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High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO2 with low dielectric constant and V2C MXene with high work function are n...

High-dielectric-constant (high-k) polymer/conductor composites with low dielectric loss are desirable for energy storage. However, high leakage currents from interfacial regions with high charge density are difficult to handle. In this work, high permittivity and low dielectric loss were achieved in poly(vinyl alcohol) (PVA)/V2C MXene nanocomposite films fabricated by solution casting by taking advantage of the interfacial compatibility and moderate interfacial charge density of the nanocomposites. Water-soluble PVA was utilized as the polymer matrix. Delaminated V2C MXene nanosheets with appropriate conductivity were prepared and used as the filler. The mild interface polarization of the nanocomposites was responsible for achieving favourable permittivity values. The small gap between the work functions of PVA and V2C contributed to moderate interfacial charge density values and thus low dielectric loss values. A proportional correlation between the interfacial charge density and the conductivity of composites was also verified. The depth of charge injection from the MXene to PVA was found to be half of the interlamellar spacing of the delaminated MXene. The dependence of the electrical properties of the nanocomposites on the frequency and MXene content was also studied. The composite with 4 wt% MXene exhibited a permittivity of ~24 (16 times that of PVA) and a dielectric loss of ~0.14 (1.5 times that of PVA) at 1 kHz, as well as breakdown strength of ~31 MV m−1 (63% of PVA). This work might enable environmentally friendly fabrication of promising composite dielectrics.

Two-dimensional conductive MXenes are employed as fillers for fabricating polymer-based high-permittivity composite dielectrics. However, high dielectric loss from high interfacial leakage conduction is a shortcoming. To obtain low interfacial leakage conduction, in this work we selected high-modulus poly(ether sulfone) (PES) as matrix and (3-aminopropyl)triethoxysilane (KH550) as interface compatibilizer. Ternary PES/Ti3C2 MXene/KH550 nanocomposites were fabricated by solution casting. Compared with PES/MXene composites, the ternary counterparts have improved permittivity and reduced dielectric loss and conductivity. The increased permittivity is ascribed to enhanced interfacial polarization. The reduction in dielectric loss and conductivity stems from lower interfacial leakage conduction as a result of improved interface compatibility. The ternary composite with 4 wt.% MXene exhibited high permittivity of ~ 81, low dielectric loss of ~ 0.12 and low conductivity of ~ 6.3 × 10−7 S m−1 at 100 Hz. This work may enable the large-scale fabrication of promising composite dielectrics.

Graphene nanosheets are widely employed for fabricating high-dielectric-constant polymer nanocomposites for energy storage. However, severely reduced electric breakdown strengths of composites with increasing graphene content limit their high-field applications. To improve breakdown strengths of polyvinylidene fluoride/graphene composites without sacrificing dielectric constants, in this work, we proposed a rational strategy of constructing MXene quantum dot inter-layers for preparing ternary composites with desirable electric properties, owing to inter-layer induced quantum confinement and Coulomb blockade effects. Graphene oxide@nitrogen-doped Ti3C2 MXene quantum-dot hybrid nanoparticles were synthesized via hydrogen-bond induced self-assembly route. Binary polymer/graphene and ternary polymer/hybrid-particle nanocomposite films were fabricated by solution cast process. Compared with binary composites, ternary counterparts have synergistically improved dielectric constants and breakdown strengths. Repeated disorder-bounce of electrons and strong coupling between electrons and holes, inside each quantum dot, might be responsible for superior electric performances of ternary composites. High dielectric constant (~53@1 kHz) and breakdown strength (~205 MV m−1) were realized in ternary composite with 0.12 wt % of nanoparticles. This work might pave a road for large-scale fabrication of high-performance nanocomposite dielectrics for energy storage.

Two-dimensional MXenes have attracted increasing attention from researchers in the optical, electrical and thermal fields due to their high electric conductivity, thermal conductivity and mechanical properties. MXene quantum dots (QDs) have been highly desired to achieve selective ion detection using highly fluorescent media. In this study, a facile route using amine-assisted solvothermal tailoring was developed to prepare in situ nitrogen-doped Ti3C2 MXene QDs. Pristine MXene was exfoliated to yield MXene with a few layers. Diethylenetriamine, few-layer MXene and N,N-dimethylformamide were blended to perform a solvothermal process, yielding in situ nitrogen-doped MXene QDs with an ~1 nm thickness and ~6.2 nm size. The formation of QDs was dynamically monitored. The reduction in the QD size depended on tailoring and in situ nitrogen doping. Fluorescence properties of those QDs were studied. Nitrogen-doped QDs exhibited different fluorescence-quenching responses to various metal cations. Selective Cu2+ detection using the nitrogen-doped QDs mainly depended on a static fluorescence-quenching mechanism. This study might provide opportunities for the large-scale fabrication of in situ element-doped MXene fluorescent QDs.

