Nitrogen-doped carbon nanotubes with well-defined tubular morphology and controllable shell thickness as efficient nonprecious oxygen reduction reaction electrocatalysts have been reported.
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•Halloysite nanotubes were used as the template for the synthesis of uniform N-CNTs.•The shell thickness of N-CNTs can be well-controlled.•N-CNTs showed excellent catalytic activity toward the oxygen reduction reaction.•N-CNTs with the pyridinic N content of 21.6% showed the best oxygen reduction reaction performance.
Halloysites were applied as the template to form halloysite/polyaniline core/shell hybrids through an oxidative polymerization route, where the amount of aniline monomer could be adjusted to precisely control the shell thickness of polyaniline. The pyrolysis process was then applied to ensure the carbonization of the polyaniline to form halloysite/nitrogen-doped carbon core/shell hybrids. Finally, halloysites were removed, resulting in the formation of nitrogen-doped carbon nanotube with a uniform morphology and a controlled shell thickness. The shell thickness and pyrolysis temperature of nitrogen-doped carbon nanotubes were optimized to improve the electrocatalytic performance involved in oxygen reduction reaction. The nitrogen-doped carbon nanotubes showed good electrocatalytic activities toward oxygen reduction reaction in 0.1 mol L−1 KOH aqueous solution, making them a promising cathode catalyst for alkaline fuel cell applications.
Protein arginine methyltransferase 1 (PRMT1) stimulates erythroid differentiation, but the signaling events upstream are yet to be identified. Ca2+ plays crucial roles during erythroid ...differentiation. Here, we show that Ca2+ enhances methylation during induced erythroid differentiation and that Ca2+ directly upregulates the catalytic activity of recombinant PRMT1 by increasing Vmax toward the substrate heterogeneous nuclear ribonucleoprotein A2. We demonstrate that PRMT1 is essential and responsible for the effect of Ca2+ on differentiation. Depletion of Ca2+ suppresses PRMT1‐mediated activation of p38α and p38α‐stimulated differentiation. Furthermore, Ca2+ stimulates methylation of p38α by PRMT1. This study uncovers a novel regulatory mechanism for PRMT1 by Ca2+ and identifies the PRMT1/p38α axis as an intracellular mediator of Ca2+ signaling during erythroid differentiation.
Exploring novel p-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27, HPPD) inhibitors has become one of the most promising research directions in herbicide innovation. On the basis of our tremendous ...interest in exploiting more powerful HPPD inhibitors, we designed a family of benzyl-containing triketone-aminopyridines via a structure-based drug design (SBDD) strategy and then synthesized them. Among these prepared derivatives, the best active 3-hydroxy-2-(3,5,6-trichloro-4-((4-isopropylbenzyl)amino)picolinoyl)cyclohex-2-en-1-one (23, IC50 = 0.047 μM) exhibited a 5.8-fold enhancement in inhibiting Arabidopsis thaliana (At) HPPD activity over that of commercial mesotrione (IC50 = 0.273 μM). The predicted docking models and calculated energy contributions of the key residues for small molecules suggested that an additional π–π stacking interaction with Phe-392 and hydrophobic contacts with Met-335 and Pro-384 were detected in AtHPPD upon the binding of the best active compound 23 compared with that of the reference mesotrione. Such a molecular mechanism and the resulting binding affinities coincide with the proposed design scheme and experimental values. It is noteworthy that inhibitors 16 (3-hydroxy-2-(3,5,6-trichloro-4-((4-chlorobenzyl)amino)picolinoyl)cyclohex-2-en-1-one), 22 (3-hydroxy-2-(3,5,6-trichloro-4-((4-methylbenzyl)amino)picolinoyl)cyclohex-2-en-1-one), and 23 displayed excellent greenhouse herbicidal effects at 150 g of active ingredient (ai)/ha after postemergence treatment. Furthermore, compound 16 showed superior weed-controlling efficacy against Setaria viridis (S. viridis) versus that of the positive control mesotrione at multiple test dosages (120, 60, and 30 g ai/ha). These findings imply that compound 16, as a novel lead of HPPD inhibitors, possesses great potential for application in specifically combating the malignant weed S. viridis.
This study aimed to propose individual phase voltage regulation strategies using the sparrow search algorithm (SSA) in the IEEE 8500-node large-scale unbalanced distribution network with high ...photovoltaic (PV) penetration. The proposed approach is capable of individual phase regulation, which coordinates the on-load tap changer (OLTC), voltage regulator (VR), switched capacitor bank (SCB), and volt–var setting controlled by a smart inverter to improve voltage variation and unbalance. Consequently, the change time of VRs, the switched times of SCBs, and the individual phase voltage magnitude and unbalance ratio are considered in the fitness function for the SSA. The simulation scenarios fully consider the unbalanced load conditions and PV power output patterns, and the numerical results demonstrate that the voltage variation and unbalance are clearly improved, by 15% and 26%, respectively. The fitness values, operation times of OLTC, VR, and SCB, and the settings of the volt–var controlled smart inverter are also optimized by the SSA. The outcomes of this study are helpful for distribution system operators in formulating voltage control strategies corresponding to different system conditions.
As robot technologies develop, many researchers have tried to use robots to support education. Studies have shown that robots can help students develop problem-solving abilities and learn computer ...programming, mathematics, and science. However, few studies discuss the use of robots to facilitate the teaching of second languages. We discuss whether language teaching needs robot support, whether robots present an appropriate medium for language instruction, and what challenges must be overcome. In order to explore the possibility of using robots as an instructional tool for teaching a second language, this paper reviews prior studies concerning educational robots and analyzes the characteristics of robots and instructional media. Furthermore, we report on the design and testing of five instruction scenarios for teaching second language. Based on our empirical experience, we provide suggestions for future research directions in the realm of robots for language education.
