Graphene is highly efficient in reinforcing metal matrix composites due to its intrinsic ultrahigh mechanical properties. Several synthesis methods have been developed to produce graphene. ...Consequently, the selection of graphene materials with various structures, such as layer number, lateral dimension and chemical modification, is a key issue to synthesize graphene-related composites. In the present study, two kinds of graphene derivatives, namely graphene nanoplatelets (GNPs) and reduced graphene oxide (RGO), were adopted to fabricate copper matrix composites through a modified molecular-level mixing process. Microstructure studies showed that GNPs exhibited flake shape, and RGO exhibited irregular strip or sheet shape in the composites powders. Some spherical-shape nanosized GNPs or RGO dispersed within Cu grain interiors were also observed under the transmission electron microscope. Both of the GNPs and RGO were well bonded with the copper matrix after sintering. GNPs showed an obvious aggregative trend when the volume fraction was above 0.5%, but 1.0 vol.% RGO was still uniformly dispersed in the matrix. Tensile tests indicated that GNPs showed good strengthening efficiency at content below 0.5 vol.% while RGO performed better when the content increased from 0.5 to 1.0 vol.%. The difference of relevant strengthening effect and mechanisms involved in the two composites were systematically discussed by combining with theory consideration and experimentation.
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•Two graphene derivatives (GNPs, RGO) were used to fabricate Cu matrix composites.•A modified molecular-level mixing process was adopted to make composite powders.•GNPs and RGO showed different strengthening effect on Cu matrix composites.•The different strengthening effect and mechanisms were theoretically discussed.
The excavation of deep foundation pits has a significant impact on the stability of adjacent buildings. On the basis of a deep foundation pit project in Xi’an, China, the deformation of a diaphragm ...wall and the settlement and deformation of an adjacent ancient building with and without MJS (Metro Jet System) pile reinforcement were studied through onsite monitoring and numerical simulation. The influence of the building’s settlement difference on the shear strain of the building’s walls was analyzed, and then the effect of MJS pile reinforcement was verified. The research results show that (1) the settlement difference serves as the primary cause of the shear strain of the building, and the shear strain rises with increasing settlement difference; (2) the maximum shear strain of the building occurs on both sides of the building’s doors and windows and on the left and right corners of the building’s walls; (3) the shear strain and settlement of the building without MJS pile reinforcement are significantly greater than those with MJS pile reinforcement; and (4) MJS pile support exhibits a better reinforcement effect within one times the excavation depth of the foundation pit. These research results have a certain guiding significance for enhancing the stability of foundation pits and ensuring the safety of adjacent buildings.
Metal-free photocatalysts have attracted growing concern in recent years. In this work, a new class of carbon quantum dots (CQDs) modified porous graphitic carbon nitride (g-C3N4) is synthesized via ...a facile polymerization method. With the optimal CQDs loading, the CQDs modified g-C3N4 exhibits ∼15 times higher degradation kinetic towards diclofenac (DCF) than that of pure g-C3N4. The enhanced photocatalytic activity can be ascribed to the improved separation of charge carriers as well as the tuned band structure. Moreover, a photosensitation-like mechanism is proposed to elucidate the photo-generated electrons transfer and reactive radicals formation. CQDs are anchored to g-C3N4 surface via C–O bond, which provide channels for the preferential transfer of photo-excited electrons on DCF molecule to the conduction band of g-C3N4. Superoxide radical (·O2−) dominates the degradation of DCF, while holes (h+) show a negligible contribution. Density functional theory (DFT) calculation successfully predicts that the sites on DCF molecule with high Fukui index (f0) are preferable to be attacked by radicals. DCF degradation pathway mainly includes ring hydroxylation, ring closure and C–N bond cleavage processes. Acute toxicity estimation indicates the formation of less toxic intermediates/products compared to DCF after photocatalysis. Moreover, the hybrid photocatalysts exhibit good reusability in five consecutive cycles. This work not only proposes a deep insight into photosensitation-like mechanism in the photocatalysis system by using C3N4-based materials, but also develops new photocatalysts for potential application on removal of emerging organic pollutants from waters and wastewaters.
