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Herein we report a practical and efficient copper-catalyzed approach for the conversion of various arenediazonium salts to the corresponding N-protected sulfonimidoyl fluorides. This operationally simple protocol tolerates a wide range of functional groups and can be applied to the late-stage modification of complex bioactive molecules. Furthermore, pharmaceutically important primary sulfonamides and sulfonimidamides derived from these valuable N-protected sulfonimidoyl fluoride units were prepared in minimal synthetic steps.

The dynamic changes in microbial diversity during the aerobic composting of agricultural crop straw with additives were evaluated using high-throughput sequencing at four phases of composting (mesophilic, thermophilic, cooling and maturation phases). In addition, the physicochemical parameters of the composting system were determined in this study. The fermentation time of the thermophilic period was prolonged with the addition of urea or urea combined with a microbial agent. The ratio of C/N and germination index variation indicated that the additives were favorable for composting, because the additives directly changed the physicochemical properties of the compost and had effects on the diversity and abundance of bacteria and fungi. The abundance of operational taxonomic units (OTUs), diversity index (Shannon) and richness index (Chao1) of fungi and bacteria were found to significantly increase when urea+microbial agents were added to straw in the thermophilic phase. The relative abundance of the predominant bacteria and fungi at the phylum and genus levels differed during different composting phases. The abundance of the phyla Firmicutes and Proteobacteria declined in the order of treatments SNW>SN>S (S is straw only compost; SN is straw+5 kg t−1 urea compost; and SNW is straw+5 kg t−1 urea+ 1 kg t−1 microbial agent compost) in the thermophilic phase. The abundance of the genera Staphylococcus, Bacillus and Thermobifida followed the same order in the mesophilic phase. Ascomycota accounted for more than 92% of the total fungal sequences. With the progression of the composting process, the abundance of Ascomycota decreased gradually. The abundance of Ascomycota followed the order of S>SN>SNW during the thermophilic phase. The abundance of Aspergillus accounted for 4–59% of the total abundance of fungi and increased during the first two sampling periods. Aspergillus abundance followed the order of SNW>SN>S. Additionally, principal component analysis (PCA) revealed that the community compositions in the straw and straw+urea treatments were similar, and that the bacterial communities in treatments S, SN and SNW in the mesophilic phase (at day 1) were different from those observed in three other phases (at days 5, 11, and 19, respectively), while the fungal communities showed only slight variations in their structure in response to changes in the composting process. Canonical correlation analysis (CCA) and redundancy analysis (RDA) showed that total carbon (TC), NO3−-N (NN), electrical conductivity (EC) and pH were highly correlated with community composition. Therefore, this study highlights that the additives are beneficial to straw composting and result in good quality compost.

Boosting sufficient Li+ ion mobility in Li4Ti5O12 (LTO) is crucial for high-rate performance lithium storage. Here, an ultrafast charge storage oxygen vacancy two-dimensional (2D) LTO nanosheet was successfully fabricated through a one-pot hydrothermal method. The selectively doped Al3+ into octahedron Li+/Ti4+ 16d sites not only provide bulk oxygen vacancy and appropriate distorted TiO6 octahedra to facilitate Li+ ions diffusion, but also serve as a "pillar" to stabilize the Ti-O framework. The oxygen vacancy lowers Li+ ion diffusion energy barrier. Moreover, the 2D structure provides open diffusion channels for fast Li+ ion transport. As a result, the sample shows excellent electrochemical performance for bifunctional lithium storage. As a lithium-ion battery anode, the capacity retention reaches 112.8 mA h g-1 after 5000 cycles at 40 C with a fading rate of 0.288% per 100 cycles. Meanwhile, as a lithium-ion capacitor anode, it exhibits an excellent rate capacity of 120 mA h g-1 after 5000 cycles at 500 C with nearly 100% Coulombic efficiency. The produced LTO shows much higher rate capacity and longer lifetime than the reported LTO. Density functional theory calculations also demonstrate that oxygen vacancy can facilitate Li+ ion diffusion kinetics. The relationship between oxygen vacancy content and Li+ ions diffusion energy barrier in LTO is quantified. This work pioneers a defect engineering strategy for synthesized high-performance electrode materials.

The strong desire for a circular economy makes obtaining fuels and chemicals via plastic degradation an important research topic in the 21st century. Here, the first example of the H2 -free polyethylene terephthalate (PET) conversion to BTX (benzene, toluene and xylene) was achieved by unlocking hidden hydrogen in the ethylene glycol part over Ru/Nb2 O5 catalyst. Among the whole process (hydrolysis, reforming and hydrogenolysis/decarboxylation), the parallel hydrogenolysis and decarboxylation were competing and the rate-determining step. Ru/Nb2 O5 exhibited superior hydrogenolysis and poorer decarboxylation performance in direct comparison with Ru/NiAl2 O4 , accordingly contributing to the distinct selectivity to alkyl aromatics among BTX. Ru species on Nb2 O5 , unlike those on NiAl2 O4 , showed more Ruδ+ species owing to the strong interaction between Ru and Nb2 O5 , restricting the undesired decarboxylation. Along with NbOx species for C-O bond activation, excellent reactivity towards the H2 -free conversion of PET back to BTX with alkyl aromatics as dominant species was achieved. This H2 -free system was also capable of converting common real PET plastics back to BTX, adding new options in the circular economy of PET.

