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Self-germinated seedlings of Citrus sinensis and C. grandis were supplied with nutrient solution with 0 mM AlCl(3)·6H(2)O (control, −Al) or 1 mM AlCl(3)·6H(2)O (+Al) for 18 weeks. The DW (Dry weights) of leaf, stem, shoot and the whole plant of C. grandis were decreased and the ratio of root DW to shoot DW in C. grandis were increased by Al, whereas these parameters of C. sinensis were not changed by Al. Al treatment dramatically decreased the sulfur (S) content in C. grandis roots and the phosphorus (P) content in both C. sinensis and C. grandis roots. More Al was transported to shoots and leaves in C. grandis than in C. sinensis under Al treatment. Al treatment has more adverse effects on C. grandis than on C. sinensis, as revealed by the higher production of superoxide anion (O(2)(·−)), H(2)O(2) and thiobarbituric acid reactive substace (TBARS) content in C. grandis roots. Via the Illumina sequencing technique, we successfully identified and quantified 12 and 16 differentially expressed miRNAs responding to Al stress in C. sinensis and C. grandis roots, respectively. The possible mechanism underlying different Al tolerance of C. sinensis and C. grandis were summarized as having following aspects: (a) enhancement of adventitious and lateral root development (miR160); (b) up-regulation of stress and signaling transduction related genes, such as SGT1, PLC and AAO (miR477, miR397 and miR398); (c) enhancement of citrate secretion (miR3627); (d) more flexible control of alternative glycolysis pathway and TCA cycle (miR3627 and miR482); (e) up-regulation of S-metabolism (miR172); (f) more flexible control of miRNA metabolism. For the first time, we showed that root development (miR160) and cell wall components (cas-miR5139, csi-miR12105) may play crucial roles in Al tolerance in citrus plants. In conclusion, our study provided a comprehensive profile of differentially expressed miRNAs in response to Al stress between two citrus plants differing in Al tolerance which further enriched our understanding of the molecular mechanism underlying Al tolerance in plants. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12298-020-00895-y) contains supplementary material, which is available to authorized users.

Recently, lightweight and highly efficient electromagnetic interference (EMI) shielding composites are crucial but changing for the development of modern electronics and telecommunication. Here, a novel polyhedral Co/C particle embedded carbon nanofiber (CNF@Co/C) aerogels were synthesized via pyrolysis of bacterial cellulose wired zeolitic imidazolate frameworks-67 (ZIF-67) aerogel under argon. The flexible CNF@Co/C aerogels exhibit a high EMI shielding effectiveness (SE) is approaching 56.07 dB at a density of only 0.023 g cm−3 in the X band, and the average absorption coefficient is as high as 0.79, indicating 79% of electromagnetic (EM) waves are absorbed in shielding process. The remarkable performance results from the three-dimensional (3D) CNF-threaded porous structure with interconnected network and the magnetic Co/C particle strung by CNF, which contribute to a conduction loss and optimal impedance matching along with multiple polarization and strong magnetic loss. This work paves a promising way for the new generation of electronic device with lightweight and efficient EMI shielding.

Transition metal phosphides (TMPs) demonstrate great potential for hydrogen evolution reaction (HER) electrocatalysis, but their activities need further improvement. Herein we report a novel Au incorporation strategy to boost the HER catalytic performance of CoP. As a proof of concept, heterostructured Au/CoP nanoparticles dispersed on nitrogen-doped carbon with unique porosity, denoted as Au/CoP@NC-3, are synthesized by thermal treatment of Au-nanoparticle-incorporated ZIF-67 precursor. It shows excellent HER activity as well as good durability in acidic and alkaline condition, respectively, greatly outperforming its Au-free analogue, namely, CoP@NC. In-depth analysis suggests that the improved HER activity of Au/CoP@NC-3 is attributed to the presence of Au nanoparticles which enlarge the electrochemical active surface areas and adjust the electronic structure of active CoP species to enhance the water adsorption and optimize H adsorption for the accelerated HER process.

To improve the mechanical property of 2, 4-dinitroanisole (DNAN)/1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) melt-cast explosives, the effects of additives, N-methyl-4-nitroaniline(MNA), polyethyl...

The accurate assessment of forest damage is important basis for the forest post-disaster recovery process and ecosystem management. This study evaluates the spatial distribution of damaged forest and its damaged severity caused by ice-snow disaster that occurred in southern China during January 10 to February 2 in 2008. The moderate-resolution imaging spectroradiometer (MODIS) 13Q1 products are used, which include two vegetation indices data of NDVI (Normalized Difference Vegetation Index) and EVI (Enhanced Vegetation Index). Furtherly, after Quality Screening (QS) and Savizky-Golay (S-G) filtering of MODIS 13Q1 data, four evaluation indices are obtained, which are NDVI with QS (QSNDVI), EVI with QS (QSEVI), NDVI with S-G filtering (SGNDVI) and EVI with S-G filtering (SGEVI). The study provides a new way of firstly determining the threshold for each image pixel for damaged forest evaluation, by computing the pre-disaster reference value and change threshold with vegetation index from remote sensing data. Results show obvious improvement with the new way for forest damage evaluation, evaluation result of forest damage is much close to the field survey data with standard error of only 0.95 and 1/3 less than the result that evaluated from other threshold method. Comparatively, the QSNDVI shows better performance than other three indices on evaluating forest damages. The evaluated result with QSNDVI shows that the severe, moderate, mild damaged rates of Southern China forests are 47.33%, 34.15%, 18.52%, respectively. By analyzing the influence of topographic and meteorological factors on forest-vegetation damage, we found that the precipitation on freezing days has greater impact on forest-vegetation damage, which is regarded as the most important factor. This study could be a scientific and reliable reference for evaluating the forest damages from ice-snow frozen disasters.

