unclear, and knowledge regarding purple soil is limited. Using the conserved cytochrome c oxidase I (COI) gene as markers, we examined the responses of the soil faunal community to different fertilization in upland purple soil of southwestern China. The accuracy of the morphological and molecular methods in characterizing soil nematodes was compared. Our results showed that different fertilization treatments significantly changed the soil faunal community structure (Adonis test, R2 = 0.43, P = 0.011). Sixteen biomarkers were identified according to LEfSe (linear discriminant analysis effect size). The diversity and species number of soil fauna were closely related to soil organic matter (SOM) and total phosphorus (TP) (P < 0.05). This study indicates that crop straw return can improve the soil fertility and diversity of soil fauna in purple soil. Additionally, the morphological approach and molecular method based on the COI gene can be considered as complementary approaches in characterizing soil nematode community. [ABSTRACT FROM AUTHOR]

Abstract: Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) was grafted onto the surface of silica nanoparticles via surface-initiated atom transfer radical polymerization to form temperature- and pH-responsive PDMAEMA brushes (silica-g-PDMAEMA). The resultant samples were characterized via 1H NMR, transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Their molecular weights and molecular weight distributions were determined by gel permeation chromatography analysis after silica content etching. The control of brush thickness and the responsive behavior were systematically investigated. Dynamic light scattering (DLS) results indicate that the brush thickness can be controlled by changing the polymerization time and the DMAEMA, initiator, and THF concentrations. According to DLS and zeta potential results, the lower critical solution temperature (LCST) of the PDMAEMA brushes shifts to a higher temperature with decreasing solution pH, which is attributed to the weak charge of the polyelectrolyte brushes. When the temperature is kept above the transition temperature, the silica-g-PDMAEMA nanoparticles aggregate into clusters and disaggregate during the cooling process. Moreover, with the heating/cooling step increasing, the aggregation and disaggregation temperatures are decreased. Meanwhile, when the molecular weight is increased from 13.6 × 104 to 23.1 × 104 g/mol, a decrease in the LCSTs at constant pH is observed. The related properties of the corresponding quaternized analog, poly{[2-(methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI) brushes, were also discussed. The hydrodynamic radius of the silica-g-PMETAI nanoparticles decreases with increasing ionic strength, and a salting-out/salting-in effect is observed when the ionic strength is adjusted using NaI instead of NaCl. [Copyright &y& Elsevier]

Silicon nanowires (Si NWs) with and without carbon coating were successfully prepared by combination of chemical vapor deposition and thermal evaporation method. The morphologies, structures, and compositions of these nanomaterials were characterized in detail. Furthermore, the electrochemical performances of uncoated and carbon-coated Si NWs as anode materials were also studied. It shows that the carbon-coated Si NWs electrode has higher capacity, better cycle stability, and rate capability than the uncoated materials. For example, it delivers 3,702 and 3,082 mAh g−1 in the initial charge and discharge processes. When cycled between 0.02 and 2.0 V at a current density of 210 mA g−1, it yields a high coulombic efficiency of 83.2%. The discharge capacity still remains around 2,150 mAh g−1 after 30 cycles. [ABSTRACT FROM AUTHOR]