Dramatic capacity fading and poor rate performance are two main obstacles that severely hamper the widespread application of the Si anode owing to its large volume variation during cycling and low intrinsic electrical conductivity. To mitigate these issues, free-standing N-doped porous carbon nanofibers sheathed pumpkin-like Si/C composites (Si/C-ZIF-8/CNFs) are designed and synthesized by electrospinning and carbonization methods, which present greatly enhanced electrochemical properties for lithium-ion battery anodes. This particular structure alleviates the volume variation, promotes the formation of stable solid electrolyte interphase (SEI) film, and improves the electrical conductivity. As a result, the as-obtained free-standing Si/C-ZIF-8/CNFs electrode delivers a high reversible capacity of 945.5 mA h g−1 at 0.2 A g−1 with a capacity retention of 64% for 150 cycles, and exhibits a reversible capacity of 538.6 mA h g−1 at 0.5 A g−1 over 500 cycles. Moreover, the full cell composed of a free-standing Si/C-ZIF-8/CNFs anode and commercial LiNi1/3Co1/3Mn1/3O2 (NCM) cathode shows a capacity of 63.4 mA h g−1 after 100 cycles at 0.2 C, which corresponds to a capacity retention of 60%. This rational design could provide a new path for the development of high-performance Si-based anodes.

High performance and low process cost are two contradictory issues, which limited the commercial application of Li4Ti5O12 (LTO). Here, defects and TiO2 co-enhanced LTO have been synthesized by a simple solid-state method. The crystal structure and morphology of the as-synthesized samples were characterized. The results show that the uniform nanoparticles with spinel structure contained defects and TiO2. Defects and TiO2 co-enhanced LTO shows outstanding reversible discharge capacity of 168.2 mAh g−1 at 1 C after 500 cycles. Further, it presents a stability discharge ability of 155 mAh g−1 at 55 °C at 1 C after 500 cycles. The advanced electrochemical performance could be attributed to the defects and TiO2 in LTO, which enhance conductivity and produce rich reaction interface, facilitating Li+ ion diffusion kinetics. The as-synthesized LTO shows high performance in conjunction with low process cost.

Hierarchical lithium titanate@erbium oxide (Li4Ti5O12@Er2O3) microspheres from coating to doping were successfully synthesised by a simple and scalable one-step co-precipitation method. Microscopic observations revealed that the Li4Ti5O12@Er2O3 microspheres present a well-defined hierarchical structure and that Li4Ti5O12 is coated by the Er2O3 layer. The X-ray photoelectron spectroscopy (XPS) results demonstrate that partial Ti4+ is reduced to Ti3+ and induces oxygen vacancy because partial Er3+ dope into octahedral 16d Li+/Ti4+ sites of Li4Ti5O12. Owing to the hierarchical microsphere structure, Er2O3 coating, and Er3+ doping, the material exhibits excess rate capacity (183.7 mAh g-1 at 30C). The hierarchical microsphere structure shortens the diffusion pathways for Li+ ions. The Er2O3 coating on the surface reduces the adverse interface reaction. Importantly, oxygen vacancy induced by Er3+ doping enhances Li+ ion diffusion kinetics and offers extra space to store Li+ ions, which endows this sample with excess rate capacity.

Wood fiber/polyethylene composite (WFPEC) is composed of a natural wood fiber and a recyclable polyethylene plastic, which is normally used as an environmental protection composite material. However, better knowledge of chip formation and surface damage mechanism of WFPEC is essential to improve its machinability for extending exterior and interior applications. In this article, machinability of WFPEC was investigated by analyzing the disparity between cutting efficiency and surface quality through a group of orthogonal cutting experiments with change of cutting depth. The chip formation process was recorded by a high-speed camera system with 5000 frames per second. Surface topography was observed by a scanning electron microscope. The results showed that the chip morphology changed from continuous cutting governed by a continuous shearing process under the shallow cutting depth, to a discontinuous cutting governed by plastic fracture under the deep cutting depth ahead of the tool tip. Flattened matrix was the main form of surface topography caused by shallow cutting depth, while matrix-fiber tearing was caused by deep cutting depth. Pullout/fracture and debonding of fibers were related to the fiber orientation angle and the diameter of fiber bundles, but not to the cutting depth. Taken together, the toughness of the workpiece material in the cutting region decreased with the increase in cutting depth. To avoid matrix-fiber tearing, shallow cutting depth should be used during finishing to maintain surface quality. In contrast, pre-cutting can be performed with a deep cutting depth in order to improve the cutting efficiency.

Prussian blue (PB) and its analogues (PBAs) are considered to be cathode materials for practical applications in sodium-ion batteries due to their open three-dimensional structure and low cost. However, PBAs synthesized by traditional methods generally have poor crystallinity and a high content of [Fe(CN)6] vacancy defects and coordinate water, which not only affect the Na+-storage capacity of PBAs, but also hinder Na+ transportation in the bulk phase and lead to a deterioration in electrochemical performance. Therefore, we propose an unconventional two-phase method to synthesize PBAs. Due to the unique reaction environment of the two-phase method, the reaction time lasts long, which is advantageous to control the synthesis of PBAs to ensure high crystallinity, low defects, and a suitable size. The as-prepared PBA at optimal condition delivers a high initial discharge specific capacity of 152 mA h g−1 at 0.2 C (1 C = 170 mA h g−1), 110 and 105 mA h g−1 even at high current densities of 10 C and 20 C,respectively, as well as a capacity retention of 84% after 200 cycles at 2 C. In particular, superior electrochemical performances also suggested that the two-phase method could be extended to the synthesis of other types of PBAs, such as Mn-PBAs and Co-PBAs, or even more materials with poor crystallinity due to rapid nucleation and growth.

