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Daily streamflow modeling is an important tool for water resources management and flood mitigation. This study compared the performance of the Xinanjiang (XAJ) model and random forests (RF) method in a daily streamflow simulation, and proposed several hybrid models based on the XAJ model, wavelet analysis, and RF method (including XAJ-RF model, WRF model, and XAJ-WRF model). The proposed methods were applied to Shiquan station, located in the Upper Han River basin in China. Five performance measures (NSE, RMSE, PBIAS, MAE, and R) were adopted to evaluate the modeling accuracy. Results showed that XAJ-RF model had a relatively higher level of accuracy than that of the XAJ model and the RF model. Compared to the RF and XAJ-RF models, the performance statistics of WRF and XAJ-WRF were better. The results indicated that the coupled XAJ-RF model can be effectively applied and provide a useful alternative for daily streamflow modeling and the application of wavelet analysis contributed to the increasing accuracy of streamflow modeling. Moreover, 14 wavelet functions from various families were tested to analyze the impact of various mother wavelets on the XAJ-WRF model. HIGHLIGHTS This study proposed several hybrid models based on the Xinanjiang (XAJ) model, wavelet analysis and the random forests (RF) method (XAJ-RF, WRF and XAJ-WRF model).; The results indicated that the XAJ-RF model can provide a useful alternative and the application of wavelet analysis contributed to the increasing accuracy in streamflow modeling.

In this study, we proposed and tested a method based on system response curve (SRC) to extract the error information of areal mean rainfall. These extracted rainfall error are then used to update the rainfall time series data and propagated through the model to update the stream-flow forecast. The method is evaluated via synthetic and real-data cases. After our statistical analysis in different application scenarios, we found that the SRC method can effectively improve the accuracy of real-time flood forecasting when an optimal updating width is selected (the average relative error was reduced from 1.65% to 0.86%). In addition, we benchmark our results against a more conventional AR (Auto-Regression) streamflow-updating method. The average accuracy improvement of SRC method is 6.3% higher than that of AR method. More importantly, we found that the optimal updating width of SRC method is highly correlated with the average lead time of the basin, it has guiding significance for selecting the optimal updating width in practical application.

Real-time flood forecasting requires accurate and reliable estimates of the uncertainty to make efficient flood event management strategies. However, the accuracy of flood forecasts can be severely affected by errors in the estimates of sediment yield in the loess region. To improve the accuracy of sediment-laden flood forecasts generated using streamflow-sediment coupled (SSC) model, an error feedback correction method based on the dynamic system response curve (DSRC) is proposed. The physical basis of the system response curve is the sediment concentration of the hydrological model. The theoretical basis of the method is the differential of the system response function of the sediment yield time series. The effectiveness of DSRC method is evaluated via an ideal case and three real-data cases with different basin scales of the Yellow River. Results suggest that the DSRC method can effectively improve the accuracy and stability of sediment transport forecasts by providing accurate estimates of the sediment yield errors. The degree of forecast improvement is scale dependent and is more significant for larger basins with lower rain gauge densities. Besides, the DSRC method is relatively simple to apply without the need to modify either the model structure or parameters in real-time flood forecasting.

PurposeThe purposes of this paper are to review the impact on food and nutrition security of several pandemic emergencies and the 2018 food price crisis from a global perspective, examine the Chinese experiences and lessons in ensuring food and nutrition security for its citizen and propose policy actions to prevent a global food and nutrition security crisis.Design/methodology/approachThe authors utilize a noncomprehensive review of peer-reviewed and nonpeer-reviewed literature, as well as a case study approach.FindingsUnder the ongoing COVID-19, China's food and nutrition are relatively secure in short run largely due to governmental proactive policies but may face uncertainties in livestock production and imports of soybean in the medium and long terms. Given that the disease has spread to almost all countries in the world, global cooperation and coordination are needed to prevent systemic risks to global food and nutrition security.Practical implicationsThe review and analysis of this paper will help policymakers in China and other countries to design strategies and actions to prevent food and nutrition security crisis under the ongoing COVID-19 emergency and other similar threats in the future.Originality/valueThis paper provides recommendations to prevent food and nutrition security crisis based on data, evidence and case studies.

In an isothermal process, applying an electric field E to a ferroelectric material can change its entropy S through two distinct mechanisms: namely, through changing the dipole alignment or configurational entropy (ΔSconf), and the vibrational entropy due to the intrinsic structure response (ΔSvib). Previous numerical investigations yield only the total entropy change ΔS but cannot separate these two contributions. Here we develop a full first-principles method to extract ΔSvib and the corresponding induced adiabatic temperature change ΔTvib under E, i.e., the electrocaloric effect (ECE), and compare them to the total ΔS and ΔT from molecular dynamics simulation based on a first-principles effective Hamiltonian model. For both single crystal PbTiO3 (PTO) and PbZr0.5Ti0.5O3 (50/50 PZT), the calculation results show that for T far from the phase transition temperature Tpt, ΔSvib plays an important and even dominant role in the ECE. On the other hand, for T close to Tpt, ΔSconf dominates the ECE. Moreover, for PTO, we find that positive E can cause positive ECE, while negative E cause negative ECE. Therefore, by combining both positive and negative ECE in a “bipolar” Ericsson cycle, the cooling energy density can significantly increase as compared to that of a unipolar cycle.