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•Facile synthesis of porous carbon quantum dots modified g-C3N4 was achieved.•New photocatalysts showed good visible light driven activity to diclofenac.•Photosensitation-like mechanism can well elucidate DCF photocatalytic degradation.•DFT calculation helped to explain the reactive sites and degradation pathways.•Toxicity of diclofenac was reduced during the photocatalytic degradation process.
Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic–inorganic perovskites, ...the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites.
This paper uses data from an employee tracking survey in China for about 6000 incumbent workers to document their dynamic labor market outcomes throughout the year 2020. I find that the employment ...situation worsened sharply during the lockdown period and then recovered gradually, showing a “V” shaped pattern. However, by the end of November 2020, about 4.4 per cent of 2019 incumbent workers were still unemployed, with few social protections. By adopting a Difference-in-Differences approach, I further estimate the impacts of city and community lockdowns on labor market outcomes of surveyed employees and their mental health. The estimation results show that lockdowns reduced the probability of resuming work by 13.2 percentage points, which in turn worsened their mental health status. My findings suggest that stringent measures to counter the virus brought about negative shocks in the labor market and reduces the welfare of workers, at least in the short run.
In this paper, we investigate the global stability of quaternion-valued neural networks (QVNNs) with time-varying delays. On one hand, in order to avoid the noncommutativity of quaternion ...multiplication, the QVNN is decomposed into four real-valued systems based on Hamilton rules: <inline-formula> <tex-math notation="LaTeX">ij=-ji=k,~jk=-kj=i </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">ki=-ik=j </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">i^{2}=j^{2}=k^{2}=ijk=-1 </tex-math></inline-formula>. With the Lyapunov function method, some criteria are, respectively, presented to ensure the global <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-stability and power stability of the delayed QVNN. On the other hand, by considering the noncommutativity of quaternion multiplication and time-varying delays, the QVNN is investigated directly by the techniques of the Lyapunov-Krasovskii functional and the linear matrix inequality (LMI) where quaternion self-conjugate matrices and quaternion positive definite matrices are used. Some new sufficient conditions in the form of quaternion-valued LMI are, respectively, established for the global <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-stability and exponential stability of the considered QVNN. Besides, some assumptions are presented for the two different methods, which can help to choose quaternion-valued activation functions. Finally, two numerical examples are given to show the feasibility and the effectiveness of the main results.
Photodynamic therapy (PDT) has been proposed in cancer treatment for decades, but its clinical translation is significantly impeded by the low yield of ROS, poor tissue penetration depth of most ...current photosensitizers, and short lifetime of ROS. These limitations directly affect the therapeutic effect of PDT in cancer therapy. Here we proposed a new strategy by collaboratively integrating rare-earth doped upconversion nanoparticles (UCNP) with graphene quantum dot (GQD) for highly efficacious PDT, based on the merits of UCNP, which can emit UV–vis light under near-infrared light (NIR) excitation, and GQD, which can produce 1O2 efficiently. For GQD-decorated UCNP nanoparticles (UCNP-GQD), the emission light from UCNP can further excite GQD with prominent 1O2 generation for NIR-triggered PDT. Furthermore, a hydrophilic rhodamine derivative, TRITC, is covalently tethered to afford the resultant UCNP-GQD/TRITC, possessing distinct mitochondrial targeting property. Thus mitochondrial specific PDT with in-situ1O2 burst in mitochondria induces sharp decrease of mitochondrial membrane potential, which initiates the tumor cell apoptosis irreversibly. Importantly, in vivo experiments demonstrate the tumor inhibition of mitochondrial targeting UCNP-GQD/TRITC with improved therapeutic efficiency compared with non-targeting UCNP-GQD. The proposed strategy highlights the advantages of precision organelles-specific PDT in cancer therapy.
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•SNCN-3 composed of 2D g-C3N4 and 1D perovskite-type NaNbO3 nanorods.•Type II heterojunction of SNCN-3 showed efficient separation of electron-hole pairs.•Ofloxacin degradation ...occurred as piperazine ring cleavage and F substitution.•DFT revealed atoms with high Fukui index (f0) were active sites for radical attack.•Transformation products had lower toxicity than ofloxacin based on QSAR analysis.
