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Nanostructured phenolic resin-based carbon aerogels with an extensive network structure are regarded as ideal energy storage materials for supercapacitors. However, the initial bulk form and low capacitance of previously reported porous carbon aerogels are problematic for practical use. Phenolic resin-based porous carbon spheres were synthesized by a simple hydrothermal process using ammonia, ethylenediamine or hexylenediamine as a catalyst. The porous carbon spheres were investigated by SEM, BET, XPS, etc. It was found that the number of ammonium groups, length of the alkyl chain and processing temperature play vital roles in determining the pore structure, size and uniformity of the carbon spheres. NH4+ is necessary to obtain the carbon spheres and but changing the other parameters has no obvious effect on their crystal structure. The sample prepared at a hydrothermal temperature of 80 °C using ammonia as the catalyst has the highest specific capacitance of 233.8 F g−1 at a current density of 1.0 A g−1. It has an excellent capacitance retention of 98% after 10,000 charge/discharge cycles at 7 A g−1, indicating its good cycling stability and rate capability. This result shows that a higher specific surface area, porosity and defect density are probably the crucial factors in improving the electrochemical capacitance.

In the past five years, biomass-derived biofuels and biochemicals were widely studied both in academia and industry as promising alternatives to petroleum. In this Review, the latest progress of the synthesis and fabrication of porous nanocatalysts that are used in catalytic transformations involving hydrogenolysis of lignin is reviewed in terms of their textural properties, catalytic activities, and stabilities. A particular emphasis is made with regard to the catalyst design for the hydrogenolysis of lignin and/or lignin model compounds. Furthermore, the effects of different supports on the lignin hydrogenolysis/hydrogenation are discussed in detail. Finally, the challenges and future opportunities of lignin hydrogenolysis over nanomaterial-supported catalysts are also presented.

BRI1-EMS-SUPPRESSOR 1 (BES1) transcription factor is closely associated with the brassinosteroid (BR) signaling pathway and plays an important role in plant growth and development. SLB3 is a member of BES1 transcription factor family and its expression was previously shown to increase significantly in tomato seedlings under drought stress. In the present study, we used virus-induced gene silencing (VIGS) technology to downregulate SLB3 expression to reveal the function of the SLB3 gene under drought stress further. The downregulated expression of SLB3 weakened the drought tolerance of the plants appeared earlier wilting and higher accumulation of H2O2 and O2−·, decreased superoxide dismutase (SOD) activity, and increased proline (PRO) and malondialdehyde (MDA) contents and peroxidase (POD) activity. Quantitative real-time PCR (qRT-PCR) analysis of BR-related genes revealed that the expression of SlCPD, SlDWARF and BIN2-related genes was significantly upregulated in SLB3-silenced seedlings under drought stress, but that the expression of TCH4-related genes was downregulated. These results showed that silencing the SLB3 gene reduced the drought resistance of tomato plants and had an impact on the BR signaling transduction which may be probably responsible for the variation in drought resistance of the tomato plants.

The rapid development of learning technologies has enabled online learning paradigm to gain great popularity in both high education and K-12, which makes the prediction of student performance become one of the most popular research topics in education. However, the traditional prediction algorithms are originally designed for balanced dataset, while the educational dataset typically belongs to highly imbalanced dataset, which makes it more difficult to accurately identify the at-risk students. In order to solve this dilemma, this study proposes an integrated framework (LVAEPre) based on latent variational autoencoder (LVAE) with deep neural network (DNN) to alleviate the imbalanced distribution of educational dataset and further to provide early warning of at-risk students. Specifically, with the characteristics of educational data in mind, LVAE mainly aims to learn latent distribution of at-risk students and to generate at-risk samples for the purpose of obtaining a balanced dataset. DNN is to perform final performance prediction. Extensive experiments based on the collected K-12 dataset show that LVAEPre can effectively handle the imbalanced education dataset and provide much better and more stable prediction results than baseline methods in terms of accuracy and F1.5 score. The comparison of t-SNE visualization results further confirms the advantage of LVAE in dealing with imbalanced issue in educational dataset. Finally, through the identification of the significant predictors of LVAEPre in the experimental dataset, some suggestions for designing pedagogical interventions are put forward.

To investigate the effect of atmospheric corrosion on the fatigue properties of 2024-T4 aluminum alloy structures during the whole corrosion period, atmospheric and accelerated pre-corrosion fatigue tests were carried out. Field exposure tests were carried out for 7, 12, and 20 years. A laboratory accelerated corrosion test method was proposed to simulate the whole atmospheric corrosion period from initial pitting to the subsequent exfoliation corrosion, and the reliability was verified through an analysis of the corrosion morphology, corrosion products, and thickness variation. Pitting and intergranular corrosion occurred after a short exposure to atmospheric corrosion, and intergranular corrosion was the dominant corrosion damage mode. The fatigue cracks initiated at the deepest boundary of intergranular corrosion. The fatigue life decreased dramatically during the initial stage of atmospheric corrosion and then decreased more slowly. Finally, the mechanism through which atmospheric corrosion affected the fatigue properties was analyzed.

The surface and sectional corrosion behavior of anodized 2024-T4 exposed for 7 and 20 years was investigated. After 7 years of exposure, mild exfoliation corrosion had partially occurred. Pitting and intergranular corrosion (IGC) coexisted in the unexfoliation corrosion area. Due to the continuous formation of corrosion products beneath the surface and their difficulty in being transported through the IGC channel, surface blisters were eventually formed. After 20 years, severe exfoliation corrosion had occurred on the entire surface and cracked corrosion products were partly covered by filamentous corrosion products Al(OH)3. The formation of filamentous corrosion products is the interaction between the ventilated environment, the long-term weathering, and the agglomeration of the Al(OH)3 particles. Interestingly, most of the continuously corroded grain boundaries with severe IGC on the longitudinal section were parallel to the extrusion direction. The grain orientation, high precipitates continuity at grain boundaries and weak restraint of material itself to the expansion of IGC products are the reasons for this phenomenon by EBSD, SEM, TEM and mechanical analyses.