High‐mountain areas such as the Tibeto‐Himalayan region (THR) host cold‐adapted biota expected to be sensitive to anthropogenic climate change. Meconopsis is a representative endangered genus confined to alpine meadow or subnival habitats in the THR. We used climate‐niche factor analysis to study the vulnerability of ten Meconopsis species to climate change, comparing current climate (representative of 1960–1990) to future climate scenarios (2070: average 2061–2080). For these ten Meconopsis species, we then identified potential future climate refugia and determined optimal routes for each species to disperse to the proposed refugia. Our results indicate that for the ten Meconopsis species, the regions with low vulnerability to climate change in the THR are the central Qinghai‐Tibet Plateau, the Hengduan Mountains (HDM), the eastern Himalayas, and the West Qinling Mountain (WQL), and can be considered potential future climate refugia. Under future climate change, we found for the ten Meconopsis species potential dispersal routes to three of the four identified refugia: the HDM, the eastern Himalayas, and the WQL. Our results suggest that past refugia on the THR will also be the future climate refugia for the ten Meconopsis species, and these species may potentially persist in multiple future climate refugia, likely reducing risks from climate change. Furthermore, climate change may affect the threat ranking of Red Listed Species for Meconopsis species, as Least Concern species were estimated to become more vulnerable to climate change than the only Near Threatened species., Under future climate change, Meconopsis species may persist in multiple refugia on the Tibeto‐Himalayan region, with these areas also coinciding with past glacial refugia. Climate change may affect the threat ranking of Red Listed Species, as Least Concern species were estimated to be more vulnerable to climate change than Near Threatened species.

A facile method for efficient synthesis of core-shell composite material was proposed. In this method, the silica microspheres were co-modified with metal organic framework (MOF-235) and polyethylene glycol polymer (PEG) and used as mixed-mode stationary phase (MOF-235@PEG@silica) for high-performance liquid chromatography. Elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller etc. methods were used to investigate the properties of the core-shell composite material. The MOF-235@PEG@silica stationary phase showed flexible selectivity for the separation of both hydrophilic and hydrophobic compounds especially for the separation of nine alkaloids, which showed superior hydrophilic separation performance than previous MOF-based composite stationary phases. Some factors including the pH of buffer salt, the ratio of organic phase and water phase in the mobile phase have been investigated, suggesting that the chromatographic retention mechanism of the column was a mixed mode of hydrophilic and reversed phase. The composite material also showed excellent chromatographic repeatability with the RSDs of the retention time found to be 0.2%–0.6% (n = 10) and the standard addition test in the actual sample proved that it can be used for practical sample analysis. In short, it provided a general way for preparing MOFs-based composites as mixed-mode chromatographic stationary phases, and changed the current status of MOF-based composite materials as single mode chromatographic stationary phases.

Electrodeposition is an effective method to prepare various materials. We have established a bipolar electrodeposition system assisted by a constant magnetic field to fabricate a Co/Fe/Ni phytate catalyst with good electrocatalytic activity for overall water splitting. The effects of magnetic and electric fields on the catalytic properties of the material were studied. The catalyst prepared with an N-pole magnetic field (NPMF) exhibited good overall water splitting performance. Benefiting from the synergistic effect of the Co/Fe/Ni-phytate and the advantages of the N-pole magnetic field the NPMF electrode has a continuous 25 hours high-efficiency hydrogen evolution and oxygen evolution reaction at a current density of 100 mA cm-2 in1.0 M KOH compared with commercial RuO2 and Pt/C. Bipolar electrodeposition with a constant magnetic field is thus an efficient means to fabricate electrocatalytic water splitting catalysts.

This paper presents an extended cell transmission model to simulate an emergency evacuation of crowd in a supermarket scenario. The supermarket scenario with a daily shopping, an emergency exit and multiple parallel shelves is discretized into a set of regular hexagonal cells. First, we verify the validity of the model by comparing the results of the model with actual data obtained from a reported pedestrian evacuation experiment. To improve the realism of the simulation, we then include three characteristics of human behavior, the unadventurous effect, inertial effect, and panic psychology, in the model as parameters and apply the extended model to the supermarket scenario. By analyzing the pedestrian density distribution, fundamental diagrams, route choice, and total evacuation time, we determine that the parameters have a significant influence on the evacuation process. By establishing a minimization model, we confirm that the total evacuation time is the least when the pedestrians’ familiarity with the emergency exit is close to the ratio of the width of the emergency exit to the total width of the two exits. Moreover, by comparing two different methods to choose exits, we can conclude that the approach, by which all pedestrians choose the closer exit, is not always the most efficient evacuation strategy. This study is conducive to devise evacuation plans and design exit layouts in facilities similar to supermarkets.

Lignin is constructed from methoxylated phenylpropanoid with plenty of hydroxys and methoxys. Its conversion to valuable products is extremely attractive but especially challenging without addition...

Silicoaluminophosphate-34 (SAPO-34) molecular sieves have important applications in the petrochemical industry as a result of their shape selectivity and suitable acidity. In this work, nanoaggregate SAPO-34 with a large external surface area was obtained by dissolving pseudoboehmite and tetraethylorthosilicate in an aqueous solution of tetraethylammonium hydroxide and subsequently adding phosphoric acid. After hydrolysis in an alkaline solution, the aluminum and silicon precursors exist as Al(OH)4− and SiO2(OH)−, respectively; this is beneficial for rapid nucleation and the formation of nanoaggregates in the following crystallization process. Additionally, to study the effect of the external surface area and pore size on the catalytic performance of different SAPO-34 structures, the alcoholysis of furfuryl alcohol to ethyl levulinate (EL) was chosen as a model reaction. In a comparison with the traditional cube-like SAPO-34, nanoaggregate SAPO-34 generated a higher yield of 74.1% of EL, whereas that with cube-like SAPO-34 was only 19.9%. Moreover, the stability was remarkably enhanced for nanoaggregate SAPO-34. The greater external surface area and larger number of external surface acid sites are helpful in improving the catalytic performance and avoiding coke deposition.

Research on perfluoroalkyl ether carboxylic acids (PFECAs) as alternatives for perfluoroalkyl substances continues with the goal of protecting the environment. However, very little is known about t...