A quick, green, and sensitive method for chiral separation and determination of fluazifop-butyl enantiomers in tobacco and soil was established by ultra-performance convergence chromatography with tandem mass spectrometry (UPC2 -MS/MS). The baseline separation was obtained on an ACQUITY UPC2 Trefoil CEL2 column in 4 minutes with CO2 and methanol as mobile phase. Column temperature, auto back pressure regulator pressure (ABPR), and modifier solvent were optimized to obtain the best separation efficiency. Under the optimal conditions, the recoveries of both enantiomers were 82.8% to 99.5% with relative standard deviations (RSDs) less than 5.5% at three different concentration levels in two matrices. Good coefficients of determination (R2 ≥ 0.9976) were achieved over the concentration range of 10 to 500 ng/mL. The limits of detection (LODs) for all enantiomers in the two matrices varied from 1.6 to 2.1 μg/kg, and the limits of quantification (LOQs) did not exceed 7.0 μg/kg. The proposed method was then successfully applied to analyze authentic samples, confirming that it was a green, convenient, and reliable strategy for the analysis of fluazifop-butyl enantiomers in tobacco and soil.

Hemp (Cannabis sativa L.) cultivars Yunma 5 (YM5, fiber-type) and Bamahuoma (BM, seed-type) were seriously affected by salt-alkali stress during germination, while the knowledge about the salt tolerance during seedling stage is deficient. Here, responses of hemp (Cannabis sativa L.) seedlings of the cultivars YM5 and BM to the stress of different concentrations of NaCl and Na2CO3 were investigated to explore the salt tolerance of hemp. Results showed that the plant height, dry weight and root length of YM5 and BM seedlings gradually decreased as the concentration of NaCl or Na2CO3 increased. Although physiological indices such as EC (Electrical conductivity), SOD (Superoxide dismutase) and Pro (Proline) increased as the salt concentration increased, the increase extent was significantly greater in YM5 than in BM. Under the conditions of 100 and 200 mM NaCl, BM had greater dry weight and root length, and lower Pro content than YM5. However, under the stress of 100 and 200 mM Na2CO3, the opposite results were recorded, with the exception for lower chlorophyll content and higher SOD activity in BM than in YM5. These findings indicated that BM had a stronger NaCl tolerance than YM5. Moreover, morphological indices of the two cultivars under Na2CO3 stress were stunted more than under NaCl stress, and the seedlings died when Na2CO3 concentration increased up to 300 mM. Some up-regulation of salt-tolerant genes were observed in the two hemp cultivars, a higher expression under NaCl stress than under Na2CO3 stress, and a higher expression in YM5 than in BM were recorded. Findings from the study indicated that hemp seedling is more sensitive to Na2CO3 stress, and the tolerance of hemp to salt stress varies with salt type and salt concentration, although both cultivars can withstand moderate doses of NaCl and Na2CO3.

Multicyclic polymers including bicyclic and tetracyclic polymers were constructed by combining atom transfer radical polymerization (ATRP) and a photo-induced coupling reaction of anthryl groups. First, 4-arm and 8-arm star polystyrenes were synthesized by ATRP using tetrafunctional and octafunctional initiators, respectively. Subsequently, after two-step modification of Br-terminated 4-arm and 8-arm star polystyrenes, including azidation and copper-catalyzed azide–alkyne cycloaddition (CuAAC) reactions with prop-2-yn-1-yl anthracene-9-carboxylate, the precursors with anthryl end groups were obtained. Finally, the photo-induced coupling reaction was conducted upon irradiation at 365 nm in a diluted solution of 4-arm and 8-arm star precursors, to produce bicyclic and tetracyclic polymers, respectively. Besides, the multicyclic polymers can convert back to the original precursors after heating at 150 °C. 1H NMR, FT-IR, GPC and UV-vis analyses were carried out to verify the resultant multicyclic structures and the topological conversion between multicyclic polystyrenes and their precursors.

Multicyclic polystyrene (PS) with hyperbranched structure was constructed in an efficient way. First, a seesaw-type PS was synthesized via atom transfer radical polymerization (ATRP) using a Y-shaped ATRP initiator containing one hydroxyl at center and bromine at each end. After azidation, the anthryl and hydroxyl groups were introduced to the ends of the polymer chain by click reaction with a trifunctional molecule bearing alkynyl, hydroxyl, and anthryl groups (alkynyl-OH-ant). By irradiation with 365 nm UV light in a highly dilute condition, cyclic polymer with three hydroxyl groups (c-PS-(OH)3) can be obtained; then it was converted to a cyclic polymer containing three azides (c-PS-(N3)3) by bromination of the hydroxyl groups and azidation. This “A3” cyclic macromonomer was then used to construct hyperbranched multicyclic polymers via self-accelerating click reaction with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The properties of obtained polymer were characterized by NMR, FT-IR, MALDI-TOF MS, a...

Dongdagou Ditch in Baiyin City was one of the key demonstration areas for remediation of heavy metal contamination in China. Solidification/stabilization (S/S) is an appropriate technology...

High-damping alloys have been used in aerospace, automobile manufacturing and other fields due to its capacity to weaken vibration and noise. The damping and tensile properties of the Ti-36Nb-2Ta-3...

