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We present a detailed timing study of the brightest persistent X-ray source Sco X-1 using the data collected by the Hard X-ray Modulation Telescope ( I n s i g h t -HXMT) from July 2017 to August 2018. A complete Z-track hardness-intensity diagram (HID) is obtained. The normal branch oscillations (NBOs) at ∼ 6 Hz in the lower part of the normal branch (NB) and the flare branch oscillations (FBOs) at ∼ 16 Hz in the beginning part of the flaring branch (FB) are found in observations with the Low Energy X-ray Telescope (LE) and the Medium Energy X-ray Telescope (ME) of I n s i g h t -HXMT, while the horizontal branch oscillations (HBOs) at ∼ 40 Hz and the kilohertz quasi-periodic oscillations (kHz QPOs) at ∼ 800 Hz are found simultaneously above 20 keV for the first time on the horizontal branch (HB) by the High Energy X-ray Telescope (HE) and ME. We find that for all types of the observed QPOs, the centroid frequencies are independent of energy, while the root mean square (rms) increases with energy; the centroid frequencies of both the HBOs and kHz QPOs increase along the Z-track from the top to the bottom of the HB; and the NBOs show soft phase lags increasing with energy. A continuous QPO transition from the FB to NB in ∼ 200 s are also detected. Our results indicate that the non-thermal emission is the origin of all types of QPOs, the innermost region of the accretion disk is non-thermal in nature, and the corona is nonhomogeneous geometrically.

The development of high-efficiency non-noble metal catalysts for the oxygen reduction reaction (ORR) is of paramount significance to sustainable energy-conversion technologies. Herein, a three-dime...

To construct photocatalysts with matched band alignments and intimate interfaces is crucial but challenging for photocatalysis. Herein, we for the first time report a strategy for band modulation a...

The development of electrocatalysts with high activity and low Tafel slope for overall water splitting has become a crucial challenge to exploit the sustainable energy. Herein, we construct a Fe–Co–P–Gr catalyst on nickel foam (NF) support through electroless composite plating to realize the co-deposition of Fe–Co–P alloys and graphene quantum dots. Interestingly, graphene quantum dots exhibit obvious effects on electron mobility and active sites of Fe–Co–P–Gr/NF catalyst. In oxygen evolution reaction, the Fe–Co–P–Gr/NF catalyst exhibits a small overpotential of 230 mV at 10 mA cm−2 and fast kinetics with Tafel slope of 37.8 mV dec−1. Meanwhile, the Fe–Co–P–Gr/NF also has a superior hydrogen evolution reaction performance in 1.0 M KOH. Compared with the Fe–Co–P alloys, the Fe–Co–P–Gr/NF both as the anode and cathode require only 1.58 V to reach a current density of 10 mA cm−2. The successful preparation of Fe–Co–P–Gr/NF electrode through electroless composite deposition provides a new path to manufacture electrocatalysts for overall water splitting.

The development of highly efficient and superior durability electrocatalysts is vital to expedite hydrogen evolution reaction (HER). Herein, a mixed amorphous and nano-crystalline Ni–Co–Fe–P alloy on Ni foam after 75 s dealloying in 3 M HCl (Ni–Co–Fe–P/NF-3-75) is synthesized by the preparation strategy of two-step method consisting of electroless deposition and dealloying process. Ni–Co–Fe–P/NF-3-75 shows an excellent HER performance and high durability in both alkaline and neutral conditions by optimizing the composition of the catalysts, acid concentration, and the time of dealloying. Benefitting from the high conductivity of Ni foam carrier, coordination between polymetallic phases, and the large exposure of defects, the as-prepared Ni–Co–Fe–P/NF-3-75 requires only a low overpotential of 56 mV and 104 mV to reach the current density of 10 mA cm−2 in 1.0 M KOH and 1.0 M phosphate buffer (PBS), respectively. Remarkably, the Ni–Co–Fe–P/NF-3-75 electrode exhibits superior cycling stability and long-term robust durability without obvious overpotential decline. The successful preparation of the Ni–Co–Fe–P/NF-3-75 catalyst indicates that this method provides an efficient way to synthesize polymetallic phosphides for hydrogen evolution reaction.