Although perfluoroalkyl ether carboxylic (PFECAs) and sulfonic acids (PFESAs) have been widely detected in environmental matrices, their occurrence in humans and impact on human health remains insufficiently understood. Here, we report on 13 PFECAs and PFESAs in 977 sera samples collected from residents living near a fluorochemical plant in Shandong, China. The sum concentration of these emerging PFECAs accounted for 13% of the total PFASs in the serum of the participants, with the frequent detection of several PFECAs (>95%) (PFMOAA, PFO4DA, and PFO5DoDA at median concentrations of 12.91, 0.142, and 0.987 ng/mL, respectively) and PFESAs (98.7%) (Nafion byproduct 2 at a median concentration of 0.097 ng/mL). Serum PFMOAA, PFO5DoDA, and 6:2 Cl-PFESA levels were significantly higher in males than in females. Positive relationships were observed between age and PFMOAA, 6:2 Cl-PFESA, and H-PFMO2OSA levels, whereas HFPO-TA and PFO5DoDA serum concentrations in the 0-40-year age group were lower than that in the >40-year age group. Furthermore, multivariate linear regression models and sensitivity analyses showed positive associations among PFO5DoDA levels, elevated lipid parameters (cholesterol, low-density lipoprotein cholesterol, and triglycerides), liver function markers (albumin levels and alanine transaminase, aspartate aminotransferase, and glutamyl transpeptidase activities), and uric acid levels. Thus, our results suggest potential health risks from exposure to novel PFESAs and PFECAs (especially PFO5DoDA).

We concern the modal choice of commuters in a transport system comprising a highway and two transit lines. For the operation of the transit lines, two market structures are considered: monopolistic...

Chemical hydrogen storage ammonia borane has attracted extensive attention as a method of efficient utilization of hydrogen energy. The high-efficiency catalysts are the main factor restricting the hydrogen production of ammonia borane. In this paper, the synergistic effect of Co and CoOx supported on graphene (named Co-CoOx @GO-II) promotes the efficient hydrogen production of ammonia borane, and its catalytic hydrogen production rate can reach 5813 mL min-1 gCo -1 at 298 K, the corresponding TOF is 15.33 min-1 . After five stability tests, Co-CoOx @GO-II maintained 65% of its original catalytic performance. The synergy of metal and metal oxide and the defects in the atomic arrangement ensure the catalytic activity, the large specific surface area of graphene ensures the dispersion and fixation. This strategy may provide a possibility to design high-performance transition metal catalysts.

Platinum-silver alloy nanoparticles (PtxAgy NPs) were synthesized in a molten salt system without using any organic surfactants or solvents; the catalytic role of Ag in the methanol electrooxidation reaction (MOR) in alkaline electrolyte over PtxAgy NPs was investigated. The TEM images suggest that Pt52Ag48 nanotubes (NTs) can be obtained when the Pt/Ag ratio in the molten salt precursor reaches 1. The methanol electrooxidation reaction test results indicate that the Pt52Ag48 NTs with a clean surface exhibits a much better catalytic performance than the conventional Pt black in MOR. Meanwhile, the catalytic activity of the Pt52Ag48 NTs is greatly related to the positive potential limit; the peak current of MOR reaches 1.61 mA/μgPt with a positive potential limit from –1.0 to 0.5 V (vs. SCE), which is 1.92 times higher than that with a positive potential limit from –1.0 to 0.1 V (vs. SCE). The Ag element in the surface layer of PtxAgy alloy may promote the MOR through a redox process during the electrochemical cycle. The insight shown in work should be beneficial to the application of PtxAgy alloy in the direct methanol fuel cells (DMFCs).

There are limited data regarding low lead exposure and iron status in Chinese children. This study aimed to examine the association between low-level lead exposure and iron status in a large population of children aged 0–5 years. We reviewed the records of children aged 0–5 years who had blood lead, iron, ferritin, and hemoglobin measurements during 2014–2017 at the Guangdong Women and Children Hospital. We identified 17,486 children with a blood lead level

Respiratory droplets are bioaerosols that originate from the respiratory tract. Knowing their deposition characteristics during exhalation would facilitate the understanding of the source of large ...

Single-responsive hydrogels will be limited in application. Therefore, the development of hydrogels with multi-stimulus response characteristics will greatly broaden its application, such as smart ...

6:2 Chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) possesses a similar structure to perfluorooctanesulfonate (PFOS) and is the third most important polyfluoroalkyl/perfluoroalkyl substance (PFAS) found in the general population of China. Studies have indicated that 6:2 Cl-PFESA exhibits a stronger bioaccumulative and toxicological potential than PFOS and is thus of considerable environmental concern. Here, the binding characteristics of PFOS and 6:2 Cl-PFESA to human serum albumin (HSA) were explored based on in vitro and in silico methods. In the cell uptake assays, supplementation of HSA in the culture medium hindered diffusion of PFOS and 6:2 Cl-PFESA from the medium into cells. With the addition of 0.5, 10, and 200 μM HSA in the culture medium, the PFOS concentration in cells decreased by 21.4%, 78.1%, and 92.8%, whereas the 6:2 Cl-PFESA concentration in cells decreased by 28.4%, 84.4%, and 93.9%, respectively. Although no statistically significant difference between the reduction of PFOS and 6:2 Cl-PFESA was observed with 200 μM HSA in medium, the significant decrease in cellular 6:2 Cl-PFESA than PFOS after addition of 0.5 and 10 μM HSA implied that 6:2 Cl-PFESA had a stronger binding affinity than PFOS to HSA. Ultrafiltration centrifugation also suggested that 6:2 Cl-PFESA (Kd = 16.7 μM) had a higher affinity than PFOS (Kd = 30.7 μM) to HSA, though the binding molar ratios were similar, with 1 M HSA binding to 3-4 M PFOS/6:2 Cl-PFESA. Limited proteolysis further identified the core HSA peptides that bind to PFOS (peptide II, aa 189-457) and 6:2 Cl-PFESA (peptide I, aa 39-310). Using purified core peptides, 6:2 Cl-PFESA showed a stronger binding affinity than PFOS to both peptides I and II. The binding modes indicated that the chlorine and oxygen atoms in 6:2 Cl-PFESA were likely responsible for its preferential binding to Sudlow site I than to Trp214 or Sudlow site II, with the latter being the optimal binding site for PFOS. Overall, the stronger binding affinity of 6:2 Cl-PFESA to HSA may contribute to its higher bioaccumulation potential than PFOS.