• Nitrate leaching accounts for over 84 % of the hydrological nitrogen loss. • Thicker soil improves crop yield and mitigates nitrate leaching loading. • The soil thickness of 60 cm is suggested as a threshold for land reclamation. Shallow soils are widely distributed in mountainous and hilly areas due to severe soil erosion. However, the impacts of soil thickness on soil productivity, water and nutrient retention in shallow cropland soils have not been well documented. This study was conducted to investigate how soil thickness affects soil productivity and nitrate leaching from sloping croplands in the upper Yangtze River Basin, China. Free-drained lysimeters on sloping cropland with soil thicknesses of 20 (ST1), 40 (ST2), 60 (ST3), 80 (ST4) and 100 (ST5) cm were used to monitor soil moisture, surface runoff and nitrate leaching. The results showed that total crop yields during an entire winter wheat-summer maize rotation year (October 2017-September 2018) for ST1 to ST5 were 2.38 ± 0.07, 3.22 ± 0.01, 6.43 ± 0.61, 8.21 ± 0.56 and 8.58 ± 0.29 Mg ha−1, respectively. The annual cumulative total nitrogen (N) loss loadings via surface runoff and leaching for ST1 to ST5 were 21.09 ± 1.54, 13.08 ± 0.79, 5.61 ± 0.36, 3.49 ± 0.27 and 1.96 ± 0.22 kg N ha−1, respectively. The annual cumulative nitrate leaching loadings for ST1 to ST5 were 18.41 ± 1.07, 11.27 ± 0.56, 4.93 ± 0.45, 3.05 ± 0.32 and 1.66 ± 0.12 kg N ha−1, respectively, which accounted for more than 84 % of the cumulative total N loss through hydrological processes. This finding indicates that leaching dominates the hydrological N loss in sloping cropland. Moreover, significant differences were observed in yield-scaled nitrate leaching losses among ST1 (7.74 ± 0.62), ST2 (3.49 ± 0.18) and ST3 (0.78 ± 0.13 kg N Mg−1) (P < 0.05), while no significant differences were found among ST3 (0.78±0.13), ST4 (0.37±0.02) and ST5 (0.19±0.01 kg N Mg−1). This finding implies that if the soil thickness is greater than 60 cm, then it may be possible to maintain crop yields and mitigate nitrate leaching losses on sloping croplands. Therefore, a soil thickness of 60 cm is recommended as a threshold soil layer for basic water and nutrient retention as well as land reclamation and restoration of degraded cropland suffering from severe soil erosion. Soil thickness is a critical index for evaluating soil functions for water and nutrient retention, crop productivity improvement and agricultural non-point source pollution control. [ABSTRACT FROM AUTHOR]

• The geometric dimension of the package shell of the sensing unit are studied by theory and experiment, and improper design of the package housing may degrade the frequency response characteristics of the sensing unit. • The influence of prestress on the frequency response characteristic of sensor is studied. • The geometric dimension of the package shell and the prestress of the sensing unit are reasonably optimized to make the working frequency of the sensor avoid the resonant frequency of the shell. • The paper provides a theoretical basis for the design and manufacture of the sensors with wide frequency response and high sensitivity in different engineering applications, such as high frequency small amplitude and low frequency large amplitude. In coal mine, military, oil well monitoring and other fields, the traditional electrical accelerometers based on piezoelectric and capacitive can not meet the needs of high-performance applications. The optical fiber acceleration sensor with high precision, large dynamic, wide frequency response, anti-electromagnetic interference and other unique advantages, can meet a variety of applications. The complete optical fiber acceleration sensor consists of a package housing and an internal sensing unit. Some factors, including the vibration and deformation of the housing itself, and the prestress of the sensing unit will directly affect the frequency response characteristics of the sensor. The experimental results show that the resonant frequency of the package housing is outside the operating frequency band of the sensor through reasonable design of shell parameters; in a certain torque range (0.2 N . m ∼ 0.8 N . m), the resonant frequency increases with the increase of the torque. The research provides a theoretical basis for the design and manufacture of the sensors with wide frequency response and high sensitivity in different engineering applications, such as high frequency small amplitude and low frequency large amplitude. [ABSTRACT FROM AUTHOR]

Polyimide (PI) fibers containing pyrimidine and amide moieties were fabricated by the copolymerization of 2,5-bis(4-aminophenyl)pyrimidine (PRM) and 4,4′-diaminobenzanilide (DABA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) via a two-step method. The effects of chemical structure of PI fibers, i.e., various molar ratios of PRM/DABA, on their thermal property, crystallinity, orientation factor, microvoid defects, and mechanical property, were investigated in detail. The glass transition temperatures (Tg) of all PI fibers ranged from 282 to 310 °C, and the temperatures at 5% weight loss (T5%) under N2 and air atmosphere were respectively within 548–584 °C and 482–540 °C, demonstrating the excellent thermal stability and thermal oxidation stability of all fibers. The wide-angle X-ray diffraction data illustrated that the co-PI fibers had lower crystallinity than the homo-PI fibers due to a marked decrease in molecular order packing by copolymerization. However, the co-PI fibers possessed higher degrees of orientation relative to the homo-PI fibers. In particular, the co-PI fiber with PRM/DABA = 5/5 showed the highest orientation factor, fc = 0.872. Moreover, the small-angle X-ray scattering results, i.e., decrease in microvoid size, revealed that DABA incorporation helps to reduce the defects in PI fibers. When the PRM/DABA molar ratio was 5/5, the co-PI fiber possessed an optimal tensile strength and initial modulus of 3.43 and 136.92 GPa, respectively. [ABSTRACT FROM AUTHOR]

