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Low-power consumption and high sensitivity are highly desirable for a vast range of NH3 sensing applications. As a new type of two-dimension (2D) material, Ti3C2Tx is extensively studied for room temperature NH3 sensors recently. However, the Ti3C2Tx MXene based gas sensors suffer mainly from low sensitivity. Herein, we report a sensitive Ti3C2Tx/WO3 composite resistive sensor for NH3 detection. The Ti3C2Tx/WO3 composite consisting of WO3 nanoparticles anchored on Ti3C2Tx nanoflakes were synthesized successfully with a facile ultra-sonication technique. The composite sensor with optimized components exhibits a high sensitivity of 22.3% for 1 ppm NH3 at room temperature, which is 15.4 times higher than the pure Ti3C2Tx sensor. Furthermore, the composite sensor has excellent reproducibility, good long-term stability, and high selectivity to NH3. The relative humidity influence on NH3 gas sensing properties of the sensors was systematically studied. This research provides an efficient route for the preparation of novel MXene-based sensitive materials for high-performance NH3 sensors.

The nanostructured two-dimensional (2D) materials for humidity sensing applications have become increasingly attractive. However, 2D materials have negative aspects of easily stacking and agglomerating multilayers. Here, a novel resistive-type humidity sensor utilizing multi-layer titanium carbide (Ti3C2Tx) films as sensitive material is demonstrated. The humidity sensor exhibits an ultrasensitive and reversible sensing performance in a wide relative humidity range. Furthermore, the ultrafast response and recovery properties are achieved at room temperature. The Fourier transform infrared spectroscopy is used to investigate the adsorption of water vapor on Ti3C2Tx surfaces. A rapid capillary condensation of water vapor on the unique accordion-like microstructures and the hierarchical nanostructures of hydroxyl-riched Ti3C2Tx surface are supposed to be responsible for the super adsorption capability for water vapor. The electrostatic field induced by adsorbed water molecules is proposed to explain the resistance change of the titanium carbide humidity sensor. This work highlights the unique advantages of humidity sensor with layered 2D materials of Ti3C2Tx MXenes, including ultrasensitive, good reversibility and fast recovery at room temperature.

Various nanoplatforms have been developed to visualize intracellular microRNAs (miRNAs) because of their clinical significance in tumor progression and diagnosis. However, the diffusion-limited motion of the nanoplatforms penalizes the miRNA imaging efficiency in cells. Herein, we fabricated a near-infrared (NIR) light-propelled Janus-based nanoplatform to advance the imaging response. The Janus nanomotor covered with an Au half-shell was loaded by the endocytosis adjuvant of the MnO2 nanosheet for delivering a miRNA-responsive hQN (hairpin DNA quadrangular nanostructure) probe with a catalyzed hairpin assembly (CHA). Once the nanoplatform entered into cells, the MnO2 nanosheet was degraded to Mn2+ by endogenous fuels (such as glutathione) to release the hQN probe. The NIR light irradiation of the nanoplatform generated a heat gradient and thus propelled motion of the nanoplatform. This process accelerated the intracellular reaction of the hQN probe with miRNAs to trigger the cascade CHA amplification with an enhanced fluorescence readout.

A series of Sn and N co-doped carbon fibers featuring rich mesoporous and controllable multichannel hollow structures (SnN-HFs) were synthesized by electrospinning for the electrochemical CO2 reaction reduction (CO2RR) toward CO. The SnN-HFs, endowed with enhanced CO2 adsorption capacity, enabled more than 4 times higher Sn-normalized CO partial current densities in a wide overpotential compared with unadjusted nanofibers without hollow structures. Kinetics simulations suggested that the intensified interfacial mass transfer of CO2 and stabilized high-loading intermediate CO2,ads contribute overwhelmingly to the improved CO2RR performance.

Aims: For a metal hyperaccumulator plant Sedum alfredii, the recruitment of unique rhizospheric bacterial communities from bulk soils has been well studied. However, in the root-soil interface, the knowledge on the establishment of endospheric microbiomes from rhizospheric soil is still scarce. Methods: In this study, we combined culture-independent that was 16S rRNA gene amplicon sequencing, and culture-dependent methods that included bacterial isolation, heavy metal tolerance and plant growth-promoting traits. Results: The Cd/Zn concentrations in endosphere were significantly higher than in soil, while Pb concentration in endosphere was significantly lower than in soil. The α-diversity in rhizosphere soils was higher than in root endosphere, and the compartments as a major determinant revealed 85.9% of the taxa variations. The relative abundance of Proteobacteria increased in endosphere compared to rhizosphere. The difference of Cd/Zn tolerance between endospheric and rhizospheric isolates was not obvious, while the Pb tolerance of endospheric isolates significantly decreased compared to rhizosphere. Conclusions: The results suggest that S. alfredii recruits Cd/Zn-tolerant but not Pb-tolerant endospheric bacterial communities from its rhizospheric soil. The difference in the microbial structure and function in the root-soil interface might be related to the selective absorption of metals in S. alfredii.

The purpose of this study was to determine the stored energy of dual-phase (DP) steels after hot rolling, coiling, and cold reduction using electron backscattered diffraction analysis. Three methods for stored energy evaluation were examined and compared: the sub-grain boundary, image quality, and kernel average misorientation methods. The results demonstrated that the sub-grain method, in which stored energy was calculated as a function of sub-grain boundary misorientations and total sub-grain boundary length, can provide more accurate stored energy values, since cold work was responsible for forming numerous dislocation structures such as shear bands, cells, and cell walls. As expected, the steels with the combination of a low coiling temperature of 580 °C and 60 pct cold reduction had the highest stored energy values. This information is important in defining how pre-anneal processing conditions might control the response of DP steels to the various transformations occurring during continuous galvanizing line simulations.

Twisted two-dimensional bilayer materials exhibit many exotic electronic phenomena. Manipulating the 'twist angle' between the two layers enables fine control of the electronic band structure, resulting in magic-angle flat-band superconductivity1,2, the formation of moire excitons3-8 and interlayer magnetism9. However, there are limited demonstrations of such concepts for photons. Here we show how analogous principles, combined with extreme anisotropy, enable control and manipulation of the photonic dispersion of phonon polaritons in van der Waals bilayers. We experimentally observe tunable topological transitions from open (hyperbolic) to closed (elliptical) dispersion contours in bilayers of α-phase molybdenum trioxide (α-MoO3), arising when the rotation between the layers is at a photonic magic twist angle. These transitions are induced by polariton hybridization and are controlled by a topological quantity. At the transitions the bilayer dispersion flattens, exhibiting low-loss tunable polariton canalization and diffractionless propagation with a resolution of less than λ0/40, where λ0 is the free-space wavelength. Our findings extend twistronics10 and moire physics to nanophotonics and polaritonics, with potential applications in nanoimaging, nanoscale light propagation, energy transfer and quantum physics.