Glyphosate-tolerant soybean is the most widely planted genetically modified crop worldwide. However, soybean remains recalcitrant to routine transformation because of the low infection efficiency of Agrobacterium to soybean and lack of useful selectable markers. In this study, several Agrobacterium strains and cell densities were compared by transient expression of the GUS gene. The results showed that Agrobacterium strain Ag10 at cell densities of OD600 of 0.6–0.9 yielded the highest infection efficiency in Agrobacterium-mediated soybean cotyledonary node transformation system. Meanwhile, a simple and rapid method was developed for identification of glyphosate tolerance in putative T0 transgenic plants, consisting of spotting plantlets with 1 µL Roundup®. The whole cycle of genetic transformation could be shortened to about 3 mon by highly efficient selection with glyphosate during the transformation process and application of the spot assay in putative T0 transgenic plantlets. The transformation frequency ranged from 2.9 to 5.6%. This study provides an improved protocol for development and identification of glyphosate-tolerant transgenic soybeans.

We investigate the quantum tunneling properties through a square potential barrier in the $$\alpha -T_3$$ model with an effective mass term. The additional mass term can be induced by the effective magnetic field or the site energy difference on different sublattices, in which the flat band is located at the center or edge of the band gap band, respectively. The linear dispersion in the $$\alpha -T_3$$ model is modified in the presence of the mass term, leading to the destroying of the Klein tunneling for the normal incidence. It is demonstrated that the additional mass term in general suppresses the transmission. When the flat band is located at the band edge, the super-Klein tunneling and the resonant tunneling are considerably suppressed with the increase in the energy gap. For the dice lattice that $$\alpha =1$$, the super-Klein tunneling is preserved when the flat band is located at the center of the band gap.

In this paper, norbornene imidazolium hexafluorophosphate (NM-MIm-PF6) was modified on the surface of aminopropyl silica by ring-opening metathesis polymerization (ROMP), and then oligo(ethylene glycol) methacrylate (OEGMA) were grafted on the surface by atom transfer radical polymerization (ATRP). Some characterizations in this article confirmed that the synthesis of P(NM-MIm-PF6)-Si-POEGMA (P1-Si-P2) is successful. The P1-Si-P2 can separate sugars, amino acids, sulfonamides in a hydrophilic interaction mode and alkyl benzene, polycyclic aromatic hydrocarbon in a reverse phase mode. The experiment also found that the column has typical characteristics of hydrophobic/hydrophilic separation mechanism. Compared to single hydrophobic C18 column and single hydrophilic Si-NH2 column, this P1-Si-P2 shows certain advantages.

Quantifying anthropogenic climate change vulnerability is essential for estimating the risk of species extinction and developing conservation strategies. The Magnolia genus is widespread in the Americas and Asia, with nearly half of species currently threatened. Here, we used climate-niche factor analysis to study the vulnerability of Magnolia species to future climate change. We found that the vulnerability of Magnolia species to future climate change is negatively related to range size. We further identified that narrow-ranged Magnolia species distributed in Asia are more vulnerable than those distributed in the Americas, with protected area coverage also lower in Asia than the Americas. Moreover, the conservation status ranking of Magnolia species classified by the IUCN Red List will likely be changed under climate change, as some Near Threatened and Least Concern species were estimated to be more vulnerable to climate change than species currently classified as Endangered. Our results highlight that conservation assessments, policies and actions need to consider spatial vulnerabilities of species to climate change.

The design and implementation of a real-time breakdown voltage and on-chip temperature monitoring system for single photon avalanche diodes (SPADs) is described in this work. In the system, an on-chip shaded (active area of the detector covered by a metal layer) SPAD is used to provide a dark count rate for the breakdown voltage and temperature calculation. A bias circuit was designed to provide a bias voltage scanning for the shaded SPAD. A microcontroller records the pulses from the anode of the shaded SPAD and calculates its real-time dark count rate. An algorithm was developed for the microcontroller to calculate the SPAD&rsquo, s breakdown voltage and the on-chip temperature in real time. Experimental results show that the system is capable of measuring the SPAD&rsquo, s breakdown voltage with a mismatch of less than 1.2%. Results also show that the system can provide real-time on-chip temperature monitoring for the range of &minus, 10 to 50 &deg, C with errors of less than 1.7 &deg, C. The system proposed can be used for the real-time SPAD&rsquo, s breakdown voltage and temperature estimation for dual-SPADs or SPAD arrays chip where identical detectors are fabricated on the same chip and one or more dummy SPADs are shaded. With the breakdown voltage and the on-chip temperature monitoring, intelligent control logic can be developed to optimize the performance of the SPAD-based photon counting system by adjusting the parameters such as excess bias voltage and dead-time. This is particularly useful for SPAD photon counting systems used in complex working environments such as the applications in 3D LIDAR imaging for geodesy, geology, geomorphology, forestry, atmospheric physics and autonomous vehicles.