Five biochars derived from lotus seedpod (LSP) were applied to examine and compare the adsorption capacity of 17β-estradiol (E2) from aqueous solution. The effect of KOH activation and the order of activation steps on material properties were discussed. The effect of contact time, initial concentration, pH, ionic strength and humic acid on E2 adsorption were investigated in a batch adsorption process. Experimental results demonstrated that the pseudo second-order model fitted the experimental data best and that adsorption equilibrium was reached within 20 hr. The efficiency of E2 removal increased with increasing E2 concentration and decreased with the increase of ionic strength. E2 adsorption on LSP-derived biochar (BCs) was influenced little by humic acid, and slightly affected by the solution pH when its value ranged from 4.0 to 9.0, but considerably affected at pH 10.0. Low environmental temperature is favorable for E2 adsorption. Chemisorption, π–π interactions, monolayer adsorption and electrostatic interaction are the possible adsorption mechanisms. Comparative studies indicated that KOH activation and the order of activation steps had significant impacts on the material. Post-treated biochar exhibited better adsorption capacity for E2 than direct treated, pre-treated, and raw LSP biochar. Pyrolyzed biochar at higher temperature improved E2 removal. The excellent performance of BCs in removing E2 suggested that BCs have potential in E2 treatment and that the biochar directly treated by KOH would be a good choice for the treatment of E2 in aqueous solution, with its advantages of good efficiency and simple technology.

Designing high-performance hydrogen evolution reaction (HER) catalysts is crucial for seawater splitting. Herein, we demonstrate a facile Anderson-type polyoxometalate-assisted synthesis route to prepare defect-rich doped 1T/2H-MoSe

Over the past few decades, nonferrous mining has produced numerous waste rock and part of the waste that has not been properly treated was generally dumped at roadsides and hill slopes. However, the vertical distributions of toxic metal(loid)s and composition of microbial communities in waste heap and the under-laid pristine soil are rarely studied. In this work, the fraction-related distributions of toxic metal(loid)s were investigated at a waste heap profile and the indigenous microbial assemblages were also analyzed by Illumina sequencing of 16 s rRNA genes. Results showed that compared to the under-laid pristine soil, content of toxic metal(loid)s, especially Cd, As and Pb, in waste rock layer were higher. Most of As in subsoil existed as non-specifically sorbed and specifically-sorbed fractions, which could be ascribed to the migration from the upper layer. The mobility was significantly correlated with Eh, EC, clay content, CEC and the total content of metal(loid)s. Phyla Proteobacteria, Acidobacteria and Firmicutes dominated the microbial communities. The microbial community compositions at the genus level were similar, but their relative abundances were mainly influenced by pH, CEC, Eh, SOM, and bioavailability content of toxic metal(loid)s. Besides, microbial functions of elements (S, Fe, Mn and As) oxidation/reduction and metabolites (siderophore, biosurfactant, organic acid, phosphatase and urease) potentially were used for pollutants bioremediation.

Bioremediation of Cd- (cadmium) contaminated soil using Cd-tolerant fungus is considered an eco-friendly and cost-effective technique. In this study, we isolated one fungal strain that was hyper-tolerant to Cd from a highly polluted river and conducted pot experiments to evaluate its effects on bioremediation. We found that the fungal strain belonging to the genus, Purpureocillium lilacinum, tolerated 12,000 mg/L Cd. SEM manifested that Cd can be bioaccumulated on the crumpled mycelial surface, generating plenty of metal precipitation particles. In addition, pot experiments showed that the inoculation of P. lilacinum N1 could reduce the total Cd content in soil (2.09% in low contaminated soil and 12.56% in high contaminated soil) and greatly promote plant growth (2.16~3.13 times). Although the Cd concentration of plants was increased by 112.8% in low contaminated soil and decreased by 9.5% in highly contaminated soil with the inoculation of P. lilacinum N1, the total uptake of Cd by plants was greatly improved—1.84~3.6 times higher than that in CK groups. All our results suggest that P. lilacinum N1 is a valuable candidate for the bioremediation of Cd-contaminated soils because of its dual effects on the total Cd content in soil and Cd uptake in plants.

Exploring cost-effective electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) have been a goal in the sustainable hydrogen-based society. Although abundant of alternative materials have been developed, Pt/C remains the most efficient electrocatalyst for the ORR and HER. Nevertheless, improving the stability and reducing Pt loading for Pt-based electrocatalysts are still big challenges. Herein, semiconductor crystals Na4Ge9O20 with richer topology structure was chosen as electrocatalyst support, subsequently, the conductive polymer polyaniline (PANI) was decorated on semiconductor Na4Ge9O20, low-content Pt nanoparticles (Pt NPs) with the size of 1–3 nm were then uniformly anchored on the surface of Na4Ge9O20-PANI to obtain the efficient bifunctional electrocatalyst for ORR and HER in the acidic solution. More importantly, the stability and mass activity of the obtained electrocatalyst 5 wt% Pt/Na4Ge9O20-PNAI are significantly higher than that of commercial 20 wt% Pt/C for ORR and HER. It was proposed that the PANI could not only promote the electron transfer from Na4Ge9O20 to Pt, but also stabilize the Pt NPs, thus, improving the electrocatalytic activity and stability of 5 wt% Pt/Na4Ge9O20-PNAI.

