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A rate-dependent cohesive zone model with the effects of interfacial viscoelasticity and progressive damage
No full textA generalized rate-dependent cohesive zone model for describing the interfacial viscoelasticity and progressive damage of mode I fracture is presented. The proposed model has efficiently extended the traditional bi-linear cohesive traction-separation law to remove the assumptions that some of the rate-dependent parameters such as elastic stiffness, initial separation and strength, critical separation are constant at different loading speeds. Furthermore, the ratedependency of the damage evolution, which is observed in experiments but largely neglected in the previous models, is established to describe the rate-dependent fracture process linked with the generalized traction-separation law, and an equivalent generalized Maxwell model (GMM), based on the Kohlrausch-William-Watts function with significant fewer material parameters required as input, is proposed to describe the time and history dependent stress-strain relationship of the viscoelastic interface material. The proposed model is validated by the simulations of the DCB tests with both the SBR/NR rubber interface and Polyurethane interface
Direct demonstration of carrier distribution and recombination within step-bunched UV-LEDs
No full textAlGaN-based solid state UV emitters have many advantages over conventional UV sources. However, UV-LEDs still suffer from numerous challenges, including low quantum efficiency compared to their blue LED counterparts. One of the inherent reasons is a lack of carrier localization effect inside fully miscible AlGaN alloys. In the pursuit of phase separation and carrier localization inside the active region of AlGaN UV-LED, utilization of highly misoriented substrates proves to be useful, yet the carrier distribution and recombination mechanism in such structures has seldom been reported. In this paper, a UV-LED with step-bunched surface morphology was designed and fabricated, and the internal mechanism of high internal quantum efficiency was studied in detail. The correlation between microscale current distribution and surface morphology was provided, directly demonstrating that current prefers to flow through the step edges of the epitaxial layers. Experimental results were further supported by numerical simulation. It was found that efficient radiative recombination centers were formed in the inclined quantum well regions. A schematic three-dimensional energy band structure of the multiple quantum wells (MQWs) across the step was proposed and helps in further understanding the luminescence behavior of LEDs grown on misoriented substrates. Finally, a general principle to achieve carrier localization was proposed, which is valid for most ternary III-V semiconductors exhibiting phase separation. (C) 2021 Chinese Laser Pres
Role of nucleus accumbens microRNA-181a and MeCP2 in incubation of heroin craving in male rats
No full textRationale Epigenetic regulation has been implicated in the incubation of drug craving (the time-dependent increase in drug seeking after prolonged withdrawal from drug self-administration). There is little information available on the role of microRNAs in incubation of heroin craving. Objective This study aimed to investigate the roles and mechanisms of miR-181a and methyl CpG binding protein 2 (MeCP2) in the nucleus accumbens (NAc) in incubation of heroin seeking. Methods MiRNA sequencing was used to predict potential miRNAs, and miRNA profiles were performed in the NAc after 1 day or 14 days after withdrawal from heroin self-administration. Following 14 days of heroin self-administration, rats were injected of lentiviral vectors into the NAc and evaluated for the effects of overexpression of miR-181a or knockdown of MeCP2 on non-reinforced heroin seeking after 14 withdrawal days. Results Lever presses during the heroin-seeking tests were higher after 14 withdrawal days than after 1 day (incubation of heroin craving). miR-181a expression in NAc was lower after 14 withdrawal days than after 1 day, and meCP2 expression in NAc was higher after 14 days than after 1 day. Luciferase activity assay showed that the 3 ' UTR of MeCP2 is directly regulated by miR-181a. Overexpression of miR-181a in NAc decreased heroin seeking after 14 withdrawal days and decreased MeCP2 mRNA and protein expression. Knockdown of MeCP2 expression in NAc by LV-siRNA-MeCP2 also decreased heroin seeking after 14 withdrawal days. Conclusions Results indicate that incubation of heroin craving is mediated in part by time-dependent decreases in NAc miR181a expression that leads to time-dependent increases in MeCP2 expression. Our data suggest that NAc miR-181a and MeCP2 contribute to incubation of heroin craving