Abstract Manure application and crop residue returning have been performed to enhance crop yield and reduce soil reactive nitrogen (N r) gas (N 2 O and NO x) emissions. However, the dynamic characteristics of soil nitrogen-cycling (N-cycling) enzyme activities, and the relationship among N-cycling enzyme activities, N r contents and Nr gas emissions are not clearly understood. Six fertilization regimes, including control (CK-no fertilizer), synthetic N fertilizer alone (N), synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure (OM), pig manure (30% of N rate) with synthetic NPK (70% of N rate) (OMNPK), and crop residues (20% of N rate) with synthetic NPK (80% of N rate) (CRNPK), were used for 11 years to form stable soil conditions. The total N application rate in each fertilization regime, except CK, is the same (130 kg N ha−1) in the winter wheat season. The results showed that the cumulative emissions of N 2 O plus NO x in OM increased significantly by 43.7%, while those in OMNPK and CRNPK decreased by 8.2 and 15.3% compared to conventional fertilization regimes of NPK. The long-term application of manure or returning crop residues to partly replace synthetic N fertilizer may significantly enhance soil hydrolase activities compared with NPK at most stages of wheat growth. In contrast to OM, OMNPK and CRNPK primarily inhibited the activities of nitrate reductase (NR) and nitrite reductase (NiR) but increased hydroxylamine reductase (HyR) activity. Redundancy analysis (RDA) and stepwise multiple linear regression showed positive NR and NiR activities, while PRO activity is negative for N 2 O emission. NO x emissions were mainly controlled by HyR activities. Thus, soil reactive nitrogen (N r) gas emissions may be mitigated by different fertilization regimes through the regulation of soil enzyme activities. Fertilization regimes, such as manure application and returning crop residues with synthetic NPK, could be recommended as optimal N fertilization strategies in Regosols to mitigate N r gas emissions. [ABSTRACT FROM AUTHOR]

Highlights • An organic Rankine cycle with heat pump system is proposed for hydraulic systems. • The proposed system applied to a 260-ton hydraulic excavator is investigated. • The optimal working fluid for the proposed system is selected. • The earning of equilibrium temperature shows a maximum at certain oil temperatures. • The economic performance decreases with the increase in ambient temperature. Abstract The operating temperature of hydraulic oils should be controlled within a reasonable range to keep hydraulic systems in good working condition. However, due to the huge energy losses of hydraulic systems, the oil temperature will increase rapidly. In addition, some hydraulic equipment often operate in cold weather conditions. The conventional cooling with radiators and preheating with electric heaters will consume extra energy for hydraulic systems. Therefore, an organic Rankine cycle with heat pump system is proposed to achieve regenerative cooling and energy-efficient preheating. The system can operate in two modes: an organic Rankine cycle mode to produce electricity instead of consuming energy while cooling the hot oil, and a heat pump mode to preheat the oil with less energy before the hydraulic system starts up in a cold environment. The system is applied to a 260-ton hydraulic excavator to investigate the technical feasibility. On average, the calorific power of the excavator is 177 kW at 245 kW of consumed power in a typical cycle. Considering the cost of heat source, the earning of equilibrium temperature is proposed to evaluate the benefit of the organic Rankine cycle. The optimal working fluid is selected by comparing the system performance. Afterward, the peak points of earning of equilibrium temperature at different ambient temperatures are observed. Corresponding to the maximum earning of equilibrium temperature, the output power of the organic Rankine cycle ranges from 7.63 kW to 2.89 kW. These results show significant energy savings by applying the proposed system in the hydraulic system. [ABSTRACT FROM AUTHOR]

