Resistive pressure sensors generally employ microstructures such as pores and pyramids in the active layer or on the electrodes to reduce the Young's modulus and improve the sensitivity. However, ...such pressure sensors always exhibit complex fabrication process and have difficulties in controlling the uniformity of microstructures. In this paper, we demonstrated a highly sensitive resistive pressure sensor based on a composite comprising of low-polarity liquid crystal (LPLC), multi-walled carbon nanotube (MWCNT), and polydimethylsiloxane (PDMS) elastomer. The LPLC in the PDMS forms a polymer-dispersed liquid crystal (PDLC) structure which can not only reduce the Young's modulus but also contribute to the construction of conductive paths in the active layer. By optimizing the concentration of LC in PDMS elastomer, the resistive pressure sensor shows a high sensitivity of 5.35 kPa
, fast response (<150 ms), and great durability. Fabrication process is also facile and the uniformity of the microstructures can be readily controlled. The pressure sensor offers great potential for applications in emerging wearable devices and electronic skins.
The absence of an effective approach to achieve free‐standing inorganic memristors seriously hinders the development of transferable artificial synapses. Here, a transferable WOx‐based memristive ...synapse is demonstrated using a nondestructive water‐dissolution method in which the NaCl substrate is selected as the sacrificial layer due to its thermotolerance and water‐solubility. The essential synaptic learning functions are achieved to comprehensively mimic the biological synapse, such as short‐term/long‐term plasticity, paired‐pulse facilitation, and spike‐timing‐dependent plasticity. This artificial synapse can be transferred and conformed onto various unconventional substrates to manifest the flexibility, 3D conformality, and biocompatibility. There is no mechanical damage during the transfer process, and all these transferred devices present excellent synaptic emulations. The memristive behavior shows no degeneration after large‐angle bending or 100 times bending tests. This result may pave a feasible way for the realization of wearable neuromorphic computing systems in the future.
Using a nondestructive water‐dissolution method, a transferable WOX memristor is demonstrated when selecting NaCl substrate as the sacrificial layer. The synaptic devices are transferred onto diverse substrates, presenting excellent flexibility and high mechanical endurance. The essential functions of synaptic plasticity are obtained in the device on the bent state. The work offers a feasible method to enable inorganic memristors for transferable applications.
The stratigraphic succession of a forearc basin provides crucial information on the history of a convergent plate margin. In particular, it helps to establish the origin of the underlying ophiolites ...and to unravel the earliest evolutionary stage of arc-trench systems, which remain poorly understood. The Xigaze forearc basin in southern Tibet is one of the best examples of a fossil forearc basin. This study illustrates detailed stratigraphic and high-precision SIMS U–Pb zircon geochronological and Hf isotopic data from the Chongdui Formation, representing the very base of the Xigaze forearc-basin succession, and reconstructs when and how the basin was formed. The Chongdui Formation includes tuffaceous chert and siliceous mudrocks deposited directly on top of pillow basalts of the Xigaze ophiolite and conformably overlain by volcaniclastic turbidites. Tuff layers are interbedded throughout the unit, and their U–Pb zircon ages range from 119 to 113 Ma in the lower member and from 113 to 110 Ma in the upper member, broadly consistent with the established radiolarian biostratigraphy. U–Pb ages and Hf isotope signatures of zircons contained in both tuff layers and turbiditic sandstones indicate clear affinity with magmatic rocks of the Lhasa terrane. Direct depositional and chronostratigraphic relationship with the underlying oceanic crust, dated between 131 and 124 Ma, proves that the Xigaze ophiolite is the basement of the Xigaze forearc basin. After an initial prolonged stage of starved siliceous sedimentation, influx of terrigenous detritus began at 113–110 Ma, reflecting the onset of topographic growth and erosion of the Lhasa terrane in response to intense magmatic activity. Formation of the ophiolitic basement during the early stage of subduction and the subsequent topographic growth of the arc source induced by subduction-related magmatism are thus two critical factors for the birth of the Xigaze forearc basin. Similar stratigraphies were identified in the Great Valley and Luzon Central Valley forearc basins, suggesting that the initial geodynamic evolution of the Xigaze forearc basin may be common to many other forearc basins worldwide.
•The Xigaze forearc basin was built above the newly formed Xigaze ophiolites.•Stratigraphic base comprises a lower siliceous member and an upper turbidite member.•Siliceous deposition with Transhimlayan tuffs followed the formation of ophiolites.•Deposition of volcaniclastic turbidites began at 113–110 Ma.•Early stages of Neotethyan subduction determined the birth of Xigaze forearc basin.
It is increasingly clear that microRNAs (miRNAs) play an important role in controlling cell survival. However, the functional significance of miRNAs in ischemic brain injury remains poorly ...understood. In the present study, we assayed the expression levels of miR-29b after ischemic brain injury, and defined the target genes and biological functions of miR-29b. We found that the miR-29b levels were significantly increased in rat brain after transient middle cerebral artery occlusion and neurons after oxygen–glucose deprivation. Moreover, ectopic expression of miR-29b promoted neuronal cell death, whereas its repression decreased cell death. Furthermore, we verified that miR-29b directly targeted and inhibited Bcl2L2 gene expression, and then increased neuronal cell death. Importantly, Bcl2L2 overexpression rescued neuronal cell death induced by miR-29b. These results suggest an important role of miR-29b in regulating neuronal cell death, thus offering a new target for the development of therapeutic agents against ischemic brain injury.