Particle acidity is a fundamental property that affects atmospheric particulate chemistry. Synchronous online monitoring was performed at two urban sites, Zhengzhou (U-ZZ) and Anyang (U-AY), and three rural sites, Anyang (R-AY), Xinxiang (R-XX), and Puyang (R-PY) in Henan Province, during a haze episode to investigate the pH value and its driving factors in the agricultural regions of China. The pH values of particles calculated by ISORROPIA-II model at rural sites were slightly higher than those at urban sites, with the median (min–max) values of 5.2 (4.8–6.9, R-PY), 5.1 (4.7–6.5, R-AY), 4.9 (4.1–6.8, R-XX), 4.8 (3.9–5.9, U-AY), and 4.5 (3.8–5.2, U-ZZ). Sensitivity tests show that TNHx (total ammonium, gas + aerosol) followed by total sulfate were the most important factors that influenced the predicted pH. Generally, particle pH increased with a cation increase and decreases in anions, temperature, and relative humidity. Similar pH values (∼3.0) at the required NHx concentrations for the five sites indicated that the presence of excess NHx was likely important for the lower acidity of PM2.5 during the severe haze episodes in this region. Moreover, the concentrations of excess NHx may drive the higher pH values at rural sites, because of the higher excess NHx concentrations at rural sites than those at urban sites. The underlying influence of regional transport on local particle pH cannot be neglected, as it differs the chemical components of PM2.5 and meteorological conditions. Air masses transported from rural and agricultural regions may enhance the particle pH value in urban aerosols given the high pH of particles and high ammonia levels. These results suggest that ammonia is urgently needed to be involved in the regional strategy for the improvement of air quality in China.

Peganum harmala L. is a perennial herbaceous plant belonging to the family of Zygophyllaceae, and is grows in semi-arid climates, such as Xinjiang, Gansu, Ningxia, Qinghai, and Inner Mongolia in Ch...

Colloidal particles in lake waters interact inevitably with cyanobacterial extracellular polymeric substance (EPS), which will change their behavior and fate. Quantitative prediction of the effects of cyanobacterial EPS on colloidal behavior is difficult due to its variability and heterogeneity. To explore the effects of molecular weight (MW) fractions and chemical properties of cyanobacterial EPS on aggregation kinetics of colloidal particles, time-series cyanobacterial samples were collected in Lake Taihu, China, from April to November (during blooming and maintenance period), with the bulk EPS matrix fractionating into low MW (LMW-,1 nm) and high MW (HMW-, 1 nm-0.45 μm) fractions. HMW-EPS was generally characterized with higher absorbance and predominant distribution of protein-like substances, while LMW-EPS contained mainly the humic- and fulvic-like substances. The absorbance, molecular size, and humification degree for each MW fraction consistently increased from April to November, showing obvious temporal variations from blooming period to maintenance period. As for the MW-dependent aggregation behaviors, the HMW-EPS provided better stability against aggregation than the LMW-EPS, and the bulk EPS matrix that consisted of HMW- and LMW-fractions exhibited the effects intermediate between that of each fraction alone. Regardless of MW fractions, the effects of EPS-induced stability enhancement were more evident in maintenance period than in blooming period. Further analysis showed that the colloidal stability was correlated positively with SUVA

This study explored the performance of unbound aggregate materials (UAM). Repeated load tests of single-size, two-size mixed, and three-size mixed gravels were conducted using the precision unbounded material analyzer (PUMA) in single-stage loading mode (SSLM) and multi-stage loading mode (MSLM). The permanent deformation and elastic modulus of the first 400 loading cycles were analyzed under the two loading modes. The modulus of PUMA repeated load tests was compared with modulus models of the repeated CBR test and with constant confining pressure (CCP) and variable confining pressure (VCP) models of the repeated load triaxial test. The results of MSLM showed that the permanent deformation of single-size gravel increased rapidly when the loading strength was lower than 340 kPa and then decreased. The maximum permanent deformation of the mixed gravels appeared as the loading strength was lower than 200 kPa. The increment of permanent deformation tended to single-peak with the large-size aggregate. The loading strength only slightly affected the permanent deformation once it reached a certain extent. The initial-stage permanent deformation of SSLM was the main part of the total, and the proportion increased with the increase in loading strength. A slight difference was observed between the single-size and mixed gravel when the loading strength was under 240 kPa. Then, the permanent deformation of single-size gravel increased rapidly. The permanent deformation of MSLM was smaller than that of SSLM. MSLM can improve the carrying capacity of the unbound materials and reveal the principle of three-stage compaction for UAM. Although the calculated equivalent modulus of the full-friction model was lower than those of the existing studies, it presented the same tendency and was appropriate for the calculation of modulus. The elastic modulus of CCP model was the largest among the four models, and the growth rate of elastic modulus was the highest for VCP model. The effect of confining pressure on the modulus increased with increasing loading strength.

Block copolymers provide a wonderful platform in the study of soft condensed matter systems. Many fascinating ordered structures have been discovered in bulk and confined systems. Among various theories, the self-consistent field theory (SCFT) has been proven to be a powerful tool for studying the equilibrium ordered structures. Many numerical methods have been developed to solve the SCFT model. However, most of these focus on the bulk systems, and little work on the confined systems, especially on general curved surfaces. In this work, we developed a linear surface finite element method, which has a rigorous mathematical theory to guarantee numerical precision, to study the self-assembled phases of block copolymers on general curved surfaces based on the SCFT. Furthermore, to capture the consistent surface for a given self-assembled pattern, an adaptive approach to optimize the size of the general curved surface has been proposed. To demonstrate the power of this approach, we investigate the self-assembled patterns of diblock copolymers on several distinct curved surfaces, including five closed surfaces and an unclosed surface. Numerical results illustrate the efficiency of the proposed method. The obtained ordered structures are consistent with the previous results on standard surfaces, such as sphere and torus. More significantly, the proposed numerical framework can be applied to study the phase behaviors of block copolymers on general surfaces accurately.

