Porous carbon directed growth of carbon modified MnO2 porous spheres for pseudocapacitor applications

Carbon modified MnO2 (CMMO) spheres have been fabricated through a facile low temperature (60 degrees C) hydrothermal method using mesoporous carbon spheres as reductive agent and sacrificial template and KMnO4 as manganese source. CMMO spheres with novel nanostructures such as flower-like and sea urchin-like are obtained by controlling the reaction time. The roles of mesoporous carbon in directing the growth of the CMMO spheres and controlling their morphologies have been investigated. The CMMO spheres are characterized by XRD, XPS, SEM, TEM, Raman spectra, TGA and N-2 adsorption-desorption technique and electrochemical measurement. The resulted samples possess unique morphologies and regular pores, and their properties changed as reaction time proceed. The peseudocapacitive behaviors of the as-prepared samples are tested in two-electrode supercapacitors using 2 mol L-1 KOH aqueous solutions as electrolyte. A high gravimetric capacitance of 344 F g(-1) at 1 A g(-1) and the capacity retaining of 75% after 5000 cycles are achieved on the electrode prepared with one of the CMMO samples. The other CMMO samples also possess excellent electrochemical performance in comparison with the pristine mesoporous carbon (p-MC). Such superior electrochemical performance makes the porous CMMO spheres to be promising materials in the application of pseudocapacitors. (C) 2017 Elsevier B.V. All rights reserved

The efficiency of Vpx-mediated SAMHD1 antagonism does not correlate with the potency of viral control in HIV-2-infected individuals

Background: The presence of a vpx gene distinguishes HIV-2 from HIV-1, the main causative agent of AIDS. Vpx degrades the restriction factor SAMHD1 to boost HIV-2 infection of macrophages and dendritic cells and it has been suggested that the activation of antiviral innate immune responses after Vpx-dependent infection of myeloid cells may explain why most HIV-2-infected individuals efficiently control viral replication and become long-term survivors. However, the role of Vpx-mediated SAMHD1 antagonism in the virological and clinical outcome of HIV-2 infection remained to be investigated. Results: Here, we analyzed the anti-SAMHD1 activity of vpx alleles derived from seven viremic and four long-term aviremic HIV-2-infected individuals. We found that effective Vpx-mediated SAMHD1 degradation and enhancement of myeloid cell infection was preserved in most HIV-2-infected individuals including all seven that failed to control the virus and developed AIDS. The only exception were vpx alleles from an aviremic individual that predicted a M68K change in a highly conserved nuclear localization signal which disrupted the ability of Vpx to counteract SAMHD1. We also found that HIV-2 is less effective than HIV-1 in inducing innate immune activation in dendritic cells. Conclusions: Effective immune control of viral replication in HIV-2-infected individuals is not associated with increased Vpx-mediated degradation of SAMHD1

The De Novo Cytosine Methyltransferase DRM2 Requires Intact UBA Domains and a Catalytically Mutated Paralog DRM3 during RNA–Directed DNA Methylation in Arabidopsis thaliana

Eukaryotic DNA cytosine methylation can be used to transcriptionally silence repetitive sequences, including transposons and retroviruses. This silencing is stable between cell generations as cytosine methylation is maintained epigenetically through DNA replication. The Arabidopsis thaliana Dnmt3 cytosine methyltransferase ortholog DOMAINS REARRANGED METHYLTRANSFERASE2 (DRM2) is required for establishment of small interfering RNA (siRNA) directed DNA methylation. In mammals PIWI proteins and piRNA act in a convergently evolved RNA–directed DNA methylation system that is required to repress transposon expression in the germ line. De novo methylation may also be independent of RNA interference and small RNAs, as in Neurospora crassa. Here we identify a clade of catalytically mutated DRM2 paralogs in flowering plant genomes, which in A.thaliana we term DOMAINS REARRANGED METHYLTRANSFERASE3 (DRM3). Despite being catalytically mutated, DRM3 is required for normal maintenance of non-CG DNA methylation, establishment of RNA–directed DNA methylation triggered by repeat sequences and accumulation of repeat-associated small RNAs. Although the mammalian catalytically inactive Dnmt3L paralogs act in an analogous manner, phylogenetic analysis indicates that the DRM and Dnmt3 protein families diverged independently in plants and animals. We also show by site-directed mutagenesis that both the DRM2 N-terminal UBA domains and C-terminal methyltransferase domain are required for normal RNA–directed DNA methylation, supporting an essential targeting function for the UBA domains. These results suggest that plant and mammalian RNA–directed DNA methylation systems consist of a combination of ancestral and convergent features

Ruthenium/cobalt binary oxides supported on hollow alumina microspheres as highly efficient catalyst for vinyl chloride oxidation

Alumina hollow microspheres (AlO-hms) were synthesized and used to support metal oxide and binary metal oxide particles to prepare three catalysts, designated as RuO/AlO-hms, CoO/AlO-hms and RuCoO/AlO-hms. Their catalytic properties in vinyl chloride oxidation were investigated and found to follow this order: RuCoO/AlO-hms > RuO/AlO-hms > CoO/AlO-hms. In comparison with a commercial AlO support, the AlO-hms provide a higher specific surface area and unique hollow spherical morphology, benefiting for uniform distribution of catalyst particles. It was also found that the strong metal-support interaction between metal nanoparticles and AlO-hms has significant effects on the low-temperature reducibility, the surface oxygen abundance and mobility, giving rise to different oxidation activities. The AlO-hms supported metal catalysts remained relatively high catalytic activity after consecutive catalytic runs and high-temperature annealing. The anti-sintering ability enhancement of metal particles was attributed to the stabilization and metal-support interaction effects with AlO-hms

Waste-cellulose-derived porous carbon adsorbents for methyl orange removal

High-performance nitrogen-doped porous carbon adsorbents were prepared from waste cellulose fibers using the spray-drying method and used to remove methyl orange (MO) from water. The carbon adsorbents possessed a honeycomb-like turbostratic microstructure with hierarchical pores. Such waste-cellulose-derived carbon adsorbents were found to exhibit a fast adsorption rate towards MO. A sample thermally treated at 800 °C with the highest specific surface area (about 1259.4 m /g) and total pore volume (about 2.7 cm /g) exhibited the best MO adsorption capacity (337.8 mg/g), which is significantly higher than that of ZnCl -activated carbon. The effect of MO initial concentration, pH and temperature on the carbon adsorption was investigated systematically. It was found that the adsorption system is heterogeneous while the isotherm data on the carbon sample can be well described by both Langmuir and Freundlich isotherm models. The high-performance and cost-effective carbon adsorbent described in this paper holds a great promise for dye removal from aqueous solutions

The electrocapacitive properties of polyaniline/VXC-72 composite electrodes

While polyaniline holds a great promise as an electrode material for pseudocapacitors, its poor stability against charge/discharge hinders its practical applications. In this work, polymerization of aniline was conducted in the presence of commercial carbon black VXC-72 to prepare polyaniline/VXC-72 composite electrodes. Results showed that the stability of the polyaniline/VXC-72 composite electrode was drastically improved with over 90% capacitance retention after 10,000 cycles at a current density of 2 A g(-1). It was found that VXC-72 particles played an important part in the chemical oxidative polymerisation process - they served not only as nucleation sites on which polymerization underwent to form polyaniline but also determined the morphology of the resultant solid product. The polyaniline/VXC-72 composite electrode materials with different contents of VXC-72 exhibited different morphologies and electrocapacitive performances. This research provides guidelines for designing polyaniline-carbon black composite electrode materials with an excellent stability against cycling, high capacitance, and low cost