Charge carrier scattering is critical to the electrical properties of two-dimensional materials such as graphene, transition metal dichalcogenide monolayers, black phosphorene, and tellurene. Beyond pristine two-dimensional materials, further tailored properties can be achieved by nanoporous patterns such as nano- or atomic-scale pores (antidots) across the material. As one example, structure-dependent electrical/optical properties for graphene antidot lattices (GALs) have been studied in recent years. However, detailed charge carrier scattering mechanism is still not fully understood, which hinders the future improvement and potential applications of such metamaterials. In this paper, the energy sensitivity of charge-carrier scattering and thus the dominant scattering mechanisms are revealed for GALs by analyzing the maximum Seebeck coefficient with a tuned gate voltage and thus shifted Fermi levels. It shows that the scattering from pore-edge-trapped charges is dominant, especially at elevated temperatures. For thermoelectric interests, the gate-voltage-dependent power factor of different GAL samples are measured as high as 509 at 400 K for a GAL with the square pattern. Such a high power factor is improved by more than one order of magnitude from the values for the state-of-the-art bulk thermoelectric materials. With their high thermal conductivities and power factors, these GALs can be well suitable for "active coolers" within electronic devices, where heat generated at the hot spot can be removed with both passive heat conduction and active Peltier cooling.

We report a novel electro-reduction process that can convert CO2 to high-valued fuels with low electrolysis energy. In a designed electrolysis cell, a chemical regenerative catalyst, phosphomolybdic acid (PMo12), was used as an electron-coupled proton carrier, and glycerol, a by-product of biodiesel synthesis, was employed as a reducing agent to provide electrons to PMo12 under photo irradiation. Glycerol was firstly oxidized to value-added products of glyceric acid and acetic acid under the catalysis under PMo12, after an electrical potential was applied, the reduced PMo12 (H PMo12(red)) releases electrons and was re-oxidized to PMo12 on the anode, while CO2 was reduced into valuable hydrocarbons by taking electrons on the cathode. The developed approach has multiple advantages over the conventional CO2 electrolysis, e.g. low electrolysis potential, and a noble metal-free anode due to the low overpotential of H PMo12(red) oxidation on the anode. The electrolysis current densities of 0.23 and 0.29 Acm−2 were achieved under 2.0 V of electrolysis voltage for the Cu and Ag cathode, respectively, which is 2–3 times of conventional electrolysis. The faradaic efficiency for CO2 reduction is 63.53% and 77.75% at 1.9 V, and the energy efficiency is 45.60% and 53.67% for the Cu and Ag electrode, respectively.

Zirconium pentatelluride (ZrTe5) has recently attracted renewed interest owing to many of its newly discovered extraordinary physical properties, such as 2D and 3D topological-insulator behavior, p...

We have investigated the magnetotransport properties of $\ensuremath{\beta}\text{-B}{\mathrm{i}}_{4}{\mathrm{I}}_{4}$ bulk crystal, which was recently theoretically proposed and experimentally demonstrated to be a topological insulator. At low temperature $T$ and magnetic field $B$ , a series of Shubnikov--De Haas (SdH) oscillations is observed on the magnetoresistivity (MR). Detailed analysis reveals a light cyclotron mass of $0.1\phantom{\rule{0.16em}{0ex}}{m}_{e}$, and the field angle dependence of MR reveals that the SdH oscillations originate from a convex Fermi surface. In the extreme quantum limit (EQL) region, there is a metal-insulator transition occurring soon after the EQL. We perform scaling analysis, and all the isotherms fall onto a universal scaling with a fitted critical exponent $\ensuremath{\zeta}\ensuremath{\approx}6.5$. The enormous value of critical exponent $\ensuremath{\zeta}$ implies this insulating quantum phase originated from strong electron-electron interactions in high fields. However, in the far end of EQL, both the longitudinal and Hall resistivity increase exponentially with $B$ , and the temperature dependence of the MR reveals an energy gap induced by the high magnetic field, signifying a magnetic freeze-out effect. Our findings indicate that bulk $\ensuremath{\beta}\text{-B}{\mathrm{i}}_{4}{\mathrm{I}}_{4}$ is an excellent candidate for a three-dimensional topological system for exploring EQL physics and relevant exotic quantum phases.

Lignin is the largest source of renewable aromatic compounds, making the recovery of aromatic compounds from this material a significant scientific goal. Recently, many studies have reported on lignin depolymerization and upgrading strategies. Electrochemical approaches are considered to be low cost, reagent free, and environmentally friendly, and can be carried out under mild reaction conditions. In this Review, different electrochemical lignin conversion strategies, including electrooxidation, electroreduction, hybrid electro-oxidation and reduction, and combinations of electrochemical and other processes (e. g., biological, solar) for lignin depolymerization and upgrading are discussed in detail. In addition to lignin conversion, electrochemical lignin fractionation from biomass and black liquor is also briefly discussed. Finally, the outlook and challenges for electrochemical lignin conversion are presented.