Waterborne microbial pollution remains poorly understood in developing countries, especially in rural areas. The transport of point (e.g. untreated domestic wastewater) and non-point sources of fecal bacteria such as Total coliform (TC) and Escherichia coli ( E. coli ) and their spatial and temporal patterns were identified in a typical small agricultural catchment in a hilly area of subtropical China. Over the sampling area, 460 water samples from 24 sites were collected during a period of 12 months, and a remediation option using an existing ecological ditch was evaluated. The results showed that 70% surface water samples exceeded the guideline of 1000 TC MPN 100 ml −1 in the catchment. Also, 90% of groundwater samples exceeded the guideline of 10 MPN E. coli 100 ml −1 for safe drinking water. Higher concentrations of TC and E. coli occurred both in the warm and rainy season in surface water and groundwater. TC and E. coli concentrations in surface water tributaries and groundwater near residential areas were greater than those in downstream water bodies. A 300 m long vegetated ecological ditch greatly reduced average concentrations TC of 97.7% and E.coli of 99.5%. TC and E. coli concentrations were significantly correlated with electrical conductivity and turbidity, both in surface water and groundwater, indicating that mixtures of organic colloids and sediment were the most important transport vector for pathogens. However, temperature only showed a controlling effect on bacteria concentration in groundwater in this particular catchment. The current research could help predict microbial risks and establish integrated management strategy to improve water quality in the hilly agricultural catchments in the subtropical region. [ABSTRACT FROM AUTHOR]

A soluble polyimide (6FDA-TFDB) was synthesized and its properties in solution were investigated. The relationship between specific viscosity and concentration is established using rheometer and applying Zimm model (dilute solution), Rouse–Zimm model (semidilute unentangled solution), and Doi–Edwards model (semidilute entangled solution). In addition, the overlapped concentration (C*) and semidilute entangled concentration (C e ) are determined. Results showed that all of the scaling exponents are higher than the theoretical values. The influence of factors, namely, electrostatic interaction, hydrogen bonding, dipole–dipole interaction and polydispersity index under different conditions (i.e., temperature, salt, and solvent) on critical concentration and scaling exponents are investigated extensively. In order to confirm the related conclusions, two soluble polyimides with different chemical structures are also synthesized and compared with the above results. The reasons for the deviation of scaling exponents are also discussed. [ABSTRACT FROM AUTHOR]

• NiFe hydroxide is prepared via ion-assisted method with ZIF-8 as precursor. • Ni 0.75 Fe 0.25 (OH) 2 /NF shows low overpotential of 259 mV at 100 mA cm−2. • The NiFe bimetal effect and nanosheets with oxygen vacancies are key for OER. Developing active water oxidation electrocatalysts with earth-abundant components is significant for bulk hydrogen supply via water electrolysis. Herein, nickel iron hydroxide nanosheets assembled particles on nickel foam are prepared through ion-assisted etching method with ZIF-8 as precursor. The sample achieves remarkable catalysis efficiency toward oxygen evolution reaction with ultralow overpotential of 259 mV at high current density of 100 mA cm−2. The superior catalysis efficiency is assigned to Ni/Fe synergisms of optimized intrinsic activity, abundant surface oxygen vacancies, enhanced charge flow, and increased active sites, as well as nanosheet structure benefits of approachable catalytic sites and shortened charge transform pathways. [ABSTRACT FROM AUTHOR]

With a view toward addressing the poor efficiency with which nitrogen is removed from wastewater below 10 °C, in this study, we isolated a novel cold-tolerant heterotrophic nitrification–aerobic denitrification (HN-AD) bacterium from a wetland and characterized its nitrogen removal performance and nitrogen metabolic pathway. On the basis of 16S rRNA gene sequencing, this strain was identified as a species of Janthinobacterium , designated J1-1. At 8 °C, strain J1-1 showed excellent removal efficiencies of 89.18% and 68.18% for single-source NH 4 +-N and NO 3 −-N, respectively, and removal efficiencies of 96.23% and 79.64% for NH 4 +-N and NO 3 −-N, respectively, when supplied with mixed-source nitrogen. Whole-genome sequence analysis and successful amplification of the amoA , napA , and nirK functional genes related to nitrogen metabolism provided further evidence in support of the HN-AD capacity of strain J1-1. The deduced HN-AD metabolic pathway of the strain was NH 4 +-N→NH 2 OH→NO 2 −-N→NO 3 −-N→NO 2 −-N→NO→N 2 O. In addition, assessments of NH 4 +-N removal under different conditions revealed the following conditions to be optimal for efficient removal: a temperature of 20 °C, pH of 7, shaking speed of 150 rpm, sodium succinate as a carbon source, and a C/N mass ratio of 16. Given its efficient nitrogen removal capacity at 8 °C, the J1-1 strain characterized in this study has considerable application potential in the treatment of low-temperature wastewater. • A new cold-tolerant bacterium, Janthinobacterium sp. J1-1 was isolated from wetland. • Strain J1-1 effectively removed 89.18 % of NH 4 +-N and 68.18 % of NO 3 −-N even at 8 °C. • The combination of removal of different nitrogen sources and genome sequencing reveal nitrogen metabolic pathway. • Strain J1-1 performs simultaneous nitrification and denitrification processes. [ABSTRACT FROM AUTHOR]