The evidences for the influence of thermonuclear (type-I) X-ray bursts upon the surrounding environments in neutron star low-mass X-ray binaries (LMXB) were detected previously via spectral and timing analyses. Benefitting from a broad energy coverage of Insight-HXMT, we analyze one photospheric radius expansion (PRE) burst, and find an emission excess at soft X-rays. Our spectral analysis shows that, such an excess is not likely relevant to the disk reflection induced by the burst emission and can be attributed to an enhanced pre-burst/persistent emission. We find that the burst and enhanced persistent emissions sum up to exceed Eddington luminosity by ∼ 40 percentages. We speculate that the enhanced emission is from a region beyond the PRE radius, or through the Comptonization of the corona.

A novel graphene oxide supported activated magnetic biochar (GO-AMBC) is fabricated for 17β-estradiol (E2) removal from aqueous solution by grafting graphene oxide (GO) and magnetite nanoparticles onto the activated biochar surface with a one-step activation, magnetization, and carbonization method. GO-AMBC is characterized using SEM, TEM, FTIR, VSM, XRD, XPS, BET surface area and zeta potential measurements. The characterization results show that GO-AMBC possesses a larger surface area and more oxygen-containing functional groups than the unmodified biochar. When the E2 initial concentration is 6 mg/L, its adsorption capacity by GO-AMBC (46.22 mg/g) is more than two times higher than that of pristine biochar (23.09 mg/g) at 298 K and pH = 7.0. Adsorption results show that E2 uptake follows by pseudo-second-order kinetic and Freundlich isothermal models. Thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic. E2 removal by GO-AMBC is significantly affected by the actual water conditions, including solution pH, ionic strength, and organic acids. Among them, organic acids have obvious inhibition effect on E2 removal, and the inhibition effect by oxalate is stronger than that of benzoate. The adsorption mechanism of E2 on GO-AMBC is mainly controlled by hydrogen bonds, electrostatic and π-π interactions. The experimental results of this study and comparative analysis with other adsorbents suggest that GO-AMBC is an economical, efficient and recyclable adsorbent and has great potential for E2 removal from contaminated water.

Metal-nitrogen doped carbon is a class of promising catalysts to replace Pt to catalyze the oxygen reduction reaction (ORR). Herein, a novel three-dimensional (3D) Fe-N-C nanosheets grown on interconnected carbon skeletons is fabricated by a facile route, i.e., in situ polymerization of aniline to obtain polyaniline nanosheets on 3D melamine foams and subsequent pyrolysis of the composites. The catalyst exhibits comparable catalytic activity but superior long-term stability to the commercial 20% Pt/C for the ORR in alkaline electrolyte in terms of the onset potential (1.01 V vs. RHE) and the half wave potential (0.86 V vs. RHE). The outstanding catalytic performance was ascribed to the populated active sites taking advantage of the large surface area, the superior electro-conductivity and the facilitated mass transportation by virtue of the unique hierarchically interconnected porous carbon structure. This work is expected to provide a new avenue to fabricate 3D interconnected porous composites for energy conversion and storage.

An extensive investigation on spatial distribution and environmental risk assessment based on total content and fractions of heavy metals, as well as the cancer risk of Cd from seven adjacent contaminated paddy fields at Xiangtan City, southern China, was conducted in this study. A total of 63 soil samples were analyzed for soil physical properties and concentrations of eight heavy metals (Cd, Cr, Co, Cu, Mn, Ni, Pb, Zn). The results showed that concentrations of metals except for Cr, Mn and Ni exceeded the background values to varying degrees, and particularly, content of Cd was as 57.4-612 times higher than background values. Principal components analysis and correlation analysis revealed three groups: industry activities for Cd and Zn; natural sources mainly for Cu, Pb, Ni and Cr, with some slight anthropogenic activities for Cu and Pb accumulation; and manganese ore associated with cobalt for Co and Mn. Combined with different indices, Cd and Zn were the major contributors to the ecological risk, and cancer risk of Cd indicated an unacceptable degree in this area. Altogether, results from this study will facilitate a better understanding of metals distribution characteristics and provide a scientific basis for further comprehensive management for these paddy fields. Combination of functional microbial agent and plants promises to be a feasible and effective remediation method for cadmium pollution in the study area.

Cobalt oxides, including spinel Co3O4 and rock-salt CoO, have been widely reported as promising catalysts for oxygen reduction reaction (ORR). However, three types of cobalt ions, i.e., Co2+ in the...

Iron phosphides show promising but limited activity as hydrogen evolution reaction (HER) catalysts due to the low number of active sites and poor electroconductivity. Herein, iron phosphide nanosheets were synthesized and assembled to three-dimensional structures for the first time via a physical-vapor-infiltration assisted hard template strategy. The 3D structured FeP nanosheet assembly exhibits excellent electrocatalytic performance for hydrogen evolution reaction over a wide pH range, outperforming most of the FeP catalysts reported to date in activity and exhibiting superior stability to the commercial Pt/C catalyst. Spectroscopic analyses and electrochemical results support that the fast electron transfer, increased active sites and expedited mass transport, due to the 3D structure of the FeP nanosheets, boost the HER performance.