The implementation of aberration-corrected electron beam lithography (AC-EBL) in a 200 keV scanning transmission electron microscope (STEM) is a novel technique that could be used for the fabrication of quantum devices based on 2D atomic crystals with single nanometer critical dimensions, allowing to observe more robust quantum effects. In this work we study electron beam sculpturing of nanostructures on suspended graphene field effect transistors using AC-EBL, focusing on the in situ characterization of the impact of electron beam exposure on device electronic transport quality. When AC-EBL is performed on a graphene channel (local exposure) or on the outside vicinity of a graphene channel (non-local exposure), the charge transport characteristics of graphene can be significantly affected due to charge doping and scattering. While the detrimental effect of non-local exposure can be largely removed by vigorous annealing, local-exposure induced damage is irreversible and cannot be fixed by annealing. We discuss the possible causes of the observed exposure effects. Our results provide guidance to the future development of high-energy electron beam lithography for nanomaterial device fabrication.

Recently, the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties. Here, we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport, scanning tunnelling microscope (STM) measurements and band structure calculations. For a bulk sample, it exhibits large magneto-resistance (MR) and Shubnikov–de Hass oscillations in ρxx and a series of Hall plateaus in ρxy at low temperatures. Meanwhile, the MoTe2 thin films were intensively investigated with thickness dependence. For samples, without encapsulation, an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness. In such thin films, we also observed a suppression of the MR and weak anti-localization (WAL) effects. We attributed these effects to disorders originated from the extrinsic surface chemical reaction, which is consistent with the density functional theory (DFT) calculations and in-situ STM results. In contrast to samples without encapsulated protection, we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride (h-BN) film protection. Our results indicate that the metallic or superconducting behavior is its intrinsic state, and the insulating behavior is likely caused by surface oxidation in few layer 1T’-MoTe2 flakes.

Here, a novel and low cost redox flow fuel cell that directly converts raw biomass to electricity at low temperature without utilizing any noble metal catalyst is reported. In this cell, Fe3+ ion, which has strong oxidizing power and is chemical stable, was directly utilized as an oxidant for biomass in anolyte. The reduced Fe2+ acted as charge carriers, transferring the electrons to the anode of the cell and being converted back to Fe3+ simultaneously. The degradation chemistry of the biomass from the oxidation reaction and the apparent oxidation kinetics were investigated using glucose as the biomass model compound. The results showed that glucose was decomposed to small organic molecules and even CO2, and the reaction rate was significantly affected by temperature and content of reactant. The apparent activation energy of the redox reaction is 127.85 kJ·mol−1 based on the linear relation equation at the initial stage of the reaction. And the preference conditions of the redox reaction are 100–110 °C, 0.2–0.5 mol·L−1 glucose and the mol ratio of C6H12O6/FeCl3 from 1:10 to 1:12. Meantime, a high potential (VO2)2SO4 solution was synthesized as catholyte which was regenerated by O2 in the present of small amount of HNO3. The power density and discharge current density of the biomass redox flow fuel cell could reach 125.7 mW·cm−2 and 314.2 mA·cm−2, respectively, which was about 755 times higher than the reported microbial fuel cell by utilizing glucose as substrate. This work provides a promising way for converting abundant natural biomasses, such as crop straws and bagasse, into electricity at low temperature (80–110 °C).

This paper proposes a structure exploiting algorithm for solving non-convex power system state estimation problems in distributed fashion. Because the power flow equations in large electrical grid networks are non-convex equality constraints, we develop a tailored state estimator based on Augmented Lagrangian Alternating Direction Inexact Newton (ALADIN) method, which can handle the nonlinearities efficiently. Here, our focus is on using Gauss-Newton Hessian approximations within ALADIN in order to arrive at at an efficient (computationally and communicationally) variant of ALADIN for network maximum likelihood estimation problems. Analyzing the IEEE 30-Bus system we illustrate how the proposed algorithm can be used to solve highly non-trivial network state estimation problems. We also compare the method with existing distributed parameter estimation codes in order to illustrate its performance.

Accessing the nonradiative near-field electromagnetic interactions with high in-plane momentum (q) is the key to achieve super resolution imaging far beyond the diffraction limit. At far-infrared and terahertz (THz) wavelengths (e.g., 300 μm = 1 terahertz = 4 meV), the study of high q response and nanoscale near-field imaging is still a nascent research field. In this work, we report on THz nanoimaging of exfoliated single and multilayer graphene flakes by using a state-of-the-art scattering-type near-field optical microscope (s-SNOM). We experimentally demonstrated that the single layer graphene is close to a perfect near-field reflector at ambient environment, comparable to that of the noble metal films at the same frequency range. Further modeling and analysis considering the nonlocal graphene conductivity indicate that the high near-field reflectivity of graphene is a rather universal behavior: graphene operates as a perfect high-q reflector at room temperature. Our work uncovers the unique high-q THz...

A high saturation velocity semiconductor is appealing for applications in electronics and optoelectronics. Thin-film black phosphorus (BP), an emerging layered semiconductor, shows a high carrier mobility and strong mid-infrared photoresponse at room temperature. Here, we report the observation of high intrinsic saturation velocity in 7 to 11 nm thick BP for both electrons and holes as a function of charge-carrier density, temperature, and crystalline direction. We distinguish a drift velocity transition point due to the competition between the electron-impurity and electron–phonon scatterings. We further achieve a room-temperature saturation velocity of 1.2 (1.0) × 107 cm s–1 for hole (electron) carriers at a critical electric field of 14 (13) kV cm–1, indicating an intrinsic current-gain cutoff frequency ∼20 GHz·μm for radio frequency applications. Moreover, the current density is as high as 580 μA μm–1 at a low electric field of 10 kV cm–1. Our studies demonstrate that thin-film BP outperforms silicon ...