The effects of molecular coplanar structure on crystallinity, orientation, and overall performances of polyimide (PI) copolymer fibers, especially mechanical properties, were investigated. In detail, three diamines with similar structures, including 4,4′-diaminobenzophenone (DABP), 4,4′-diaminobenzanilide (DABA), and benzidine (Bz), were introduced as third monomers into the classical heterocyclic 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)/2,5-bis(4-aminophenyl)pyrimidine (PRM) system, eventually the high-performance PI fibers being fabricated successfully via dry-jet wet spinning process. The conformation simulations illustrated the different coplanar levels found in three similar diamines: DABP (worst), DABA (better), and Bz (best). Thus, the BPDA/Bz dimer showed excellent coplanar structures, and the dihedral angle of the farthest benzene rings was only 4.42°. The wide-angle X-ray diffraction patterns indicated that the crystallinity and orientation of fibers increased with the increase of the coplanarity degree and molecular packing. Interestingly, the Bz-PI fiber possessed the strongest mechanical properties, i.e., fracture strength of 4.01 GPa and initial modulus of 137.34 GPa, which was primarily contributed by optimal molecular coplanarity and highest orientation. [Display omitted] • High-performance polyimide copolymer fibers were fabricated via molecular coplanar structure design. • Both H-bonding interactions and molecular coplanarity effectively enhance the packing coefficient of molecular chains. • Better molecular coplanar structures are beneficial to increase the crystallinity and orientation of fiber. • The optimal fracture strength and initial modulus reach 4.01 and 137.34 GPa, respectively, corresponding to Bz-PI fiber. [ABSTRACT FROM AUTHOR]

The volumetric energy density of today's lithium-ion batteries is limited mostly by the graphitic carbon anode. Silicon is a promising replacement but its excessive volume expansion on lithiation limits its long-term cyclability performance. A nano-sized aluminium containing silicon, leached in acid, with a porous structure is shown to maintain its capacity higher than pure bulk silicon or nano-sized silicon by over 700 mAh/g. The capacity of leached silicon is maintained at 1400 mAh/g for more than 60 cycles. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nuclear magnetic resonance spectroscopy have been used to correlate the electrochemical performance with the materials' morphology and composition. [ABSTRACT FROM AUTHOR]

Polyimde (PI) samples with different molecular weights were synthesized. Based on SEC coupled with multidetectors measurement and Yamakawa-Fujii-Yoshizaki (YFY) model, eight soluble samples with absolute M from 40,600 g/mol to 197,000 g/mol are chosen and applied to investigate the influence of molecular weight on scaling exponents and critical concentrations at 20-45 °C in dilute, semidilute unentangled, and semidilute entangled solutions. Most of the scaling exponents are higher than the theoretical values in three concentration regions, and scaling exponent increases with molecular weight; overlap concentration (C*) increases and entanglement concentration (C) decreases with molecular weight. Considering bead-bead interaction, corrected bead-spring model can explain the related results. Finally, the relationship among C, C, and molecular weight is established at different temperatures (from 20 °C to 45 °C), and two linear equations are available at each temperature. Thus, both C and C are calculated at a fixed molecular weight. And from C/C and C/C ratios, the morphology of PI fiber during electrospinning can be controlled. These results are helpful to guide the preparation of polyimide solutions for different processing. [ABSTRACT FROM AUTHOR]