Aim: The plant species sharing ancestors now disjunctly distributed in eastern Asia (EAS) and eastern North America (ENA) have long been a biogeographic puzzle. Species within the EAS–ENA disjunct genera are presumed to exhibit niche conservatism, the tendency of closely related species to be more ecologically similar, reflecting lineages’ common evolutionary history. However, the hypothesis has not been well examined at the species level. Location: EAS and ENA. Time period: Current. Major taxa studied: Species within the EAS–ENA disjunct genera. Methods: We compiled data on climate, species occurrence, growth form, and phylogeny to examine niche conservatism. We first built a phylogenetic tree to select intercontinental congeneric pairwise species and obtained their divergence times. We then quantified the observed niche overlaps with Schoener’s D, which has a 0–1 range, based on species occurrence and climate of species’ native ranges. To obtain projected distributions, each species’ niche was projected to the non-native region using ensemble ecological niche models. Projected-related niche overlaps were then calculated using projected distributions and the corresponding climatic conditions. Results: Average observed niche overlaps of congeneric pairwise species were relatively small:.124,.211 and.109 for all, herbaceous and woody species, respectively. Both observed and projected-related niche overlaps had significant negative relationships with divergence times of intercontinental congeneric pairwise species, with niche overlap for herbaceous species being higher than that for woody plants when controlling for divergence times. Main conclusions: We conclude that the significant negative relationships between niche overlap and divergence times of congeneric pairwise species confirm niche conservatism among species of EAS–ENA disjunct plants and that the extent of niche conservatism is slightly different for herbaceous and woody plants. These findings suggest the potential role of allopatric speciation in EAS, and could help to understand the evolutionary history and the Asian-bias diversity pattern of the EAS–ENA disjunct plants.

This paper proposes an adaptive control scheme for hypersonic vehicle with external disturbances, parametric uncertainties, actuator failures, input saturation and state constraints. Firstly, the longitudinal model of generic hypersonic vehicle is divided into velocity subsystem and altitude subsystem. Secondly, based on the tangent barrier Lyapunov function and auxiliary system, two adaptive fault tolerant controllers are designed for velocity subsystem and altitude subsystem, respectively, which can solve the problem of input saturation. By using the controllers, the flight states containing the angle of attack, flight path angle, pitch angle and pitch angle rate can be guaranteed in prospective ranges. Finally, the Lyapunov stability theory and numerical simulations are adopted to verify the effectiveness of the presented controllers.

A magnetic solid-phase extraction (MSPE) technique coupled with high performance liquid chromatography (HPLC) was developed and used for bioaccumulation investigation of bisphenol A (BPA) in HepG2 cells and zebrafishes. Cobalt magnetic polystyrene microsphere derived carbon (C-Co@PST) as an adsorbent was prepared by in situ polymerization reaction and further annealing treatment. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction were employed to confirm successful synthesis of C-Co@PST. A series of extraction parameters including the amount of the sorbent, the type of elute, extraction time and elution time were investigated to achieve high extraction efficiency. C-Co@PST based MSPE combined with HPLC was successfully established for bioaccumulation research of BPA in living creatures. It was found that the bioconcentration values of BPA in HepG2 cells underwent an increase, then a decrease, and finally reached an equilibrium level of 11.60 μg kg-1 at 8 h. The concentration of BPA in zebrafishes increased ranging from 6.05 μg kg-1 to 31.84 μg kg-1 over a culture time from 1 h to 12 h. Furthermore, linear and exponential models were employed to analyse the bioconcentration variation of BPA in organisms over the exposure time. Mathematical models have been developed to predict the transfer characteristics of BPA.

We concern the modal choice of commuters in a transport system comprising a highway, which is only used by autos, in parallel to a transit line, which is only used by buses. In the transport system, the in-vehicle congestion of passengers in bus carriages is treated as a negative externality cost of affecting the modal choice of commuters and commuters choose their travel modes according to the perceived travel costs of transport modes. We propose two trial-and-error operation schemes for the transport system without resorting to both the function of in-vehicle congestion costs and the distribution of perceived travel cost errors. In the first operation scheme, the manager (or the government) determines the transit fare charged from (or financial subsidy to) bus users from period to period so as to minimize the system time cost of the transport system. The second operation scheme is established from the viewpoint of a private firm that operates the public transit line. The operator determines the transit fare and bus run frequency from period to period in order to maximize its operating profit. Moreover, we demonstrate the effectiveness of the two operation schemes for optimizing the system time cost and the operating profit by both theoretical analyses and numerical examples.

The Feigenbaum-Kadanoff-Shenker equation for universal scaling in circle maps characterizes the quasiperiodic route to chaos. In this paper, using two different iterative methods, we construct all strictly decreasing continuous solutions. Furthermore, we present respectively the corresponding conditions to guarantee \begin{document}$ C^1 $\end{document} smoothness of those continuous solutions.

Non-invasive sonodynamic therapy (SDT) was developed because of its advantages of high penetration depth and low side effects; however, tumor hypoxia greatly restricts its therapeutic effect. In this study, we aimed to develop ideal O2 self-supplementing nanoparticles for imaging-guided enhanced sonodynamic therapy of tumors with the adept coalescence of biology with nanotechnology. Methods: Based on the natural enzyme system of red blood cells (RBC), biomimetic nanoparticles (QD@P)Rs were fabricated by encapsulating Ag2S quantum dots (QD) in RBC vesicle membranes. The anti-tumor drug PEITC was employed to increase the intracellular H2O2 concentration in tumor cells. Results: In vitro and in vivo experiments demonstrated excellent biocompatibility and prolonged blood circulation of (QD@P)Rs. Following oral administration of PEITC in mice to improve the H2O2 concentration, the enzyme in the nanoprobe catalyzed endogenous H2O2 to increase O2 content and effectively alleviate tumor hypoxia. Triggered by ultrasound under the guidance of fluorescence imaging, (QD@P)Rs generated reactive oxygen species (ROS) to induce tumor cell death, and the increased content of O2 significantly enhanced the effect of SDT. Conclusion: Ag2S QDs were used, for the first time, as a sonosensitizer in the SDT field. In this study, we integrated the advantages of the natural enzyme system and SDT to develop a novel approach for effective non-invasive treatment of cancer.