In recent years, efficient conversion of sustainable and renewable woody biomass to high value-added processable chemicals or materials has drawn a great attention. In this study, we investigated the potential of a two-step oxidation strategy for efficient fractionation of woody biomass to well-defined aromatic monomers and carbohydrate pulp. Firstly, pre-oxidation treatment was performed to convert the active Cα OH groups of lignin fraction in woody biomass to stable Cα O. Then the pre-oxidized woody biomass was cooked with oxygen in methanol for fractionation of woody biomass. As a result, the lignin fraction in woody biomass was solubilized and depolymerized into well-defined aromatic monomers (e.g. vanillin, methyl vanillate, syringaldehyde, and methyl syringate) with high yield of 29.4 %. Compared with oxygen cooking strategy, the aromatic monomers yield could be double with two-step oxidation. Simultaneously, most cellulose and hemicellulose fractions were remained as carbohydrate pulp with high delignification of 92.3 %, which mainly consist of 3.9 % lignin, 68.7 % glucan, and 18.3 % xylan. Overall, our strategy provides a possibility for the effective fractionation of entire woody biomass to value-added products.

The Yangtze River, the third largest river in the world, has been polluted by various organic chemicals. In 2018, China decided to implement ecological restoration of the Yangtze River to protect the river. However, except for some conventional pollution indices such as COD (Chemical Oxygen Demand) and NH4+-N, the overall levels and risks of a wide variety of organic micropollutants (OMPs) in the Yangtze Estuary is not clear. Herein, results from a wide-range screening on levels and risks of OMPs in the Yangtze Estuary water were reported. 36 water samples were collected at 9 sites in the Yangtze Estuary in 2012 and 2013. Approximately 1200 OMPs were screened. A total of 131 OMPs were detected with total concentrations ranging from 1.8×103 to 9.7×103 ng/L. A tiered strategy was proposed to simplify the assessment of multi-substance ecological risks. Results showed that risk quotient (RQ) for 77% of the OMPs was less than 0.1. For 20 OMPs with RQ ≥ 0.1, joint probabilistic risks were assessed by species sensitivity distribution models. The joint risks as expressed by multi-substance potentially affected fractions are > 5%, and are not insignificant. The results may serve as a benchmark for protecting biodiversity in the Yangtze Estuary, as China motivated to have a fundamental improvement on the environmental quality by 2035.

Fifteen compounds were obtained from Polygonatum prattii Baker, which could be divided into four steroids, nine flavonoids, one lignanoid and one acidamide. The chemotaxonomic significance of P. prattii and the some other species among Asparagaceae was also discussed. As a result, Polygonatum may have close relationships with Liriope, Disporopsis, Ophiopogon and Aspidistra. Additionally, homoisoflavanones and steroids can be recognized as typical biomarkers for the above genus.

The synergistic effect of H3PMo12O40 or H3PW12O40 polyoxometalate solution (POM) and TiO2 to catalyze formic acid oxidation was investigated. Under UV irradiation, hole and electron were photogenerated by TiO2. Formic acid was oxided by the photogenerated hole and photogenerated electron was transferred to reduce polyoxometalate. With this design, formic acid can be converted into electricity in the fuel cell and hydrogen can be generated in the electrolysis cell without noble metal catalyst. Unlike other noble metal catalysts applied in the fuel cells and electrolysis cell, POM and TiO2 are stable and low cost. The maximum output power density of liquid formic acid fuel cell after 12 h UV irradiation is 5.21 mW/cm2 for phosphmolybdic acid and 22.81 mW/cm2 for phosphotungstic acid respectively. The applied potential for the hydrogen evolution is as low as 0.8 V for phosphmolybdic acid and 0.6 V for phosphotungstic acid. Keywords: TiO2, UV, Polyoxometalate solution (POM), Fuel cell, Hydrogen evolution

Pristine graphene has low thermoelectric performance due to its ultra-high thermal conductivity and a low Seebeck coefficient, the latter of which results from the zero-band gap of graphene. To improve the thermoelectric performance of graphene-based materials, various methods have been proposed to open a band gap in graphene. Graphene antidot lattices is one of the most effective methods to reach this goal by patterning periodic nano- or sub-1-nm pores (antidots) across graphene. In high-porosity graphene antidot lattices, charge carriers mainly flow through the narrow necks between pores, forming a comparable case as graphene nanoribbons. This will open a geometry-dependent band gap and dramatically increase the Seebeck coefficient. The antidots also strongly scatter phonons, leading to a dramatically reduced lattice thermal conductivity to further enhance the thermoelectric performance. In computations, the thermoelectric figure of merit of a graphene antidot lattices was predicted to be around 1.0 at 300 K but experimental validation is still required. The electrical conductivity and Seebeck coefficient of graphene antidot lattices on various substrates including SiO2, SiC and hexagonal boron nitride were measured. The antidots were drilled with a focused ion beam or reactive ion etching.

A low energy electrolysis process that directly converts native biomasses to hydrogen at low temperature was reported. Practically, an environmentally-friendly proton exchange membrane electrolysis cell (PEMEC) uses a simple redox ion pair, Fe 3+ /Fe 2+ , as the catalyst which functions as an oxidation agent (oxidizing biomass), charge carrier (transferring the charge to anode) and discharge agent (discharge on anode electrode). The electro-catalytic activity of Fe 3+ /Fe 2+ ion was demonstrated by cyclic voltammetry and the rate for hydrogen evolution was measured at different current densities. At very low cell potential, smaller than 0.7 V, hydrogen begins to be produced, which is much less than the any noble metal catalysis water splitting hydrogen evolution. The electric energy consumption in our experiments for glucose-Fe ion system is 1.845 kW h Nm −3 H 2 at 100 mA cm −2 , which can save about 60.74% electric energy of traditional typical alkaline water electrolysis (4.7 kWh Nm −3 H 2 at U H2O = 2 V, the current density is 100 mA cm −2 ). Different from reported alcohol electrolysis, the biomass based electrolysis process does not require any noble-metal catalyst on the anode.