Self-supported nanoporous metals are promising catalysts and battery materials due to their continuous channels, excellent conductivity and high surface area. In this work, we found that Cu2+ cations could promote the spontaneous formation of AgCl on Ag surface via microcell reactions. Applying a potential to the silver electrode promotes the surface enrichment of Cu2+ cations, and further speeds the formation of AgCl. After electro-reduced, AgCl was transformed to self-supported silver electrode with nanoporous structures, which shows good catalytic activity for the oxygen reduction reaction and electrochemical stability together with superior methanol tolerance property, compared to the pristine silver electrode. The approach used in this work provides an alternative way to prepare self-supported nanoporous metals.

At present, it is difficult for electrocatalytic electrode materials with high-Performance to be prepared at low cost and large area under mild conditions. Therefore, we adopt a facile electroless plating method to deposit the Fe Co P alloys on the nickel foam (NF) with different areas of 1 cm2, 4 cm2, 8 cm2 and 16 cm2. The Fe Co P/NF catalysts exhibit extraordinary catalytic activity for the oxygen evolution reaction (OER) in alkaline media and are comparable to the state-of-the-art IrO2 in 1.0 M KOH, capable of yielding a current density of 10 mA cm−2 at an overpotential of only 250 mV. Furthermore, the Fe Co P/NF catalysts show efficient activity towards the hydrogen evolution reaction (HER) with an overpotential of 163 mV at j = 10 mA cm−2 as well. Remarkably, when used as both the anode and cathode, a low potential of 1.68 V (vs. RHE) is required to reach the current density of j = 10 mA cm−2, making the Fe Co P/NF alloys as an active bifunctional electrocatalyst for overall water splitting. The Fe Co P/NF alloy catalysts with high catalytic activity, facile preparation and low cost would provide a new pathway for the design and large-scale application of high-performance bifunctional catalysts for electrochemical water splitting.

Amorphous materials have been extensively studied in the field of catalysis due to their unique properties. Herein, we report a nanoporous and amorphous Ni–Fe–P array on Ni foam, which acts as a highly efficient overall water splitting catalyst synthesized by electroless deposition and fast dealloying.

A novel attapulgite/biochar (ATP/BC) nanocomposite was synthesized via simultaneous activation and carbonization for 17β-estradiol (E2) removal in water. The one-step synthetic process significantly enlarged specific surface area and increased oxygen-contained functional groups. Compared to the pristine biochar (BC) and attapulgite (ATP), the ATP/BC nanocomposite exhibited higher adsorption capacity for E2 with the maximum adsorption capacity (qmax) of 154.23 mg/g. The pseudo-second-order and Langmuir model were more suitable for E2 adsorption by ATP/BC. The adsorption capacity of ATP/BC for E2 was affected by initial solution pH and the low pH was favorable for the adsorption of E2. The presence of monovalent cations (Na+ and K+) improved the adsorption efficiency for E2, whereas the presence of divalent cations of (Ca2+ and Mg2+) inhibited the adsorption process of E2. Ionic strength had slight promoting effect at low concentration for the E2 adsorption. The presence of surfactant and humic acid inhibited the adsorption capacity of ATP/BC. Electrostatic attraction, π-π interactions and hydrogen bonds between ATP/BC and E2 molecules might be potential adsorption mechanisms. The results showed that the ATP/BC nanocomposite was a high efficiency and reusable adsorbent in the removal of E2 from water.

Patients with chronic kidney disease (CKD) are often complicated with heart failure with preserved ejection fraction (HFpEF). However, several drugs, including angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB), have not shown apparent benefits in terms of morbidity and mortality of HFpEF. PARAMOUNT and other studies have shown the potential benefits of Sacubitril/Valsartan on patients with HFpEF, but its effects on renal function and the effect of low-dose Sacubitril/Valsartan in actual clinical conditions have not been thoroughly evaluated. In our longitudinal and observational research, 353 patients were followed up for 12 weeks. We evaluated renal function [urinary protein, serum creatinine and estimated glomerular filtration rate (eGFR)] and cardiac function [NT-proBNP (brain natriuretic peptide), New York Heart Association (NYHA) classification, left ventricular ejection fraction (LVEF), left atrial width and left ventricular end-diastolic width] at baseline and during follow-up. Worsening renal function (WRF) was defined as an increased serum creatinine≥26.5umol/L or decreased eGFR≥20%. The decline of eGFR in the Sacubitril/Valsartan group was slower than that in the control group (p = 0.021). The outcome of proteinuria in the ACEI/ARB group was significantly better than that in the Sacubitril/Valsartan group (p = 0.001). In terms of echocardiogram, the average left atrial width in Sacubitril/Valsartan group decreased by 1.38 ± 3.02 mm, which was significantly lower than that in the ACEI/ARB group (p = 0.02). The increase of urine protein class in the ACEI/ARB group increased the risk of WRF with statistical significance (OR = 2.36, 95%CI 1.01-5.49, p = 0.047), but no statistical significance was found in all the patients or Sacubitril/Valsartan group. In conclusion, Sacubitril/Valsartan could more effectively slow down renal function decline and reverse myocardial remodeling in patients with CKD and HFpEF than ACEI/ARB, even at low doses, though its protective effect on urinary protein is not as good as that of ACEI/ARB.