To investigate the influence of nitrogen injection and sealing (N2 I S) on the fracture and permeability of coal reservoirs, two low-rank coal samples from the Fukang (FK) and Wudong (WD) mining areas in the southern margin of the Junggar Basin, China, were collected and used for N2 I S experiments. A Chandler Model 6100 Formation Response Tester (FRT) from the Chandler Company was used for N2 I S experiments with sealing times of 6, 18 and 36 h and a sealing pressure of 584 psi for the samples, and the real-time permeability changes were monitored during the N2 I S process. An NDP-605 NanoDarcy Permeameter was used to test the permeability with different effective stresses before and after N2 I S, and the difference in pore distribution before and after N2 I S was determined by low-field nuclear magnetic resonance (NMR) for the samples. X-ray CT (μCT) was used to observe the changes in the distribution of fractures before and after N2 I S. The results showed that the permeability of FK increased by 43.75%, 91.67% and 162.99% and that of WD increased by 13.96%, 49.92% and 73.68% after 6, 18 and 36 h of sealing time, respectively. For each N2 I S period, the permeability increased with increasing sealing time, while the change rate gradually decreased, as demonstrated by a curve similar to the “Langmuir isotherm adsorption” curve. The stress sensitivity of permeability increased after N2 I S, and the decrease in permeability with increasing effective stress was greater than that of non-N2 I S-treated samples. Low-field NMR showed that the amplitude of 100% water saturation had no obviously changes after N2 I S, which means that no new fracture formed after that. Meanwhile, X-ray CT images also showed that no new fracture formed after N2 I S, but the connectivity is enhanced. Further analysis showed that N2 I S dispersed fracture fillers and opened up the fractures of the coal reservoir, resulting in an enhancement in permeability, but also increased the degree of fracture closure, which caused an increase in the stress sensitivity of the permeability.

Exposure to airborne fine particulate matter (PM2.5) is associated with cardiovascular diseases (CVDs). Nevertheless, a comprehensive understanding of the underlying biological mechanisms by which PM2.5 exposure induces or aggravates CVDs remain insufficiently clear. In the present study, the flow cytometry was employed to investigate the apoptosis of human umbilical vein endothelial cells (HUVECs) induced by PM2.5 in culture. The underlying apoptotic pathway was also studied through the determination of the protein expression and activation of p53, Bax, Bcl-2, caspases-9, -7, -3, and PARP by western blot. The results showed that PM2.5 could significantly induce the apoptosis of HUVECs at the tested concentrations (0.2, 1, 5, 25 μg mL-1), compared with the negative control (p

High dielectric response and electric insulation are desired in high-energy-density polymer/ceramic composites. Low dielectric response is found in polymer composites with semiconductors. To balance a high dielectric constant and breakdown strength, in this work, the polymer-based composites with de novo synthesized V2C MXene-CuO hybrid-particles were fabricated. High dielectric response of composites was attributed to strong electron polarization at ceramic/ceramic heterojunction. High insulation was ascribed to fluorine-induced electron-trap effect. The first principle calculations verified the electron-transfer mechanism at V2C/CuO van der Waals heterojunctions. Compared with polymer/CuO binary composites, polymer/V2C-CuO ternary composites exhibited the improved comprehensive electric properties (remarkably improved dielectric response and slightly damaged insulation). Ternary composite with 10 wt% V2C-CuO showed a high dielectric constant of 89, low dielectric loss of 0.23, low conductivity of 6.8 × 10−7 S m−1 at 100 Hz and high breakdown strength of 204 MV m−1. This study might enable a facile preparation of cutting-edge nanocomposite dielectrics.

This work presents a systematical experimental and density functional theory (DFT) studies to reveal the mechanism of NO reduction by H2 reaction over platinum nanoparticles (NPs) deposited on boron-doped graphene (denoted as Pt/BG) catalyst. Both characterizations and DFT calculations identified boron (in Pt/BG) as an additional NO adsorption site other than the widely recognized Pt NPs. Moreover, BG led to a decrease of Pt NPs size in Pt/BG, which facilitated hydrogen spillover. The mathematical and physical criteria of the Langmuir-Hinshelwood dual-site kinetic model over the Pt/BG were satisfied, indicating that adsorbed NO on boron (in Pt/BG) was further activated by H-spillover. On the other hand, Pt/graphene (Pt/Gr) demonstrated a typical Langmuir-Hinshelwood single-site mechanism where Pt NPs solely served as active sites for NO adsorption. This work helps understand NO-H2 reaction over Pt/BG and Pt/Gr catalysts in a closely mechanistic view and provides new insights into roles of active sites for improving the design of catalysts for NO abatement.