Cholesterol in lipid membranes plays an important role in the pathogenesis of Alzheimer’s disease. However, the exact mechanism of cholesterol in the effect on the interaction between Aβ and lipid membranes still remains elusive. Previous experiments and simulations research are also full of contradictions. The addition of cholesterol to the lipid membrane will cause changes in the stiffness and elasticity of the membrane, and the changes in the mechanical properties of the membrane may affect the interaction between amyloid and the lipid membrane. Therefore, in this study, we have carried out MD simulations to research the interaction between p3 peptide (Aβ 17-42 pentamers) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membrane. We adjust the membrane mechanical properties by changing the potential of lipid atoms, thereby discuss the influence of the mechanical properties of the lipid membrane on the interaction between them. Simulation results show that the when the membrane mechanical property is in some range, p3 peptide could insert into the membrane while out of this range, p3 peptide could only deposited on the membrane surface, resulting in different degrees of membrane damage. This study indicates that the cell membrane may be the reason for the Aβ peptide attacking the cell membrane. Improving the cell membrane property may prevent the toxic effect of Aβ peptide.

Protein folding research has always been a significant research topic in biological sciences. However, due to the diversity of protein structures and the unpredictability of folding pathways, the folding mechanism of the natural structure of proteins have not been clearly explained. In this work, ubiquitin is used as the research object to analyze the process of protein unfolding through molecular dynamics (MD) simulation. The aim to do protein unfolding is to enlighten the research on the issue about protein folding mechanism in reverse. Our simulation reveals the order of secondary structures to unfolding and the segmentation in the unfolding process. The results can confirm the difference in stability between various secondary structures. After that, the changes in the number of hydrogen bonds and energy during the unfolding process are focused on. It indicates that both of them also have the same step phenomenon. It is presumed that the protein folding may have the similar step phenomenon. It is hopeful for the results obtained from protein unfolding to guide and inspire protein folding mechanisms.

This study investigates the temporal variation of stable isotopic composition in precipitation, soil water, and streamflow water during the plum rainfall events in an upland headwater watershed which is mainly covered with bamboo. The results show that the isotopic composition of various water sources exhibit significant temporal variation. The local meteoric water line is established by using the relationship between the stable isotope of oxygen-18 and deuterium, which is slightly different from the meteoric water line of China. The isotopic temporal variation of precipitation is closely related to exchange effect between raindrops and environmental vapor, evaporation fractionation and rainfall intensity. The isotopic variation of shallow soil water is mainly determined by canopy interception, ground evaporation and the mixing with pre-event water; as for the isotopic variation of deep soil water, it is virtually influenced by pre-event water. The most enriched isotopic composition of streamflow and deuterium excess (d-excess) differences between streamflow and rainfall both indicate that streamflow is recharged not only by event water but also by pre-event water. Hence, a better understanding of precipitation formation and the hydrological response under the plum rainfall system may be instructive for the management of water resources in humid watersheds in southern China.

An efficient and general visible-light-mediated trifluoromethylthiolation of N-(o-cyanobiaryl)acrylamides has been successfully accomplished using N-trifluoromethylthiosaccharin as an effective source of SCF3 radicals. The reaction was proposed to proceed via a domino radical trifluoromethylthiolation/cyano insertion/cyclization to afford the corresponding SCF3-containing ring-fused phenanthridine derivatives in moderate to good yields.

Understanding the mechanism of water infiltration through nanopores is essential for wide applications ranging from membrane separation to gene therapy. In this paper, the molecular dynamics simula...

Wollastonite glass ceramics were prepared using the reactive crystallization sintering method by mixing waste glass powders with gehlenite. The crystallization property, thermodynamics, and kinetics of the prepared wollastonite glass ceramics were determined by X-ray diffraction analysis, scanning electron microscopy, energy-dispersive spectroscopy, high-resolution transmission electron microscopy, and differential thermal analysis. Results showed that crystals of wollastonite and alumina could be found in the gehlenite through its reaction with silicon dioxide. The wollastonite crystals showed a lath shape with a certain length-to-diameter ratio. The crystals exhibited excellent bridging and reinforcing effects. In the crystallization process, the aluminum ions in gehlenite diffused into the glass and the silicon ions in the glass diffused into gehlenite. Consequently, the three-dimensional frame structure of gehlenite was partially damaged to form a chain-like wollastonite. The results of crystallization thermodynamics and kinetics indicated that crystallization reaction could occur spontaneously under a low temperature (1173 K), with 20 wt% gehlenite added as the reactive crystallization promoter. The crystallization activation energy was evaluated as 261.99 kJ/mol by using the Kissinger method. The compression strength of the wollastonite glass ceramic samples (7.5 cm×7.5 cm) reached 251 MPa.

The concentration of acetaldehyde (AA) is the main quality index of poly(ethylene terephthalate) (PET) used in food and drink packaging. A new method for AA removal has been developed by using supercritical carbon dioxide (scCO2) during the solid-state polycondensation of PET. The influence factors of AA removal including the temperature, pressure, reaction time and the size of pre-polymer particles are systematically studied in this work. The results indicate that it is a highly efficient way to obtain high molecular weight PET with relative low concentration of AA. Correspondingly, the polymerization degree of PET could increase from 27.9 to 85.6 while the concentration of AA reduces from 0.229 × 10−6 to 0.055 × 10−6 under the optimal operation conditions of 230 °C, 8 MPa and size of 0.30–0.45 mm. Thermodynamic performance tests show the increasing extent of PET crystallinity due to the fact that the plasticization of scCO2 is not obvious with extended reaction time, therefore the increasing crystallinity has no significant influence on AA removal. SEM observations reveal that the effects of scCO2-induced plasticization and swelling on PET increase significantly with the decrease of prepolymer size, and the surface of PET becomes more loose and porous in favor of the AA removal.

The bimodal-sized (micron+nano) TiCp/Al-Cu composites were successfully fabricated by adding the in situ micron-sized and nano-sized TiCp-Al master alloys into the molten Al-Cu alloy. The composites reinforced with bimodal-sized TiCp exhibited finer α-Al grains and smaller θ′ precipitates, and possessed enhanced room- and high-temperature strength and relatively high ductility compared with the Al-Cu matrix alloy and their counterparts reinforced with monomodal-sized TiCp. The improved tensile properties may be attributed to the more significant precipitation strengthening due to the smaller θ′ precipitates, grain refinement and strengthening effects of the nano-sized and micron-sized TiCp.