Catheter-based intravascular optical coherence tomography (IVOCT) is a powerful imaging modality for visualization of atherosclerosis with high resolution. Quantitative characterization of various tissue types by attenuation coefficient (AC) extraction has been proven to be a potentially significant application of OCT attenuation imaging. However, existing methods for AC extraction from OCT suffer from the challenge of variability in complex tissue types in IVOCT pullback data such as healthy vessel wall, mixed atherosclerotic plaques, plaques with a single component and stent struts, etc. This challenge leads to the ineffectiveness in the tissue differentiation by AC representation based on single scattering model of OCT signal. In this paper, we propose a novel method based on multiple scattering model for parametric imaging of optical attenuation by AC retrieval from IVOCT images conventionally acquired during cardiac catheterization. The OCT signal characterized by the AC is physically modeled by Monte Carlo simulation. Then, the pixel-wise AC retrieval is achieved by iteratively minimizing an error function regarding the modeled and measured backscattered signal. This method provides a general scheme for AC extraction from IVOCT without the premise of complete attenuation of the incident light through the imaging depths. Results of computer-simulated and clinical images demonstrate that the method can avoid overestimation at the end of the depth profile in comparison with the approaches based on the depth-resolved (DR) model. The energy error depth and structural similarity are improved by about 30% and 10% respectively compared with DR. It provides a useful way to differentiate and characterize arterial tissue types in IVOCT images.

Ferroptosis is a new form of regulated cell death that shows promise for tumor treatment. Most current ferroptosis tumor therapies are based on the intrinsic pathological features of the malignancies, and it would be of clinical significance to develop ferroptosis-inducing strategies with improved tumor specificity and modulability. Here we report a polydopamine-based nanoplatform (FeII PDA@LAP-PEG-cRGD) for the efficient loading of Fe2+ and β-lapachone (LAP), which could readily initiate ferroptosis in tumor cells upon treatment with near-infrared light. PDA nanostructures could generate mild hyperthermia under NIR irritation and trigger the release of the ferroptosis-inducing Fe2+ ions. The NIR-actuated photothermal effect would also activate cellular heat shock response and upregulate the downstream NQO1 via HSP70/NQO1 axis to facilitate bioreduction of the concurrently released β-lapachone and enhance intracellular H2 O2 formation to promote the Fe2+ -mediated lipid peroxidation.

This work presents a simple, rapid and green chiral analysis method for five triazole fungicides (penconazole, tebuconazole, triadimefon, myclobutanil, and triadimenol) in tobacco, by which the samples were cleaned up by the novel pass-through solid phase extraction and subsequently the stereoisomers were separated and determined by the supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS). Optimized separation of the stereoisomers was achieved on an ACQUITY UPC2 Trefoil AMY 1 column within 6 min. Under fortified concentration levels of 0.1, 0.5 and 2.0 mg/kg, the mean recoveries were 82.8-106.6%, the intra-day relative standard deviations (RSDs) were 1.1-6.6%, and the inter-day RSDs were 2.5-5.6%. The correlation coefficient was greater than 0.9926 for all studied analytes within the range of 10-500 ng/mL. The limits of detection (LODs) for all stereoisomers ranged from 0.26 μg/kg to 3.24 μg/kg. The established method was subsequently successfully applied to analyze authentic samples, confirming that this method is a novel, rapid and environmentally friendly method for the stereoselective separation of triazole fungicides in tobacco.

Compared with silicon power devices, SiC devices have attracted much attention due to their advantages in high voltage, frequency, and operating temperature. With the continuous improvement of the voltage level and switching speed of SiC MOSFET devices, a higher transient electric field will be generated, during the turn-on and turn-off process of the device. When a semiconductor device dynamic test system is used to evaluate the switching characteristics, the distributed capacitance in the test circuit will introduce an additional current difference under a high transient electric field, thereby affecting the evaluation of the switching characteristics of the device. In order to study the influence of distributed capacitance on the switching characteristics of high-voltage SiC MOSFET devices, this paper establishes an equivalent circuit model considering distributed capacitance, theoretically analyzes the influence of distributed capacitance on the switching characteristics of the device, and the influence law of distributed capacitance is studied with the simulation tools. Finally, The switching waveforms of the 6500V SiC MOSFET device are obtained through actual measurement to verify the correctness of the theory.

Silicon carbide (SiC) devices have attracted much attention due to their superior characteristics of high blocking voltage, high frequency and high operating temperature. In recent years, with the continuous development of SiC device technology, domestic and foreign high-voltage SiC devices have made certain breakthroughs. In this paper, a 6.5kV/400A SiC module is prepared using the 6.5kV SiC MOSFET chip and 6.5kV SiC SBD chip independently developed by the research group. The on-resistance of the module is 20.8mΩ at a junction temperature of 150°C, and the drain leakage current is 146μA under a voltage of 6.5kV, indicating that the module has excellent conduction and blocking characteristics. The switching characteristics of the 6.5kV/400A SiC module are tested and evaluated based on high-voltage SiC dynamic test platform. At a junction temperature of 150°C, the turn-on energy is 714.2mJ, and the turn-off energy Eoff is 448mJ, compared with the Si IGBT module of the same voltage and current, the SiC module has faster switching speed, lower switching loss, and has obvious advantages in high-voltage and high-frequency applications.

In nuclear magnetic resonance gyroscopes (NMRGs), an ambient stray field should be suppressed to maximize performance of the in situ parametrically modulated alkali magnetometer (PMAM). Transfer functions of the PMAM of NMRGs decoupled with lock-in amplifiers are obtained by theoretical and simulation identification. It is found that the frequency bandwidth of the PMAM of NMRGs decoupled by lock-in amplifiers depends largely upon the low-pass filter of the lock-in amplifiers. A dynamic Kalman filter is used to estimate the stray field disturbance that is fed back to field coils to compensate the disturbance in the PMAM. Simulation and experiment results show that the dynamic Kalman filter has adaptiveness to the frequency shift of the nuclear spin precession signal of NMRGs that is quasi-sinusoidal. The dynamic Kalman filter for the PMAM is efficient in suppressing the ambient stray field noise of broad band and low frequency.