Among reported stretchable conductors, electrically conductive composites (ECCs) have the advantages of low cost, simplicity in circuit design and fabrication, and good reliability. However, the resistivity of conventional stretchable ECCs usually increases during stretching as a result of the loss of contact between neighboring conductive fillers. Here we prepared stretchable ECCs filled with silver dendrites. Due to the high aspect ratio, hierarchy structure, and multiple contact points in all dimensions, ECCs filled with silver dendrites have lower percolation threshold compared with conventional ECCs filled with silver particles or flakes. Moreover, ECCs filled with silver dendrites show a unique decrease in resistivity during stretching. The resistivity can decrease from 5 × 10−4 Ω·cm to as low as 1.1 × 10−4 Ω·cm at 100% elongation. Due to the high conductivity during stretching, the ECCs are used to prepare stretchable capacitors and antennas, demonstrating the stable electrical performance of ECCs under strain.

Food security in China is under additional stress due to climate change. The risk analysis of maize yield losses is crucial for sustainable agricultural production and climate change impact assessment. It is difficult to quantify this risk because of the constraints on the high-resolution data available. Moreover, the current results lack spatial comparability due to the area effect. These challenges were addressed by using long-term county-level maize yield and planting area data from 1981 to 2010. We analyzed the spatial distribution of maize yield loss risks in mainland China. A new comprehensive yield loss risk index was established by combining the reduction rate, coefficient of variation, and probability of yield reduction after removing the area effect. A total of 823 counties were divided into areas of lowest, low, moderate, high, and highest risk. High risk in maize production occurred in Heilongjiang and Jilin Provinces, the eastern part of Inner Mongolia, the eastern part of Gansu-Xinjiang, west of the Loess Plateau, and the western part of the Xinjiang Uygur Autonomous Region. Most counties in Northeast China were at high risk, while the Loess Plateau, middle and lower reaches of the Yangtze River and Gansu-Xinjiang were at low risk.

Broadband photodetectors are essential for various applications including spectroscopy, communication, imaging and sensing. Even though few materials show broadband photodetection, they are only capable of detecting light in limited spectral ranges from infrared (IR) to ultraviolet (UV) wavelengths. However, their functionalities at much shorter wavelengths such as ionizing radiation still present a challenge because of the limitations from the material properties. Here we demonstrate a room temperature, high performance broadband photodetector based on van der Waals (vdWs) magnetic material CrSiTe3 (CST) that can efficiently detect both soft X-rays and light in the near-infrared (NIR) and visible wavelength ranges. The CrSiTe3 based device can work with a high sensitivity (≈463 μC Gyair−1 cm−2) under synchrotron soft X-rays, which is more than twenty times more sensitive than the conventional α-Se device. In the NIR range, the device can achieve a maximum responsivity of around 206 A W−1 at 785 nm, an extremely high external quantum efficiency (EQE) of 32 600%, a detectivity of 1.25 × 1012 cm Hz1/2 W−1 and a relatively fast photoresponse time (rise time ∼43 ms under X-rays, 17 ms under a 785 nm laser). Together these results demonstrate a high-performance broadband photo and X-ray detector, offering intriguing opportunities for novel optoelectronic applications.

Sedum alfredii Hance is a cadmium (Cd)/zinc (Zn) hyperaccumulator native to China. However, its relatively low biomass restricted the large-scale application for heavy metal contamination remediation. The chromosome set doubling of S. alfredii in vitro was achieved by 0.1%-0.2% (W/V) colchicine treatment. The plant DNA ploidy was analyzed by flow cytometry and chromosome set doubling plants (CSD) were identified based on the obvious different sharp peak. A tissue culture experiment with different Cd treated levels and a field trial with natural polluted mined soil were conducted to study the effects of chromosome doubling on plant biomass and Cd accumulation in shoots. The results suggested that S. alfredii is a mixoploid. Compared with the wild type plants (WT), CSD exhibited typical "gigas" characteristics in morphology including stem thickness, root hair production, number of leaves and size of stoma guard cell. Fresh weight and dry weight of CSD were increased to 1.62-2.03-fold and 2.26-3.25-fold of WT. And Cd content of CSD showed a 17.49%-42.82% increase and 59% increase under tissue culture and field condition, accordingly. In addition, the TF and in BCF of CSD were 2.37- and 1.59-fold of WT, respectively. These results proved that it is feasible to promote phytoextraction efficiency of S. alfredii in Cd contaminated soils through chromosomal engineering, which provides a novel approach for hyperaccumulator application in phytoremediation.

Type 2 diabetes mellitus (T2DM) has been one of the most prevalent metabolic disorders. Nonetheless, the commonly used anti-T2DM drugs failed to substant to treat T2DM when anti-T2DM was withdrawn. Here we put forward a superior and sustainable anti-diabetic strategy using intraperitoneal administration of amino-acid-functionalized gadofullerene nanoparticles (GFNPs) in db/db diabetic mice. Highly accumulated in the pancreas and liver, GFNPs could prominently decrease hyperglycemia, along with permanently maintaining normal blood sugar levels in T2DM mice and even stopping administration. Importantly, GFNPs reversed the pancreas islets dysfunctions by reducing oxidative stress and inflammation responses and fundamentally normalized the insulin secretory function of the pancreas islets. Mechanistically, GFNPs improved hepatic insulin resistance by regulating glucose and lipid metabolism through the activation of IRS2/PI3K/AKT signal pathways, resulting in inhibiting gluconeogenesis and increasing glycogenesis in the liver. Additionally, GFNPs relieved hepatic steatosis in the liver, ultimately maintaining systemic glucose and lipid metabolic homeostasis without obvious toxicity. Together, GFNPs reverse the dysfunctions of the pancreas and improve hepatic insulin resistance, providing a promising approach for T2DM treatment.

The method of characteristics which is an effective method for neutron transport calculation with high flexibility in complex geometry has been applied to high temperature gas-cooled pebble-bed reactor geometry. The MOCP (the Method of Characteristics for Pebble-bed high temperature gas-cooled reactor) code was developed in Institute of Nuclear and New Energy Technology, Tsinghua University to achieve this goal. The first stone standing ahead is the geometry modeling for pebble-bed district. In this work, a solid modeling method called constructive solid geometry (CSG) is introduced to model the pebble-bed district. A universal ray tracing technique is developed to arrange tracks in 3-D cylinder geometry. Furthermore, tree search method is implemented into MOCP to improve the ray tracing efficiency. Automatic meshing is implemented to improve the geometry modeling efficiency. A redundant tree was constructed to mesh the interspace among pebbles. The geometry modeling capability of MOCP is verified by fast converging single group benchmarks.