Adding various amounts of nano-sized TiCp (0.1–0.7 wt%) made a simultaneous improvement in high-temperature strength and ductility of the Al-Cu matrix alloy. The influences of temperature and strain rate on the high-temperature tensile properties and θ′ precipitate sizes in the Al-Cu matrix alloy and the nano-sized TiCp/Al-Cu composites were investigated. Theoretical calculations suggest that the yield strength increment of the composites at 453 K was primarily attributed to the strengthening effect of both the refined θ′ precipitates and TiCp, while at 493 K only the strengthening effect of TiCp was predominant due to the significant coarsening of θ′ precipitates at this temperature.

The creep resistance of the bimodal-sized (micron+nano) TiCp/Al-Cu composite was 10–38 times and 3–6 times higher than that of the Al-Cu matrix alloy and monomodal-sized composites, respectively, attributed to strengthening effects of nano-TiCp and larger number of finer θ′ precipitates.

Summary Verticillium dahliae isolates are most virulent on the host from which they were originally isolated. Mechanisms underlying these dominant host adaptations are currently unknown. We sequenced the genome of V. dahliae Vd991, which is highly virulent on its original host, cotton, and performed comparisons with the reference genomes of JR2 (from tomato) and VdLs.17 (from lettuce). Pathogenicity-related factor prediction, orthology and multigene family classification, transcriptome analyses, phylogenetic analyses, and pathogenicity experiments were performed. The Vd991 genome harbored several exclusive, lineage-specific (LS) genes within LS regions (LSRs). Deletion mutants of the seven genes within one LSR (G-LSR2) in Vd991 were less virulent only on cotton. Integration of G-LSR2 genes individually into JR2 and VdLs.17 resulted in significantly enhanced virulence on cotton but did not affect virulence on tomato or lettuce. Transcription levels of the seven LS genes in Vd991 were higher during the early stages of cotton infection, as compared with other hosts. Phylogenetic analyses suggested that G-LSR2 was acquired from Fusarium oxysporum f. sp. vasinfectum through horizontal gene transfer. Our results provide evidence that horizontal gene transfer from Fusarium to Vd991 contributed significantly to its adaptation to cotton and may represent a significant mechanism in the evolution of an asexual plant pathogen.

The creep resistance of Al-Cu alloys deteriorates significantly at high temperatures owing to the coarsening of θ′ precipitates during creep, which limits their applications at elevated temperatures. We fabricated a cast Al-Cu matrix composite containing finer and denser θ′ precipitates by adding 0.3 wt% in situ nano-sized TiC p into an Al-Cu alloy. The steady creep rates of the nano-sized TiC p /Al-Cu composite were 3–17 times lower than those of the Al-Cu matrix alloy at 453–493 K under applied stresses of 120–200 MPa, respectively, which was attributed to the higher threshold stresses of the composite due to the strengthening effect of the nano-sized TiC p and the larger number of θ′ precipitates with smaller diameters. The accelerated coarsening of θ′ precipitates after higher temperature creep could contribute to the decrease of threshold stress with increasing temperature. The analysis of the true stress exponent indicates that the dislocation climb mechanism is dominant in both the matrix alloy and the composite during creep.

The climate change impacts on maize yields are quantified in this paper using statistical models with panel data from 3731 farmers' observations across nine sample villages in Hebei Province of China. The marginal impacts of climate change and the simulated impacts on maize yields based on scenarios of Representative Concentration Pathways 2.6, 4.5, 6.0, and 8.5 from the global climate models of Model for Interdisciplinary Research on Climate version 5 (MIROC5) and Meteorological Research Institute Coupled General Circulation Model version 3 (MRI-CGCM3) were then calculated, analyzed, and explained. The results indicate that, first, the most important finding was that climate change impacts on maize yields were significant and a 1°C warming or a 1mm decrease in precipitation resulted in a 150.255kg or a 1.941kg loss in maize yields per hectare, respectively. Second, villages with latitudes of less than 39.832 and longitudes of more than 114.839 in Hebei province suffered losses due to warm weather. Third, the simulated impacts for the full sample are all negative based on scenarios from MIROC5, and their magnitudes are more than those of MRI-CGCM3 are. Based on scenarios in the 2050s, the biggest loss for maize yields per hectare for the full sample accounts for about one-tenth of the mean maize yield from 2004 to 2010, and all of the villages are impacted. Hence, it is important to help farms adopt an adaptation strategy to tackle the risk of loss for maize yields from climate change, and it is necessary to develop agricultural synthesis services as a public adaptation policy at the village level to interact with the adaptation strategy at the farm level.

Targeted identification of potentially bioactive molecules from herbal medicines is often stymied by the insufficient chromatographic separation, ubiquitous matrix interference, and pervasive isomerism. An enhanced targeted identification strategy is presented and validated by the selective identification of flavonoid O-glycosides (FOGs) from Carthamus tinctorius. It consists of four steps: (i) enhanced separation and detection by offline two-dimensional liquid chromatography/LTQ-Orbitrap MS (offline 2D-LC/LTQ-Orbitrap MS) using collision-induced dissociation (CID) and high-energy C-trap dissociation (HCD); (ii) improved identification of the major aglycones by acid hydrolysis and LC-SPE-NMR; (iii) simplified spectral elucidation by high-resolution diagnostic product ions/neutral loss filtering; and (iv) more convincing structural identification by matching an in-house library. An offline 2D-LC system configuring an Acchrom XAmide column and a BEH Shield RP-18 UPLC® column enabled much better separation of the easily co-eluting components. Combined use of CID and HCD could produce complementary fragmentation information. The intensity ratios of the aglycone ion species ([Y0-H]-/Y0- and [Y0-2H]-/Y0-) in the HCD-MS2 spectra were found diagnostic for discriminating the aglycone subtypes and characterizing the glycosylation patterns. Five aglycone structures (kaempferol, 6-hydroxykaempferol, 6-methoxykaempferol, carthamidin, and isocarthamidin) were identified based on the 1H-NMR data recorded by LC-SPE-NMR. Of the 107 characterized flavonoids, 80 FOGs were first reported from C. tinctorius. Unknown aglycones, pentose, and novel acyl substituents were discovered. A new compound thereof was isolated and fully identified, which could partially validate the MS-oriented identification. This integral strategy can improve the potency, efficiency, and accuracy in the detection of new compounds from medicinal herbs and other natural sources.