The capability of palladium (Pd) nanoparticles photo-deposited on BiVO4 (BV) nanosheets support to effectively activate persulfate (PS) and degrade pharmaceutical residues amiloride (AML) in aqueous solution under visible light was investigated. The removal efficiency of AML in Pd/BV/PS/vis system reached to 96.43% within 30 min as compared to only 50.73%, 70.87% and 77.70% in BV/vis, Pd/BV/vis and BV/PS/vis respectively under the identical experimental conditions. One inherent reason for the enhanced performance was possibly owing to the fact that visible light absorption of photocatalyst was improved through the surface plasma resonance (SPR) effect of Pd nanoparticles. For another respect, the photo-induced electron-hole pairs separation rate was firstly strengthened with Pd as electron traps and then by PS oxidants as electrons acceptors. Influencing factors including PS dosage, AML concentration, humic acid (HA) concentration, coexisting anions and cations and water sources on the AML degradation in the Pd/BV/PS/vis system were explored in details. Higher photocatalytic activity was still maintained in raw wastewater containing dyes, phenols and antibiotics. More generation of oxidative species such as O2−, OH and SO4 − were verified by radical quenching experiment and electron spin resonance (ESR) test. The major products of AML decomposition were identified and the correspondent degradation pathways were also proposed. This founding allows for the construction of highly efficient BV-based photocatalysts and provides a new opportunity for the treatment of wastewater containing refractory pollutants by SO4 −-based advanced oxidation processes (AOPs).

Endophytes are highly associated with plant growth and health. Exploring the variation of bacterial communities in different plant niches is essential for understanding microbe-plant interactions. In this study, high-throughput gene sequencing was used to analyze the composition and abundance of bacteria from the rhizospheric soil and different parts of the Macleaya cordata. The results indicated that the bacterial community structure varied widely among compartments. Bacterial diversity was observed to be the highest in the rhizospheric soil and the lowest in fruits. Proteobacteria, Actinobacteria, and Bacteroidetes were found as the dominant phyla. The genera Sphingomonas (∼47.77%) and Methylobacterium (∼45.25%) dominated in fruits and leaves, respectively. High-performance liquid chromatography (HPLC) was employed to measure the alkaloid content of different plant parts. Significant correlations were observed between endophytic bacteria and alkaloids. Especially, Sphingomonas showed a significant positive correlation with sanguinarine and chelerythrine. All four alkaloids were negatively correlated with the microbiota of stems. The predicted result of PICRUST2 revealed that the synthesis of plant alkaloids might lead to a higher abundance of endophytic microorganisms with genes related to alkaloid synthesis, further demonstrated the correlation between bacterial communities and alkaloids. This study provided the first insight into the bacterial community composition in different parts of Macleaya cordata and the correlation between the endophytic bacteria and alkaloids.

Based on Insight-HXMT data, we report on the pulse fraction evolution during the 2017–2018 outburst of the newly discovered first Galactic ultraluminous X-ray (ULX) source Swift J0243.6+6124. The pulse fractions of 19 observation pairs selected in the rising and fading phases with similar luminosity are investigated. The results show a general trend of the pulse fraction increasing with luminosity and energy at supercritical luminosity. However, the relative strength of the pulsation between each pair evolves strongly with luminosity. The pulse fraction in the rising phase is larger at luminosity below 7.71 × 1038 erg s−1, but smaller at above. A transition luminosity is found to be energy independent. Such a phenomenon is first confirmed by Insight-HXMT observations and we speculate that it may have relation with the radiation-pressure-dominated accretion disc.