A novel interchain crosslinking system was designed to improve the thermal performance of PI films. A diamine containing Cl atom (Cl-DAXBA) was prepared and polycondensed with pyromellitic dianhydride and 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, respectively. Two series of PI films (PM and BP) were prepared under different curing temperatures in the range of 320–380 °C. The crosslinking of free radicals produced by Cl-DAXBA decomposition occurred between the molecular chains, and the crosslinking degree increased with raising the curing temperature. The network structure formed by crosslinking effectively inhibited the movement of molecular chains and promoted their close packing. The glass transition temperature (T g) of PM films increased from 378 °C to >450 °C, and the coefficient of thermal expansion (CTE) decreased from 66.3 ppm·K−1 to 4.9 ppm·K−1. The T g of BP films increased from 349 °C to >450 °C, and the CTE decreased from 50.4 ppm·K−1 to 17.7 ppm·K−1. Definitely, the tunable interchain crosslinking provides an effective strategy to improve both T g and CTE simultaneously. [Display omitted] • A novel interchain crosslinking system was designed to improve the thermal performance of PI films. • The maximum T g of the PI film is >450 °C. • The minimum CTE of the PI film is 4.9 ppm·K−1. [ABSTRACT FROM AUTHOR]

A main-chain structured electroactive polyimide (EPI) based on nona-aniline was synthesized via oxidative coupling between p -phenylenediamine (p-PDA) and a monodisperse tetra-aniline precursor. The structure and electrochemical properties of the EPI were studied by FTIR, UV–vis and cyclic voltammetry (CV), respectively. The thermal and anticorrosion properties of the EPI were compared with its penta-aniline analogue. The conductivity of the EPI is 6.27 × 10−5 S･cm−1 which is about ten times higher than that of its penta-aniline analogue. T 10% of EPI is 509 °C, significantly higher than those of reported main-chain polyaniline or side-chain polyaniline. Moreover, compared with its penta-aniline analogue, the anti-corrosion protecting efficiency of the EPI is increased by 12%. Results show that conjugated length extension of oligoanilines in a main-chain structured electroactive polymer system can significantly facilitate intra-molecular and inter-molecular charge transporting abilities, and consequently increase the functional efficiency of the materials. By extending the length of oligoaniline, polyimides based on these oligoaniline can achieve better intermolecular and intramolecular charge transfer efficiency. Thus, the functional efficiency of the material is improved. [Display omitted] • A main-chain electroactive polyimide (EPI) based on nona-aniline is obtained via oxidative coupling method. • The conductivity of nona-aniline EPI doped with HCl is ten times higher than that of penta-aniline EPI. • The main-chain EPI exhibits better thermal property than the side-chain EPI. • Nona-aniline EPI exhibits a protection efficiency of 90%, higher than 78% of penta-aniline EPI. [ABSTRACT FROM AUTHOR]

A series of polyaniline/polyimide (PANi/PI) composite fibers was prepared via dry-jet wet spinning followed by in situ polymerization growth. The resultant composite fibers showed good mechanical properties with a tensile strength of 0.90 GPa, a tensile modulus of 6.79 GPa, and an elongation at break of 14.63%. Thermogravimetric and thermal mechanical analyses revealed that the composite fibers had considerably good thermal stabilities in air and nitrogen atmospheres, as well as good size stabilities at 50–150 °C. Current–voltage curves indicated the transformation from electric insulation to electrical conductivity along the fiber axial direction. The composite fibers exhibited a sensitive response to immersion in solutions with different pH values. This work provides a simple approach to fabricate PANi/PI composite fibers that could be applied in the antistatic textile and military industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two series of novel aromatic polyimide films containing xanthone moiety and amide groups were prepared through a two-step procedure. • The maximum T g of the PI film is 400 °C. • The minimum CTE of the PI film is 2.3 ppm·K−1. • The PI films has fluorescence properties and the highest absolute fluorescence quantum efficiency is 2.9%. In recent years, an increasing amount of attention has been paid to polyimide (PI) substrate materials with high glass transition temperature (T g) and low coefficient of thermal expansion (CTE) due to the rapid development of the flexible OLED field. To improve T g and CTE, rigid conjugated structure and hydrogen bonds are designed. Two diamines containing amide and rigid xanthone groups were synthesized (p -DAXBA and m -DAXBA). Two series of PI films, PIa and PIb, were prepared by polymerization of DAXBA with different dianhydrides, i.e., pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 4,4′-oxydiphthalic anhydride (ODPA). PIa films prepared by p -DAXBA have more hydrogen bonding, closer molecular chain packing, and stronger molecular charge transfer (CT) effect, as well as better heat resistance, dimensional stability, and mechanical properties than PIb films prepared by m -DAXBA. However, their absolute fluorescence quantum efficiency and transparency are weaker than those of PIb films. A PIa-1 film prepared by p -DAXBA/PMDA has a T g of 400 °C, tensile strength of 192 MPa, modulus of 6.14 GPa, and CTE as low as 2.3 ppm·K−1. Both PIa-4 and PIb-4 films prepared by ODPA show fluorescent property with maximum emission wavelengths at 509 and 508 nm, and their absolute fluorescence quantum efficiencies are 1.5% and 2.9%, respectively. The as-prepared PI films exhibit potential application in the flexible OLED field. [ABSTRACT FROM AUTHOR]