V2O5/poly(3,4-ethylenedioxythiophene) nanocables with oxygen vacancies gradually decreasing from the surface to the core (G-V2O5/PEDOT nanocables) were prepared as electrodes for supercapacitors. G...

Arbuscular mycorrhizal fungi (AMF) could influence plant abilities of total nitrogen (N) acquisition. Global changes have been influencing availabilities of different N forms and water resources in soil. However, it is uncertain whether and how AMF colonization affects plant uptake and preference of different N forms and how are they affected by soil water conditions. We conducted a pot experiment with Funneliformis mosseae (a common arbuscular mycorrhizal fungal species) colonized and non-colonized maize (Zea mays L.) growing at low and high water conditions, the growth medium contained much more nitrate (NO3−) than ammonium (NH4+). F. mosseae colonization and high water availability increased maize biomass and total N uptake. Enhanced water supply increased proportional contributions of NH4+ to colonized and non-colonized maize because high water conditions may increase NH4+ accessibility to maize. F. mosseae colonization weakened proportional contributions and preference of NH4+ in maize, indicating that AMF enable plants to prefer using the more abundant N form and develop more beneficial N uptake strategies considering that NO3− was more dominant than NH4+ in growth medium. Furthermore, maize NH4+ preference was decreased by F. mosseae colonization more under high than low water conditions. This demonstrated greater effects of AMF on regulating plant N uptake strategies in soils with greater water availability. This work revealed the regulation of AMF colonization on plant N uptake strategies under different soil water conditions. The findings enriched our knowledge of plant N use in the context of global changes.

Phonon polaritons-light coupled to lattice vibrations-in polar van der Waals crystals offer unprecedented opportunities for controlling light at the nanoscale due to their anisotropic and ultralow-loss propagation. While their analog plasmon polaritons-light coupled to electron oscillations-have long been studied and exhibit interesting reflections at geometrical edges and electronic boundaries, whether phonon polaritons can be reflected by such barriers has been elusive. Here, the effective and tunable reflection of phonon polaritons at embedded interfaces formed in hydrogen-intercalated α-MoO3 flakes is elaborated upon. Without breaking geometrical continuity, such intercalation interfaces can reflect phonon polaritons with low losses, yielding the distinct phase changes of -0.8π and -0.3π associated with polariton propagation, high efficiency of 50%, and potential electrical tunability. The results point to a new approach to construct on-demand polariton reflectors, phase modulators, and retarders, which may be transplanted into building future polaritonic circuits using van der Waals crystals.

Microchannel manufacturing is one of the fastest growing areas in advanced manufacturing with numerous applications, including turbine blade cooling structures, compact microchannel heat exchangers, and electronic cooling devices. Recent development of metallic additive manufacturing (AM) based on direct metal laser sintering technology is capable of fabricating microscale structures with high complexity and design flexibility. However, powder bed laser sintering process produces rough surface characteristics caused by hatch overlaps and particle attachments, leading to channel size reductions and rough surfaces. In this paper, dimensional metrology of cross-sectional views of multirow microchannels made by AM was conducted by a scanning electron microscope (SEM) at different locations along the printing direction. Channel size reduction, surface roughness, and circularity tolerance of the as-printed channels were analyzed based on micrographs captured by SEM. Results showed that both channel sizes and hole pitches affected the printing qualities of microchannels. The as-printed channel sizes reduced by more than 15% compared to the designed values. Two approaches were made in this paper to improve printing qualities. The first one was to redesign channel size in computer-aided design (CAD) model to make the as-printed channel sizes closer to the objective values. Electrochemical polishing (ECP) was then applied as a second way using sulfuric acid solutions. Surface roughness value was reduced by more than 40% after the ECP process.

Despite the success of pedestrian detection, there is still a significant gap in the performance of the detection of pedestrians at different scales. Detecting small-scale pedestrians is extremely challenging due to the low resolution of their convolution features which is essential for downstream classifiers. To address this issue, we observed pedestrian datasets and found that pedestrians often gather together in crowded public places. Then we propose MagnifierNet, a simple but effective small-scale pedestrian detector towards multiple dense regions. MagnifierNet uses our proposed sweep-line based grouping algorithm to find dense regions based on the number of pedestrians in the grouped region. And we adopt a new definition of small-scale pedestrians through grid search and KL-divergence. Besides, our grouping method can also be used as a new strategy for pedestrian data augmentation. The ablation study demonstrates that MagnifierNet improves the representation of small-scale pedestrians. We validate the effectiveness of MagnifierNet on CityPersons and KITTI datasets. Experimental results show that MagnifierNet achieves the best small-scale pedestrian detection performance on CityPersons benchmark without any external data, and also achieves competitive performance for detecting small-scale pedestrians on KITTI dataset without bells and whistles.

Rationale Nitrogen (N) isotopic ratios (δ15 N values) of plants are primarily determined by the δ15 N values of their N sources. Metallic nutrients affect plant N uptake. However, there is little knowledge of the relationships between leaf δ15 N values and leaf metallic nutrients. The δ15 N values are often lower in soil nitrate (NO3 - ) than in ammonium (NH4 + ) due to large isotopic fractionation during nitrification. Plants acquire more NO3 - than NH4 + when accumulating high potassium (K), calcium (Ca) and magnesium (Mg) to maintain charge balance. In addition, plants that absorb more NO3 - than NH4 + increase the soil pH and decrease the availability of iron (Fe), manganese (Mn) and zinc (Zn). We therefore hypothesized that leaf δ15 N values correlate negatively with K, Ca and Mg contents, while positively with Fe, Mn and Zn contents. Methods Leaves of non-N-fixing plants were sampled across an approx. 6000 km transect in China and their δ15 N values and metallic nutrient content were determined using elemental analyzer/isotope ratio mass spectrometry. Results Inconsistent with the hypothesis, leaf δ15 N values correlated positively with leaf K, Ca and Mg, indicating higher δ15 N values of soil NO3 - than NH4 + . Higher δ15 N values of soil NO3 - revealed stronger denitrification than nitrification in the study regions because isotopic fractionation occurs during both processes. Leaf δ15 N values correlated negatively with Fe, relating to decreases in soil Fe availability, which might be attributed to oxidation of Fe2+ to Fe3+ supplying electrons for denitrification, while greater uptake of NO3 - than NH4 + of plants increases soil pH. Leaf δ15 N values correlated positively with Zn and did not correlate with Mn. These observed relationships between leaf δ15 N values and metallic nutrients, except Mn, were independent of vegetation or soil types. Conclusions This study has enriched our knowledge of associations between metallic nutrients and N cycling in plant-soil systems, especially for the roles of Fe in soil N transformations and K, Ca and Mg in plant N uptake.