Revisiting the designing criteria of advanced solid electrolyte interphase on lithium metal anode under practical condition
No full textReducing the ratio of Negative/Positive ratio (N/P ratio) is critical to increase the energy density of Li metal batteries (LMBs). Typically, stable Li deposition with high Coulombic Efficiency (CE) can be easily achieved with ether-based electrolyte, but the low oxidation stability restrains its applications in batteries with high-voltage cathodes. Herein, we performed cryogenic electron microscopy (Cryo-EM), in-depth X-ray Photoelectron spectrum (XPS) and Atomic Force Microscopy (AFM) on the Solid Electrolyte Interphase (SEI) layer formed in carbonate-based electrolyte and ether-based electrolyte to probe the characteristics of good SEI layer and aimed to design good SEI layer in carbonate-based electrolyte by tuning the electrolyte composition. The results suggest that the organic composition in the SEI layer determine the CE of LMBs. Further theoretical calculation suggests the highly reactive nature of carbonate molecules with Li results in the organic-rich SEI layer with low elastic modulus. On the basis of these insights, we propose design methodology for an advanced SEI layer in carbonate electrolyte by tuning the electrolyte composition. The designed SEI exhibits multilayer structure with a dense inorganic inner layer. Consequently, a 4 V full cell was assembled and delivered a high energy density of 760 Wh/kg (calculated based on the weight of cathode and anode) with long cycle life of 200 cycles in carbonate electrolyte
Graphdiyne-Based Thermal Fluids
No full textGraphdiyne (GDY) exhibits great application potential. However, large-yield and scalable exfoliation of few-layered GDY nanosheets (GDYNSs) remains a huge challenge. Here, we reported a liquid-phase, facile and efficient hydrothermal exfoliation approach to produce mono- or few-layered GDYNSs, which can achieve 82 wt% of high actual yield and 5 mg/ml concentration. The GYDNSs were then dispersed in mineral oil (MO) to act as heat transfer NANOfluids for the first time. Typically, at a fraction of 1.0 vol %, the nano-oils showed significantly enhanced thermal conductivity ((K-eff/K-0)-1) %, up to similar to 122%. The low filler fraction and high thermal conductivity enhancement for this GYDNSs/MO nano-oil demonstrates several thermal transfer applications of heavy equipment. Our work provides reasonable insight into the exfoliation and thermal-fluid applications of GDYNSs. (C) 2021 Elsevier Ltd. All rights reserved
Magnetohydrodynamic Interface-Rearranged Lithium Ions Distribution for Uniform Lithium Deposition and Stable Lithium Metal Anode
No full textUneven lithium (Li) electrodeposition hinders the wide application of high-energy-density Li metal batteries (LMBs). Current efforts mainly focus on the side-reaction suppression between Li and electrolyte, neglecting the determinant factor of mass transport in affecting Li deposition. Herein, guided Li+ mass transport under the action of a local electric field near magnetic nanoparticles or structures at the Li metal interface, known as the magnetohydrodynamic (MHD) effect, are proposed to promote uniform Li deposition. The modified Li+ trajectories are revealed by COMSOL Multiphysics simulations, and verified by the compact and disc-like Li depositions on a model Fe3O4 substrate. Furthermore, a patterned mesh with the magnetic Fe-Cr2O3 core-shell skeleton is used as a facile and efficient protective structure for Li metal anodes, enabling Li metal batteries to achieve a Coulombic efficiency of 99.5 % over 300 cycles at a high cathode loading of 5.0 mAh cm(-2). The Li protection strategy based on the MHD interface design might open a new opportunity to develop high-energy-density LMBs
Reversible filtration redox of methylene blue in dimethylsulfoxide by manganese oxide loaded carbonaceous nanofibrous membrane through Fenton-like oxidation
No full textThe reversible redox of methylene blue in organic solvents was highly attractive, yet was rarely reported. In this study, we realized the continuous filtration redox of methylene blue (MB) in dimethylsulfoxide (DMSO) through Fenton-like oxidization by using MnO2 loaded carbonaceous nanofibrous membrane (cPAN-MnO2). The carbonaceous nanofibrous membrane (cPAN) was fabricated through electrospun of polyacrylonitrile and subsequent carbonization. The obtained cPAN nanofibrous membrane showed excellent stability in polar DMSO. MnO2 can be readily coated on cPAN nanofibers through an in situ redox reaction between cPAN and potassium permanganate. The fabricated cPAN-MnO2 membrane exhibited instantaneous reduction property towards MB in DMSO during a gravity-driven continuous filtration process. Interestingly, MB reduction was initiated by a typical Fenton-like oxidization, where hydroxyl radicals were firstly generated from hydrogen peroxide catalyzed by MnO2 in DMSO. Then hydroxyl radicals attacked DMSO to further produce methyl radicals, which resulted in the reduction of MB. In addition, MB reduction process in DMSO was reversible. Our study provides a novel strategy for continuous redox of MB in polar organic solvent and might give new ideas for MB applications. (C) 2020 Elsevier Inc. All rights reserved
