An efficient, durable, and low‐cost hydrogen evolution reaction (HER) catalyst is an essential requirement for practical hydrogen production. Herein, an effective approach to facilitate the HER kinetics of molybdenum carbide (Mo2C) electrocatalysts is presented by tuning its electronic structure through atomic engineering of nitrogen implantation. Starting from the organoimido‐derivatized polyoxometalate nanoclusters with inherent Mo? N bonds, the formation of N‐implanted Mo2C (N@Mo2C) nanocrystals with perfectly adjustable amounts of N atoms is demonstrated. The optimized N@Mo2C electrocatalyst exhibits remarkable HER performance and good stability over 20 h in both acid and basic electrolytes. Further density functional theory calculations show that engineering suitable nitrogen atoms into Mo2C can regulate its electronic structure well and decrease Mo? H strength, leading to a great enhancement of the HER activity. It could be believed that this ligand‐controlled atomic engineering strategy might influence the overall catalyst design strategy for engineering the activation sites of nonprecious metal catalysts for energy conversions. 相似文献
Long-term pre-release evaluations of how invasive plants respond to herbivory in introduced ranges can help identify the most effective biological control agents. However, most evaluations have been conducted within only one generation of introduced invasive species. This study tested effects across seven generations of simulated herbivory (i.e., defoliation) and habitat types on the invasive weed Alternanthera philoxeroides. We found total biomass of A. philoxeroides was decreased by defoliation during the first three generations when grown in a simulated aquatic habitat, but was decreased by defoliation only in the first generation when grown in a simulated terrestrial habitat. Defoliation significantly decreased stem diameter and collenchyma thickness and increased cortex thickness and total phenol production in A. philoxeroides grown in a simulated terrestrial or aquatic habitat during the first generation, but showed little effect during the following six successive generations. The associations between stem anatomical structural parameters and biomass significantly differed between non-defoliation and defoliation treatments in the simulated aquatic habitat, but not in the simulated terrestrial habitat. Our results suggest simulated herbivory exerted successful biological control on A. philoxeroides during the first generation in a simulated terrestrial habitat and the first three generations in a simulated aquatic habitat, but failed to restrain the vegetative offspring of A. philoxeroides. This failure of long-term biological control on A. philoxeroides might be caused by changes in the stem anatomical structure and compensatory growth. Our study highlights the need for long-term pre-release evaluation when testing the efficiency of biological control agents.
NADPH oxidase-2 (Nox2)/gp91(phox) and p47(phox) deficient mice are prone to hyper-inflammatory responses suggesting a paradoxical role for Nox2-derived reactive oxygen species (ROS) as anti-inflammatory mediators. The molecular basis for this mode of control remains unclear. Here we demonstrate that IFNγ/LPS matured p47(phox-/-)-ROS deficient mouse dendritic cells (DC) secrete more IL-12p70 than similarly treated wild type DC, and in an in vitro co-culture model IFNγ/LPS matured p47(phox-/-) DC bias more ovalbumin-specific CD4(+) T lymphocytes toward a Th1 phenotype than wild type (WT) DC through a ROS-dependent mechanism linking IL-12p70 expression to regulation of p38-MAPK activation. The Nox2-dependent ROS production in DC negatively regulates proinflammatory IL-12 expression in DC by constraining p38-MAPK activity. Increasing endogenous H(2)O(2) attenuates p38-MAPK activity in IFNγ/LPS stimulated WT and p47(phox-/-) DC, which suggests that endogenous Nox 2-derived ROS functions as a secondary messenger in the activated p38-MAPK signaling pathway during IL-12 expression. These findings indicate that ROS, generated endogenously by innate and adaptive immune cells, can function as important secondary messengers that can regulate cytokine production and immune cell cross-talk to control during the inflammatory response. 相似文献
AbstractHow microbes respond to substantial and increasing anthropogenic disturbance remains an open question in river systems. We tested the hypothesis that the source and distribution of anthropogenic organic matter (OM) were significant factors affecting the spatial variation of the microbial community composition of the Yangtze River sediments. Bulk geochemical proxies and lignin phenols suggested a general decrease of terrestrial C3 plants or soil OM input from the middle to the lower reaches. Fecal sterols inferred higher sewage contamination levels in the middle reaches. Polycyclic aromatic hydrocarbons (PAHs) distribution indicated a dominant biomass and coal combustion signal in the middle reaches, whereas a mixed source including petroleum combustion in the lower reaches. Phylogenetic analysis revealed a large portion of Methanobacteria and Verrucomicrobia enriched in the middle reaches, whereas OM-degrading bacteria, including Flavobacteria, Acidobacteria, and Alphaproteobacteria were dominant in the lower reaches. Quantitative PCR analyses and multivariate analysis further demonstrated that sources and distribution of OM had combined effects in shaping alpha and beta-diversity of sediment microbial communities. Sewage discharge and incomplete OM combustion, respectively, were associated with Methylococcaceae, Chloroflexi, and Bacteroidetes groups. This study provides a foundation for further understanding of the river sediment microbial composition, considering the continued increase of anthropogenic influences. 相似文献