Plant growth-promoting bacteria (PGPB) can promote root uptake and shoot accumulation of cadmium (Cd) in hyperaccumulator plants, but the mechanisms by which PGPB accelerate root-to-shoot transport of Cd is still unknown. A better understanding of these mechanisms is necessary to develop the strategies that can promote the practical phytoextraction of Cd-polluted soils. In this study, we found that Pseudomonas fluorescens accelerates a reversed and a long-distance transport of Cd and sucrose in Sedum alfredii, by examining the xylem and phloem sap and by quantifying the concentrations of Cd and sucrose in shoot and root. The transcriptome sequencing has revealed the up-regulated expressions of starch metabolism and sucrose biosynthesis related genes in the shoots of Cd hyperaccumulator plant S. alfredii that was inoculated with PGPB P. fluorescens. In addition, the genes of sugar, cation and anion transporters were also up-regulated by bacterial treatment, showing a complicated co-expression network with sucrose biosynthesis related genes. The expression levels of Cd transporter genes, such as ZIP1, ZIP2, HMA2, HMA3 and CAX2, were elevated after PGPB inoculation. As a result, the PGPB successfully colonized the root, and promoted the sucrose shoot-to-root transport and Cd root-to-shoot transport in S. alfredii. Since non-photosynthetic root-associated bacteria usually obtain sugars from photosynthetic plants, our results highlight the importance of PGPB-induced changes in hyperaccumlator plants for both the host and the PGPB.

Phytoremediation coupled with co-cropping is assumed to be good for safety utilization and remediation of heavy metal contaminated farmland, which can ensure farmers’ income without increasing health risks for human. In this study, the effects on plant cadmium (Cd) accumulation and health risk of consuming the vegetable plant were compared between monoculture and co-cropping of cauliflower (Brassica oleracea) with two ecotypes of Sedum alfredii in a moderately (0.82 mg kg−1) Cd contaminated greenhouse vegetable field. The results showed that co-cropping with S. alfredii raised Cd concentratio n in edible part of cauliflower with slightly growth promotion. The health risk of consuming cauliflower to different groups of people have been evaluated by calculating Hazard Quotient (HQ) and all HQ value were less than 1.0, which indicated that eating co-cropped cauliflower would not cause health risks to adults and children. Besides, the Cd concentration of hyperaccumulating ecotype (HE) of S. alfredii was 27.3 mg kg−1 in monoculture and it increased to 51.2 mg kg−1 after co-cropping with cauliflower, suggesting that the co-cropping system promoted HE Cd absorption capacity. Therefore, the “Phytoextraction Coupled with Agro-safe-production” (PCA) model of cauliflower and HE can serve as an alternative sustainable strategy in the Cd moderate polluted greenhouse.

Planting leafy vegetables, especially pakchoi, in cadmium (Cd) polluted farmland is easy to lead to excessive Cd content in edible parts, which results in high risk of food chain. In this study, a field experiment was carried out to study the effects of intercropping of pakchoi with Cd hyperaccumulator Sedum alfredii Hance, and the roles of endophytic bacterium SaMR12 was also investigated. When intercropping with Sedum, the growth of pakchoi was not affected but their Cd concentration and accumulation were significantly increased, while which were obviously decreased by SaMR12 inoculation. After intercropping, the biomass of Sedum was significantly reduced, but their Cd concentration increased. SaMR12 inoculation significantly increased Cd accumulation of Sedum, and which increased to 3 times in Sedum monoculture. Those results showed that although intercropping with hyperaccumulator could lead to higher risk of pakchoi in Cd polluted field, intercropping with SaMR12 inoculated Sedum can decrease Cd concentration of pakchoi and promote Cd absorption of Sedum, which indicated that this endophyte can be made into a microbial inoculum as a soil additive for the safe production of vegetables and the soil Cd pollution remediation.

Background Microbes isolated from hyperaccumulating plants have been reported to be effective in achieving higher phytoextraction efficiency. The plant growth-promoting bacteria (PGPB) SaMR12 from the cadmium (Cd)/zinc hyperaccumulator Sedum alfredii Hance could promote the growth of a non-host plant, oilseed rape, under Cd stress. However, the effect of SaMR12 on Brasscia juncea antioxidative response under Cd exposure was still unclear. Results A hydroponic experiment was conducted to study the effects of Sphingomonas SaMR12 on its non-host plant Brassica juncea (L.) Czern. under four different Cd treatments. The results showed that SaMR12 could colonize and aggregate in the roots and then move to the shoots. SaMR12 inoculation promoted plant growth by up to 71% in aboveground biomass and 81% in root biomass over that of the non-inoculated plants. SaMR12-inoculated plants significantly enhanced root Cd accumulation in the 10 and 20 μM Cd treatments, with 1.72- and 0.86-fold increases, respectively, over that of the non-inoculated plants. SaMR12 inoculation not only decreased shoot hydrogen peroxide (H2O2) content by up to 38% and malondialdehyde (MDA) content by up to 60% but also reduced proline content by 7–30% in shoots and 17–32% in roots compared to the levels in non-inoculated plants. Additionally, SaMR12 inoculation promoted the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) and facilitated the relative gene expression levels of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in the glutathione (GSH)-ascorbic acid (AsA) cycle. Conclusions The results demonstrated that, under Cd stress, SaMR12 inoculation could activate the antioxidative response of B. juncea by decreasing the concentrations of H2O2, MDA and proline, increasing the activities of antioxidative enzymes, and regulating the GSH-AsA cycle. These results provide a theoretical foundation for the potential application of hyperaccumulator endophytic bacteria as remediating agents to improve heavy metal tolerance within non-host plant species, which could further improve phytoextraction efficiency. Graphical abstract

