20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal

A superconducting transition temperature Tc as high as 100 K was recently discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery immediately ignited efforts to identify the mechanism for the dramatically enhanced Tc from its bulk value of 7 K. Currently, there are two main views on the origin of the enhanced Tc; in the first view, the enhancement comes from an interfacial effect while in the other it is from excess electrons with strong correlation strength. The issue is controversial and there are evidences that support each view. Finding the origin of the Tc enhancement could be the key to achieving even higher Tc and to identifying the microscopic mechanism for the superconductivity in iron-based materials. Here, we report the observation of 20 K superconductivity in the electron doped surface layer of FeSe. The electronic state of the surface layer possesses all the key spectroscopic aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer state is found to have a moderate Tc of 20 K with a smaller gap opening of 4 meV. Our results clearly show that excess electrons with strong correlation strength alone cannot induce the maximum Tc, which in turn strongly suggests need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.Comment: 5 pages, 4 figure

Speciation of vanadium in the dissolved, colloidal, and sediment phase under dynamic redox-conditions in a V contaminated soil treated and untreated with biochar

Vanadium is a redox-sensitive toxic element and can exist in a variety of oxidation states: −1, 0, +2, +3, +4, and +5. Vanadium (+5) is considered as a potentially dangerous pollutant. Biochar (BC) can be used to remediate soils contaminated with potential toxic elements (PTEs) including V. However, the efficiency of BC to immobilize V and its on speciation of V in the dissolved and colloidal phase and its mobilization and phytoavailability in the sediment phase under dynamic redox-conditions in highly contaminated soils under dynamic redox conditions has not been studied up to date. Thus, we have i) quantified the impact of pre-definite redox conditions on the speciation and release dynamics of V in the dissolved and colloidal phase as well as on the mobilization and phytoavailability of V in the soil sediments phase in a highly contaminated alkaline soil (CS) (non-treated) (pH = 7.44 and total V = 1,040 mg kg-1) collected from China and in the same soil treated with BC (CS+BC), and ii) assessed the impact of rice husk biochar as soil amendment on the same parameters. The impact of redox potential (EH), pH, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), iron (Fe), manganese (Mn), and sulfate (SO42-) on speciation and release dynamics of V was also determined under dynamic redox conditions. In addition, the used biochar was characterized using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and nuclear magnetic resonance spectroscopy (NMR). The experiment was conducted in stepwise from moderate reducing (-30 mV in CS and -12 mV in CS+BC) to oxidizing (+218 mV in CS and +333 mV in CS+BC) soil conditions in different cycles using a highly sophisticated automated biogeochemical microcosm apparatus. Flooding of the CS and CS+BC caused significant changes of pH values which varied from 6.15 to 8.33 in the CS and from 5.14 to 7.91 in the CS+BC and the EH correlated negatively with pH. The dissolved concentrations of V varied from 15.2-46.4 mg L-1 in the CS to 14.9-50.2 mg L-1 in the CS+BC, while the colloidal concentrations of V varied from 39.5-49.9 mg L-1 in the CS to 31.8-50.2 mg L-1 in the CS+BC. Different redox cycles affected significantly the speciation and release dynamics of V in the dissolved and colloidal phase and its mobilization and phytoavailability in the sediment phase

Effects of biochar and polyacrylamide on decomposition of soil organic matter and ¹⁴C-labeled alfalfa residues

© 2016, Springer-Verlag Berlin Heidelberg.Purpose: Various soil conditioners, such as biochar (BC) and anionic polyacrylamide (PAM), improve soil fertility and susceptibility to erosion, and may alter microbial accessibility and decomposition of soil organic matter (SOM) and plant residues. To date, no attempts have been made to study the effects of BC in combination with PAM on the decomposition of soil SOM and plant residues. The objective of this study was to evaluate the effects of BC, PAM, and their combination on the decomposition of SOM and alfalfa residues. Materials and methods: An 80-day incubation experiment was carried out to investigate the effects of oak wood biochar (BC; 10 Mg ha−1), PAM (80 kg ha−1), and their combination (BC + PAM) on decomposition of SOM and 14C-labeled alfalfa (Medicago sativa L.) residues by measuring CO2 efflux, microbial biomass, and specific respiration activity. Results and discussion: No conditioner exerted a significant effect on SOM decomposition over the 80 days of incubation. PAM increased cumulative CO2 efflux at 55–80 days of incubation on average of 6.7 % compared to the soil with plant residue. This was confirmed by the increased MBN and MB14C at 80 days of incubation in PAM-treated soil with plant residue compared to the control. In contrast, BC and BC + PAM decreased plant residue decomposition compared to that in PAM-treated soil and the respective control soil during the 80 days. BC and BC + PAM decreased MBC in soil at 2 days of incubation indicated that BC suppressed soil microorganisms and, therefore, decreased the decomposition of plant residue. Conclusions: The addition of oak wood BC alone or in combination with PAM to soil decreased the decomposition of plant residue