Low-rank coal, such as lignite, normally has low combustion heat and little commercial value. Combustion of low-rank coals will generate large amount of fly ashes and cause serious environmental problems. New technology for more effective use of low-rank coals with significantly less pollution is highly desired. In this study, we report an alternative method to convert coal chemical energy directly to electricity using flow fuel cell without complicated pretreatment. Practically, low-rank coal particles were first oxidized by polyoxometalate (H3[PMo12O40], denoted as POM-A) in solution on anode tank at 100–200 °C. The reduced POM transferred the accepted electrons to the anode of the flow fuel cell. These electrons passed through the external circuit and were captured by another polyoxometalate (H12[P3Mo18V7O85], denoted as POM-B) at cathode tank. The novel conversion method does not generate any fly ashes. The power density of the direct lignite flow fuel cell could reach as high as 120 mW cm−2.

Nowadays, the demand for sustainable energy devices (e.g. lithium ion batteries, supercapacitors, solar cells) has increased rapidly in recent decades. Nanocelluloses (NCs) from plants or bacteria have shown promising potential as their excellent physical, mechanical and optical properties, which are important for fabricating high-performance energy devices. NC materials and their applications in different areas have been extensively reviewed in literature. However, those reviews focused on more broad properties and applications of NC materials but the discussion on the energy applications are far from comprehensive. Technically, NCs are not electrically conductive; however, conductivity is essential for some core components of an energy device. Therefore, various chemical or physical modification approaches have been developed to prepare conductive NC-based materials. Because of the excellent physical properties of NC materials as well as the rapidly increasing demands on renewable materials based energy devices, enormous research efforts have been devoted to the NC-based conductive materials and energy devices. This paper is a comprehensive review focusing on the recent progress of fabricating conductive NC materials and the energy devices, including supercapacitors, lithium ion batteries and solar cells.

Knowledge of soil moisture is essential for soil conservation and efficient water resources management especially related to control nonpoint-source pollution. Soil topographic indices (STI) are often used to understand the soil moisture patterns in landscapes and make effective landscape management decisions. This study assessed the relationships between soil moisture measurements and STI values in two study sites in North-central New Jersey, USA. The soil moisture measurements were taken in these study sites using a time domain reflectometry probe during thirteen sampling events between April 2013 and July 2015. The STI values at the sampling points were derived from a 3-m LiDAR digital elevation model and SSURGO soil database. The Spearman’s correlation analysis based on these data in all sampling points identified a significant positive correlation between soil moisture and STI. Strong positive relationships between soil moisture and STI were also identified when using binned data to eliminate the impacts of unevenness in data distribution and the impacts of micro-variations in topography, vegetation, soil compaction, and instrumental errors. The linear mixed modeling results revealed significant and positive impacts of STI and precipitation, and significant but negative impacts of temperature on soil moisture. The degrees of these effects vary across two study sites, which reflect the complex and dynamic interactions among soils, topography and climate in landscapes that affect soil moisture. Given the stochastic nature of climate factors such as precipitation and temperature, the static STI would be a reliable factor to predict soil moisture patterns in the landscape. The findings support various STI-based conservation planning efforts in New Jersey and beyond such as targeting hydrologically sensitive areas for natural resources protection and preservation and best management practice implementation.

Hybrid solution process is a powerful liquid deposited strategy merging the advantage of molecular precursor solution and nanocrystals ink. A novel hybrid solution approach is presented to fabricate Cu(In,Ga)(S,Se)2 (CIGSSe) absorber layer using fully dissolved CIGS precursor solution and the CIGS nanocrystals. Such attractive strategy could significantly improve the single deposited thickness and enhance the quality of as-prepared CIGS film compared with the pure CIGS molecular precursor solution and the CIGS nanocrystals ink. Photovoltaic absorber layers based on CIGSSe chalcopyrite structure show the high-quality microstructural performance and are incorporated into solar cells with power conversion efficiency of 10.19%. The high performance of resulted optoelectronic devices represents a chance to extend the hybrid solution process to other inorganic semiconductor thin film solar cells.

Hereby we present a novel proton exchange membrane (PEM) electrolysis process in which lignin was used as the hydrogen source at anode for hydrogen production. Either polyoxometalate (POM) or FeCl3 was used as the catalysts and charge transfer agents in anode. Over 90% Faraday efficiency was achieved. In a thermal insulation reactor, the heat energy can be maintained at a very low stage for continuous operation. Compared to the best alkaline water electrolysis reported in literature, the electrical energy consumption could be 40% lower with novel lignin electrolysis method. At the anode, the Kraft lignin (KL) was oxidized to aromatic chemicals by POM or FeCl3, and reduced POM or iron ions were regenerated during the electrolysis. Structure analysis of the residual KL indicated the reduction of hydroxyl group number and the cleavage of ether bonds. Our results suggest that POM or FeCl3 mediated electrolysis process can significantly reduce the electrolysis energy consumption in hydrogen production and, simultaneously, depolymerize lignin to low molecular weight value-added aromatic chemicals.

Groundwater serves as a main drinking water source for rural residents in China. However, little is known regarding the pollution of organic micropollutants in groundwater that may pose health risks. In this study, more than 1300 organic micropollutants were screened in the groundwater samples collected from 13 drinking water wells distributed across five rural regions of Liaodong Peninsula in China. A total of 80 organic micropollutants including 12 polycyclic aromatic hydrocarbons, 11 alkanes, 9 pesticides, 7 substituted phenols, 7 perfluoroalkyl acids, 6 heterocyclic compounds, 5 alcohols, 5 phthalic acid esters, 5 pharmaceutical and personal care products, 3 ketones, 2 polychlorinated biphenyls (PCBs), 2 alkylbenzenes and 2 chlorinated benzenes were detected, with their total concentration of 32–1.5 × 10 4 ng/L. Noncarcinogenic and carcinogenic risks of a part of pollutants were assessed. Exposure through skin absorption and oral ingestion was considered in the assessment. Generally the risks are within the acceptable limits, except for that the carcinogenic risk at two sites in Jinzhou is higher than 10 −6 . To the best of our knowledge, this is the first report on health risks of groundwater micropollutants in China.