Cadmium (Cd) pollution in soil is a serious problem affecting environmental safety and human health, and the majority of Cd in human body comes from edible vegetables, especially leafy vegetables. Therefore, it is necessary to understand the absorption and transport of Cd soil by leafy vegetables. In this study, the meta-analysis method was firstly employed to study the relationship of Cd in leafy vegetables and soil systems. The results showed that different kinds of leafy vegetables have different abilities of Cd accumulation (measured by bioconcentration factor (BCF)) and transportation (measured by translocation factor (TF)): Brassica juncea (BCF = 5.10) and Brassica pekinensis (BCF = 1.90) had significantly higher ability to absorb cadmium in soil among the 19 studied species, Brassica pekinensis (TF = 2.52), Coriandrum sativum (TF = 2.18) had significantly higher cadmium transport capacity than other 11 species. To further clarify the influence of the three main factors of soil pH, Cd content and leafy vegetable species on the Cd enrichment ability of leafy vegetables, the regression equation was obtained by meta-regression analysis. BCF is affected by species, soil pH, soil cadmium content in the order from high to low. It was found that the estimated range of SOM for safe production of leafy vegetables is 20–30 g/kg. It could also be observed that soil cation exchange capacity (CEC) had a negative correlation with BCF, while soil salinity had a strong positive correlation with BCF. This study can provide a reliable reference for leafy vegetable security production in the Cd polluted field and aids in selecting species suitable for avoiding the absorption of heavy metals from polluted soil.

Phonon polaritons (PhPs) have attracted significant interest in the nano-optics communities because of their nanoscale confinement and long lifetimes. Although PhP modification by changing the local dielectric environment has been reported, controlled manipulation of PhPs by direct modification of the polaritonic material itself has remained elusive. Here, chemical switching of PhPs in α-MoO3 is achieved by engineering the α-MoO3 crystal through hydrogen intercalation. The intercalation process is non-volatile and recoverable, allowing reversible switching of PhPs while maintaining the long lifetimes. Precise control of the intercalation parameters enables analysis of the intermediate states, in which the needle-like hydrogenated nanostructures functioning as in-plane antennas effectively reflect and launch PhPs and form well-aligned cavities. We further achieve spatially controlled switching of PhPs in selective regions, leading to in-plane heterostructures with various geometries. The intercalation strategy introduced here opens a relatively non-destructive avenue connecting infrared nanophotonics, reconfigurable flat metasurfaces and van der Waals crystals., G.Á.-P. acknowledges support through the Severo Ochoa Program from the Government of the Principality of Asturias (PA20-PF-BP19-053). P.A.-G. and J.D. acknowledge support from the European Research Council under starting grant no. 715496, 2DNANOPTICA. Q.B. acknowledges support from the Australian Research Council (ARC, FT150100450 and IH150100006). Q.B. and Q.O. acknowledge support from the Australian Research Council Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET) (project number: CE170100039).

Uncertainty analyses of fission product yields are indispensable in evaluating reactor burnup and decay heat calculation credibility. Compared with neutron cross section, there are fewer uncertainty analyses conducted and it has been a controversial topic by lack of properly estimated covariance matrix as well as adequate sampling method. Specifically, the conventional normal-based sampling method in sampling large uncertainty independent fission yields could inevitably generate nonphysical negative samples. Cutting off these samples would introduce bias into uncertainty results. Here, we evaluate thermal neutron-induced U-235 independent fission yields covariance matrix by the Bayesian updating method, and then we use lognormal-based sampling method to overcome the negative fission yields samples issue. Fission yields uncertainty contribution to effective multiplication factor and several fission products’ atomic densities at equilibrium core of pebble-bed HTGR are quantified and investigated. The results show that the lognormal-based sampling method could prevent generating negative yields samples and maintain the skewness of fission yields distribution. Compared with the zero cut-off normal-based sampling method, the lognormal-based sampling method evaluates the uncertainty of effective multiplication factor and atomic densities are larger. This implies that zero cut-off effect in the normal-based sampling method would underestimate the fission yields uncertainty contribution. Therefore, adopting the lognormal-based sampling method is crucial for providing reliable uncertainty analysis results in fission product yields uncertainty analysis.

We report a hollow dumbbell-shaped manganese dioxide (MnO2) colloidal kayaker capable of converting a pair of breathing oxygen bubbles into self-propelled movement. The bubble pair generated by catalytic decomposition of hydrogen peroxide fuel grew either synchronously or asynchronously, driving the colloidal kayaker to move along a fluctuating circle. The synchronous or asynchronous breathing mode of bubble pair is governed by the asymmetric catalytic sites of the colloidal kayakers. This imbalanced distribution of bubble propulsion force generates the driving force and the centripetal force on the colloidal kayaker. The dynamics of colloidal kayakers is well-described by the overdamped Langevin equation and fluid field simulation. Such bubble-pair propelled colloidal kayakers could advance applications of catalytic nanomotors, offering effective implementation for diverse tasks for a wide range of practical applications.

The multi-object counting in visual question answering (VQA) is still a challenging problem. Existing VQA models mainly adopt object detection network to extract image features and combine soft attention mechanism to further increase the model accuracy. However, repeated counting of the same object may occur when the object detection network extracts image features. In addition, the sum of attention weights of all objects calculated by soft attention mechanism is 1, which leads to the constant quantity information of objects being 1. We propose a new counting attention mechanism based on classification confidence. The main idea is to calculate the initial attention with sigmoid function and similarity with the object location generated by object detection network; we introduce classification confidence to calculate a more accurate similarity and solve the problem that the quantity information under existing soft attention mechanism is always 1. The experiment compares the proposed counting attention mechanism with the baseline model and the related work under the VQA v2 dataset. The results show that the counting attention mechanism improves the counting accuracy by 6.4% compared with the baseline model and surpasses most VQA models.

Electrical responsive scaffolds are important for regulating adhesion, mitigation, and proliferation of electroactive cells in tissue engineering. Conventional approaches to fabricate suitable scaffolds with enhanced electrical conductivity require multiple steps including the surface coating of conductive polymers or the encapsulation of conductive fillers. In this work, a new type of three-dimensional porous carbon fiber sponge-based electrical conductive scaffold with a fiber diameter of 8.1 (±2.1) μm was fabricated by one-step high-temperature carbonization at 800 °C from an abundantly available biomaterial - cotton. The as-carbonized cotton has a suitable pore size from several dozens to hundreds of micrometers, low toxicity, and good biocompatibility. Its hydrophilicity and biocompatibility were further modified by surface oxidation and polydopamine coating. The topological feature, surface functional groups, hydrophilicity, and electrical conductivity of the carbonized cotton were studied. The as-carbonized, oxidized, and polydopamine-coated scaffolds have electrical conductivities of 32.6, 44.9 and 128.2 S/m, respectively. The cytocompatibility and the effect of electrical stimulation on cell behavior were evaluated by cell culture with and without electrical stimulation. It was observed that the polydopamine coating significantly improved the hydrophilicity and cytocompatibility. The electrical stimulation accelerated cell proliferation and differentiation of nerve cells. This work demonstrated that carbonized biomaterial represents a promising material category that can be used for tissue engineering especially in electroactive tissues.