Concerns over the health risk of the widely distributed, commonly used silica nanoparticles (SiNPs) are increasing worldwide. Yet, up to now, there are still many major knowledge gaps over the potential adverse effects of SiNP exposure on human cardiovascular health and the underlying mechanisms. In this study, comet assay and micronucleus test were employed to determine the genotoxic potentials of four sizes (10, 25, 50, 100 nm) of SiNPs to human umbilical vein endothelial cells (HUVECs) in culture. The intracellular redox statuses were explored through the determination of the levels of reactive oxygen species (ROS) and reduced glutathione (GSH) with kits, respectively. The protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) were also detected by Western blot. The results showed that at the administrative levels (1, 5, 25 μg/mL), all the four sizes of SiNPs could induce an increase of both DNA damages and MN frequencies in HUVECs in culture, with a positive dose- and negative size-dependent effect relationship (S100

Concerns over the health risk of the widely distributed, commonly used titanium dioxide nanoparticles (nano-TiO2 ) are increasing worldwide. Yet, up-to-now, our understanding in their potential effects on the cardiovascular system is very limited and the toxicological mechanisms are still unclear. In the present study, the CCK-8 assay was performed to determine the cytotoxicity of four sizes (10, 30, 50, and 100 nm) of anatase nano-TiO2 on human umbilical vein endothelial cells (HUVECs) in culture, and the flow cytometry was employed to investigate the potential of these nano-TiO2 to induce the apoptosis of HUVECs. The apoptotic pathway was also probed through the determination of the protein expression and activation of p53, Bax, Bcl-2, caspases-9, -7, -3, and PARP by western blot. The results showed that at the administrative levels (1, 5, 25 μg/mL), all the four sizes of nano-TiO2 could significantly inhibit the viability of HUVECs and elicit significant apoptosis in them, compared with the negative control (P < .05, P < .01). Moreover, the apoptotic rates of HUVECs were increased respectively with the elevating levels and decreasing sizes of the administrative nano-TiO2 , showing a clear dose- and size-dependent effect relationships. Interestingly, the increasing phosphorylation of p53, decreasing ratio of Bcl-2/Bax, and enhancing activation of the downstream proteins caspase-9, -7, -3, and PARP, were also observed with the decreasing sizes of the administrative nano-TiO2 in the western blot, indicating that the intracellular approach of apoptosis, the p53-caspase pathway, is the major way of the nano-TiO2 -mediated apoptosis in HUVECs in culture and that the size is an important parameter that may determine the potential of nano-TiO2 to induce cellular response. In conclusion, these results suggested that high levels of nano-TiO2 exposure may pose potential risks to human cardiovascular health by inducing cardiovascular EC apoptosis.

With the growing production and applications of silica nanoparticles (SiNPs), human exposure to these nanoparticles continues to increase. However, the possible hazards that SiNP exposure may pose to human cardiovascular system and the underlying mechanisms remain unclear. In the present study, the flow cytometry was employed to investigate the potential of four sizes (10, 25, 50, 100 nm) of SiNPs to induce the apoptosis of human umbilical vein endothelial cells (HUVECs) in culture. The apoptotic pathway was also explored through the determination of the protein expression and/or activation of p53, Bcl-2, Bax, caspases-9, -7, -3, and PARP by western blot. The results showed that all the four sizes of SiNPs could significantly elicit apoptosis in HUVECs at the tested concentrations (1, 5, 25 μg/mL), compared with the negative control (p

The effects of lead were investigated in forest trees (Sophora japonica and Platycladus orientalis) grown in soil and exposed to Pb(CH3COO)2·3H2O (0, 300, 500, 1,000 mg kg−1) with different levels of water stress (100, 80, 60, 40 % soil relative water content, SRW). The results showed that, in the presence of Pb, the ground diameter, height and dry weight were greater than the control for S. japonica and P. orientalis. The proportions of biomass allocation of S. japonica were root > stem > leaf, and of P. orientalis leaf > stem > root except for 40 % SRW. SOD (superoxide dismutase) and POD (peroxidase) activities in leaves were activated by soil Pb for P. orientalis, while SOD activities increased but POD activities decreased compared with control under Pb stress for S. japonica. Water stress increased SOD and POD activities under different Pb concentrations, also increased MDA (malondialdehyde) content significantly. For S. japonica, the Pb concentration in the root was up to 91.9 mg kg−1, while the Pb concentration in the aboveground part was 37.5 mg kg−1. The Translocation Factor (TF value) increased with the increase of water stress intensity, under the same Pb concentration. For P. orientalis, the Pb accumulation in the roots was significantly higher than that in the aboveground part (TF