With an attempt to replace petroleum-derived commercial graphite (CG) with biomass-derived carbon, microcrystalline cellulose (MCC) dissolved in 1-butyl-3-methylimidazolium acetate (BMIMAcO) was ...facilely carbonized to prepare cellulose-derived carbon under a low-temperature range of 250–1600 °C. TEM and AFM results revealed structural evolution of carbon nanosheets starting from carbon dots. The XRD and Raman results showed that the degree of crystallinity of the MCC-derived carbon was apparently enhanced as the temperature was increased to 93.02% at 1600 °C, while the XPS results revealed that the nitrogen content was greatly reduced with increasing temperature. BMIMAcO not only induced low-temperature graphitization of MCC-derived carbon but also provided nitrogen doping for the carbon. Used as an anode of lithium-ion batteries (LIBs), the carbon synthesized at 750 °C showed the best cyclic stability and reversible capacity (1052.22 mAh g–1 at 0.5 A g–1 after 100 cycles and 1017.46 mAh g–1 at 1 A g–1 after 1000 cycles) compared to other MCC-derived carbon and CG. In addition, the costs of cellulose-derived carbon are much lower than those of the petroleum-derived graphite, showing environmental and economical merits for LIB anode production.
It is significant to make full use of solar energy to reduce the deterioration of asphalt pavements and the negative impact on the environment due to temperature changes. Using phase change materials ...(PCMs) in asphalt mixture could increase temperature regulation and reduce thermal degradation due to temperature cycling. In order to study the effect of a new solid–solid PCM called PPGC-PCM on the performance of asphalt mixture, a series of tests were carried out. The control group and six different contents of PPGC-PCM were added into AC-13 asphalt mixtures. The effects of PPGC-PCM on the mechanical, moisture resistance, high-temperature, and low-temperature cracking resistance properties of asphalt mixture was analyzed. The influence of PPGC-PCM on the thermal properties in asphalt mixture was analyzed by thermal conductivity test. Results showed that the addition of PPGC-PCM could improve the moisture resistance and low-temperature cracking resistance of asphalt mixtures, as well as greatly reduce the thermal conductivity of the asphalt mixture. The optimal application could be achieved by using the PPGC-PCM with 7.5% addition ratio. In addition, the cooling test proved that the addition of PPGC-PCM could significantly improve the heat preservation capacity of the asphalt mixture. The temperature difference between PPGC-PCM and control testing groups was up to 3.8°C, and the mixture was cooled from 21°C to 0°C with a delay of 18–21 min.
79Se, one of the key radionuclides for nuclear waste disposal, threatens the quality of the environment, as well as human health. Therefore, it needs to be permanently isolated from the biosphere. ...The aim of the study was to investigate the effects of Fe(II)/Fe(III) on the removal of 79Se using bentonite in the pH range of 2.0–10.0 under oxic/anoxic conditions. Under oxic conditions, Se(IV) prefers to form inner-sphere complexes with Fe(III)-oxyhydroxide, derived from the oxidization of Fe(II) using oxygen. Interestingly, Se(IV) will interact with Fe(III) and form a poorly soluble ferric selenite at pH ∼4 under oxic conditions. Under anoxic conditions, however, the concentration of Fe(II) is closely related to the sorption process of Se(IV) on bentonite. When the concentration of Fe(II) was less than 1%, Fe(II) combined with the hydroxyl, forming Fe(OH)2, which generated a disproportionation at pH ∼8 and formed a new sorbent, Fe3O4. However, when the concentration of Fe(II) was increased to 5%, reduction precipitation was the primary way to remove Se(IV) in aqueous solution. XANES (X-ray Absorption Near Edge Structure) spectra showed that higher pH values are beneficial for the formation of the final thermodynamic reduction product, Fe selenide. These results suggested that Fe(II) significantly affect the Se(IV) sorption. Overall, this study confirmed the significant role of Fe(II) on the retardation of 79Se and on remediation for Se(IV) contamination in the hydrosphere.
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•Fe(II) species could greatly enhance the sorption efficiency of Se(IV) via bentonite.•Formation of ferric selenite contributes to the sorption under aerobic condition.•Under anoxic conditions, Se(IV) can be reduced by a two-step sorption/reduction mechanism.•Fe selenide is the finally thermodynamic reduction product of Se(IV).•Fe(II) plays an important role on the remediation of Se(IV) contamination in groundwater.
The significant role of Fe(II) on retardation of 79Se via bentonite and on remediation of Se(IV) contamination in groundwater was demonstrated.