Nanopore is a kind of powerful tool to detect single molecules and investigate fundamental biological processes. In biological cells or real detection systems, concentration of DNA molecules is various. Here, we report an experimental study of the effects of DNA concentration on capture rate and translocation configuration with different sized nanopores and applied voltages. Three classes of DNA translocation configurations have been observed including linear translocation, folded translocation, and cotranslocation. In the case of relatively large sized nanopore or high applied voltage, considerable cotranslocation events have been detected. The percentage of cotranslocation events also increases with DNA concentration, which leads to the relationship between capture rate and DNA concentration deviates from linearity. Therefore, in order to reflect the number of translocation molecules accurately, the capture rate should be corrected by double-counting cotranslocation events. These results will provide a valuable reference for the design of nanopore sensors.

Resistive pulse sensing with nanopores is expected to enable identification and analysis of nanoscale objects in ionic solutions. However, there is currently no remarkable method to characterize the three-dimensional shape of charged biomolecules or nanoparticles with low-cost and high-throughput. Here we demonstrate the sensing capability of solid-state nanopores for shape characterization of single nanoparticles by monitoring the ionic current blockades during their electrophoretic translocation through nanopores. By using nanopores that are a bit larger than the particles, shape characterization of both spherical and cubic silver nanoparticles is successfully realized due to their rapid rotation with respect to the pore axis, which is further validated by our all-atom molecular dynamics simulations. The single-molecule approach based on nanopores will allow people to measure the dimension and to characterize the shape of single nanoparticles or proteins simultaneously in real time, which is significant for its potential application in investigation of structural biology and proteomics in the near future.

Understanding the mechanism of ion transport and the related ionic current through a nanopore is significant for improving the sensing accuracy of biophysical and diagnostic applications using the nanopore technology. Here, systematic theoretical studies of ionic current dependence on the geometry of a nanopore were performed. Surprisingly, it was found that the ionic current through a nanopore with a smaller perimeter was obviously larger than that through a nanopore with a larger perimeter although all the nanopores had consistent cross-sectional areas; this was also found for nanopores with different hydrophobicities. This interesting result originates from the decrease in ion concentration, mobility and conductivity in proximity to the nanopore surface. Besides, an obvious ionic current enhancement was observed for hydrophobic nanopores compared to that for the hydrophilic nanopores, which was caused by the increased ion mobility through the hydrophobic nanopores. A simple model that combined the distribution of ion conductivity as well as the traditional Ohm's law was successfully applied to predict the ionic current through difform nanopores with different hydrophobicities. This work will aid the development of high-resolution nanopore sensors in the near future.

The Coulter counter is expected to detect the size of particles in ionic solutions by measuring resistive pulses when they are passing through nanopores. The magnitude of resistive pulse is used to infer the size of a particle. Nevertheless, there is currently no remarkable method to characterize the size of charged biomolecules or nanoparticles with low-cost and high-throughput. Here we demonstrated the sensing capability of solid-state nanopores for size characterization of single nanoparticles by observing the ionic current blockades during their electrophoretic translocation through nanopores. By using nanopores that are a bit larger than the particles, size characterization of silver nanoparticles with different diameters were successfully realized due to conductance change caused by their physical occupying. Resistive pulse sensing with nanopores here will allow people to measure the dimension of single nanoparticles or proteins in real time in the near future. It is significant for its potential applications of investigation of structural biology and proteomics.

The shortage of fresh water resources is a major challenge that should be resolved by the society, and sea water desalination is a potential way to solve this problem at present. With the development of nanopore technology, various kinds of nanopore sea water desalination methods have been reported, by controlling the pore size and functionalizing the nanopore, the nanopore can effectively reject salt ions. Here we show, by performing molecular dynamics simulations, that a double graphene nanopore system with charged nanopores can successfully remove K+ and Cl− ions from the water in the area separated by the two membranes under the electric field and people can obtain fresh water without salt. However, if the atoms around the nanopore were not charged, the double pore system would not be able to act as a water purifier, where ions can not be separated from water by electric field forces alone. Based on the result of our work, the charged double pore system has the potential to be used in seawater desalination in the future.

Gangliosides, widely distributed in tissues and body fluid, have been connected to the therapy of cancer and brain related diseases. The complexity of the gangliosides structures with different polar moieties coexisting, a carbohydrate moiety and a ceramide chain, make it a great challenge in separation and analysis science. This study aimed to develop a strategy on the basis of high-accuracy data collected by an offline two-dimensional (2D) supercritical fluid chromatography (SFC) × reversed phase liquid chromatography (RPLC)/quadrupole time-of-flight (Q-ToF) system, and to integrate an in-house library with self-developed software for fast screening and identification of gangliosides from a complex sample (swine brain extract). Subsequent positive-mode MS/MS was used to validate the identified gangliosides. Finally, 153 gangliosides were separated and 79 of them were identified by the in-house library and self-developed software, 4-fold more than those by manual identification (18 gangliosides). Among the identified ones, 20 were detected in swine brain for the first time. This study established an offline 2D SFC × RPLC system and provided a new method for fast screening and automatic identification of gangliosides in complex mixtures. It will be conducive to further study of biological functions of gangliosides.