Effects of biochar and polyacrylamide on decomposition of soil organic matter and 14C-labeled alfalfa residues

© 2016 Springer-Verlag Berlin Heidelberg Purpose: Various soil conditioners, such as biochar (BC) and anionic polyacrylamide (PAM), improve soil fertility and susceptibility to erosion, and may alter microbial accessibility and decomposition of soil organic matter (SOM) and plant residues. To date, no attempts have been made to study the effects of BC in combination with PAM on the decomposition of soil SOM and plant residues. The objective of this study was to evaluate the effects of BC, PAM, and their combination on the decomposition of SOM and alfalfa residues. Materials and methods: An 80-day incubation experiment was carried out to investigate the effects of oak wood biochar (BC; 10 Mg ha−1), PAM (80 kg ha−1), and their combination (BC + PAM) on decomposition of SOM and 14C-labeled alfalfa (Medicago sativa L.) residues by measuring CO2 efflux, microbial biomass, and specific respiration activity. Results and discussion: No conditioner exerted a significant effect on SOM decomposition over the 80 days of incubation. PAM increased cumulative CO2 efflux at 55–80 days of incubation on average of 6.7 % compared to the soil with plant residue. This was confirmed by the increased MBN and MB14C at 80 days of incubation in PAM-treated soil with plant residue compared to the control. In contrast, BC and BC + PAM decreased plant residue decomposition compared to that in PAM-treated soil and the respective control soil during the 80 days. BC and BC + PAM decreased MBC in soil at 2 days of incubation indicated that BC suppressed soil microorganisms and, therefore, decreased the decomposition of plant residue. Conclusions: The addition of oak wood BC alone or in combination with PAM to soil decreased the decomposition of plant residue

ATP-dependent DNA binding, unwinding, and resection by the Mre11/Rad50 complex

ATP-dependent DNA end recognition and nucleolytic processing are central functions of the Mre11/Rad50 (MR) complex in DNA double-strand break repair. However, it is still unclear how ATP binding and hydrolysis primes the MR function and regulates repair pathway choice in cells. Here, Methanococcus jannaschii MR-ATP gamma S-DNA structure reveals that the partly deformed DNA runs symmetrically across central groove between two ATP gamma S-bound Rad50 nucleotide-binding domains. Duplex DNA cannot access the Mre11 active site in the ATP-free full-length MR complex. ATP hydrolysis drives rotation of the nucleotide-binding domain and induces the DNA melting so that the substrate DNA can access Mre11. Our findings suggest that the ATP hydrolysis-driven conformational changes in both DNA and the MR complex coordinate the melting and endonuclease activity.1120Ysciescopu

Metal sorption by biochars : a trade-off between phosphate and carbonate concentration as governed by pyrolysis conditions

Three feedstocks, pine wood, grass and cow manure, were pyrolyzed under various conditions and tested on their ability to sorb metals in aquatic systems. The feedstocks were pyrolyzed at 2 different temperatures (350 degrees C and 550 degrees C) and 2 different residence times (10 and 60 min) and resulting biochars were assessed on their capability to immobilize Pb, Cu, Cd and Zn. Manure-based chars, and to a lesser extent grass-based chars, featured high concentrations of phosphates and carbonates, These anions play an important role in metal sorption because they form insoluble complexes with the metals. Washing reduced the concentration of these anions, leading to a reduced sorption of metals by the biochar. The carbonate concentration on the biochars' surface increased at higher reactor temperature and longer residence times. The opposite trend was observed for the phosphate concentration and the cation exchange capacity. Accordingly, the optimal temperature-residence time combination for sorption was a trade-off between these properties. Biochar produced from cow manure and pyrolyzed at 550 degrees C for 10 min showed the best sorption for all metals considered

Time-delayed Spatial Patterns in a Two-dimensional Array of Coupled Oscillators

We investigated the effect of time delays on phase configurations in a set of two-dimensional coupled phase oscillators. Each oscillator is allowed to interact with its neighbors located within a finite radius, which serves as a control parameter in this study. It is found that distance-dependent time-delays induce various patterns including traveling rolls, square-like and rhombus-like patterns, spirals, and targets. We analyzed the stability boundaries of the emerging patterns and briefly pointed out the possible empirical implications of such time-delayed patterns.Comment: 5 Figure