N′-nitrosonornicotine (NNN) is one of the most prevalent and toxic tobacco-specific nitrosoamines. A chiral center at its 2′-position results in R and S enantiomers, the partial double bond character of the N N = O group also results in E and Z isomers, therefore, NNN can form a total of four absolute configurations (E-(R)-NNN, E-(S)-NNN, Z-(R)-NNN, and Z-(S)-NNN). This study investigated the resolution of R/S enantiomers and E/Z isomers of NNN by supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS). The baseline separation of E/Z-(R,S)-NNN isomers/enantiomers was accomplished through the optimization of chiral columns and co-solvents. Due to the lack of single standard of E/Z isomers, only R-NNN (sum of E-(R)-NNN and Z-(R)-NNN) and S-NNN (sum of E-(S)-NNN and Z-(S)-NNN) were further examined. Through the comprehensive optimization of SFC-MS/MS conditions, R-NNN and S-NNN were separated with a run time of 5 min, the developed method was validated, and its applicability to the determination of NNN enantiomers in burley tobacco samples was demonstrated. This study could be applied to preparative separation of single enantiomer and/or isomer of NNN, and could provide potential benefits to biologic activity studies on these enantiomers and isomers.

Due to rapid urbanization, industrialization, agricultural development, and mining activities, soil heavy metal pollution has become a severe issue in China. To explore the regional heavy metal ecological risk of lake sediment and surrounding topsoil, we analyzed 237 lakes, with 1797 lake sediment sampling points and 1164 surrounding topsoil sampling points. Lower mean concentrations were detected for most heavy metals in soils than sediment (except for Hg). Cd and Hg in sediments and soils showed a more significant variation, with the coefficient of variation exceeding 110%. Linear regressions and Pearson's correlation analyses demonstrated that sediments and soils exhibited significant positive correlations. The principal heavy metals exceeding the Agricultural Soil Control Standard (ASCS) in sediments and soils were As and Cd, respectively. The Yunnan-Guizhou Plateau Lake Region (YGPLR) was the most seriously affected, exceeding the ASCS for Cd. The lakes with the most severe pollution were located in YGPLR impacted by the high background concentration of heavy metals in soil and mineral development activities. The Eastern Plain Lake Region, the Southeast Lake Region, and the Northeast Plain and Mountain Lake Region showed a clear anthropogenic impact. Lakes in the Inner Mongolia-Xinjiang Lake Region and the Tibetan Plateau Lake Region were estimated to have relatively low ecological risks due to their sparse population and slight environmental disturbance. The impact of geochemical factors on the ecological risk of heavy metals in lake sediments is more substantial than that of human activities at the regional scale.

The trade-off between plant growth and resistance to herbivory is thought to be at least partly mediated by the interactions between jasmonates and gibberellins (GAs). Insect herbivory activates jasmonate biosynthesis and signaling, and plant growth is concomitantly inhibited. Whether or not the herbivory-induced jasmonates suppress the accumulation of GAs and thus reduce plant growth, and which jasmonates are functional in this process, remain unclear. In this study, we show that herbivory-induced stunted growth of Nicotiana attenuata was completely dependent on allene oxide cyclase (AOC) and coronatine insensitive1 (COI1), which encode a JA biosynthetic enzyme and the receptor, respectively, but only partially dependent on jasmonic acid-isoleucine conjugate (JA-Ile), the bioactive jasmonate. Quantification of GAs and exogenous treatments indicated that herbivory-induced growth inhibition was caused by GA4 deficiency, and that the reduction in GA4 accumulation was strongly associated with both decreased concentrations of GA biosynthetic gene transcripts and transcriptional activation of GA catabolic genes. We further show that JA-Ile only positively regulated the levels of GA catabolic genes, while the accumulation of GA biosynthetic gene transcripts was controlled by certain AOC-derived jasmonate(s) rather than by JA-Ile. This work sheds light on the mechanisms by which plants adapt to herbivory by using intricate phytohormone signaling and transcriptional regulatory networks.

We present studies of protein (insulin) efflux rates from nano-sized core–shell systems with a gelled core and a lipid bilayer (nanolipogels). The efflux control mechanism is the manipulation of mesh size, and we show that diffusion control via crosslinking is the dominant mechanism for efflux control. The concept is inspired by the macromolecular crowding effect in human cells, which may be considered as a physical network of undefined mesh size. Our bio-inspired system is made of chemically crosslinked water-swellable poly(ethylene glycol) diacrylate cores, whose mesh size can be manipulated to yield a quantifiable crowding effect that then leads to predictable release rates for biomacromolecules.

Citrus grandis seedlings were irrigated with nutrient solutions with four Al-P combinations [two Al levels (0 mM and 1.2 mM AlCl3·6H2O) × two P levels (0 μM and 200 μM KH2PO4)] for 18 weeks. Al dramatically inhibited the growth of C. grandis seedlings, as revealed by a decreased dry weight of roots and shoots. Elevating P level could ameliorate the Al-induced growth inhibition and organic acid (malate and citrate) secretion in C. grandis. Using a comparative proteomic approach revealed by the isobaric tags for relative and absolute quantification (iTRAQ) technique, 318 differentially abundant proteins (DAPs) were successfully identified and quantified in this study. The possible mechanisms underlying P-induced alleviation of Al toxicity in C. grandis were proposed. Furthermore, some DAPs, such as GLN phosphoribosyl pyrophosphate amidotransferase 2, ATP-dependent caseinolytic (Clp) protease/crotonase family protein, methionine-S-oxide reductase B2, ABC transporter I family member 17 and pyridoxal phosphate phosphatase, were reported for the first time to respond to Al stress in Citrus plants. Our study provides some proteomic details about the alleviative effects of P on Al toxicity in C. grandis, however, the exact function of the DAPs identified herein in response to Al tolerance in plants must be further investigated.