SaNRAMP3 gene cloned from a Zn/Cd hyperaccumulator Sedum alfredii was ectopicly expressed in Brassica juncea, a fast-growing and high-biomass crop plant. In a tissue culture experiment, transgenic plants were grown on MS medium with 0, 25, 50, 100, 200 μM Cd. It was shown that, at the same Cd treatment, the Cd tolerance of transgenic plants had no significant difference with those of wild-type plants (WT). However, the shoot Cd content and accumulation were improved significantly while the root Cd content and accumulation were descended significantly by SaNRAMP3 gene expression, which obviously enhanced the Cd root-to-shoot translocation factor (TF). In the hydroponic experiment, plants were cultured in nutrition solution with 0, 2.5, 25 μM Cd. Data showed that the Cd tolerance of transgenic plants had no significant difference with that of WT under the same Cd exposure. Whereas, the shoot Cd content and accumulation was increased 1.43–1.81 times and the TF was enhanced 3.09–3.51 times by SaNRAMP3 gene expression. Those results indicated that ectopic expression of SaNRAMP3 in B. juncea didn’t lead to Cd sensitivity, but enhanced Cd root-to-shoot transport, so that increased shoot Cd accumulation. This study provided a possibility to improve phytoextraction efficiency of heavy metal through gene engineering.

The Helical coiled tube Once-Through Steam Generator (H-OTSG) is key equipment in the High-Temperature Gas-cooled Reactor (HTGR) system, where the fission energy is transferred from the helium side to the water side, together with the complicated heat transfer and phase change phenomenon. In detail, the water is heated to the water-steam two-phase flow by the hot helium and further to the superheated steam. As a result, the H-OTSG is a multi-phases, multi-physics, and multi-domain highly nonlinear system due to the complex constitutive equations in the two-phase flow model. The accuracy and efficient solution of this highly nonlinear system is a key point for the successful simulation of the H-OTSG. In this work, the advanced Jacobian-Free Newton Krylov (JFNK) method is used instead of the traditional semi-implicit iteration method to pursue high computational performance. An efficient physical-based preconditioner is proposed, which is derived from the original semi-implicit based method. Moreover, the numerical technologies of the phase generation/disappearance and the global convergence algorithms of JFNK method are implemented and discussed. The two-phase drift-flux model is used to describe the two-phase flow in the waterside and the second-order accuracy temporal and spatial numerical scheme is employed to discrete the conservation equations. A new H-OTSG simulation code based on JFNK method is developed in this work and applied to analyze the steady and transient state behavior of the H-OTSG in the 10 MW high-temperature gas-cooled reactor (HTR-10). The simulation results show that the accuracy of the newly developed H-OTSG simulation code agrees well with the design data under different operating conditions. Furthermore, the computational performance of the JFNK method with the physical-based preconditioner is the best compared with the traditional Picard iteration method, Newton–Krylov method and JFNK method without preconditioner.

Humidity sensors with fast response, high accuracy and low-power consumption are critical importance in smart home and health monitoring applications. Herein, we demonstrate an excellent impedance relative humidity sensor based on all-inorganic halide perovskite CsPbBr3 nanoparticles (NPs) under low working-voltage (20 mV). The CsPbBr3 NPs humidity sensor exhibits fast response and recovery behavior at room temperature. Moreover, the sensor demonstrates excellent repeatability, low hysteresis and good stability. The humidity sensing mechanism of CsPbBr3 NPs is further studied and discussed by employing an electrochemical impedance spectroscopy measurement. Furthermore, the respiratory monitoring face mask based on CsPbBr3 humidity sensor shows accurate and stable performance, suggesting perovskite CsPbBr3 NPs based humidity sensor have great potential in future real-time health status monitoring applications.

This study proposes an integrated simulation approach, which consists of a microscopic traffic simulation model, a vehicle dynamics model, and an emission estimation model, in order to estimate emissions based on more reliable vehicle performance measures. The vehicle performance measures such as engine power and engine speed significantly relate to the amount of emissions, and road curvatures and inclinations are the core inputs affecting these vehicle performance measures. Therefore, providing reliable vehicle performance measures reflecting the road geometric attributes is critical for a reliable emission estimation. This study proposes to use the microscopic traffic simulation model for generating vehicle trajectories, which is advantageous in modeling various traffic situations, and the vehicle dynamics model for producing the vehicle performance measures based on the vehicle trajectories. Finally, the outputs from the vehicle dynamics model are fed into the emission estimation model to compu...

Near-infrared (NIR) light-responsive hydrogels are important for biomedical applications, such as remote-controlled release, but the NIR agents previously used were largely limited to heavy-metal inorganic materials such as gold nanoparticles. In this article, we report a new type of NIR photothermal-responsive hydrogel that can undergo structural changes in response to NIR light for biomedical applications in drug delivery and controlled release. The hydrogels synthesized by integrating a narrow-bandgap semiconductor polymer poly(diketopyrrolopyrrole-alt-3,4-ethylenedioxythiophene) with the polymerization of N-isopropylacrylamide show rapid and reversible mechanical shrinkage upon NIR light irradiation and can serve as carriers for anticancer drug loading and spatial/temporal control of drug release. These stimuli-responsive hydrogels, which can be prepared in different sizes and shapes, integrate photothermal properties and hydrogel characteristics and can provide on-demand, repeated, remote-controlled drug delivery for biomedical applications such as cancer treatment. MOE (Min. of Education, S’pore) Accepted version

In order to evaluate the ecological influence of hydraulic projects, aquatic habitat suitability modeling was proposed. Compared with other environmental flow methods, this method, for the first time, integrated considering hydrology parameters and ecology attributes, quantitatively describing the relationships between species and habitat. Aquatic habitat suitability models began with one-dimensional physical habitat simulation model (PHABSIM) at micro-scale physical habitat. Afterwards, habitat suitability models for meso- and macro-scale were developed; eco-factors indicating physical habitat and water quality situation were included; two- and three-dimensional model were employed to provide the situation of eco-factors. Based on field survey or mathematical models, the state of habitat eco-factors can be obtained. By establishing habitat suitability evaluation criteria, the impact of aquatic habitats on the particular life stage of indicate species can be assessed, the effect of reservoir regulation mode and habitat restoration projections can be predicted. Here, we summarized aquatic habitat suitability models in different spatial scale, and the advantages and disadvantages of each model were analyzed and concluded.