Fe–P alloys with high phosphorous content have been targeted as promising anode materials because of their high theoretical capacity. However, the synthesis and cycling performance remain great challenges. Hereby FeP y (3 ≤ y ≤ 4) nanoparticles are facilely synthesized through a dry mechanochemical method by reacting iron and red phosphorus powders in an inert atmosphere. The morphology and crystal structure of this material are characterized by SEM and XRD, respectively, while the electrochemical performance is evaluated by a number of different techniques. The 1st and 2nd discharge capacity of FeP y reaches 1984 mAh g −1 and 1486 mAh g −1 , respectively, and after 10 cycles at 0.03 mA cm −2 (20 mA g −1 , 0.03C), the capacity remains 1089 mAh g −1 with a coulombic efficiency of 97%, much higher than the reported results to date. The cyclability of this material becomes fairly better at a higher current density, but the specific capacity is lower compared to that of the smaller current density. By adding fluoroethylene carbonate (FEC) to the electrolyte, the cycling performance of this material was improved. The EIS analysis has also been performed in order to better understand the capacity fade mechanism of FeP y . [ABSTRACT FROM AUTHOR]

The spatial patterns of microbial communities are largely determined by the combined effects of historical contingencies and contemporary environmental disturbances, but their relative importance remains poorly understood. Empirical biogeographic data currently available are mostly based on the traditional method of observational survey, which typically involves comparing indigenous microbial communities across spatial scales. Here, we report a long-term soil transplantation experiment, whereby the same two soils (red Acrisol and purple Cambisol from Yingtan) were placed into two geographic locations of ~1000 km apart (i.e., Yingtan in the mid-subtropical region and Fengqiu in warm-temperate region; both located in China). Twenty years after the transplantation, the resulting soil microbial communities were subject to high-throughput 454 pyrosequencing analysis of 16S and 18S rRNA genes. Additionally, bacteria and archaea involved in nitrogen cycling were estimated using clone library analysis of four genes: archaeal amoA, bacterial amoA, nirK, and nifH. Data of subsequent phylogenetic analysis show that bacteria, fungi, and other microbial eukaryotes, as well as the nitrogen cycling genes, are grouped primarily by the factor of geographic location rather than soil type. Moreover, a shift of microbial communities toward those in local soil (i.e., Chao soil in Fengqiu) has been observed. The results thus suggest that the historical effects persistent in the soil microbial communities can be largely erased by contemporary disturbance within a short period of 20 years, implicating weak effects of historical contingencies on the structure and composition of microbial communities in the soil. [ABSTRACT FROM AUTHOR]