In this letter, we report optical pump terahertz (THz) near-field probe (n-OPTP) and optical pump THz near-field emission (n-OPTE) experiments of graphene/InAs heterostructures. Near-field imaging contrasts between graphene and InAs using these newly developed techniques as well as spectrally integrated THz nano-imaging (THz s-SNOM) are systematically studied. We demonstrate that in the near-field regime (λ/6000), a single layer of graphene is transparent to near-IR (800 nm) optical excitation and completely "screens" the photo-induced far-infrared (THz) dynamics in its substrate (InAs). Our work reveals unique frequency-selective ultrafast dynamics probed at the near field. It also provides strong evidence that n-OPTE nanoscopy yields contrast that distinguishes single-layer graphene from its substrate.

The ability to localize and manipulate individual quasiparticles in mesoscopic structures is critical in experimental studies of quantum mechanics and thermodynamics, and in potential quantum information devices, e.g., for topological schemes of quantum computation. In strong magnetic field, the quantum Hall edge modes can be confined around the circumference of a small antidot, forming discrete energy levels that have a unique ability to localize fractionally charged quasiparticles. Here, we demonstrate a Dirac fermion quantum Hall antidot in graphene in the integer quantum Hall regime, where charge transport characteristics can be adjusted through the coupling strength between the contacts and the antidot, from Coulomb blockade dominated tunneling under weak coupling to the effectively non-interacting resonant tunneling under strong coupling. Both regimes are characterized by single -flux and -charge oscillations in conductance persisting up to temperatures over 2 orders of magnitude higher than previous reports in other material systems. Such graphene quantum Hall antidots may serve as a promising platform for building and studying novel quantum circuits for quantum simulation and computation., Comment: 17 pages, 4 figures + 18 pages supplementary

The concentrations and characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in 48 oil samples randomly collected from 30 catering services that employ six cooking methods were quantified via high-performance liquid chromatography (HPLC). These 16 PAHs were detected in almost all of the samples. The levels of Σ16PAHs, Σ4PAHs, benzo[a]pyrene (BaP), and total BaP equivalents (ΣBaPeq) for the six cooking methods exceeded the legal limit. The concentrations of Σ4PAHs were approximately 9.5 to 16.4 times the legal limit proposed by the European Commission (Off J Eur Union 215:4-8, 2011), and the level of BaP exceeded the national standard in China by 4.7- to 10.6-fold, particularly in oil from fried foods. Low molecular weight PAHs (LMW PAHs) were predominant in fried food oil from different catering services and accounted for 94.8 % of these oils, and the ΣBaPeq of the high molecular weight PAHs (HMW PAHs) was 11.5-fold higher than that of the LMW PAHs. The concentrations of Σ16PAHs (3751.9-7585.8 μg/kg), Σ4PAHs (144.6-195.7 μg/kg), BaP (79.7-135.8 μg/kg), and ΣBaPeq (231.0-265.4 μg/kg) were highest in the samples from fast food restaurants/buffets (FB), followed by those from fried food stalls (FS) and then cooking restaurants/cafeterias (RC). The results of this study suggest that the government should strengthen control and supervision of PAH contamination in food and edible oils.

Ternary metastable wurtzite structure Cu2SnS3 nanocrystals were successfully synthesized via solvothermal way. As-synthesized Cu2SnS3 nanocrystals were characterized in detail by X-ray powder diffraction, energy dispersive X-ray spectrometry, UV–Vis–NIR spectrometry and transmission electron microscopy. Hybrid solution has been obtained by mixing Cu2SnS3 nanocrystals ink and Zn molecule precursor solution. Hybrid solution process was used to fabricate Cu2ZnSn(S,Se)4 thin film.

CuIn0.9R0.1(S,Se)2 (R = Al, Ni, Co) thin films were obtained via a solution process based on homogeneous precursor solutions and selenization. The as-prepared thin films were characterized by XRD, EDS and SEM. The CdS buffer layer was deposited by a solution process on the CuIn0.9R0.1(S,Se)2 (R = Al, Ni, Co) thin films, and Mo/CuIn0.9R0.1(S,Se)2 (R = Al, Ni, Co)/CdS/i-ZnO/ITO/Al thin-film solar cells were fabricated. The efficiencies of the as-fabricated CuIn0.9R0.1(S,Se)2 (R = Al, Ni, Co) thin-film solar cells were 4.33%, 2.38% and 1.98%, respectively.

Local humidity and temperature monitoring of ground parking aircraft were carried out in this study. Changes in the humidity of different bays and the relationship between local humidity and local temperature were investigated. Moreover, the concept as well as a method of calculating the humidity characteristic coefficient (HCC) were put forward, and two models of aircraft local humidity were established using the humidity and temperature of the thermometer shelter as arguments. Furthermore, bays of an airplane were divided into three groups according to differences in local humidity, and the range of the HCC of each group were determined. The results suggest that the rates of change of local humidity and local temperature are negatively correlated, moreover, the theoretical model shows a linear relationship between humidity and temperature, with a negative slope suggesting changes in humidity are inversely proportional to temperature. The ratio of the local environment slope to the external environment slope has a constant value. Finally, bay sealing and temperature features were found to significantly affect local humidity, and average deviations between the monitored humidity and humidity values predicted using the two temperature models were all less than, or equal to, 7.3% relative humidity.