Most of the studies in humid catchments have discovered a similar conclusion that runoff generation was dominated by overland flow and interflow. However, the Hemuqiao watershed with long-t...

The relative stability of three-dimensional icosahedral quasicrystals in multi-component systems has been investigated based on a coupled-mode Swift-Hohenberg model with two-length-scales. A recently developed projection method, which provides a unified numerical framework to study periodic crystals and quasicrystals, is used to compute free energies to high accuracy. Compared with traditional approaches, the advantage of the projection method has been also discussed detailedly. A rigorous and systematical computation demonstrates that three-dimensional icosahedral quasicrystal, two-dimensional decagonal quasicrystal are stable phases in such a simple multi-component coupled-mode Swift-Hohenberg model. The result extends the multiple length-scales interaction mechanism which can stabilize quasicrystals from single-component to multi-component systems., 17 pages, 11 figures

A novel HTIB-promoted direct intramolecular dehydrogenative C–S bond coupling reaction of thioamides has been developed to provide 1,3-benzothiazine derivatives in good yields. The reaction proceeds smoothly to reach completion at room temperature within 1 min under metal-free conditions. This protocol provides a mild and efficient strategy for the synthesis of six-membered N,S-containing heterocycles. Preliminary mechanistic studies indicate that a spirocyclic intermediate might be involved.

Nanopore sensing has emerged as a versatile approach to detection and identification of biomolecules. Presently, researchers rely on experience and intuition for choosing or modifying the nanopores to detect a target analyte. The field would greatly benefit from a computational method that could relate the atomic-scale geometry of the nanopores and analytes to the blockade nanopore currents they produce. Existing computational methods are either computationally too expensive to be used routinely in experimental laboratories or not sensitive enough to account for the atomic structure of the pore and the analytes. Here, we demonstrate a robust and inexpensive computational approach-the steric exclusion model (SEM) of nanopore conductance-that is orders of magnitude more efficient than all-atom MD and yet is sensitive enough to account for the atomic structure of the nanopore and the analyte. The method combines the computational efficiency of a finite element solver with the atomic precision of a nanopore conductance map to yield unprecedented speed and accuracy of ionic current prediction. We validate our SEM approach through comparison with the current blockades computed using the all-atom molecular dynamics method for a range of proteins confined to a solid-state nanopore, biological channels embedded in a lipid bilayer membranes, and blockade currents produced by DNA homopolymers in MspA. We illustrate potential applications of SEM by computing blockade currents produced by nucleosome proteins in a solid-state nanopore, individual amino acids in MspA, and by testing the effect of point mutations on amino acid distinguishability. We expect our SEM approach to become an integral part of future development of the nanopore sensing field.

A new tandem arylation/nucleophilic addition/fragmentation/C–S bond formation reaction involving diaryliodonium salts as electrophiles was developed with Cu(OTf)2 as the catalyst. A series of unexpected bis(arylthio)imine derivatives were generated in good yields. The reaction proceeds under mild conditions, and the bis(arylthio)imines are readily transformed to other useful products.

Nanopore devices have attracted a lot of attention for their potential application in DNA sequencing. Here, we study how an occluding object placed near a nanopore affects its access resistance by integrating an atomic force microscopy with a nanopore sensor. It is found that there exists a critical hemisphere around the nanopore, inside which the tip of an atomic force microscopy will affect the ionic current. The radius of this hemisphere, which is a bit smaller than the theoretical capture radius of ions, increases linearly with the applied bias voltage and quadratically with the nanopore diameter, but is independent of the operation modes and scanning speeds of the atomic force microscopy. A theoretical model is also proposed to describe how the tip position and geometrical parameters affect the access resistance.

A whole-cell bioelectrochemical biosensing system for amperometric detection of riboflavin was developed. A "bioelectrochemical wire" (BW) consisting of riboflavin and cytochrome C between Shewanella oneidensis MR-1 and electrode was characterized. Typically, a strong electrochemical response was observed when riboflavin (VB2) was added to reinforce this BW. Impressively, the electrochemical response of riboflavin with this BW was over 200 times higher than that without bacteria. Uniquely, this electron rewiring process enabled the development of a biosensing system for amperometric detection of riboflavin. Remarkably, this amperometric method showed high sensitivity (LOD = 2.2 nM, S/N = 3), wide linear range (5 nM ∼ 10 μM, 3 orders of magnitude), good selectivity, and high resistance to interferences. Additionally, the developed amperometric method featured good stability and reusability. It was further applied for accurate and reliable determination of riboflavin in real conditions including food, pharmaceutical, and clinical samples without pretreatment. Both the cost-effectiveness and robustness make this whole-cell amperometric system ideal for practical applications. This work demonstrated the power of bioelectrochemical signal amplification with exoelectrogen and also provided a new idea for development of versatile whole-cell amperometric biosensors.

Optical nanopore methods are widely believed to be practical approaches to address the flicker noise and the throughput limitations of nanopore detection. However, most optical nanopore methods in the literature are based on fluorescent labeling, which perplexes the detection operation and limits their applications. In this paper, we demonstrate a brand new optical nanopore technique named “scattering nanopore method”. This method achieves single nanopore readouts without the introduction of dyes by detecting scattering light through a single subwavelength aperture on Au film. The single particle induced optical fluctuations could be detected simultaneously with the nanopore ionic current readouts. The method we demonstrated here opens a new direction for nanopore sensing of single particles, even single molecules in the near future.

