High-surface-area carbon aerogels are synthesized by pyrolysis of nanocellulose aerogels that are prepared by dissolving of cellulose microcrystalline in NaOH aqueous solutions followed by gelation, ...regeneration and freeze drying or supercritical CO2 drying. The obtained carbon aerogels are further treated via a CO2 activation process. The result shows that the nanocellulose aerogels dried by supercritical CO2 exhibit a high specific surface area (299 m2/g) and the obtained carbon aerogels preserve the interconnected 3D nanostructure and have a high specific surface area of 892 m2/g and a high pore volume of 1.80 cm3/g, which increase to 1873 m2/g and 2.65 cm3/g respectively after CO2 activation. The highly porous and interconnected nanostructure provides efficient migration of electrolyte ions and electrons, which makes the resultant activated carbon aerogels exhibit excellent electrochemical performance for supercapacitors. The specific capacitances reach 302 and 205 F/g at a current density of 0.5 and 20 A/g respectively within a potential window of −1.0 to 0 V in 6 M KOH solution. The capacitance retains 92% after 4000 cycles of charge/discharge, implying a good cycling stability.
We show that the electroweak monopole can be regularized with a non-vacuum electromagnetic permittivity. This allows us to set a new BPS bound for the monopole mass, which implies that the mass may ...not be smaller than 2.98 TeV, more probably 3.75 TeV. We demonstrate that the same method can also regularize the Dirac monopole, which enhances the possibility to construct the Dirac monopole of mass of a few hundred meV in condensed matters. We discuss the physical implications of our result.
Research on van der Waals heterostructures based on stacked 2D atomic crystals is intense due to their prominent properties and potential applications for flexible transparent electronics and ...optoelectronics. Here, nonvolatile memory devices based on floating‐gate field‐effect transistors that are stacked with 2D materials are reported, where few‐layer black phosphorus acts as channel layer, hexagonal boron nitride as tunnel barrier layer, and MoS2 as charge trapping layer. Because of the ambipolar behavior of black phosphorus, electrons and holes can be stored in the MoS2 charge trapping layer. The heterostructures exhibit remarkable erase/program ratio and endurance performance, and can be developed for high‐performance type‐switching memories and reconfigurable inverter logic circuits, indicating that it is promising for application in memory devices completely based on 2D atomic crystals.
Nonvolatile ambipolar memory devices are developed based on stacked black phosphorus–boron nitride–molybdenum disulphide heterostructure floating‐gate field‐effect transistors. The memory device exhibits a fairly large memory window with a width (ΔV) of ≈60 V for a maximum control gate voltage of 40 V and can be switched well between the erase and program state.
Relativistic quantum dynamics of twisted (vortex) Dirac particles in arbitrary electric and magnetic fields are constructed for the first time. This allows us to change the controversial contemporary ...situation when the nonrelativistic approximation is used for relativistic twisted electrons. The relativistic Hamiltonian and equations of motion in the Foldy-Wouthuysen representation are derived. A critical experiment for a verification of the results obtained is proposed. The new important effect of a radiative orbital polarization of a twisted electron beam in a magnetic field resulting in a nonzero average projection of the intrinsic orbital angular momentum on the field direction is predicted.
In this paper, first of all, the configuration, optical and thermal properties of WO3-based gasochromic (GC) smart window are briefly reviewed. Subsequently, using the eQUEST building simulation ...program, the effect of GC smart window on the energy consumption for a commercial office building has been calculated and compared with various glazing systems currently available on the market, including SAGE@ electrochromic (EC) smart window. Simulation results indicate that the hot summer and cold winter regions are the most suitable testing grounds employing smart windows, and the decrease of HVAC loads in shanghai is 28.4% and 11.5% when using GC smart window to replace the single clear float glass and the colored absorbing double glass unit, respectively. Despite the limitation of coloration depth, GC smart window consumes less energy in Harbin than EC does. Also, according to the simulation data, there is no need to change the window’s state hourly unless the occurrence of extreme weather condition.
•First of all, a new technique of low cost fabrication of WO3-based gasochromic smart window to reduce the building energy consumption is briefly discussed.•For the first time, the effect of gasochromic smart windows on the energy consumption of building in typical climate regions of China has been calculated and compared with other currently available glazing systems, including SAGE@ electrochromic smart window.•The results indicate that gasochromic smart window can significantly reduce heating and cooling loads in comparison with current static glazing types in all five typical climate zones of China, especially applicable to hot summer and cold winter regions.•At last, the feasibility, potential application areas and the way forward of improvements of gasochromic smart window are discussed.