DNA methylation and demethylation have been proposed to play an important role in somatic cell reprogramming. Here, we demonstrate that the DNA hydroxylase Tet1 facilitates pluripotent stem cell ...induction by promoting Oct4 demethylation and reactivation. Moreover, Tet1 (T) can replace Oct4 and initiate somatic cell reprogramming in conjunction with Sox2 (S), Klf4 (K), and c-Myc (M). We established an efficient TSKM secondary reprogramming system and used it to characterize the dynamic profiles of 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), and gene expression during reprogramming. Our analysis revealed that both 5mC and 5hmC modifications increased at an intermediate stage of the process, correlating with a transition in the transcriptional profile. We also found that 5hmC enrichment is involved in the demethylation and reactivation of genes and regulatory regions that are important for pluripotency. Our data indicate that changes in DNA methylation and hydroxymethylation play important roles in genome-wide epigenetic remodeling during reprogramming.
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► Tet1 facilitates iPSC induction by promoting Oct4 demethylation and reactivation ► Tet1 can replace Oct4 to generate fully pluripotent TSKM iPSCs ► Both 5mC and 5hmC increase on the genome during TSKM 2° reprogramming ► 5hmC promotes the demethylation of pluripotency genes during reprogramming
Tet1 promotes reprogramming by accelerating changes in DNA methylation at a broad range of loci, including Oct4, and can replace Oct4 as a core reprogramming factor.
4-Hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) has been recognized as one of the most promising targets in the field of herbicide innovation considering the severity of weed resistance ...currently. In a persistent effort to develop effective HPPD-inhibiting herbicides, a structure-guided strategy was carried out to perform the structural optimization for triketone-quinazoline-2,4-diones, a novel HPPD inhibitor scaffold first discovered in our lab. Herein, starting from the crystal structure of
(
)HPPD complexed with 6-(2-hydroxy-6-oxocyclohex-1-ene-1-carbonyl)-1,5-dimethyl-3-(
-tolyl)quinazoline-2,4(1
,3
)-dione (
), three subseries of quinazoline-2,4-dione derivatives were designed and prepared by optimizing the hydrophobic interactions between the side chain of the core structure at the R
position and the hydrophobic pocket at the active site entrance of
HPPD. 6-(2-Hydroxy-6-oxocyclohex-1-ene-1-carbonyl)-1,5-dimethyl-3-(3-(trimethylsilyl)prop-2-yn-1-yl)quinazoline-2,4(1
,3
)-dione (
) with the best inhibitory activity against
HPPD was identified to be the first subnanomolar-range
HPPD inhibitor (
= 0.86 nM), which significantly outperformed that of the lead compound
(
= 8.2 nM). Further determination of the crystal structure of
HPPD in complex with compound
(1.85 Å) and the binding energy calculation provided a molecular basis for the understanding of its high efficiency. Additionally, the greenhouse assay indicated that 6-(2-hydroxy-6-oxocyclohex-1-ene-1-carbonyl)-1,5-dimethyl-3-propylquinazoline-2,4(1
,3
)-dione (
) and compound
showed acceptable crop safety against peanut and good herbicidal activity with a broad spectrum. Moreover, compound
also showed superior selectivity for wheat at the dosage of 120 g ai/ha and favorable herbicidal efficacy toward the gramineous weeds at the dosage of as low as 30 g ai/ha. We believe that compounds
and
have promising prospects as new herbicide candidates for wheat and peanut fields.
The production of α-melanocyte-stimulating hormone (α-MSH), a peptide hormone composed of 13 amino acids, is attempted by recombinant expression using E. coli as the host. To achieve this aim, a ...synthetic gene containing eight tandem repeats of msh gene (8msh) was designed for ribosomal synthesis of 8 α-MSH. The merit of the strategy is to diminish the peptide toxicity against the host cell and to achieve a higher production yield. Pepsin cleavage sites are introduced between the peptides for enzymatic proteolysis to obtain the monomeric peptide of α-MSH. The constructed plasmid was transformed into different strains of E. coli hosts, and E. coli XL1-Blue with gene 8msh revealed the highest yield of 8 α-MSH. Although 8 α-MSH was fractionalized in the insoluble pellets after cell lysis, pepsin cleavage was able to produce soluble α-MSH peptide, as analyzed and confirmed by mass spectrometry and peptide activity assays. The production of α-MSH was quantified using HPLC with a yield of 42.9 mg/L of LB culture. This study demonstrates the feasibility of producing α-MSH using recombinant expression of tandem repeat gene. The production procedure involves minimal post-treatment and processing and can be scaled up for industrial application.
This study aims to advocate that a visual programming environment offering graphical items and states of a computational problem could be helpful in supporting programming learning with computational ...problem-solving. A visual problem-solving environment for programming learning was developed, and 158 college students were conducted in a computational problem-solving activity. The students' activities of designing, composing, and testing solutions were recorded by log data for later analysis. To initially unveil the students' practice and strategies exhibited in the visual problem-solving environment, this study proposed several indicators to quantitatively represent students' computational practice (Sequence, Selection, Simple iteration, Nested iteration, and Testing), computational design (Problem decomposition, Abutment composition, and Nesting composition), and computational performance (Goal attainment and Program size). By the method of cluster analysis, some empirical patterns regarding the students' programming learning with computational problem-solving were identified. Furthermore, comparisons of computational design and computational performance among the different patterns of computational practice were conducted. Considering the relations of students' computational practice to computational design and performance, evidence-based suggestions on the design of supportive programming environments for novice programmers are discussed.
•A visual problem-solving environment was proposed to support programming learning.•Students exhibited different patterns of computational practice in the environment.•Patterns of computational practice were correlated with computational design and performance.
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