In this study soils at different depths were collected in a Zn smelting site located in Zhuzhou City, China, in order to understand toxic metal(loid)s distribution and microbial community in vertical soil profile at a smelting site. Except Soil properties and metal(loid)s content, the richness and diversity of microbial communities in soil samples were analyzed via high-throughput Illumina sequencing of 16s rRNA gene amplicons. The results showed that the content of As, Pb, Cu, Cd, Zn, and Mn was relatively high in top soil in comparison to subsoil, while the concentration of Cr in subsoil was comparable with that in top soil due to its relative high background value in this soil layer. The bioavailability of Cd, Mn, Zn, and Pb was relative higher than that of As, Cr, and Cu. The diversity of soil microbial communities decreased with increasing depth, which might be ascribed to the decrease in evenness with increase in depth duo to the influence by environmental conditions, such as pH, TK (total potassium), CEC (cation exchange capacity), ORP (oxidation reduction potential), and Bio-Cu (bioavailable copper). The results also found Acidobacteria, Proteobacteria, Firmicutes, and Chloroflexi were dominant phyla in soil samples. At the genus level, Acinetobacter, Pseudomonas, and Gp7 were dominant soil microorganism. Besides, Environmental factors, such as SOM (soil organic matter), pH, Bio-Cu, Bio-Cd (bioavailable cadmium), and Bio-Pb (bioavailable lead), greatly impacted microbial community in surface soil (1&ndash, 3 m), while ORP, TK, and AN concentration influenced microbial community in the subsoil (4&ndash, 10 m).

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846–031 during its outburst in 2019 with the observations of Insight-HXMT, NICER and MAXI. This outburst can be classified roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1–6 Hz) and Insight-HXMT (about 0.7–8 Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency. The QPO rms–frequency relationship in the energy band 1–10 keV indicates that there is a turning pointing in frequency around 2 Hz, which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms, hardness, total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type–C QPOs is non-thermal.

Low-frequency quasi-periodic oscillations (LFQPOs) are commonly found in black hole X-ray binaries, and their origin is still under debate. The properties of LFQPOs at high energies (above 30 keV) are closely related to the nature of the accretion flow in the innermost regions, and thus play a crucial role in critically testing various theoretical models. The Hard X-ray Modulation Telescope (Insight-HXMT) is capable of detecting emissions above 30 keV, and is therefore an ideal instrument to do so. Here we report the discovery of LFQPOs above 200 keV in the new black hole MAXI J1820+070 in the X-ray hard state, which allows us to understand the behaviours of LFQPOs at hundreds of kiloelectronvolts. The phase lag of the LFQPO is constant around zero below 30 keV, and becomes a soft lag (that is, the high-energy photons arrive first) above 30 keV. The soft lag gradually increases with energy and reaches ~0.9s in the 150-200 keV band. The detection at energies above 200 keV, the large soft lag and the energy-related behaviors of the LFQPO pose a great challenge for most currently existing models, but suggest that the LFQPO probably originates from the precession of a small-scale jet., 36 pages, 12 figures, 3 tables; published in Nature Astronomy

Cadmium (Cd) pollution poses a serious risk to human health and ecological security. Bioremediation can be a promising and effective remediation technology for treating Cd contaminated soils. In this study, seven heterotrophic strains were isolated from Cd contaminated soil and 7 autotrophic strains were isolated from acid mine drainage. Cd removal efficiencies were compared after leaching with autotrophic bacteria (Att-sys), heterotrophic isolates (Htt-sys) and cooperative leaching systems (Co-sys) in laboratory agitating reactors. The results indicated that Cd removal efficiency of Co-sys (32.09%) was significantly higher than that of Att-sys (23.24%) and Htt-sys (0.74%). By analyzing the soil microbial community in different bioleaching systems, we found that the addition of heterotrophic isolates significantly promoted the growth of some heavy metal resistant inhabitants (Massilia, Alicyclobacillus, Micromonospora, etc.), and Co-sys had a minor effect on the growth of soil indigenous microbes. In Co-sys, the content of the four Cd fractions all decreased compared with other leaching systems. The analysis of soil physicochemical parameters during the leaching process showed that pH and ORP (oxidation reduction potential) were not the only determinants for Cd removal efficiency in Co-sys, synergistic metabolic activities of autotrophic and heterotrophic strains may be other determinants. This study demonstrated that cooperative bioremediation may prove to be a safe and efficient technique for field application in heavy metal soil pollution.

The improper stacking of chromium (Cr) slag poses a great threat to the environment and human health. The toxicity of Cr in soil is not only related to its total amount, but also to its fractions. A simulated experiment was conducted in laboratory to assess the environmental risk of Cr fractions migration and distribution in red soil. The results showed the content of acid-soluble and reducible Cr significantly decreased (P &lt, 0.05) in top layer but increased in middle and substratum layers over time. This indicated that acid-soluble and reducible Cr migrated downward with time and the relative mobility of acid-soluble Cr (0.038 mg/kg&middot, d&middot, m) was higher than that of reducible Cr (0.028 mg/kg&middot, m). Furthermore, correlation analysis between microbial community and chromium fraction showed the relative abundance of Lysobacter, Flavihumibacter, Flavisolbacter, and Altererythrobacter was significantly (P &lt, 0.05) correlated with acid-soluble and reducible fractions. Thus, these microorganisms might be evaluators to assess the migration of acid-soluble and reducible fractions in red soil. In summary, this study provided a new comprehension on remediation of Cr-contaminated soil by monitoring the migration of acid-soluble and reducible fractions and the changes of related microbial groups.