The gross primary production (GPP) at individual CO 2 eddy covariance flux tower sites (GPP Tower ) in Dali (DL), Wenjiang (WJ) and Linzhi (LZ) around the southeastern Tibetan Plateau were determined by the net ecosystem exchange of CO 2 (NEE) and ecosystem respiration ( R e ). The satellite remote sensing-VPM model estimates of GPP values (GPP MODIS ) used the satellite-derived 8-day surface reflectance product (MOD09A1), including satellite-derived enhanced vegetation index (EVI) and land surface water index (LSWI). In this paper, we assembled a subset of flux tower data at these three sites to calibrate and test satellite-VPM model estimated GPP MODIS , and introduced the satellite data and site-level environmental factors to develop four new assimilation models. The new assimilation models’ estimates of GPP values were compared with GPP MODIS and GPP Tower , and the final optimum model among the four assimilation models was determined and used to calibrate GPP MODIS . The results showed that GPP MODIS had similar temporal variations to the GPP Tower , but GPP MODlS were commonly higher in absolute magnitude than GPP Tower with relative error (RE) about 58.85%. While, the assimilation models’ estimates of GPP values (GPP MODEL ) were much more closer to GPP Tower with RE approximately 6.98%, indicating that the capacity of the simulation in the new assimilation model was greatly improved, the R 2 and root mean square error (RMSE) of the new assimilation model were 0.57–4.90% higher and 0.74–2.47 g C m −2 s −1 lower than those of the GPP MODIS , respectively. The assimilation model was used to predicted GPP dynamics around the Tibetan Plateau and showed a reliable result compared with other researches. This study demonstrated the potential of the new assimilation model for estimating GPP around the Tibetan Plateau and the performances of site-level biophysical parameters in related to satellite-VPM model GPP. [ABSTRACT FROM AUTHOR]

We present herein a mild and rapid method to create diblock copolymer brushes on a silicon surface via photoinitiated 'thiol-ene' click reaction. The silicon surface was modified with 3-mercaptopropyltrimethoxysilane (MPTMS) self-assembled monolayer. Then, a mixture of divinyl-terminated polydimethylsiloxane (PDMS) and photoinitiator was spin-coated on the MPTMS surface and exposed to UV-light. Thereafter, a mixture of thiol-terminated polyethylene glycol (PEG) and photoinitiator were spin-coated on the vinyl-terminated PDMS-treated surface, and the sequent photopolymerization was carried out under UV-irradiation. The MPTMS, PDMS, and PEG layers were carefully identified by X-ray photoelectron spectroscopy, atomic force microscopy, ellipsometry, and water contact angle measurements. The thickness of the polydimethylsiloxane- block-poly(ethylene glycol) (PDMS- b-PEG) diblock copolymer brush could be controlled by the irradiation time. The responsive behavior of diblock copolymer brushes treated in different solvents was also discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) could improve crop yield by nutrient uptake from soil. However, how AMF of topsoil and subsoil respond to long-term differential application of mineral and organic fertilizers and how they are influenced in presence of different crops and growth stages have never been assessed together. Next generation sequencing was applied to profile soil AMF communities in both topsoil and subsoil from a typical arable soil (Eutric Regosol) in the Sichuan Base, southwest China. Soils were collected at anthesis and harvest of winter wheat and maize after 15-years of differential fertilization of an annual maize-wheat rotation (same inputs of nitrogen, N; but different in carbon, C; phosphorus, P; and potassium, K): (i) no-fertilization control (CT), (ii) 100% mineral NPK fertilizer (NPK), (iii) 60% mineral N and 100% mineral PK plus 40% N as crop residues (NPKCR); and (iv) 60% mineral N and 100% mineral PK plus 40% N as pig (organic) manure (NPKOM). Compared to CT, AMF diversity significantly decreased in topsoil, but increased in subsoil for both wheat and maize under NPK, NPKCR and NPKOM. The AMF community composition differed between NPK and CT in both topsoil and subsoil of maize and wheat. Both distance-based redundancy analysis (db-RDA) and structural equation modeling (SEM) suggested that AMF communities in topsoil and subsoil of maize and wheat responded in differences in soil available P, soil organic carbon, fertilization and climate (temperature and/or rainfall). Fertilization and available N, not AMF community, had significantly positive effects on wheat and maize aboveground dry matter and grain yield. Results from the present study shed light on how AMF communities in topsoil and subsoil respond to different soil fertility management over the long-term. Insights of this study are valuable in managing an important part of biological soil fertility. • AMF communities differed between fertilization regimes and soil depths. • AMF communities correlated with available phosphorus in topsoil and nitrogen in subsoil. • Soil organic carbon and rainfall correlated with AMF community Chao1 index and diversity. • Fertilization, but not AMF Chao1 index, determined plant biomass and grain yield. • AMF communities in subsoil were influenced by N fertilization. [ABSTRACT FROM AUTHOR]