An environmentally benign and homogeneous base-free route for 5-hydroxymethyl-2-furfural (HMF) aerobic oxidation to 2,5-furandicarboxylic acid (FDCA) in water was reported using Mg–Al–CO3 hydrotalcite-supported Pd nanoparticles (xPd/HT-n) as catalyst. The influences of the Mg/Al molar ratio of hydrotalcite and Pd loading amount on the catalytic performance of these catalysts were originally systematically investigated. These catalysts exhibited excellent catalytic activity and FDCA selectivity in the HMF oxidation, especially for 2%Pd/HT-5 and 2%Pd/HT-6; >99.9% FDCA yields were achieved for 8 h under ambient pressure and homogeneous base-free conditions. The remarkably improved catalytic performance could be attributed to the suitable basicity of the Mg–Al–CO3 hydrotalcite and the abundant OH– groups on the surface of hydrotalcite. The plausible reaction mechanism was proposed based on the results of a series of controlled experiments. Furthermore, these catalysts were quite stable and could be reused at ...

Additive manufacturing (AM) including Stereolithography (SLA) and more recent 3D printing derivatives is an innovative manufacturing technology, where objects can be manufactured by accumulation of successive layers of materials. Such technology enables the fabrication of highly customized radar absorbing materials (RAM) and novel RAM structures. The microwave absorption, printability, complex electromagnetic parameters were measured, acrylic ester photopolymer with carbon nanotubes (CNTs) content ranging from 0.5% to 1.5% prepared with digital masking AM technology. Good dispersion and the content of CNTs have major influences on the successful preparation. The printability limit of multiwalled CNT is found to be 1.6%.The maximum absorption of 6 mm-thick composites is measured to be −15.98 dB with 1.5% CNT content. The real part ( ) of permittivity increases from 2.5 to 7 and the imaginary part ( ) of permittivity increases from 0.2 to 1.0 with the increasing content of CNTs. Frequencies, thickness, uniformly distribution of CNT and CNT content are the main factors affecting the RAM properties. The calculated reflection loss, for 12 mm-thick composites, are −7 dB, −26 dB, and −34 dB for 0.5%, 1%, and 1.5% of CNT contents, respectively, and the matching frequency shifts to lower frequencies with the increase of thickness or CNT content, which is in agreement with electromagetic theory and experiment results. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

YAG and Yb:YAG transparent ceramic nanopowders for laser crystal were synthesized by microwave-assisted alkoxide hydrolysis precipitation method. The YAG and Yb:YAG nanopowders were characterized by differential thermal analysis and thermo gravimetric analysis (DTA-TG), infrared spectrum (IR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and photoluminescence (PL) spectrum. The results show that the crystallizing temperature of the precursor of YAG and Yb:YAG is about 930 °C. The pure phase YAG and Yb:YAG nanopowders can be obtained at microwave radiation power of 385 W, microwave radiation time of 30 min and sintering temperature of 1100 °C. The average particle size of YAG is about 120 nm. Yb:YAG is uniform sphere and the average sizes is about 100 nm. The intensity of luminescence of Yb:YAG nanopowders decreased with the increasing of microware time. The maximum luminous intensity of the Yb:YAG nanopowders can be obtained when the microwave radiation is 30 min.

Although microbial fuel cells (MFCs) is considered as one of the most promising technology for renewable energy harvesting, low power output still accounts one of the bottlenecks and limits its further development. In this work, it is found that Cu(2+) (0.1μgL(-1)-0.1mgL(-1)) or Cd(2+) (0.1μgL(-1)-1mgL(-1)) significantly improve the electricity generation in MFCs. The maximum power output achieved with trace level of Cu(2+) (∼6nM) or Cd(2+) (∼5nM) is 1.3 times and 1.6 times higher than that of the control, respectively. Further analysis verifies that addition of Cu(2+) or Cd(2+) effectively improves riboflavin production and bacteria attachment on the electrode, which enhances bacterial extracellular electron transfer (EET) in MFCs. These results unveil the mechanism for power output enhancement by Cu(2+) or Cd(2+) addition, and suggest that metal ion addition should be a promising strategy to enhance EET as well as power generation of MFCs.

The Y3Al5O12 (YAG) nanocrystals were synthesized by ultrasound-assisted and ultrasound-microwave-assisted alkoxide hydrolysis precipitation methods. The structures and morphology of the YAG were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesis kinetics of two kinds of YAG nanocrystals was investigated using differential thermal analysis and thermo gravimetric analysis (DTA-TG) at different heating rates in argon gas. The results show that two kinds of YAG precursors have one obvious endothermic peak at 315-600 K. The apparent activation energy of two kinds of YAG precursors was calculated using the Doyle-Ozawa and Kissinger methods, the coefficients of reaction order, frequency factor and kinetic equations were also determined. The average apparent activation energy for the YAG precursor prepared by ultrasound-microwave assisted was calculated to be 80.76 kJ·mol-1 higher than the YAG precursor prepared by ultrasound-assisted synthesis (56.56 kJ·mol-1).

The nano-sized TiCp/Al-Cu composites were fabricated using the self-propagating high-temperature synthesis (SHS) reaction of Al-Ti-CNT master alloys in molten aluminum alloys. The tensile strength and ductility of the alloys were simultaneously improved by the addition of nano-sized TiC particles. The yield strength, ultimate tensile strength and fracture strain of the 0.3 wt% nano-sized TiC particles reinforced Al-Cu matrix composite increased to 350 MPa, 554 MPa and 14.75%, improved by 15.5%, 14.2% and 123.5%, respectively, compared with the unreinforced Al-Cu alloy (303 MPa, 485 MPa and 6.6%). The enhanced mechanical properties are attributed to the refined α-Al dendrites, a larger amount of smaller θ′ precipitates and the dispersed nano-sized TiC particulates. This study provides a feasible method to fabricate the nano-sized TiCp/Al-Cu composites with superior strength and ductility.

The authors would like to call the reader's attention to the fact that unfortunately there was a mistake in Table 1 of this contribution.