The issue of global environmental contamination of microplastics has recently been receiving widespread attention. However, the effects of polystyrene nanoparticles (Nano-PS) on the female ...reproductive system remain unclear. We investigated the toxicity and explored the potential underlying mechanisms of Nano-PS in both mouse ovarian tissue in vivo and human ovarian granulosa cell lines in vitro. In vivo experiments: Mice were fed different concentrations of Nano-PS for 8 weeks. In vitro experiments: COV434 cells were treated with increasing concentrations of Nano-PS. In the present study, ovarian reserve was found to decrease significantly, while oxidative stress and apoptosis levels increased. Nano-PS increased the proportion of metestrum and diestrus periods, and decreased the proportion of estrous period. The implantation rates and the number of pups per litter decreased. In COV434 cells, Nano-PS reduced cell viability and mitochondrial membrane potential, increased the expression of apoptotic and oxidative stress markers and led to subsequent cell cycle arrest. Specifically, Nano-PS exert their toxic effects on mouse ovarian tissue and COV434 cells by inducing oxidative stress. A potential strategy to overcome this could be to activate the nuclear factor-E2-related factor 2 (Nrf2) signaling pathway to mitigate Nano-PS-induced oxidative stress.
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•Nano-PS exposure reduces the growing follicle number and fertility in mice.•Nano-PS exposure on mice affects sex hormone and oxidation-antioxidant status.•Nano-PS exposure inhibited Nrf2 expression and increase apoptosis in mouse ovaries.•Nrf2 plays a protective role against Nano-PS-induced oxidative stress.
Robust, highly thermally stable, MO x /(MO x –SiO2)/SiO2 core–shell nanostructured metal oxide aerogels with a MO x core and (MO x –SiO2)/SiO2 shell are produced via novel alkoxide chemical liquid ...deposition techniques. The core–shell nanostructure not only significantly reinforces the nanoparticles but also effectively inhibits the crystal growth and phase transition of metal oxide upon heat treatment, which enhances the heat resistance from approximate 400–800 °C up to 1000–1300 °C. The resultant core–shell nanostructured Al2O3, ZrO2, and TiO2 aerogels can support at least 5800 times their weight and exhibit high surface areas of 139, 186, and 154 m2/g after fired at 1300, 1000, and 1000 °C, respectively, which are the highest surface areas for metal oxide aerogels ever reported. We demonstrate that the core–shell ZrO2 and TiO2 aerogels show enhanced adsorption and photocatalytic performances, respectively, for dye after fired at 1000 °C. The core–shell Al2O3 aerogel/mullite fiber/TiO2 composite possesses ultralow thermal conductivities of 0.058, 0.080, and 0.11 W/mK at 800, 1000, and 1200 °C, respectively, which are the lowest values for inorganic aerogels ever reported. The resulting materials are promising candidates as high-temperature (400–1300 °C) thermal superinsulators, adsorbents, and catalysts.
Silica–titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially ...hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica–titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m2/g, a small particle size of 5–14 nm, and a large pore volume and pore size of 2.41 cm3/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica–titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (<200 m2/g at 600 °C) at high temperatures combined with the simple method makes the silica–titania aerogels promising candidates as photocatalysts.
Two-party collaborative signature scheme is an important cryptographic technology for user authentication and data integrity protection when using mobile devices for financial and securities ...transactions. However, the two-party collaboration scheme has the following shortcomings: firstly, it is not flexible enough, and it requires the collaborating parties to be secure and trusted; secondly, the two-party collaboration security still needs to be improved. Once a hacker obtains the signature private key and collaborative identity of a mobile device, it can construct a legitimate two-party collaborative signature. Third, the application scenario of two-party co-signature is limited and cannot meet the application scenario of multi-device co-signature. For this reason, this paper designs a multi-party collaborative signature scheme based on SM2 digital signature algorithm in the standard "SM2 Elliptic Curve Public Key Cryptography" of GM/T003-2012. This scheme consists of multiple (more than 2) participants to jointly generate the signature group public key and valid signature in an interactive manner, while ensuring that each user cannot know the signature key other than their own during the signing process. We implement this scheme based on the GMP library. The experimental results show that this scheme is not only flexible but also more secure and trustworthy to meet the application scenario of multi-device collaborative signing. In addition, the time for multiple participants to construct signatures in this scheme is similar, and the time for signature verification is less different from that of the original SM2 signature.
This study explored the factors that influence respondents' willingness to pay (WTP) for CO2 mitigation under climate change. A questionnaire survey combined with contingent valuation and ...psychometric paradigm methods were conducted in the city of Suzhou, Jiangsu Province in China. Respondents' traditional demographic attributes, risk perception of greenhouse gas (GHG), and attitude toward the government's risk management practices were established using a Tobit model to analyze the determinants. The results showed that about 55% of the respondents refused to pay for CO2 mitigation, respondent's WTP increased with increasing CO2 mitigation percentage. Important factors influencing WTP include people's feeling of dread of GHGs, confidence in policy, the timeliness of governmental information disclosure, age, education and income level.
•We examined public WTP and the determinants for CO2 mitigation in Suzhou, China.•Trust crisis and people's low responsibility are the leading causes of zero-bid.•Increasing income and education will increase people's WTP.•Lower dread, longer duration and greater influence of GHG risk will increase WTP.•High confidence in policy and timely information disclosure will increase WTP.
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