For the efficient and safe operation of experimental advanced superconducting tokamak (EAST), it is necessary to accurately identify and control the plasma current and its central position. In this article, neural network is used to identify the position of the plasma current center. The model trained by the basic back-propagation neural network can well match the relationship between the electromagnetic diagnostic signals and plasma current center positions. Both noisy simulation data and experimental data are applied to train and test the neural network inference model. Adding 0.1% noise to the training data is proven to improve the noise immunity of the inference model. Basic neural networks trained with both noisy simulation data and actual experimental data show good results with sufficient inputs; however, in both cases, the performance degrades significantly when only the poloidal field coil currents are given as inputs. For this kind of time-series problem, the dynamic neural network containing delay and feedback architecture is introduced, and an improved model requiring much fewer inputs is trained and tested for current center inference. Some parameters of this model are compared and analyzed in this article. With suitable neural network architecture, the mapping between the controlled variables (poloidal field coil currents) and response variables (plasma current center) can be well-established.

Earth-abundant sodium is a promising alternative to lithium in rechargeable batteries. However, graphite, the commercial anode material of lithium-ion batteries, cannot be used for sodium-ion batteries (SIBs). Herein, carbon block anodes with columnar nanopores constructed from amine-functionalized carbon nanosheets were synthesized using modified polyacrylonitrile as the carbon source through a simple and economical low-temperature pyrolysis process, delivering high reversible capacity, superior rate capability and remarkable cyclic stability. The surface-dominated redox reaction mechanism in Na storage is the origin of the fast kinetics, since the columnar nanopores which are considered as curled and sealed ultrathin nanosheets, like microjars, not only shorten the ion and electron diffusion length, but also expand the redox sites from the surface to the inner part. This is similar to the storage mechanism in supercapacitors. Moreover, density functional theory computations reveal that the high-level amine groups play an important role in Na storage in the low potential region, endowing the block anode material with both high energy and power density.

The dual-body tethered satellite system, which consists of two spacecraft connected by a single tether, is one of the most promising configurations in numerous space missions. To ensure the stability of deployment, the radial basis function neural network-based adaptive terminal sliding mode controller is proposed for the dual-body tethered satellite system with the model uncertainty and external disturbance. The terminal sliding mode controller serves as the main control framework for its properties of the strong robustness and finite-time convergence. The radial basis function neural network is adopted to approximate the model uncertainty, in which the weight vector of the radial basis function neural networks and the unknown upper bound of the external disturbance are estimated by using two adaptive laws. Finally, the Lyapunov theory and numerical simulations are used to prove the validity of the proposed controller.

Amines, especially primary amines, are value-added fine chemicals widely used in modern industries. Here, a PtCo/CeO2 catalyst is designed for the hydrogen-borrowing amination of alcohols, especially the conversion of cyclopentanol to cyclopentanylamine. CoOx decoration over Pt/CeO2 is able to enhance both selectivity to primary amine and catalytic activity. These CoOx species play two roles in alcohol amination, enhancing alcohol dehydrogenation and inhibiting overhydrogenation of a Schiff base intermediate (cyclopentyl cyclopentylidene amine). Comprehensive characterization demonstrates that promotional effects of the CoOx additive have two causes: (1) CoOx species provide an additional Pt-CoO interface for the rate-determining dehydrogenation step; (2) CoOx species block low-coordinated Pt sites for H2 activation in the overhydrogenation of the Schiff base intermediate, thus suppressing the formation of undesirable secondary amines. This work provides an in-depth understanding of the role of the CoOx additive in PtCo/CeO2 and new insights into the design of Pt-based catalysts for primary amine production via hydrogen-borrowing amination.

The efficient utilization of lignocellulosic biomass has tremendous potential to reduce the excessive dependence on fossil fuels. Here, we provide an overview on the recent achievements in the catalytic production of value-added chemicals and fuels. When targeting chemicals, a key objective is to maximize the product selectivity to favor the subsequent separation. This can be achieved through the design of catalysts and optimization of catalytic systems based on the deep understanding of the catalytic mechanism. For production of fuels, attention should be paid to the establishment of an energy-efficient process for high-quality fuels. This can be realized through the design of C–C coupling reactions and the development of multifunctional catalysts to minimize the reaction steps from lignocellulose to fuels. In addition, the full utilization of lignocellulose into biofuels and chemicals in a single process is separately introduced. Finally, several personal perspectives on the opportunities and challenges within this promising field are discussed.

In this work, we report a new type anode material, MoO 2 combined carbon dots (CDs) with nanoparticle-stacking structure via a facile hydrothermal route. Herein, CDs is introduced as the reductant which in-situ reduces Mo VI to Mo IV . It is further confirmed that the particles of MoO 2 with evenly distributed beset of carbon dots form a nanoparticle-stacking structure. Thanks to this specific structure, the as-made MoO 2 -CDs manifest high performance in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The capacities maintain 854 and 236 mAh g −1 at 0.50 A g −1 after 300 cycles for LIBs and 600 cycles for SIBs, respectively. Furthermore, we explored the structure-stability relationship by the electrochemical measurement and morphology, found the mechanisms of charge/discharge composed of dominant redox reaction and auxiliary intercalation reaction, and explained the characteristics of a high rate performance through kinetic issues and extrinsic pseudocapacitance contributions. This green synthetic method of anode material could make it possible to obtain high-performance alkali-ion batteries and other energy storage devices.

CuxO@polypyrrole nanofibre (PpyNF) composites were synthesized by a simple and fast microwave method. The samples were characterized using X-ray diffraction, X-ray photoelectron spectroscop...

The production of hydrogen from the aqueous-phase reforming (APR) of oxygenated hydrocarbons is promising. Herein, the performances of Pt loaded on NiAl2O4 spinel and γ-Al2O3 were investigated in t...