The wake flow characteristics of a spherical bubble against the interface contaminated degree are deeply investigated at moderate Reynolds number (Re = 25–200) based on the 3D rear stagnant cap model. The interface contaminated degree is controlled by changing the magnitude of the cap angle, for θ = 0–180°. It is found that the vortex size does not change obviously when θ = 0–67.5°; when θ > 67.5°, it decreases until it is equal to zero when θ > 135°. The variations of vortex size and separation angle are related to the deceleration of fluid near the lee face of the bubble. The vortexes display the 3D characteristic due to the skip of pressure coefficient component in the flow direction at the leading edge of the stagnant cap when θ = 45°, 67.5°, 112.5° and 135°.

A deep understanding of the basic geologic characteristics of the fine-grained shale layers in the Paleogene 1st sub-member of Kong 2 Member (Ek21) in Cangdong sag, Bohai Bay Basin, is achieved through observation of 140 m continuous cores and systematic analysis of over 1 000 core samples from two wells. Basic geological conditions for shale oil accumulation are proposed based on the unconventional geological theory of oil and gas. The shale rock system mainly developed interbedded formation of felsic shale, calcareous and dolomitic shale and carbonates; high quality hydrocarbon source rock formed in the stable and closed environment is the material base for shale oil enrichment; intergranular pores in analcite, intercrystalline pores in dolomite and interlayer micro-fractures make tight carbonate, calcareous and dolomitic shale and felsic shale effective reservoirs, with brittle mineral content of more than 70%; high abundance laminated shale rock in the lower section of Ek21 is rich in shale oil, with a total thickness of 70 m, burial depth between 2 800 to 4 200 m, an average oil saturation of 50%, a sweet spot area of 260 km2 and predicted resources of over 5×108 t. Therefore, this area is a key replacement domain for oil exploration in the Kongdian Formation of the Cangdong sag. At present, the KN9 vertical well has a daily oil production of 29.6 t after fracturing with a 2 mm choke. A breakthrough of continental shale oil exploration in a lacustrine basin is expected to be achieved by volume fracturing in horizontal wells. Key words: shale oil, fine grained deposits, horizontal well, volume fracturing, shale reservoir sweet spot, Paleogene Kongdian Formation, Cangdong sag, Bohai Bay Basin

The as-cast multi-element Mg–4Gd–1Y–1Zn–0.5Ca–1Zr alloy with low rare earth additions was prepared, and the solution treatment was applied at different temperatures. The microstructural evolution of the alloy was characterized by optical microscopy and scanning electron microscopy, and corrosion properties of the alloy in 3.5% NaCl solution were evaluated by immersion and electrochemical tests. The results indicate that the as-cast alloy is composed of the α-Mg matrix, lamellar long-period stacking-ordered (LPSO) structure and eutectic phase. The LPSO structure exists with more volume fraction in the alloy solution-treated at 440 °C, but disappears with the increase in the solution temperature. For all the solution-treated alloys, the precipitated phases are detected. The corrosion rates of the alloys decrease first and then increase slightly with the increase in the solution temperature, and the corrosion resistance of the solution-treated alloys is more than four times as good as that of the as-cast alloy. In addition, the alloy solution-treated at 480 °C for 6 h shows the best corrosion property.

This paper investigates the influences of various topside cell structures of insulated gate bipolar transistor (IGBT) on the current crowding effect during high current turn-OFF by symmetrical multicell numerical simulations. It is observed that lower breakdown electric field in the drift region can reduce the negative differential resistance in the forward blocking curve and therefore suppress the current crowding effect during high current turn-OFF. We refer to this characteristic as the self-suppressing current crowding effect (SSCCE). Different topside cell structures of IGBT have considerable influence on the SSCCE. A modest increment of the SSCCE by proper topside structure design provides an alternative solution to improve the ruggedness of IGBT, especially for the strong punchthrough or low current gain IGBTs.

Hydraulic fracturing is one of the most effective and efficient methods to enhance oil and gas recovery from reservoirs. Well productivity is mainly determined by the propped dimensions of the fracture. However, the propped dimensions are controlled by proppant transport and proppant placement, of which settling and convection are the controlling mechanisms. In this paper, a new concept is described to overcome the problem of proppant settling during a foam fracturing treatment and prior to fracture closure. This new concept consists of introducing nanoparticles into the base fracturing fluid system to stabilize the foam structure and reduce proppant settling. The results show that foam stability directly influences proppant placement and final fracture conductivity. When foam fracturing fluids experience long closure times, most often as a result of low leakoff, foam breakage occurs. This breakage results in proppant settling and accumulation at the bottom of the fracture, reducing propped dimensions. Whilst, high pumping rates and foam quality provide greater initial propped area, foam stability is major factor controlling the final propped area and productivity. Experimental results show that foam stability increases 2–3-fold in presence of 0.8-wt% silica nanoparticles under 90 °C. The enhancement of foam stability using nanoparticles, particularly foam life-time, allows better proppant suspension, maintains post-fracture conductivity, and minimizes productivity losses. This work is intended to guide the practitioner in the use of nano-stabilized foam to improve unconventional reservoir stimulation.