Graphitic carbon nitride (g-C3N4) is widely used as a visible-light-driven photocatalyst but limited by the rapid photoexcited electron-hole pairs recombination rate. To promote the photocatalytic activity of g-C3N4, a class of heterojunction photocatalysts, perovskite-type sodium niobate (NaNbO3) nanorods modified g-C3N4 (SNCN), was fabricated through a two-step hydrothermal and thermal polymerization method in this study. X-ray powder diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) demonstrated the successful decoration of NaNbO3 onto g-C3N4, as well as the formation of material interface with high reactivity. The optimal material (SNCN-3) exhibited an extremely high degradation efficiency of ofloxacin (OFL) under simulated solar light, as the kinetic rate constant (k) was 29.6 and 10.4 times of that for the neat g-C3N4 and NaNbO3, respectively. Energy band structure analysis indicated that SNCN-3 was a type II heterojunction. Moreover, surface photovoltage (SPV), photoluminescence (PL) and transient photocurrent response measurements confirmed SNCN-3 had the highest electron-hole separation efficiency compared with NaNbO3, g-C3N4 and the other SNCN composites. Quenching tests indicated that O2– and holes were the primary reactive species for OFL degradation. Density functional theory (DFT) calculation on further revealed the atoms of OFL with high Fukui index (f0) preferred to be attacked by the produced radicals. Cleavage of piperazine moiety and substitution of F were the key OFL degradation pathways. In addition, the reduced toxicity of transformation products after photocatalysis verified the proposed technique was a green method. This work provided the promising application of g-C3N4/NaNbO3 heterojunction photocatalysts for degradation of antibiotic pollutants in water.
The interferon (IFN)-mediated antiviral response is a central aspect of host defense; however, viruses have evolved multiple strategies to counteract IFN-mediated responses in order to successfully ...infect the host. Herpes simplex virus 1 (HSV-1), a typical human-restricted DNA virus, is capable of counteracting host immune responses via several distinct viral proteins, thus establishing a lifelong latent infection. In this study, we demonstrate that the VP24 protein, a serine protease of HSV-1 essential for the formation and maturation of capsids, is a novel antagonist of the beta interferon (IFN-β) pathway. Here, VP24 was shown for the first time to dampen interferon stimulatory DNA (ISD)-triggered IFN-β production and inhibit IFN-β promoter activation induced by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) and by STING, respectively. Further study demonstrated that ectopic expression of VP24 selectively blocked IFN regulatory factor 3 (IRF3) but not NF-κB promoter activation. In addition, VP24 was demonstrated to downregulate ISD-induced phosphorylation and dimerization of IRF3 during HSV-1 infection with a VP24 stable knockdown human foreskin fibroblast cell line. The underlying molecular mechanism is that VP24 abrogates the interaction between TANK-binding kinase 1 (TBK1) and IRF3, hence impairing IRF3 activation. These results illustrate that VP24 is able to block the production of IFN-β by inhibiting IRF3 activation, which may represent a critical adaptation to enable viral effective replication within the host.
This study demonstrated that HSV-1 protein VP24 could inhibit IFN-β production and promoter activation triggered by ISD, cGAS and STING and by STING, respectively. VP24 selectively blocked IRF3 promoter activation and ISD-induced phosphorylation and dimerization of IRF3 without affecting the NF-κB promoter activation during viral infection. VP24 also inhibited IRF3 activation by impeding the interaction between TBK1 and IRF3 during viral infection. This study provides new insights into the immune evasion mediated by HSV-1 and identifies VP24 as a crucial effector for HSV-1 to evade the host DNA-sensing signal pathway.
Purine metabolism in the circulatory system yields uric acid as its final oxidation product, which is believed to be linked to the development of gout and kidney stones. Hyperuricemia is closely ...correlated with cardiovascular disease, metabolic syndrome, and chronic kidney disease, as attested by the epidemiological and empirical research. In this review, we summarize the recent knowledge about hyperuricemia, with a special focus on its physiology, epidemiology, and correlation with cardiovascular disease. This review also discusses the possible positive effects of treatment to reduce urate levels in patients with cardiovascular disease and hyperuricemia, which may lead to an improved clinical treatment plan.
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