Carbon nanofibers (CNFs) are self-standing, lightweight and stable materials that naturally suitable for electromagnetic interference (EMI) shielding and Joule heating applications. However, ...intrinsic low conductivity severely restricts the operational performance of CNFs. Current methods that can improve the conductivity of CNFs inevitably sacrifice their flexibility for exchange. This work develops a nitride forming metal and magnetic metal codope method of nitrogen-doped CNFs by using electrospinning and annealing, and obtains highly conductive and flexible CNFs embedded with TiN and Co nanoparticles (TCCNFs). Multiple characterizations and electrical and mechanical tests are carried out to reveal that the strong Ti–N covalent bond can enhance the mechanical robustness and the Co nanoparticles contribute to improve the conductivity of CNFs. As a result, a multilayer porous TCCNF mat exhibits an ultrahigh EMI shielding effectiveness of 93 dB in the 8.2–12.4 GHz frequency range due to the combined effects of multi-reflection, dielectric polarization relaxation, and conducting and magnetic loss processes. Additionally, the TCCNF mat-based heater shows the highest Joule heating efficiency of 1508 °C W−1 cm2 among the flexible conductive materials and a superfast Joule heating (cooling) rate of 28 (31) °C/s. The TCCNF mat-based heater is able to reduce the restoring time of Ti3C2Tx MXene humidity sensor by about 78%. The TCCNF mats should also be potential electrode materials for wearable electronics.
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•Excessive Fertilizer and manure were applied into greenhouse vegetable production systems (GVPS).•Soil nutrients accumulation and their changes with vegetable cultivation in GVPS were ...investigated.•GVPS soil nutrients were imbalance with the C, N, and P ratios significantly different from other systems and other lands.•Available N and P, SOC, and soluble salts were the main factors caused soil acidification in GVPS.
The total area of greenhouse crop production is increasing in China. However, this adversely influences soil physical and chemical properties due to special environmental conditions and agricultural management in greenhouse production. In this study, we evaluated soil properties of greenhouse vegetable systems with different planting years, a long-term greenhouse strawberry system, and an open-field wheat-maize rotation system in a typical agricultural production area of North China. The annual fertilizer application rates of nitrogen (N), phosphorus (P), and potassium (K) in the greenhouse vegetable system were 842.15, 809.14, and 931.55 kg ha−1, respectively, which were 3 times more than those in the wheat-maize rotation system and led to great changes of soil properties. Bulk density and soil pH gradually declined with increased cultivation time from new to 15 years in the greenhouse vegetable system. Bulk density declined from 1.58 g/cm3 in the new greenhouse fields to 1.25 g/cm3 in the 15-year greenhouse fields, and pH decreased from 5.72 to 4.55 with a rate of 0.08 unit per year. The contents of soil organic carbon (SOC), soil soluble salts, total NPK, and available NPK rose steadily until the 10th or 11th year, then decreased. By comparison with another two cropping systems, the greenhouse vegetable fields showed the lowest bulk density and pH, but the highest contents of SOC, soil soluble salts, total NPK, and available NPK due to heavy fertilizer inputs. The contents of soil N, P, and K in greenhouse vegetable fields were imbalanced, as indicated by C:N (11.58), C:P (16.06), and N:P (1.71) molar ratios in soils, which were significantly lower than the level in China and the rest of the world. In addition, the C:P and N:P ratios of greenhouse vegetable fields were also lower than those of wheat-maize rotation fields and greenhouse strawberry fields. Regression analysis indicated that the contents of SOC and soluble salts were positively correlated with pH, while available N and P contents showed negative linear relationships. These results demonstrate dramatic adverse changes of soil properties in intensive greenhouse vegetable fields in China. Our results also emphasize the need to regulate appropriate fertilizer application for intensive greenhouse vegetable management.
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•Cu-doped Mo2C catalyst is synthesized by a solid-state pyrolysis method.•Cu species are incorporated into Mo2C lattice.•Cu tunes the morphologies and intrinsic properties of ...carbides.•Synergistic effect between Cu and Mo2C is observed in DMO hydrogenation.•Cu–Mo2C can retain the excellent activity for longer than 300h.
Several copper-doped molybdenum carbide (Cu–Mo2C) nanomaterials for the hydrogenation of dimethyl oxalate (DMO) to ethanol at low temperature (e.g., 473K) have been developed through a facile solid-state pyrolysis method. Characterization techniques including X-ray diffraction, scanning/transmission electron microscopy, N2-physisorption, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy were employed to reveal the morphology, structure and properties of the synthesized nanomaterials. The characterization and reaction results suggest that the incorporation of copper species in Mo2C plays a crucial role in modifying the morphologic structure of Cu–Mo2C as well as tuning the electronic state of Mo active sites, resulting in an important enhancement in the catalytic performance. Moreover, a strong synergistic effect between Cu and Mo2C is observed in DMO hydrogenation. Accordingly, the 67.2% yield of ethanol can be attained at a low temperature of 473K over the Cu–Mo2C nanomaterials with a suitable atom ratio (e.g., Cu:Mo=0.03:1), which are higher than those obtained by using a pure Mo2C (e.g., 13.7%) under the same reaction conditions. The Cu-doped Mo2C nanomaterials also display excellent catalytic stability during the hydrogenation of DMO to ethanol for longer than 300h.
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