Recently, graphene has attracted great research interest and produced superior properties for polymer composites at low filler content. However, the lowest filler content is limited because the graphene must provide enough conducting paths to substantially improve the thermal and electrical performances. In this study, three-dimensional interconnected graphene foam (GF) was prepared to overcome the limitation and GF filled poly(methyl methacrylate) (PMMA) composite was fabricated by an in situ polymerization method with an ultralow graphene content of 0.4 wt%. The thermal conductivity of GF/PMMA composite reaches 0.27 W m−1 K−1 and the electrical conductivity achieves 3.5 × 10−2 S m−1, 50% and 8 orders of magnitude higher than that of pure PMMA, respectively. The local mechanical strength of composite is also enhanced by the addition of GF. Furthermore, the composite presents a superior performance in heat dissipation of high power devices and has a stable performance in thermal cycling test. This work provides a method to greatly improve the thermal, electrical and mechanical performances of graphene/polymer composites at an ultralow graphene content and proves that graphene foam filled poly(methyl methacrylate) composite is effective as a thermal interface material (TIM).

Benzo[a]pyrene (BaP) is considered as one of the most carcinogenic pollutants in cigarette smoke. The development of simple and sensitive BaP screening methods can help assess the risk of cigarette exposure to the human body rapidly. In this report, a rapid fluorescence immunoassay (RFIA) method for the detection of BaP is proposed, the core of which is the synthesis of bifunctional covalent antibody–DNA conjugates for target recognition and signal amplification. Based on the optimization of the SYBR Green I and PAH–BSA concentrations, as well as DNA–antibody immune complex's dilution in the RFIA system, a serial dilution of BaP was tested with this method. The results showed that the linear working range of the RFIA for BaP is 0.46 to 333 ng mL−1, which is much wider than traditional ELISA. The detection limit was 0.32 ng mL−1, which was more sensitive than other methods such as the redox-labeled electrochemical immunoassay method and the competitive piezoelectric biosensor. Then the cross-reactions (CR) of other PAHs in cigarette smoke were evaluated using this RFIA and found that the cross-reactions of naphthalene, anthracene, and pyrene were very low (

Shale gas is one of the most promising resources for unconventional natural gas. Several shale samples were collected from the Silurian Longmaxi Formation in the Yibin region, Sichuan Province, China. The basic geological parameters of the shale samples including total organic carbon, clay mineral content, and vitrinite reflectance were detected. Pore structure characteristics were analyzed with scanning electron microscopy, high-pressure mercury injection, and low-temperature nitrogen and carbon dioxide adsorption methods. Isothermal adsorption and desorption experiments were carried out using gravimetric methods. The isosteric heat of the shale adsorption was calculated using the isothermal adsorption experimental results. According to the experimental results, the shale samples have high maturity, low porosity and penetration. The surface morphological structures include organic pores, clay mineral pores, intergranular pores of authigenic minerals, dissolution pores and micro-cracks. Micropores comprised the majority of the developed pores in the shale samples and play a major role in adsorption processes. The adsorption and desorption results show that the adsorption amount of gas mainly undergoes a rapid increase phase, a slowly rising transition phase and a gentle phase, and desorption hysteresis generally occurs during gas desorption. Adsorption thermodynamics results show that the volume of adsorbed gas decreases with the increase of adsorption temperature and the isosteric heat increases with the increase of the volume of the adsorbed gas.

Thermal management has become a serious problem with development of miniaturized, high integration and high performance electronics devices, where the improvement of thermal conductivity on polymer composites is crucial for the internal heat transfer and dissipation. In this work, graphene aerogels (GA) with three-dimensional (3D) structure were prepared by a simple method and reduced by different ways. Then, GA were used as fillers to prepare high thermal conductivity polymer composites. A thermal conductivity of 3.36 W m −1 K −1 at room temperature was obtained when use polyurethane filling the hydroiodic acid reduced GA composite (HI-RGA/PU), and the graphene loading was as low as 2.5 wt.%. This result is better than most researches of polymer-based thermal conductive composites. Furthermore, the heat transfer test and thermal cycling test show that HI-RGA/PU has a good and stable performance in the practical application as thermal interface material (TIM), which proves that GA is a promising filler for thermal conductive material.

To fabricate ceramic components with a complex structure, the bottom-up mask-projection stereolithography (MP-SL) technique is currently employed. However, a fracture or a defect is normally found because of the large separation force formed between the newly cured layer and the bottom surface of the slurry tank. Hence, to overcome this issue, an oxygen-permeable layer is integrated into the conventional MP-SL system for printing a β-TCP ceramic slurry in this study. The system is based on the fact that oxygen inhibits the photopolymerization process by consuming free radicals. The effects of the light exposure time and oxygen concentration on the curing depth and thickness of the oxygen-inhibition layer were investigated. Moreover, the separation forces were indirectly determined using a weight sensor. The results show that the oxygen-inhibition layer helped in reducing the separation force by 60% compared to that wherein oxygen is not employed. The solid loading could be increased by up to 44 vol% and the printable cross-sectional area by 5 times. In summary, the proposed oxygen-controlled bottom-up MP-SL technique helped in improving the ceramic printing efficiency and product quality.

Nitrate treatment performance and denitrification activity were compared between denitrifying biological filters (DNBFs) based on dewatered alum sludge (DAS) and neutralized used acid (NUA). The spatiotemporal distribution of denitrifying genes and the genetic potential associated with denitrification activity and nitrate removal in both DNBFs were also evaluated. The removal efficiency of NUA–DNBF increased by 8% compared with that of DAS–DNBF, and the former NUA–DNBF emitted higher amount of N2O. Analysis of abundance and composition profiles showed that denitrifying gene patterns varied more or less in two matrices with different depths at three sampling times. Burkholderiales, Rhodocyclales, and Rhizobiales were the most commonly detected in both media during stable periods. Denitrification was determined by the abundance of specific genes or their ratios as revealed by controlling factors. The enhanced nitrate removal could be due to increasing qnosZ or decreasing ∑qnir/qnosZ. Furthermore, NUA–DNBF solely reduced nitrate by increasing the denitrification enzyme activity.