Excessive input of nitrogen fertilizer causes nitrogen pollution in aquatic environments. Utilizing microbial inoculants seems to be effective in decreasing the extent of nitrogen fertilize...

Developing cost-effective electrocatalysts for oxygen evolution reaction (OER) in basic media is critical to hydrogen production from renewable energy. Herein, in-situ electrodeposited flower-like NiFeOxHy and NiFeOxHy/rGO composite electrocatalysts on Ni foam for OER are reported. The active sites of the flower-like electrocatalysts are increased significantly due to the enhanced NiFeOxHy surface areas and numerous exposed layered edges and edge defects. Reduced graphene oxide (rGO) has been introduced to fabricate NiFeOxHy/rGO composite film, further improving the conductivity and OER performance of the flower-like NiFeOxHy. The optimized NiFeOxHy/rGO exhibits superior OER performance with a Tafel slope of 29.11 mV/decade, an overpotential of 200 mV at 10 mA/cm2 in 1 mol/L KOH and favorable long-term stability.

We recently reported a new quantitation method using mass spectrometry (MS) in combination with electrochemistry (EC, J. Am. Soc. Mass Spectrom., 2019, 30, 685). The strength of this method is that no reference standard or isotope-labeled compound is required for absolute quantitation. The method relies on electrochemical oxidation of an electrochemically active target compound to determine the amount of the oxidized compound using Faraday's Law. On the other hand, the oxidation reaction yield can be determined based on the MS signal change following electrolysis. Therefore, the absolute amount of the analyte can be calculated. Our experiment is carried out using a coupled liquid chromatography/electrochemistry/mass spectrometry (LC/EC/MS) apparatus. In this study, the method is further optimized. First, quantifying the compounds in a mixture is possible after the chromatographic separation. Gradient elution is used for separation and each compound can be quantified using the electrochemical mass spectrometry method. Second, for compounds that are already purified, LC column is not necessary and can be removed (i.e., flow-through analysis), thus shortening the analysis time for each injected sample from 10 min to 2 min. With using an LC auto-sampler, multiple samples can be injected sequentially. All the quantitation errors shown in this study are within 5%, indicating a good accuracy of our method.

Low charge-separation transport efficiency resulting from structural defects largely limits photocatalytic hydrogen production over polymeric graphitic carbon nitride (PCN) photocatalyst. Herein, an electron-donating group, namely p-phenylene, is incorporated into PCN by a polycondensation reaction between carbon nitride and p-phenylenediamine (or p-benzoquinone) to repair the structural defects. The p-phenylene-modified PCN exhibits an almost fivefold increase in H2 evolution, a threefold increase in photocurrent density, and higher nonradiative rate (0.285 ns-1 ). Spectroscopic studies confirm that p-phenylene tends to bridge the heptazine-based oligomers through a polycondensation reaction. Theoretical calculations reveal that anchoring of the heptazine units by p-phenylene induces localization of h+ and e- on the phenylene and melem moieties, respectively, which effectively separates the charge carriers. This strategy provides an opportunity to overcome structural defects in carbon nitride for efficient photocatalytic solar energy conversion.

Aldol condensation is of significant importance for the production of fuel precursors from biomass-derived chemicals and has received increasing attention. Here we report a Nb 2 O 5 catalyst with excellent activity and stability in the aldol condensation of biomass-derived carbonyl molecules. It is found that in the aldol condensation of furfural with 4-heptanone, Nb 2 O 5 has obviously superior activity, which is not only better than that of other common solid acid catalysts (ZrO 2 and Al 2 O 3 ), more importantly, but also better than that of solid base catalysts (MgO, CaO, and magnesium-aluminum hydrotalcite). The detailed characterizations by N 2 sorption/desorption, NH 3 -TPD, Py-FTIR and DRIFTS study of acetone adsorption reveal that Nb 2 O 5 has a strong ability to activate the C=O bond in carbonyl molecules, which helps to generate a metal enolate intermediate and undergo the nucleophilic addition to form a new C–C bond. Furthermore, the applicability of Nb 2 O 5 to aldol condensation is extended to other biomass-derived carbonyl molecules and high yields of target fuel precursors are obtained. Finally, a multifunctional Pd/Nb 2 O 5 catalyst is prepared and successfully used in the one-pot synthesis of liquid alkanes from biomass-derived carbonyl molecules by combining the aldol condensation with the sequential hydrodeoxygenation.

The β subunit of soybean [Glycine max (L.) Merr.] seed storage protein is of great significance in sulfur-containing amino acid balance and soybean processing properties. The objective of this study was to elucidate the relationship between the β subunit and sulfur-containing amino acid composition, and the potential regulatory mechanism. The β subunit was independently accumulated in comparison with other major subunits (α/α′, acidic, basic, and A3) during seed filling, and a low level of β subunit content (BSC) was formed during the accumulation process. In low-BSC mature seeds, crude protein, oil content, and fatty acid composition were not changed, but sulfur-containing amino acids (Cys + Met) in the low-BSC seeds increased significantly (by 31.5%), suggesting that an internal regulatory mechanism within seed might be responsible for the rebalance of seed protein composition and that sulfur assimilation might be deeply involved in β subunit accumulation. Transcriptomic analysis revealed that genes involved in anabolism of cysteine, methionine, and glutathione were up-regulated but those involved in the catabolism of these compounds were down-regulated, suggesting a relationship between the elevation of methionine and glutathione and low BSC. Our study sheds light on seed composition in low BSC lines and on the potential molecular regulatory mechanism of β subunit accumulation, broadening our understanding of soybean seed protein synthesis and its regulation. Keywords: Soybean, β subunit, Transcriptome analysis, Sulfur-containing amino acids, Sulfur assimilation