Two organic-inorganic hybrid compounds, (Bu4N)2[Mo6O18(NAr)] (Ar = 2-CH3-4-BrC6H3 (1) or 2,6-CH3-4-BrC6H2 (2)) have been synthesized via the DCC dehydrating protocol of the reaction of [α-Mo8O26]4− with 2-methyl-4-bromoaniline hydrochloride or 2,6-dimethyl-4-bromoaniline hydrochloride in anhydrous acetonitrile, which have been characterized by UV-Vis spectra, 1H NMR, IR, cyclic voltammetry and X-ray single-crystal diffraction study. Both compounds crystallize in the monoclinic space group , which are featured in a terminal phenylimido group linked to a Mo atom of a hexamolybdate cluster by a Mo-N triple bond. Interestingly, there are two conformational isomers of the cluster anions of 1 and 2 in the crystals. By cyclic voltammetry study, their special redox properties were also found in the end. 相似文献
NF-κB essential modulator (NEMO) and cylindromatosis protein (CYLD) are intracellular proteins that regulate the NF-κB signaling pathway. Although mice with either CYLD deficiency or an alteration in the zinc finger domain of NEMO (K392R) are born healthy, we found that the combination of these two gene defects in double mutant (DM) mice is early embryonic lethal but can be rescued by the absence of TNF receptor 1 (TNFR1). Notably, NEMO was not recruited into the TNFR1 complex of DM cells, and consequently NF-κB induction by TNF was severely impaired and DM cells were sensitized to TNF-induced cell death. Interestingly, the TNF signaling defects can be fully rescued by reconstitution of DM cells with CYLD lacking ubiquitin hydrolase activity but not with CYLD mutated in TNF receptor-associated factor 2 (TRAF2) or NEMO binding sites. Therefore, our data demonstrate an unexpected non-catalytic function for CYLD as an adapter protein between TRAF2 and the NEMO zinc finger that is important for TNF-induced NF-κB signaling during embryogenesis. 相似文献
The increasing threat of drug-resistant strains of Mycobacterium tuberculosis (M. tb) and co-infection with human immunodeficiency virus (HIV) has worsened the international public health crisis and challenged conventional chemotherapy. Therapeutic vaccines, which possess the capacity to stimulate the immune system and affect the disease progression, deserve reconsideration to aid chemotherapy. Vaccines based on Ag85B-ESAT6 fusion protein were tested as potential immunotherapeutic vaccines against ongoing intravenous infection in a mouse model. Therapeutic efficacy was evaluated by enumeration of bacilli in infected tissues and by histological examination of the lungs. Ag85B-ESAT6 with the adjuvant dimethyl dioctadecylammonium bromide (DDA) - monophosphoryl lipid A (MPL) did not reduce bacterial load, however induced a sharp weight loss and worsened pathology. Recombinant virus-based vaccines failed to protect mice against tuberculosis either. More efforts should be taken to search for protective candidates and elucidate the mechanism for immunotherapy. 相似文献
Aims Why invasive plants are more competitive in their introduced range than native range is still an unanswered question in plant invasion ecology. Here, we used the model invasive plant Solidago canadensis to test a hypothesis that enhanced production of allelopathic compounds results in greater competitive ability of invasive plants in the invaded range rather than in the native range. We also examined the degree to which the allelopathy contributes increased competitive ability of S. canadensis in the invaded range.Methods We compared allelochemical production by S. canadensis growing in its native area (the USA) and invaded area (China) and also by populations that were collected from the two countries and grown together in a 'common garden' greenhouse experiment. We also tested the allelopathic effects of S. canadensis collected from either the USA or China on the germination of Kummerowia striata (a native plant in China). Finally, we conducted a common garden, greenhouse experiment in which K. striata was grown in monoculture or with S. canadensis from the USA or China to test the effects of allelopathy on plant–plant competition with suitable controls such as adding activated carbon to the soil to absorb the allelochemicals and thereby eliminating any corresponding allopathic effects.Important findings Allelochemical contents (total phenolics, total flavones and total saponins) and allelopathic effects were greater in S. canadensis sampled from China than those from the USA as demonstrated in a field survey and a common garden experiment. Inhibition of K. striata germination using S. canadensis extracts or previously grown in soil was greater using samples from China than from the USA. The competitive ability of S. canadensis against K. striata was also greater for plants originating from China than those from the USA. Allelopathy could explain about 46% of the difference. These findings demonstrated that S. canadensis has evolved to be more allelopathic and competitive in the introduced range and that allelopathy significantly contributes to increased competitiveness for this invasive species. 相似文献