Thermal management has become a serious problem with the development of electronics, where thermal interface material (TIM) is crucial for heat transfer from the device to heat sink. In this work, reduced graphene oxide/thermoplastic polyurethane (RGO/TPU) composites with a segregated structure were proposed and prepared by a simple method to obtain superior thermal conductive property and used as TIM. The microstructures and thermal properties of RGO/TPU composites were characterized, as well as heat transfer performance and thermal fatigue resistance. The obtained composite, at an ultralow graphene loading of 1.04 wt.%, exhibits a high thermal conductivity (0.8 W m −1 K −1 ). Furthermore, the composite as a TIM presents a good performance in practical application and has a stable performance in the thermal cycling test.

Decreasing the chip thickness of insulated gate bipolar transistor (IGBT) to improve the performance makes the current crowding effect become more pronounced during short-circuit turn-off, especially in the self-clamping mode (SCM). Former researchers have investigated the failure mechanisms during short-circuit turn-off. But the measures to further improve the robustness of IGBT during short-circuit turn-off and performance simultaneously still need more investigations. This paper focuses on the influences of the major device parameters on the robustness of IGBT during short-circuit turn-off, especially in the SCM, and its tradeoff characteristics with performance via symmetrical multicell electrothermal simulations. The results show that wider drift region combined with higher doping concentration, lower saturation current, and larger cell pitch can achieve higher robustness during short-circuit turn-off, but the performance will degrade. Besides, as the current gain increases, there exists the optimum value at which the robustness of IGBT during short-circuit turn-off is the highest. In order to achieve high performance and high robustness during short-circuit turn-off simultaneously, combined with decreasing the chip thickness and current gain, the saturation current should be decreased without compromising the conducting voltage by novel device structure, such as trench shielded planar gate IGBT and high-conductivity IGBT.

Aromatic amines in mainstream cigarette smoke have long been monitored due to their carcinogenic toxicity. In this work, a reliable and rapid method was developed for the simultaneous determination of 9 aromatic amines in mainstream cigarette smoke by modified dispersive liquid liquid microextraction (DLLME) and ultraperformance convergence chromatography tandem mass spectrometry (UPC2-MS/MS). Briefly, the particulate phase of the cigarette smoke was captured by a Cambridge filter pad, and diluted hydrogen chloride aqueous solution is employed to extract the aromatic amines under mechanical shaking. After alkalization with sodium hydroxide solution, small amount of toluene was introduced to further extract and enrich aromatic amines by modified DLLME under vortexing. After centrifugation, toluene phase was purified by a universal QuEChERS cleanup kit and was finally analyzed by UPC2-MS/MS. Attributing to the superior performance of UPC2-MS/MS, this novel approach allowed the separation and determination of 9 aromatic amines within 5.0min with satisfactory resolution and sensitivity. The proposed method was finally validated using Kentucky reference cigarette 3R4F, and emission levels of targeted aromatic amines determined were comparable to previously reported methods At three different spiked levels, the recoveries of most analytes were ranged from 74.01% to 120.50% with relative standard deviation (RSD) less than 12%, except that the recovery of p-toluidine at low spiked level and 3-aminobiphenyl at medium spiked level was 62.77% and 69.37% respectively. Thus, this work provides a novel alternative method for the simultaneous analysis of 9 aromatic amines in mainstream cigarette smoke.

The World Health Organization Study Group on Tobacco Product Regulation (WHO TobReg) proposed mandated ceilings on 9 prioritized mainstream cigarette smoke constituents determined from the market-specific median of nicotine-normalized yield distributions. Considering the requirements for assessing and reporting of compliance with ceilings, it is of great importance to estimate the measurement uncertainty. To have a better understanding of influence of measurement uncertainty on the WHO recommended regulation for cigarette smoke constituents, in the present study, the measurement uncertainties were evaluated systematically based on series of collaborative studies reported by three different authorities over the years from 2012 to 2016, according to the approaches guided in ISO/TS 21748. Furthermore, the compliance assessment of 20 representative cigarette samples with proposed ceilings was conducted by taking measurement uncertainty into account. This work demonstrated that measurement uncertainty had great influence on the implementation of the regulated mandated lowering of toxic smoke constituents, both on the setting of ceilings and the compliance assessment as well.

Regarding the novel application of nanoparticles in enhanced oil recovery, the objective of this study was to investigate the potential of silica nanoparticles to stabilize foam under high-temperature conditions and exhibit an improved capacity to suspend proppants for hydraulic fracturing applications. In this study, a regular anionic surfactant was employed as the foaming agent and a worm-like micelle (WLM) surfactant was employed as the foam viscosifer and silica nanoparticles. The results indicate that the SiO 2 nanoparticles and WLMs exhibit a synergistic effect in terms of foam rheology and stability, which significantly improves the proppant suspension capabilities for petroleum applications.

Sub-harmonic mixers are the core element of terahertz room temperature, high spectral resolution heterodyne receivers for planetary science, and remote sensing. Here, terahertz sub-harmonic mixer up to 400 GHz using discrete Schottky diode is presented. Measured performance is in agreement with results from the linear and nonlinear co-simulations, and this methodology shows its practicability for the discrete planar GaAs Schottky diode-based terahertz core circuit design.

Calophaca sinica Rehd. is a tree species with high economic value, whose resource has been declining due to unreasonable exploitation. In this study, we sequenced, assembled, and annotated the complete chloroplast genome of C. sinica. The whole chloroplast genome size is 129,345 bp, it lacks an inverted repeat (IR) region. The GC content of the whole chloroplast genome is 34.51%. The chloroplast genome comprises 112 unique genes, including 77 protein-coding genes (PCGs), 30 transfer RNA (tRNA) genes, and 5 ribosomal RNA (rRNA) genes. Phylogenetic analyses of chloroplast genomes derived from 15 species indicated that C. sinica is close to Caragana and Tibetia species in Papilionoideae.