Novel three-dimensional (3D) island-chain structured vanadium pentoxide (V2O5)/graphene (GN)/multiwalled carbon nanotube (MWCNT) hybrid aerogels (VGMA) are synthesized by a sol–gel method. In this process, V2O5 in situ grows along the surface of both MWCNT and GN by the coordination effect. These two kinds of one-dimensional fibers (V2O5 nanofibers and V2O5 coated MWCNT) and one kind of two-dimensional sheets (GN) co-assemble into a 3D porous island-chain structure. VGMA exhibit enhanced specific capacitance (504 F g−1), large energy density (70 W h kg−1) and outstanding cyclic property (82.9% retention after 32 500 cycles). All these excellent electrochemical properties of ternary VGMA can be attributed to the well-designed nanostructure and synergistic effect of the individual components. This also demonstrates that the unique island-chain nanostructured VGMA can be a good candidate for supercapacitors.

The magnetohydrodynamic (MHD) micro-angular vibration sensor is a significant component of the MHD Inertial Reference Unit (MIRU) and measures micro-amplitude and wide frequency angular vibration. The MHD micro-angular vibration sensor must be calibrated in orbit since the ground calibration parameters may change after lift-off. An on-orbit dynamic calibration method for the MHD micro-angular vibration sensor is proposed to calibrate the complex sensitivity of the sensor in high frequency. An absolute calibration method that combines a homodyne laser interferometer and an angular retroreflector was developed. The sinusoidal approximation method was applied, and the calibration system was established and tested using a manufactured MHD sensor. Furthermore, the measurement principle and installation errors were analyzed, including the eccentric installation error of the retroreflector, the tilt installation error of the retroreflector, and the optical path tilt error. This method can be realized within a rotation range of &plusmn, 3 ∘ and effectively avoid the installation error caused by mechanical errors. The results indicate that the calibratable angular vibration frequency range is 25&ndash, 800 Hz, and the angular velocity range is 0 . 076 &ndash, 7590 mrad/s. The expanded uncertainties of the sensitivity amplitude and phase shift of the calibration system for the MHD micro-angular sensor are 0 . 04 % and 1 . 2 ∘ ( k = 2 ) .

This work introduces a novel method for classification and the dyskinesia quantification of Parkinson's disease patients. We merely utilized the data from two 9-axis inertial sensors (only use 3D gyroscope and 3D accelerometer) located at wrist and ankle. And an SVM classifier with RBF kernel was applied for classifying the data frame of PD subjects and controls and finally got an accuracy of 87.1%. Additionally, a pr value was proposed for quantification the dyskinesia into three levels in a fixed sample time period. Combining with the quadratic weighted Kappa coefficient, we evaluated the interrater reliability of artificial quantification and our proposed method in the end (k=0.961). The outcome indicates that our method is effective for identifying the PD patients and healthy individuals and quantitative evaluating the dyskinesia severity levels of PD patients, which has the application prospect of continual illness monitoring and levodopa dosing assessment for PD patients in the future.

Visual Question Answering (VQA) tasks must provide correct answers to the questions posed by given images. Such requirement has been a wide concern since this task was presented. VQA consists of four steps: image feature extraction, question text feature extraction, multi-modal feature fusion and answer reasoning. During multi-modal feature fusion, outer product calculation is used in existing models, which leads to excessive model parameters, high training overhead, and slow convergence. To avoid these problems, we applied the Variational Autoencoder (VAE) method to calculate the probability distribution of the hidden variables of image and question text. Furthermore, we designed a question feature hierarchy method based on the traditional attention mechanism model and VAE. The objective is to investigate deep questions and image correlation features to improve the accuracy of VQA tasks.

We report multiscale structured fibers and patterned films based on a semiconducting polymer, poly(3-hexylthiophene) (P3HT), as photoconductive biointerfaces to promote neuronal stimulation upon light irradiation. The micro/nanoscale structures of P3HT used for neuronal interfacing and stimulation include nanofibers with an average diameter of 100 nm, microfibers with an average diameter of about 1 μm, and lithographically patterned stripes with width of 3, 25, and 50 μm, respectively. The photoconductive effect of P3HT upon light irradiation provides electrical stimulation for neuronal differentiation and directed growth. Our results demonstrate that neurons on P3HT nanofibers showed a significantly higher total number of branches, while neurons grown on P3HT microfibers had longer and thinner neurites. Such a combination strategy of topographical and photoconductive stimulation can be applied to further enhance neuronal differentiation and directed growth. These photoconductive polymeric micro/nanostructures demonstrated their great potential for neural engineering and development of novel neural regenerative devices. Ministry of Education (MOE) Nanyang Technological University M.W. is grateful to the funding support by a start-up grant of Nanyang Assistant Professorship (M4080992) from Nanyang Technological University and AcRF Tier 2 (ARC 36/13: M4020172) from the Ministry of Education, Singapore.

The engineering of self-propelled micro-/nanomotors (MNMs) with continuously variable speeds, akin to macroscopic automobiles equipped with a continuously variable transmission, is still a huge challenge. Herein, after grafting with salt-responsive poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes, bubble-propelled Janus microcapsule motors with polyelectrolyte multilayers exhibited adjustable speeds when the type and concentration of the counterion was changed. Reversible switching between low- and high-speed states was achieved by modulating the PMETAC brushes between hydrophobic and hydrophilic configurations by ion exchange with ClO4- and polyphosphate anions. This continuously variable regulation enabled control of the speed in an accurate and predictable manner and an autonomous response to the local chemical environment. This study suggests that the integration of polymer brushes with precisely adjustable responsiveness offers a promising route for motion control of smart MNMs that act like their counterparts in living systems.

Optical remote sensing data are used widely in many fields (such as agriculture, resource management and the environment), especially for the vast territory of China, however, the application of these data is usually limited by clouds. Although it is valuable to analyze the probability of acquiring cloud-free imagery (PACI), PACI using different sensors at the pixel level across China has not been reported. In this study, the PACI of China was calculated with daily Advanced Very High Resolution Radiometer (AVHRR) cloud mask data from 1990 to 2019. The results showed that (1) PACI varies dramatically in different regions and months in China. The value was larger in autumn and winter, and the largest figure reached 49.55% in October in Inner Mongolia (NM). In contrast, relatively small values occurred in summer, and the minimum value (5.26%) occurred in June in South China (SC). (2) As the climate changes, the PACI has increased significantly throughout the country and most regions, especially in North China (NC), with a growth rate of 1.9% per decade. The results can be used as a reference for selecting appropriate optical sensors and observation times in areas of interest.