Strain-induced lattice deformation affects electron hopping between the atoms. This effectively gives rise to a gauge field which impacts on the charge transport. In graphene, such gauge field is associated with a vector potential which mimics that of a magnetic field. Understanding the impact of the gauge field on charge transport is of essential importance for emerging topics including straintronics and valleytronics in two-dimensional materials. While extensive theoretical works have been carried out over the past decade, experimental progress has been largely limited to local probe and optical studies. Experimental charge transport study has been baffled by the challenge in creating an effective and independent tuning knob of strain without compromising the quality of graphene. Here we studied high quality suspended graphene field effect transistors fabricated on flexible Polyimide substrates. Applying uniaxial strain by bending the substrate, we observed a strain-induced resistivity with power-law carrier density dependence. The power factor is found to be correlated with the surface fractal dimension of the rippled graphene, in good agreement with the random gauge field scattering theory. Both phase coherent transport and magnetotransport properties are found to be strain-dependent, which can be understood in terms of a strain-tunable disorder.

This work aims to make the crack growth prediction on 2024-T6 aluminum alloy by using Markov chain Monte Carlo (MCMC). The fatigue crack growth test is conducted on the 2024-T62 aluminum alloy standard specimens, and the scatter of fatigue crack growth behavior was analyzed by using experimental data based on mathematical statistics. An empirical analytical solution of Paris’ crack growth model was introduced to describe the crack growth behavior of 2024-T62 aluminum alloy. The crack growth test results were set as prior information, and prior distributions of model parameters were obtained by MCMC using OpenBUGS package. In the additional crack growth test, the first test point data was regarded as experimental data and the posterior distribution of model parameters was obtained based on prior distributions combined with experimental data by using the Bayesian updating. At last, the veracity and superiority of the proposed method were verified by additional crack growth test.

Studying the interplay between superconductivity and quantum magnetotransport in two-dimensional materials has been a topic of interest in recent years. Towards such a goal it is important to understand the impact of magnetic field on the charge transport at the superconductor-normal channel (SN) interface. Here we carried out a comprehensive study of Andreev conductance under weak magnetic fields using diffusive superconductor- graphene Josephson weak links. We observe that the Andreev conductance is suppressed even in magnetic fields far below the upper critical field of the superconductor. The suppression of Andreev conductance depends on and can be minimized by controlling the ramping of the magnetic field. We identify that the key factor behind this suppression is the reduction of the superconducting gap due to the piling of vortices on the superconducting contacts. In devices where superconducting gap at the superconductor-graphene interface is heavily reduced by proximity effect, the enlarged vortex cores overlap quickly with increasing magnetic field, resulting in a rapid decrease of the interfacial gap. However, in weak links with relatively large effective superconducting gap the AR conductance persists up to the upper critical field. Our results provide guidance to the study of quantum material-superconductor systems in presence of magnetic field, where 'survival' of induced superconductivity is critical., Comment: 22 pages, 4 figures. Typos corrected, reference added

We report on noise and thermal conductance measurements taken in order to determine an upper bound on the performance of graphene as a terahertz photon detector. The main mechanism for sensitive terahertz detection in graphene is bolometric heating of the electron system. To study the properties of a device using this mechanism to detect terahertz photons, we perform Johnson noise thermometry measurements on graphene samples. These measurements probe the electron-phonon behavior of graphene on silicon dioxide at low temperatures. Because the electron-phonon coupling is weak in graphene, superconducting contacts with large gap are used to confine the hot electrons and prevent their out-diffusion. We use niobium nitride leads with a $T_\mathrm{c}\approx 10$ K to contact the graphene. We find these leads make good ohmic contact with very low contact resistance. Our measurements find an electron-phonon thermal conductance that depends quadratically on temperature above 4 K and is compatible with single terahertz photon detection., Comment: 6 Pages, 4 Figures, Conference Proceedings from LTD-15

We use variable-temperature x-ray thermal diffuse scattering and inelastic scattering to investigate the lattice dynamics in single crystals of multiferroic ${\mathrm{CaMn}}_{7}{\mathrm{O}}_{12}$ which undergo a series of orbital and magnetic transitions at low temperatures. Upon approaching the charge and orbital ordering temperature ${T}_{o}=250$ K from above, we observe intense diffuse scattering features and a pronounced optical phonon softening centered around the superstructure reflections of the incommensurately modulated structure. The phonon anomaly appears well above ${T}_{o}$ and continuously increases upon cooling, following a canonical power-law temperature dependence that confirms the transition at ${T}_{o}$ to be of second order and related to a soft-phonon lattice instability. Microscopic mechanisms for the incommensurate charge and orbital ordering based on competing interactions and on momentum-dependent electron-phonon coupling could both account for the observed extended momentum width of the phonon softening. Our results highlight the importance of the lattice interactions in the physics of this magnetically induced ferroelectric system.

Polysaccharide, one of the main components in Schisandra chinensis, has been discovered to have an antidiabetic effect. In this study, we further observed the effect of the secondary component of S...

To demonstrate the variation and affecting factors of dissolved oxygen under different aeration strategies in polluted urban river sediment, simulation systems constructed with collected sediment and in situ overlaying water were aerated up or beneath the sediment-water interface 6 h day−1 for 15 days. The results showed that aeration greatly altered the spatial pattern of DO in overlying water regardless of the way of treatment. Within the first 5 min of aeration, DO in overlying water increases rapidly from 0.86–3.13 mg L−1 to the saturated range of 6.12–8.14 mg L−1. During the first 5 days, aeration to water costed 5 min to reach the highest DO, while aeration to sediment costed 30 min to reach a lower highest level of DO in overlaying water. Analysis showed that DO was significantly negatively correlated with NO2 −-N and COD Mn , suggesting that DO was synergistically consumed by biochemical processes of organic matter degradation and nitrification. Aeration to sediment (ES group) and aeration to water (EW group) differently influenced nitrification and organic matter degradation. After daily aeration treatment, nitrification was the main oxygen-depleting process in EW group, especially after the action of the second stage of nitrification, where organic matter was probably largely degraded during aeration. However, in ES group, DO was consumed by both organic matter oxidation and nitrification processes.