The ongoing trade war between the United States and China is having profound impacts on the global economy. As recent studies have found substantial amounts of carbon dioxide and air pollution embedded in the global supply chains, the Sino-US trade war may also affect emissions and health burdens worldwide, which has not been quantified. Here, we estimate the potential changes in gross domestic product (GDP), anthropogenic emissions and particulate matter (PM2.5) related premature deaths worldwide under two Sino-US trade war scenarios. We find that for the US and China, the trade war would reduce their GDP and, less significantly, emissions and mortality, suggesting that the trade war is not an effective means of environmental protection. The trade war would increase both GDP and mortality in many developing regions, because of their increased production of goods targeted in the Sino-US trade war. Surprisingly, Western Europe and Latin America and Caribbean would have higher GDP but lower emissions and mortality, an economic and environmental win-win outcome as a net result of the complex changes in the global supply chains. Neighbour regions of the US and China such as Canada, Japan and Korea would also have higher GDP but lower mortality, because of reduced atmospheric transboundary transport from the US and China overcompensating for increased local emissions of these neighbours. The complex consequences of the Sino-US trade war highlight the strong inter-regional and economic-environmental linkage in support of a global collaborative strategy to foster economic growth and environmental protection.

The Wuliyasitai southern sag is an oil-rich area in the Erlian Basin. The geochemical characteristics of the organic matter were comprehensively analyzed by a combined investigation of Rock-Eval pyrolysis, molecular geochemistry, vitrinite reflectance, and thin section observation. The studied samples have vitrinite reflectance (Ro) values of 0.33–1.22% and pyrolysis parameter Tmax values of 424–456 °C, suggesting that organic matter is mainly present in the low mature to mature stage. The values of the abundance indicators including total organic carbon (TOC), chloroform bitumen “A,” potential hydrocarbon generation amount (PG), hydrogen index (HI), and total hydrocarbon (HC) suggest a good to very good hydrocarbon generation potential. The pyrolysis parameter Tmax and HI obtained imply that the samples are dominated by the type Ⅱ1-Ⅱ2 organic matter. The composition characteristics of n-alkanes, steranes, and terpanes confirm that the organic matter has mixed input sources. The Aershan Formation (K1ba) in the southeastern part of the sag show higher contributions of algae and bacteria due to fertilization by volcanic ash. The hydrocarbon generation threshold was determined from the hydrocarbon index (HCI), production index (PI), chloroform bitumen “A"/TOC, and HC/TOC. By analyzing the relationships between TOC and pyrolysis parameter HCI, chloroform bitumen “A”/TOC, the lower limits of the TOC values for effective source rocks were established to be 2.5 wt % in the K1bt1 and 1.5 wt % in the K1ba. The pristane/phytane (Pr/Ph), gammacerane/C31 22R hopane, C35/C34 homohopane and trace element ratios suggest that the source rocks are primarily deposited in a freshwater sub-oxidizing environment. The TOC and HI are negatively correlated with Pr/Ph, indicating that redox conditions play an important role in source rock preservation. Most molecular maturity parameters are not recommended owing to their poor correlations with Ro.

Ion transport through nanopores is a process of fundamental significance in nature and in engineering practice. Over the past decade, it has been found that the ion conductivity in nanopores could be drastically enhanced, and different mechanisms have been proposed to explain this observation. To date, most reported studies have been carried out with relatively dilute electrolytes, while ion transport in nanopores under high electrolyte concentrations (>1 M) has been rarely explored. Through systematic experimental and atomistic simulation studies with NaCl solutions, here we show that at high electrolyte concentrations, ion mobility in small nanopores could be significantly reduced from the corresponding bulk value. Subsequent molecular dynamics studies indicate that in addition to the low mobility of surface-bound ions in the Stern layer, enhanced pairing and collisions between partially dehydrated ions of opposite charges also make important contributions to the reduced ion mobility. Furthermore, we show that the extent of mobility reduction depends on the association constant between cations and anions in different electrolytes with a more drastic reduction for a larger association constant.

Nanopore sensor has been developed as a promising technology for DNA sequencing at the single-base resolution. However, the discrimination of homopolymers composed of guanines from other nucleotides has not been clearly revealed due to the easily formed G-quadruplex in aqueous buffers. In this work, we report that a tiny silicon nitride nanopore was used to sieve out G tetramers to make sure only homopolymers composed of guanines could translocate through the nanopore, then the 20-nucleotide long ssDNA homopolymers could be identified and differentiated. It is found that the size of the nucleotide plays a major role in affecting the current blockade as well as the dwell time while DNA is translocating through the nanopore. By the comparison of translocation behavior of ssDNA homopolymers composed of nucleotides with different volumes, it is found that smaller nucleotides can lead to higher translocation speed and lower current blockage, which is also found and validated for the 105-nucleotide long homopolymers. The studies performed in this work will improve our understanding of nanopore-based DNA sequencing at single-base level.

Owing to the widespread use of bisphenol analogues (BPs) as substitutes for bisphenol A (BPA), the presence of BPs in multiple environments is of increasing concern. However, there is a limited understanding of the effects of colloids on the distribution and risk assessment of BPs traditionally dissolved in surface water. In this study, seven BPs were investigated in both the truly dissolved (5 kDa) and colloidal (5 kDa to 1 μm) phases with water, with mean concentrations in the range of 71.6-671 ng/L and 5.84-76.6 ng/L, respectively. BPA and bisphenol S (BPS) were the dominant BPs in both phases, but a clear positive correlation was found between the adsorption contribution proportions of colloids to BPs and their hydrophobicity (octanol-water partition coefficient). The colloids contributed 50.4% of bisphenol AF, 33.4% of tetrabromobisphenol A, 25.2% of bisphenol F, 10.9% of BPA and 9.50% of BPS in the traditionally dissolved phase (1 μm), which suggests that colloids play an important role in regulating the transformation and transportation of BPs in aquatic environments. Based on BP concentrations in the truly dissolved phase, only moderate risk levels for BPs towards algae, daphnia and fish were posed, and no oestrogenic risk existed in the study area.