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results., 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.04434

We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of $\sim$ 1.5. The pulse profile shape during the flares can be significantly different than that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and super-critical accretion regimes on a short time scale. We also observe that at comparable luminosities the flares' pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e., the mass accretion rate., 11 pages, 8 figures, accepted for publication in MNRAS

In this study, activated magnetic biochars (AMBCs) were successfully synthesized via one-step synthetic method with different temperature (300, 500 and 700 °C). Characterization experiments indicated that AMBCs had larger surface area, higher pore volume and more contained‑oxygen functional groups compared to the pristine biochar. In addition, AMBCs showed better adsorption performance for 17β-estradiol (E2) and copper (Cu(II)) in single/binary-solute systems than unmodified pristine biochar. AMBC-700 exhibited the highest capacity (153.2 mg/g) for E2, while the AMBC-300 showed the best adsorption capacity (85.93 mg/g) for Cu(II) in single-solute system. Adsorption of Cu(II) and E2 both followed by pseudo-second-order and Langmuir isothermal model. The initial pH of the solution had an effect on the adsorption of E2 and Cu(II) in single-solute system. Coadsorption experiments indicated that there existed site competition and enhancement of E2 and Cu(II) on the sorption in binary-solute system. Results from this study indicated that the E2 was adsorbed by hydrogen bonds, π-π EDA interactions. Cu(II) was mainly adsorbed via chemical complexation between contained‑oxygen functional groups and Cu(II) ions. Therefore, the AMBCs via one-step synthesis could be converted into value-added biochar as effective sorbent for simultaneous removal of E2 and Cu(II) from water.

Increasingly applications of graphene nanomaterials have resulted in their release into the water environments where lot kinds of chemicals and inorganic nanoparticles co-exist. In this work, the influences of two common inorganic nanoparticles (INPs), namely SiO2 and Al2O3, on the adsorption of 17β-estradiol (E2) onto graphene oxide (GO) were examined by using batch adsorption experiments in combination with microscopic, spectroscopic, and computational methods. Results exhibited that the presence of INPs significantly inhibited the adsorption and increased the time to reach adsorption equilibrium for the adsorption of E2 onto GO. Besides, the impact of Al2O3 was greater than that of SiO2 due to the enhanced electrostatic attraction between positively charged Al2O3 and negatively charged GO. Derjaguin-Landau-Verwey-Overbeek calculation revealed that GO tended to first homoaggregate and then heteroaggregate with SiO2. However, oppositely charged Al2O3 and GO were likely to heteroaggregation rather than homoaggregation. This was also demonstrated by the zeta potential measurement, and scanning electron microscope. These observations highlighted the significant influence of INPs on the adsorption of contaminants onto GO, and also provided new insights into the fate and transport of GO and pollutants in natural water environments.

Exploring advanced electrocatalysts to accelerate the sluggish oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) is a promising route to alleviate the current challenges of fossil fuel exhaustion and environment pollution. Herein, a carbon-supported highly dispersed PtNi nanocatalyst (Pt0.61Ni/C) with low platinum content of 2.76 wt % was prepared simply based on galvanic replacement for a high-efficiency ORR process. It presents a mass activity of ∼5 times of the conventional Pt-based catalyst at 0.9 V (vs reversible hydrogen electrode (RHE)) and a remarkable durability and methanol tolerance. The acidic fuel cell with such cathode catalyst (Pt0.61Ni/C) presents a striking performance with maximum power density up to 1.1 W cm–2 at 80 °C. Due to the extremely low platinum loading in the whole fuel cell, its Pt utilization (0.093 gPt kW–1) is the highest reported ever in H2/O2 fuel cells. Such impressive performance of Pt0.61Ni/C makes the obtained Pt0.61Ni/C catalyst a ve...

In this research, adsorption of two estrogens, namely, 17β-estradiol (E2) and 17α-ethynylestradiol (EE2), by graphene nanosheets with different reduction degrees (rGOs) were investigated; and the effects of solution chemistry, such as natural organic matter (NOM), pH and ionic strength (IS), on the E2 and EE2 adsorption behaviors were also examined. Results indicated that adsorption abilities of estrogens increased with increasing the reduction degree of rGOs; the π–π stacking interaction could be considered as a predominant interaction to the enhanced adsorption capacities of rGOs. Among the solution chemistry, NOM exhibited the significant influence on estrogens adsorption, which suggested that once released into water environments, graphene materials will adsorb estrogens but with a lower adsorption ability than that in ultrapure water due to the ubiquitous presence of NOM in aquatic environments. Besides, estrogens adsorption on rGOs was pH-dependent, but the influence of acid rain would be insignificant due to slight change in low pH range. However, IS within the typical range in natural waters did not exhibit significant influence on the uptake of estrogens by rGOs. Above findings of this work might have significant implications for the fate and transport of estrogens with graphene materials in the environment.

