Nonexistence for mixed-type equations with critical exponent nonlinearity in a ball

AbstractIn this work, we consider the following isotropic mixed-type equations: (0.1)y|y|α−1uxx+x|x|α−1uyy=f(x,y,u) in Br(0)⊂R2 with r>0. By proving some Pohozaev-type identities for (0.1) and dividing Br(0) naturally into six regions Ωi(i=1,2,3,4,5,6), we can show that the equation (0.2)yuxx+xuyy=sign(x+y)|u|2u with Dirichlet boundary conditions on each natural domain Ωi has no nontrivial regular solution in Br(0)

Fabrication of β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes composites and application for paraben removal

In this work, the novel β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes (MWCNTs) composites were synthesized and applied for the removal of parabens in aqueous solution. The prepared MWCNTs/SiO2/β-CD composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The effects of the amount of adsorbent, pH and elution solvents on the removal efficiency of parabens from water solutions were investigated. Under the optimized conditions, over 95% removal efficiency was achieved by using 40 mg of MWCNTs/SiO2/β-CD adsorbents to absorb the parabens from 60 mL of 0.5 μg/mL parabens solutions. The solution pH in the range from 5 to 9 has no influence on the removal efficiency and the parabens sorption capacity of the prepared adsorbents were around 0.75 μg/mg. Furthermore, the stability and reusability studies demonstrated that the prepared MWCNTs/SiO2/β-CD composites are cost-effective adsorbents for the removal of parabens from water with high regeneration efficiency. The composites fabricated in this study could become an attractive candidate for water purification

Modeling Occasion Evolution in Frequency Domain for Promotion-Aware Click-Through Rate Prediction

Promotions are becoming more important and prevalent in e-commerce to attract customers and boost sales, leading to frequent changes of occasions, which drives users to behave differently. In such situations, most existing Click-Through Rate (CTR) models can't generalize well to online serving due to distribution uncertainty of the upcoming occasion. In this paper, we propose a novel CTR model named MOEF for recommendations under frequent changes of occasions. Firstly, we design a time series that consists of occasion signals generated from the online business scenario. Since occasion signals are more discriminative in the frequency domain, we apply Fourier Transformation to sliding time windows upon the time series, obtaining a sequence of frequency spectrum which is then processed by Occasion Evolution Layer (OEL). In this way, a high-order occasion representation can be learned to handle the online distribution uncertainty. Moreover, we adopt multiple experts to learn feature representations from multiple aspects, which are guided by the occasion representation via an attention mechanism. Accordingly, a mixture of feature representations is obtained adaptively for different occasions to predict the final CTR. Experimental results on real-world datasets validate the superiority of MOEF and online A/B tests also show MOEF outperforms representative CTR models significantly

High-Power and Ultralong-Life Aqueous Zinc-Ion Hybrid Capacitors Based on Pseudocapacitive Charge Storage

© 2019, © 2019, The Author(s). Rechargeable aqueous zinc-ion hybrid capacitors and zinc-ion batteries are promising safe energy storage systems. In this study, amorphous RuO2·H2O for the first time was employed to achieve fast and ultralong-life Zn2+ storage based on a pseudocapacitive storage mechanism. In the RuO2·H2O||Zn zinc-ion hybrid capacitors with Zn(CF3SO3)2 aqueous electrolyte, the RuO2·H2O cathode can reversibly store Zn2+ in a voltage window of 0.4–1.6 V (vs. Zn/Zn2+), delivering a high discharge capacity of 122 mAh g−1. In particular, the zinc-ion hybrid capacitors can be rapidly charged/discharged within 36 s with a very high power density of 16.74 kW kg−1 and a high energy density of 82 Wh kg−1. Besides, the zinc-ion hybrid capacitors demonstrate an ultralong cycle life (over 10,000 charge/discharge cycles). The kinetic analysis elucidates that the ultrafast Zn2+ storage in the RuO2·H2O cathode originates from redox pseudocapacitive reactions. This work could greatly facilitate the development of high-power and safe electrochemical energy storage.[Figure not available: see fulltext.]