Mixed Metal Metal-Organic Frameworks Derived Carbon Supporting ZnFe2O4/C for High-Performance Magnetic Particle Imaging
No full textRecently, magnetic particle imaging (MPI) has shown diverse biomedical applications such as cell tracking, lung perfusion, image-guided hyperthermia, and so forth. However, the currently reported MPI agents cannot achieve the possible theoretical detection limit of MPI (20 nM). A previous theoretical study has shown that the MPI performance of superparamagnetic iron oxide nanoparticles (SPIONs) can be enhanced by carbon supporting and metal doping. In the current study, a series of mixed metal metal-organic framework-derived carbon supporting SPIONs were synthesized by pyrolysis. Among the synthesized SPIONs, the MPI signal intensity of ZnFe2O4/C@PDA was found to be 4.7 times higher than the commercial MPI contrast (Vivotrax) having the same Fe concentration. ZnFe2O4/C@PDA also showed the highest MPI intensity in tumor-bearing-mice among all tested samples. Furthermore, they were found highly biocompatible and showed linear cell quantification. This work can open new avenues for the design and development of novel and high-performance MPI agents
H2O2-Responsive Gold Nanoclusters @ Mesoporous Silica @ Manganese Dioxide Nanozyme for Off/On Modulation and Enhancement of Magnetic Resonance Imaging and Photodynamic Therapy
No full textIn order to achieve safe and high-efficient photodynamic therapy (PDT), it was a powerful strategy of constructing O-2-generated nanozyme with intelligent off/on modulation and enhancement. Herein, a kind of H2O2-responsive nanozyme was developed for off/on modulation and enhancement of magnetic resonance (MR) imaging and PDT, in which great amounts of gold nanoclusters (AuNCs) were loaded into mesoporous silica to form nanoassembly, and manganese dioxide (MnO2) nanosheets were wrapped as switching shield shell (AuNCs@mSiO(2)@MnO2). In a neutral physiological environment, stable MnO2 shells eliminated singlet oxygen (O-1(2)) generation to switch off PDT and MR imaging. However, in an acidic tumor microenvironment, the MnO2 shell reacted with H2O2, in which MnO2 degradation switched on MR imaging and PDT, and the generated O-2 further enhanced PDT. H2O2-responsive MnO2 degradation brought about excellent MR imaging with a longitudinal relaxation rate of 25.31 mM(-1) s(-1), and simultaneously sufficient O-2 generation guaranteed a 74% high O-1(2) yield. Under the irradiation of a 635 nm laser, the viability of MDA-MB-435 cells was reduced to 4%, and the tumors completely disappeared, demonstrating strong PDT performance. Therefore, H2O2-responsive AuNCs@mSiO(2)@MnO2 nanozyme showed excellent off/on modulation and enhancement of MR imaging and PDT and was a promising intelligent nanoprobe for safe and high-efficiency theranostics
Multifunctional superhydrophobic adsorbents by mixed-dimensional particles assembly for polymorphic and highly efficient oil-water separation
No full textSupra-wetting materials, especially superhydrophobic absorption materials, as an emerging advanced oil-water separation material have attracted extensive concern in the treatment of oil spillage and industrial oily wastewater. However, it is still a challenge to fabricate robust and multifunctional superhydrophobic materials for the multitasking oil-water separation and fast clean-up of the viscous crude oil by an environment-friendly and scalable method. Herein, a solid-solid phase ball-milling strategy without chemical reagent-free modification was proposed to construct heterogeneous superhydrophobic composites by using waste soot as the solid-phase superhydrophobic modifier. A series of covalent bond restricted soot-graphene (S-GN) or soot-Fe3O4 (S-Fe3O4) composite materials with a peculiar micro-nano structure are prepared. Through glue+superhydrophobic particles method, the prepared soot-based composite particles are facilely loaded on the porous skeleton of the sponge to obtain multifunctional superhydrophobic adsorbents. The reported superhydrophobic adsorbents exhibited robust chemical and mechanical stability, convenient magnetic collection, the high oil absorption capacity of 60-142 g g(-1), durable recyclability (>250 cycles), efficient separation efficiency (>99.5%) and outstanding self-heated performance, which enable them to be competent for oil-water separation in multitasking and complex environment (floating oils, continuous oil collection, oil-in-water emulsion, and viscous oil-spills)