The impacts of ambient PM2.5 on public health have become great concerns worldwide, especially in the developing countries. Epidemiological and toxicological studies have shown that PM2.5 does not only induce cardiopulmonary disorders and/or impairments, but also contributes to a variety of other adverse health effects, such as driving the initiation and progression of diabetes mellitus and eliciting adverse birth outcomes. Of note, recent findings have demonstrated that PM2.5 may still pose a hazard to public health even at very low levels (far below national standards) of exposure. The proposed underlying mechanisms whereby PM2.5 causes adverse effects to public health include inducing intracellular oxidative stress, mutagenicity/genotoxicity and inflammatory responses. The present review aims to provide an brief overview of new insights into the molecular mechanisms linking ambient PM2.5 exposure and health effects, which were explored with new technologies in recent years.

In order to compare the different eco-toxicological effects of lead nitrate and lead acetate on forest tree seed, a biological incubation experiment was conducted to testify the inhibition effects of two lead compounds on rates of seed germination, root and stem elongation, and seedling fresh weight for six plants (Amaorpha fruticosa L., Robinia psedoacacia L., Pinus tabuliformis Carr., Platycladus orientalis L., Koelreuteria paniculata Laxm., Hippophae rhamnoides L.) in soil. The results indicate that the inhibition effects of the two lead compounds on the rates of root elongation of plants were greater than other indices; root elongation can possibly be used as indices to investigate the relationship between lead toxicity and plant response. The response of trees to lead toxicity varied significantly, and the order of tolerance to lead pollution was as follows: Amaorpha fruticosa L. > Platycladus orientalis L. > Koelreuteria paniculata Laxm. > Robinia psedoacacia L. > Pinus tabuliformis Carr. > Hippophae rhamnoides L. Therefore, we suggest that Amaorpha fruticosa L. and Platycladus orientalis L. be used as tolerant plants for soil phytoremediation and Hippophae rhamnoides L. as an indicative plant to diagnose the toxicity of lead pollution on soil quality. Lead nitrate and lead acetate differentially restrain seeds, with seeds being more sensitive to lead nitrate than lead acetate in the soil. Thus, the characteristics of lead compounds should be taken into full consideration to appraise its impact on the environment.

Headspace solid-phase microextraction (SPME) coupled to gas chromatography-flame ionization detection (GC-FID) has been applied to the analysis of six phenolic compounds in water samples. A laboratory-made fiber with 25,27-dihydroxy-26,28-oxy(2′,7′-dioxo-3′,6′-diazaoctyl)oxy-p-tert-butylcalix[4]arene/hydroxy-terminated silicone oil (Amide bridged-C[4]/OH-TSO) coating was used to extract the analytes from the aqueous samples. The parameters affecting the sorption of analytes onto the fiber, such as extraction temperature and time, pH, salt addition, desorption temperature and time, were optimized. The extraction ability of this new fiber to phenols was compared with the laboratory-made C[4]/OH-TSO fiber and the commercially available polyacrylate (PA, 85 μm) fiber. The results revealed that this new calixarene fiber shows high affinity for the phenolic compounds due to the introduction of the polar Amide bridge in calix[4]arene. The linearity was three or four orders of magnitude for the tested compounds with regression coefficients ranging from 0.9968 to 0.9996. The detection limits ranged from 0.47 to 9.01 μg/l and the reproducibility of the measurements was

With the rapid development of information technology, network security issues become increasingly serious. Forwarding and Control Elements Separation (ForCES) architecture advanced by ForCES working group of IETF routing area can solve network security problems well, which has become an important research direction of next generation Internet. This paper first illustrates the design of stateful packet inspection firewall (SPIF) based on ForCES architecture, and then focuses on the implementation based on network processor. Finally, we test our work and the result verifies the correctness and feasibility of SPIF based on ForCES architecture.

Load-Capacity models are usually used for analyzing the network fault-tolerance and survivability. The node's capacity reflects its redundant resources. We propose an evolutionary algorithm to search an optimized capacity allocation strategy, which makes the network achieve optimal robustness with the same resources. Our algorithm is implemented by the following two steps repeatedly: (1) Construct a new capacity allocation strategy by transferring the capacity among network nodes; and (2) Evaluate the network robustness and then decide whether or not to accept this strategy. It can be considered as a process of simulated annealing. We find that the Load-Capacity relationship seems to be neither the linear nor the preferential-attachment relation. Our works can provide algorithm support for trustworthy network design and the information security emergency response.