Advances on transition metal oxides catalysts for formaldehyde oxidation:a review

This article highlights recent advances in the development of transition metal-based catalysts for formaldehyde oxidation, particularly the enhancement of their catalytic activity for low-temperature oxidation. Various factors that enhance low-temperature activity are reviewed, such as morphology and tunnel structures, synthesis methods, specific surface area, amount and type of active surface oxygen species, oxidation state, and density of active sites are discussed. In addition, catalyst immobilization for practical air purification, reaction mechanism of formaldehyde oxidation, and the reaction parameters affecting the overall efficiency of the reaction are also reviewed

Opposite effects of Co and Cu dopants on the catalytic activities of birnessite MnO2 catalyst for low-temperature formaldehyde oxidation

Defect engineering is an effective strategy to enhance the activity of catalysts for various applications. Herein, it was demonstrated that in addition to enhancing surface properties via doping, the influence of dopants on the surface-intermediate interaction is a critical parameter that impacts the catalytic activity of doped catalysts for low-temperature formaldehyde (HCHO) oxidation. The incorporation of Co into the lattice structure of δ-MnO2 led to the generation of oxygen vacancies, which promoted the formation of surface active oxygen species, reduced activation energy, and enhanced catalytic activity for low-temperature oxidation of HCHO. On the contrary, Cu doping led to a drastic suppression of the catalytic activity of δ-MnO2, despite its enhanced redox properties and slight increase in the surface concentration of active oxygen species, compared to pristine δ-MnO2. Diffuse reflectance infrared Fourier transform analysis revealed that in the presence of Cu, carbonate intermediate species accumulate on the surface of the catalysts, leading to partial blockage of active sites and suppression of catalytic activity

Edible Bird’s Nest Prevents Menopause-Related Memory and Cognitive Decline in Rats via Increased Hippocampal Sirtuin-1 Expression

Menopause causes cognitive and memory dysfunction due to impaired neuronal plasticity in the hippocampus. Sirtuin-1 (SIRT1) downregulation in the hippocampus is implicated in the underlying molecular mechanism. Edible bird’s nest (EBN) is traditionally used to improve general wellbeing, and in this study, we evaluated its effects on SIRT1 expression in the hippocampus and implications on ovariectomy-induced memory and cognitive decline in rats. Ovariectomized female Sprague-Dawley rats were fed with normal pellet alone or normal pellet + EBN (6, 3, or 1.5%), compared with estrogen therapy (0.2 mg/kg/day). After 12 weeks of intervention, Morris water maze (four-day trial and one probe trial) was conducted, and serum estrogen levels, toxicity markers (alanine transaminase, alkaline phosphatase, urea, and creatinine), and hippocampal SIRT1 immunohistochemistry were estimated after sacrifice. The results indicated that EBN and estrogen enhanced spatial learning and memory and increased serum estrogen and hippocampal SIRT1 expression. In addition, the EBN groups did not show as much toxicity to the liver as the estrogen group. The data suggested that EBN treatment for 12 weeks could improve cognition and memory in ovariectomized female rats and may be an effective alternative to estrogen therapy for menopause-induced aging-related memory loss

Simultaneous measurement of multiple organic tracers in fine aerosols from biomass burning and fungal spores by HPLC-MS/MS

Three monosaccharide anhydrides (MAs: levoglucosan, mannosan, and galactosan) and sugar alcohols (arabitol and mannitol) are widely used as organic tracers for source identification of aerosols emitted from biomass burning and fungal spores, respectively. In the past, these two types of organic tracer have been measured separately or conjointly using different analytical techniques, with which a number of disadvantages have been experienced during the application to environmental aerosol samples, including organic solvent involved extraction, time-consuming derivatization, or poor separation efficiency due to overlapping peaks, etc. Hence, in this study a more environment-friendly, effective and integrated extraction and analytical method has been developed for simultaneous determination of the above mentioned organic tracers in the same aerosol sample using ultrasonication and high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The ultrasonication assisted extraction process using ultrapure water can achieve satisfactory recoveries in the range of 100.3 ± 1.3% to 108.4 ± 1.6% for these tracers. All the parameters related to LC and MS/MS have been optimized to ensure good identification and pronounced intensity for each compound. A series of rigorous validation steps have been conducted. This newly developed analytical method using ultrasonication and HPLC-MS/MS has been successfully applied to environmental aerosol samples of different pollution levels for the simultaneous measurement of the above mentioned five organic tracers from biomass burning and fungal spores