This paper describes our work on mining pollutant data to assess air quality in urban areas. Notable aspects of this work are that we mine social media and structured data in a domain-specific context, incorporate commonsense knowledge in mining media opinions and focus on the urban planning domain in a multicity environment. The results of mining are useful for predictive analysis in urbanization. A significant contribution is that we provide useful information on urban health impacts.

In Dirac materials, the low energy excitations behave like ultra-relativistic massless particles with linear energy dispersion. A particularly intriguing phenomenon arises with the intrinsic charge transport behavior at the Dirac point where the charge density approaches zero. In graphene, a 2-D Dirac fermion system, it was predicted that charge transport near the Dirac point is carried by evanescent modes, resulting in unconventional pseudo-diffusive charge transport even in the absence of disorder. In the past decade, experimental observation of this phenomenon remained challenging due to the presence of strong disorder in graphene devices which limits the accessibility of the low carrier density regime close enough to the Dirac point. Here we report transport measurements on ballistic suspended graphene-Niobium Josephson weak links that demonstrate a transition from ballistic to pseudo-diffusive like evanescent transport below a carrier density of $(10^{10} cm^{-2})$.Approaching the Dirac point, the sub-harmonic gap structures due to multiple Andreev reflections display a strong Fermi energy-dependence and become increasingly pronounced, while the normalized excess current through the superconductor-graphene interface decreases sharply. Our observations are in qualitative agreement with the longstanding theoretical prediction for the emergence of evanescent transport mediated pseudo-diffusive transport in graphene., Comment: 17 pages, 3 figures. New version after peer review and publication.Typos corrected

We exploit nanoscale mechanically induced switching of an artificially layered ferroelectric material, used as an active substrate, to achieve the local manipulation of the electrical transport properties of graphene. In Graphene Ferroelectric Field Effect Transistors (GFeFETs), the graphene channel's charge state is controlled by an underlying ferroelectric layer. The tip of an atomic force microscope (AFM) can be used to mechanically 'write' nanoscale regions of the graphene channel and 'read' off the modulation in the transport behavior. The written features associated with the switching of ferroelectric domains remain polarized until an electrical reset operation is carried out. Our result provides a method for flexible and reversible nano-scale manipulation of the transport properties of a broad class of 2D materials.

The characteristics of topological insulators are manifested in both their surface and bulk properties, but the latter remain to be explored. Here we report bulk signatures of pressure-induced band inversion and topological phase transitions in ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Sn}}_{x}\mathrm{Se}$ ($x=0.00$, 0.15, and 0.23). The results of infrared measurements as a function of pressure indicate the closing and the reopening of the band gap as well as a maximum in the free carrier spectral weight. The enhanced density of states near the band gap in the topological phase gives rise to a steep interband absorption edge. The change of density of states also yields a maximum in the pressure dependence of the Fermi level. Thus, our conclusive results provide a consistent picture of pressure-induced topological phase transitions and highlight the bulk origin of the novel properties in topological insulators.

To achieve the state-of-the-art photon detectors, extensive research has been carried out on graphene-based bolometers. These utilize graphene’s promising properties including its small heat capacity, weak electron-phonon coupling, and small resistance. This article reviews the recent development of cryogenic graphene-based bolometers, which are of particular interest and importance for understanding as well as for taking advantage of the intrinsic properties of graphene. We summarize the major theoretical and experimental developments in the field, including the phonon cooling mechanism and its dependence on temperature, doping, and disorder, and the experimental approaches for realizing bolometric detectors.We also estimate the ultimate performance of an ideal graphene bolometer as a power detector and a single-photon detector if superconducting contacts are employed.

We have investigated the low-frequency 1/f noise of both suspended and on-substrate graphene field-effect transistors and its dependence on gate voltage, in the temperature range between 300K and 30K. We have found that the noise amplitude away from the Dirac point can be described by a generalized Hooge's relation in which the Hooge parameter {\alpha}H is not constant but decreases monotonically with the device's mobility, with a universal dependence that is sample and temperature independent. The value of {\alpha}H is also affected by the dynamics of disorder, which is not reflected in the DC transport characteristics and varies with sample and temperature. We attribute the diverse behavior of gate voltage dependence of the noise amplitude to the relative contributions from various scattering mechanisms, and to potential fluctuations near the Dirac point caused by charge carrier inhomogeneity. The higher carrier mobility of suspended graphene devices accounts for values of 1/f noise significantly lower than those observed in on-substrate graphene devices and most traditional electronic materials.

When high quality bismuth or graphite crystals are placed in a magnetic field directed along the c-axis (trigonal axis for bismuth) and the temperature is lowered, the resistance increases as it does in an insulator but then saturates. We show that the combination of unusual features specific to semimetals, i.e., low carrier density, small effective mass, high purity, and an equal number of electrons and holes (compensation), gives rise to a unique ordering and spacing of three characteristic energy scales, which not only is specific to semimetals but which concomitantly provides a wide window for the observation of apparent field induced metal-insulator behavior. Using magnetotransport and Hall measurements, the details of this unusual behavior are captured with a conventional multi-band model, thus confirming the occupation by semimetals of a unique niche between conventional metals and semiconductors., 4 pages, 4 figs, data and discussion on bismuth added, final published version