We study the formation of bismuth oxide hollow nanoparticles by the Kirkendall effect using liquid cell transmission electron microscopy (TEM). Rich dynamics of bismuth diffusion through the bismuth ...oxide shell have been captured in situ. The diffusion coefficient of bismuth through bismuth oxide shell is 3-4 orders of magnitude higher than that of bulk. Observation reveals that defects, temperature, sizes of the particles, and so forth can affect the diffusion of reactive species and modify the kinetics of the hollowing process.
Controlled synthesis of transition‐metal hydroxides and oxides with earth‐abundant elements have attracted significant interest because of their wide applications, for example as battery electrode ...materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition‐metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used. The Ni2+, Mn2+, and Co2+ ion‐containing aqueous solution undergoes photo‐induced reactions and produces hollow metal‐oxide nanospheres (Ni0.18Mn0.45Co0.37Ox) or core–shell metal hydroxide nanoflowers (Ni0.15Mn0.15Co0.7(OH)2(NO3)0.2⋅H2O), depending on the laser wavelengths. We propose two reaction pathways, either by photo‐induced redox reaction or hydrolysis reaction, which are responsible for the formation of distinct nanostructures. The study of photon‐induced materials growth shines light on the rational design of complex nanostructures with advanced functionalities.
Photon‐induced chemical reactions: Two reaction pathways, namely, photon‐induced redox reactions under 532 nm laser‐light irradiation and hydrolysis under 1064 nm laser‐light irradiation, are comparatively studied. Distinct transition‐metal hydroxide and oxide nanostructures are controllably fabricated by irradiating the aqueous precursor solutions with laser light.
We present a systemic investigation of a galvanic replacement technique in which active‐metal nanoparticles are used as sacrificial seeds. We found that different nanostructures can be controllably ...synthesized by varying the type of more noble‐metal ions and liquid medium. Specifically, nano‐heterostructures of noble metal (Ag, Au) or Cu nanocrystals on active‐metal (Mg, Zn) cores were obtained by the reaction of active‐metal nanoparticles with more noble‐metal ions in ethanol; Ag nanocrystal arrays were produced by the reaction of active‐metal nanoparticles with Ag+ ions in water; spongy Au nanospheres were generated by the reaction of active‐metal nanoparticles with AuCl4− ions in water; and SnO2 nanoparticles were prepared when Sn2+ were used as the oxidant ions. The key factors determining the product morphology are shown to be the reactivity of the liquid medium and the nature of the oxidant–reductant couple, whereas Mg and Zn nanoparticles played similar roles in achieving various nanostructures. When microsized Mg and Zn particles were used as seeds in similar reactions, the products were mainly noble‐metal dendrites. The new approach proposed in this study expands the capability of the conventional nanoscale galvanic replacement method and provides new avenues to various structures, which are expected to have many potential applications in catalysis, optoelectronics, and biomedicine.
A noble solution: Active‐metal nanoparticles have been used as reactants for galvanic replacement reactions. It was found that different nanostructures can be synthesized in a controlled fashion by varying the type of noble‐metal ions and the liquid medium (see scheme). The approach expands the capability of the conventional nanoscale galvanic replacement approach and provides new avenues to various structures.
The cylinder linear induction motor (CLIM) is a variation of the rotary induction motor. Its structure is simple, it has a low manufacturing cost, and it can generate linear thrust without the need ...for a conversion mechanism. It is particularly suitable for electromagnetic catapults, magnetic levitation transport, and industrial production fields, due to its strong environmental adaptability. Designing a high-thrust and high-efficiency CLIM is a great challenge due to its inherent drawbacks, such as the low thrust density and power density of induction motors. In this article, two CLIMs with different topologies are proposed to meet the demand for control-rod drives in high-temperature and high-pressure environments. The article elucidates the topologies of the two CLIMs and proposes an analytical computational approach for the CLIM. Modern optimization algorithms were utilized to optimize the design of the structural parameters of both CLIMs. A 3D-FEA simulation was used to compare and analyze the air-gap magnetism and thrust characteristics of two CLIMs. The results indicate that the copper-ring secondary CLIM has a higher thrust density and is more suitable for use in control-rod drive mechanism (CRDM) systems.
Pesticide resistance and resurgence are serious problems often occurring simultaneously in the field. In our long‐term study of a fenpropathrin‐resistant strain of Tetranychus cinnabaribus, ...enhancement of detoxification and modified fecundity mechanisms were both observed. Here we investigate the network across these two mechanisms and find a key node between resistance and resurgence. We show that the ecdysone pathway is involved in regulating the fecundity of T. cinnabaribus. The concentration change of ecdysone is consistent with the fecundity curve; the concentration of ecdysone is higher in the fenpropathrin‐resistant strain which has stronger fecundity. The enhancement of ecdysone is due to overexpression of two P450 genes (CYP314A1 and CYP315A1) in the ecdysone synthesis pathway. Silencing expression of these CYP genes resulted in lower concentration of ecdysone, reduced expression of vitellogenin, and reduced fecundity of T. cinnabaribus. The expression of CYP315A1 is regulated by transcription factors Cap‐n‐collar isoform C (CncC) and Musculoaponeurotic fibrosarcoma protein (Maf), which are involved in regulating other P450 genes functioning in detoxification of fenpropathrin in T. cinnabaribus. A similar regulation is established in citrus pest mite Panonychus citri showing that the CncC pathway regulates expression of PcCYP315A1, which affects mite fecundity. Transcription factors are activated to upregulate detoxification genes facilitating pesticide resistance, while the “one to multiple” regulation mode of transcription factors simultaneously increases expression of metabolic enzyme genes in hormone pathways and alters the physiology of pests. This is an important response of arthropods to pesticides which leads to resistance and population resurgence.