Auxin is a vital plant growth regulator and can also take a part in plant defense. The study focused on the efficacy of the major active form of auxin, indole-3-acetic acid (IAA), on inhibition of blue mold rot caused by Penicillium expansum in pear fruit wounds and the possible action mechanisms involved. Results indicated that IAA at 100–500 μg mL−1 significantly enhanced the resistance of pear fruit against blue mold rot when the treating interval was between 24 and 48 h, while it had no direct antifungal activities towards P. expansum in vitro. Moreover, IAA induced a significant increase on the activities of β-1,3-glucanase (GLU), chitinase (CHI) and phenylalanine ammonia-lyase (PAL) in pear fruit. Furthermore, the data revealed that the expressions of endoglu9, CHI4, PR1, PR4 and PAL were up-regulated substantially in pear fruit treated with IAA. The all findings highlight the efficiency of IAA on inducing the natural resistance of pear fruit against P. expansum and suggest that the mechanisms may be closely related to the elicitation of defense-related enzymes and genes.

Introducing exogenous species to an indigenous microbial community is an effective way to reveal the connections between metabolic processes, ecological function and microbial community structure. Herein, three different functional consortia (ferrous oxidizers, sulfur oxidizers and ferrous/sulfur oxidizers) were added to a natural leaching solution system derived from Zijin copper mine, China. The leaching experiment showed that the copper extraction rate of the community invaded by a sulfur-oxidizing consortium was 50.40% higher than that of the indigenous leachate at the endpoint of bioleaching. The variations of ferrous content, total iron, pH and redox potential in leachates also provided evidence that the community with exogenous sulfur oxidizers was more efficient. XRD analysis demonstrated that a proper addition of the sulfur-oxidizing consortium could eliminate sulfur passivation, promote production of chalcocite and enhance leaching. Furthermore, an exogenous ferrous-oxidizing consortium and a sulfur-oxidizing consortium greatly changed the community structure and microbial succession and promoted the cell growth rate during the bioleaching process, while ferrous/sulfur oxidizers showed no obvious effects on the indigenous community. Exogenous ferrous oxidizers, mainly L. ferriphilum, and sulfur oxidizers, mainly A. thiooxidans, successfully established and colonized in the indigenous community. However, only colonized A. thiooxidans, rather than L. ferriphilum, showed advantageous enhancement in the dissolution of chalcopyrite. Results indicated that exogenous sulfur oxidizer A. thiooxidans, which was scarce in the indigenous community, could easily colonize in the indigenous community, significantly change the community structure, sufficiently execute its function, and greatly enhance copper dissolution.

Nowadays, using graphene oxide (GO) as an adsorbent for removing pollutants from wastewater has attracted increasing attention due to its unique physic-chemical properties. Nitrogen-containing amino (NA) compounds have excellently complexing properties due to their abundant amino functional groups. In order to obtain an innovative adsorbent, functionalized GO (NAGO) has been developed by combining the properties of GO with the advantages of NA compounds. The obtained NAGO composites usually exhibit great improvement in adsorption properties and can be used as a promising adsorbent for decontamination of wastewater. This paper reviewed recent progress of synthetic technologies about fabricating various NAGOs, and their morphologies, structures and functional characteristics. Meanwhile, important applications of NAGOs for different kind of pollutants and theory of the adsorption phenomena are discussed based on the isothermal and kinetic adsorption models. Furthermore, the affecting factors, underlying mechanisms and comparison with other adsorbents for the removal of pollutants are reviewed. Conclusively, the perspectives and challenges involved in the application of NAGOs for decontamination of wastewater have also been proposed to promote sustainable development of this new exciting field.

Two-phase gas/liquid flows coupled with electrochemical reactions in the anode of direct methanol fuel cell (DMFC) are quite complicated transport phenomena. The methanol transport is a key factor influencing the performance as well as fuel utilization efficiency. In this paper, a dimensionless correlation of methanol mass transfer in DMFC anode is proposed. Firstly, a method for detecting methanol concentration in catalyst layer was developed, which is the key parameter to obtain the mass transfer coefficient. Then, the influences of the various factors on the mass transfer coefficient, including physical properties of fluid, structures of the electrode, cell configuration and cell operation conditions, were investigated. And a correlation between four dimensionless groups, i.e., Sh, Re, Sc and Π (ratio of consumption and feeding rate of methanol), was deduced using the dimensional analysis. Finally, MEA optimization and fuel utilization efficiency evaluation based on the above analysis is performed. A maximum power density of 178 mW cm−2 at 80 °C and atomistic air is achieved, 40% higher than that of commercial one made by Johnson Matthery.