Newton-Krylov (NK) method with the explicit Jacobian matrix is a promising method to solve the nonlinear multi-physics coupling system. However, how to form the Jacobian matrix efficiently is a key issue that is the most cumbersome step in NK method. In this work, a new solution with the finite difference Jacobian based NK (DJNK) method is proposed, where the Jacobian matrix is calculated by finite difference approximation instead of the analytical form. Moreover, DJNK is further improved to form Jacobian by calculating the diagonals of the submatrixes, leading to significant reduction of the time cost. Two benchmarks and a complicated transient neutronics/thermal-hydraulics coupling problem are conducted. Results show that DJNK outperforms widely used Jacobian-free NK (JFNK) method, because of the higher performance in matrix-vector product calculation and the more efficient preconditioning in Krylov iteration. A speedup ratio of DJNK over JFNK is observed to be 1.7.

We report a fuel-free, near-infrared (NIR)-driven Janus microcapsule motor. The Janus microcapsule motors were fabricated by template-assisted polyelectrolyte layer-by-layer assembly, followed by spraying of a gold layer on one side. The NIR-powered Janus motors achieved high propulsion with a maximum speed of 42 µm·s-1 in water. The propulsion mechanism of the Janus motor was attributed to the self-thermophoresis effect: The asymmetric distribution of the gold layer generated a local thermal gradient, which in turn generated thermophoretic force to propel the Janus motor. Such NIR-propelled Janus capsule motors can move efficiently in cell culture medium and have no obvious effects on the cell at the power of the NIR laser, indicating considerable promise for future biomedical applications.

Plant growth-promoting bacteria (PGPB) that inhabit hyperaccumulating plants assist cadmium (Cd) absorption, but the underlying mechanism has not been comprehensively studied. For this reason, we combined the fluorescence imaging, and transcriptomic and metabolomic methods in a Cd hyperaccumulator, Sedum alfredii, inoculated or not with PGPB Pseudomonas fluorescens. The results showed that the newly emerged lateral roots, that were heavily colonized by P. fluorescens, are the main entry for Cd influx in S. alfredii. Inoculation with P. fluorescens promoted a lateral root formation of its host plant, leading to a higher Cd phytoremediation efficiency. Furthermore, the plant transcriptome revealed that 146 plant hormone related genes were significantly up-regulated by the bacterial inoculation, with 119 of them showing a complex interaction, which suggests that a hormonal crosstalk participated root development. The targeted metabolomics analysis showed that P. fluorescens inoculation significantly increased indole acetic acid concentration and significantly decreased concentrations of abscisic acid, brassinolide, trans-zeatin, ethylene and jasmonic acid in S. alfredii roots, thereby inducing lateral root emergence. Altogether, our results highlight the importance of PGPB-induced lateral root formation for the increased Cd uptake in a hyperaccumulating plant.

Helical tubes are widely used in heat exchangers in various industries. Due to the secondary flow caused by centrifugal forces, flow and heat transfer characteristics in helical tubes are more complicated than that in straight tubes. The centrifugal effects depend on Reynolds number, curvature ratio and the helical pitch. In the current investigation, friction factors of laminar and turbulent flows in helical tubes are measured to validate the correlations in the literature. Friction factor correlations for laminar and turbulent flows with large applicable ranges of Reynolds numbers and curvature ratios are recommended. Friction factor correlation of Zhao et al. (2016) for rough helical tube is recommend when Reynolds number is higher than 105. By relating pressure drops and heat transfer coefficients, new Nusselt number correlations for laminar and turbulent convections in helical tubes are obtained by regression analysis of experimental data in the literature. The new correlations show good prediction with wide ranges of Reynolds numbers and curvature ratios.

Plant growth-promoting bacteria (PGPB) can promote photosynthesis and biomass production of hyperaccumulators, achieving enhanced phytoremediation efficiency of cadmium (Cd). A better understanding of the mechanisms controlling photosynthesis of hyperaccumulating plants by PGPB is necessary for developing strategies that promote the practical phytoextraction of Cd-polluted soils. In this study, chlorophyll fluorescence, gas exchange, and transcriptome sequencing were conducted to evaluate the physiological and transcriptional changes on photosynthesis and carbon fixation in hyperaccumulator Sedum alfredii after inoculation with PGPB Pseudomonas fluorescens. The results showed that bacterial inoculation significantly enhanced maximum quantum yield of PS II (Fv/Fm), effective quantum yield of PS II (ΦPSII), photochemical quenching (qP) and chlorophyll concentration, while reduced non-photochemical quenching (NPQ) of S. alfredii. Further, inoculation resulted in an increased net photosynthetic rates (Pn), intercellular CO 2 concentration (Ci), transpiration rate (Tr) and stomatal conductance (Gs) of the studied plant. At the transcriptional level, 70 photosynthetic genes and 42 C4-pathway carbon fixation related genes were significantly up-regulated in response to inoculation, which could be the reason for enhanced photosynthesis and dry biomass. To sum up, this P. fluorescens strain can simultaneously promote growth and Cd uptake of S. alfredii, which can be a promising bacterial agent applied to Cd phytoremediation practices.

Endophyte-assisted phytoremediation has gained increasing attention. However, the interacting mechanisms of endophytes and metal hyperaccumulators are still not clear. An endophytic bacterium Pseudomonas fluorescens Sasm05 inoculation promoted Sedum alfredii Hance rooting and root development, in which the specific root length (SRL) and average number of root tips (ART) increased to 2.09- and 3.35-fold, respectively. Sasm05 inoculation promoted plant growth, increased the chlorophyll content, and elevated Zn uptake of plant at excess Zn supply. At 200 μM Zn treatment level, Sasm05 inoculation increased plant biomass and the chlorophyll content by more than 40%, and root Zn content by 40%. Furthermore, Sasm05 inoculation upregulated the expression of the Zn transporter SaIRT1 to 3.43-fold in the roots, while another transporter SaNramp1 expression was increased to 38.66-fold in the roots and 7.53-fold in the shoots. Time course study showed the best effects of Sasm05 on plant biomass and the chlorophyll content were detected at 30 d, while for Zn content at 3 d. These results firstly provided molecular evidences of endophytic bacteria in facilitating host plant Zn uptake, which will absolutely benefit the understanding of interacting mechanisms between hyperaccumulators and their endophytes.