Aluminum (Al) treatment significantly decreased the dry weight (DW) of stem, shoot and whole plant of both Citrus sinensis and C. grandis, but did not change that of root. Al significantly decreased leaf DW of C. grandis, increased the ratio of root to shoot and the lignin content in roots of both species. The higher content of Al in leaves and stems and lignin in roots of C. grandis than that of C. sinensis might be due to the over-expression of Al sensitive 3 (ALS3) and cinnamyl alcohol deaminase (CAD) in roots of C. grandis, respectively. By using yeast-two-hybridazation (Y2H) and bimolecular fluorescence complementation (BiFC) techniques, we obtained the results that glutathione S-transferase (GST), vacuolar-type proton ATPase (V-ATPase), aquaporin PIP2 (PIP2), ubiquitin carboxyl-terminal hydrolase 13 (UCT13), putative dicyanin blue copper protein (DCBC) and uncharacterized protein 2 (UP2) were interacted with ALS3 and GST, V-ATPase, Al sensitive 3 (ALS3), cytochrome P450 (CP450), PIP2, uncharacterized protein 1 (UP1) and UP2 were interacted with CAD. Annotation analysis revealed that these proteins were involved in detoxification, cellular transport, post-transcriptional modification and oxidation-reduction homeostasis or lignin biosynthesis in plants. Real-time quantitative PCR (RT-qPCR) analysis further revealed that the higher gene expression levels of most of these interacting proteins in C. grandis roots than that in C. sinensis ones were consistent with the higher contents of lignin in C. grandis roots and Al absorbed by C. grandis. In conclusion, our study identified some key interacting components of Al responsive proteins ALS3 and CAD, which could further help us to understand the molecular mechanism of Al tolerance in citrus plants and provide new information to the selection and breeding of tolerant cultivars, which are cultivated in acidic areas.

Quantum repeaters -- important components of a scalable quantum internet -- enable the entanglement to be distributed over long distances. The standard paradigm for a quantum repeater relies on a necessary demanding requirement of quantum memory. Despite significant progress, the limited performance of quantum memory makes practical quantum repeaters still a great challenge. Remarkably, a proposed all-photonic quantum repeater avoids the need for quantum memory by harnessing the graph states in the repeater nodes. Here we perform an experimental demonstration of an all-photonic quantum repeater using linear optics. By manipulating a 12-photon interferometer, we implement a 2-by-2 parallel all-photonic quantum repeater, and observe an 89% enhancement of entanglement-generation rate over the standard parallel entanglement swapping. These results open a new way towards designing repeaters with efficient single-photon sources and photonic graph states, and suggest that the all-photonic scheme represents an alternative path -- parallel to that of matter-memory-based schemes -- towards realizing practical quantum repeaters., Published online in Nature Photonics

Magnesium (Mg) deficiency is one of the major constraining factors that limit the yield and quality of agricultural products. Uniform seedlings of the Citrus sinensis were irrigated with Mg deficient (0 mM MgSO4) and Mg sufficient (1 mM MgSO4) nutrient solutions for 16 weeks. CO2 assimilation, starch, soluble carbohydrates, TBARS content and H2O2 production were measured. Transcriptomic analysis of C. sinensis leaves was performed by Illumina sequencing. Our results showed that Mg deficiency decreased CO2 assimilation, but increased starch, sucrose, TBARS content and H2O2 production in C. sinensis leaves. A total of 4864 genes showed differential expression in response to Mg deficiency revealed by RNA-Seq and the transcriptomic data were further validated by real-time quantitative PCR (RT-qPCR). Gene ontology (GO) enrichment analysis indicated that the mechanisms underlying Mg deficiency tolerance in C. sinensis may be attributed to the following aspects: a) enhanced microtubule-based movement and cell cycle regulation, b) elevated signal transduction in response to biotic and abiotic stimuli, c) alteration of biological processes by tightly controlling phosphorylation especially protein phosphorylation, d) down-regulation of light harvesting and photosynthesis due to the accumulation of carbohydrates, e) up-regulation of cell wall remodeling and antioxidant system. Our results provide a comprehensive insight into the transcriptomic profile of key components involved in the Mg deficiency tolerance in C. sinensis and enrich our understanding of the molecular mechanisms by which plants adapted to a Mg deficient condition.

The Giant Steerable Science Mirror (GSSM) is the tertiary mirror system of the Thirty Meter Telescope (TMT) that relays optical beams from the secondary mirror to active instruments on Nasmyth platforms. One of the key technologies involved in GSSM functions is the error budget allocation from the system engineering of TMT. A novel approach of error analysis and allocation with strong adaptability, which is based on normalized Point Source Sensitivity (PSSn), is proposed. The relay optical function including the quality of the wavefront, the rationality of the mechanism, and the stability of the light were achieved based on the proposed method. The experiments validate the proposed method.

Approximately 4000 diseases are associated with malfunctioning genes in a particular cell type. Gene-based therapy provides a platform to modify the disease-causing genes expression at the cellular level to treat pathological conditions. However, gene delivery is challenging as these therapeutic genes need to overcome several physiological and intracellular barriers in order, to reach the target cells. Over the years, efforts have been dedicated to develop efficient gene delivery vectors to overcome these systemic barriers. Chitosan, a versatile polysaccharide, is an attractive non-viral vector material for gene delivery mainly due to its cationic nature, biodegradability and biocompatibility. The present review discusses the design factors that are critical for efficient gene delivery/transfection and highlights the recent progress of gene therapy using chitosan-based carriers. Published version