Phosphorus is an important macronutrient. To understand the molecular and cellular responses to phosphorus stress better, transcriptome profiling in combination with biochemical investigations was ...conducted in the model diatom Phaeodactylum tricornutum. Out of 10 402 predicted genes, 2491 and 405 genes were significantly upregulated or downregulated respectively. Unsurprisingly, genes associated with phosphate uptake were upregulated, such as the phosphate transporters and alkaline phosphatases. Genes encoding stress‐shock proteins were accordingly upregulated, including genes associated with stress‐responsive proteins, signal transduction and secondary metabolism. Additionally, genes related to protein translation, carbon fixation, glycolysis and the citric acid cycle were also upregulated. Genes associated with gene transcription were downregulated, thereby resulting in the upregulation of translation to compensate for the limited supply of messenger RNA. The downregulation of genes related to β‐oxidation could contribute to the accumulation of fatty acids. Accordingly, triacylglycerols, which are important for energy storage, were determined to increase by 1.65‐fold. Intracellular membranes, other than chloroplast membranes, tended to be dispersed; this finding was in accordance with the increased transcription of a total of 11 genes encoding putative phospholipases. Taken together, this work revealed the coordination of multiple metabolic pathways and certain key genes in the adaptation of P. tricornutum to phosphorus stress.
Bacteroides fragilis, one of the potential next-generation probiotics, but its protective mechanism is not yet known. We aimed to characterize the anti-inflammatory effect of B. fragilisATCC25285 and ...to elucidate its mechanism through in vivo and in vitro experiments. An in vitro model of inflammation by induction of colonic cells with TNF-a, and co-cultured with B. fragilis to detect cell viability, apoptosis and invasive capacity. Furthermore, critical proteins of the TLR/NF-κB pathway and the inflammatory cytokines were measured. For animal trials, C57BL/6 J male mice were orally administered B. fragilis or PBS once daily for 21 days. Colitis was induced by drinking 2.5% DSS from days 0 to 7. The mice were weighed daily and rectal bleeding, stool condition and blood in the stool were recorded. We found that B. fragilis treatment alone was harmless and had no effect on cell viability or apoptosis. While predictably TNF-α decreased cell viability and increased apoptosis, B. fragilis attenuated this deterioration. The NF-κB pathway and inflammatory cytokines IL-6 and IL-1β activated by TNF-α were also blocked by B. fragilis. Notably, the metabolic supernatant of B. fragilis also has an anti-inflammatory effect. Animal studies showed that live B. fragilis rather than dead strain ameliorated DSS-induced colitis, as evidenced by weight loss, shortened colon length and enhanced barrier function. The colonic tissue levels of inflammatory cytokines (TNF-α, IL-1β, IL-6) were decreased and IL-10 was increased as a result of B. fragilis administration. In conclusion, B. fragilis ATCC25285 exhibited anti-inflammatory effects whether in vivo or in vitro, and it may be a potential probiotic agent for improving colitis.
The hemispherical dynamic pressure motor (HDPM) has the advantages of high speed, wear resistance and stability, which is widely used in inertial instruments to produce the gyroscopic effect. The ...ultra-thin gas film between the stator and rotor of the motor provides dynamic pressure lubrication and bearing capacity, whose dynamic characteristics determine the motor performance. However, the influence mechanism of some key factors such as ball center distance on the film characteristics is not clear, which has become the bottleneck restricting the performance improvement of HDPMs. Therefore, in this paper, a series of gas film similarity models were solved under different geometric and working parameters, and the influence law of the ball center distance, rotor displacement and stopping process on the aerodynamic characteristics was obtained, the results show that these primary parameters have significant effects on the pressure distribution, resistance moment and frictional heat of the ultra-thin gas film. This work can not only provide a theoretical basis for the aerodynamic performance optimization of HDPMs, but also serve as a reference for the design of other aerodynamic instruments.
Ganoderma
is a globally distributed genus that encompasses species with forestry ecological, medicinal, economic, and cultural importance. Despite the importance of this fungus, the studies on the ...species diversity of
Ganoderma
in Yunnan Province, China (YPC) have poorly been carried out. During this study, opportunistic sampling was used to collect 21 specimens of
Ganoderma
from YPC. Morphology and multigene phylogeny of the internal transcribed spacer (ITS) regions, the large subunit of nuclear ribosomal RNA gene (nrLSU), the translation elongation factor 1-α gene (TEF1-α), and the second largest subunit of RNA polymerase II (RPB2) were used to identify them. Morphological and molecular characterization of the 21 specimens showed that they belong to 18 species of
Ganoderma
, of which three are novel
viz. G. artocarpicola
,
G. obscuratum
and
G. yunnanense
.
Ganoderma artocarpicola
is characterized by the sessile and concrescent basidiomata, reddish brown to yellowish brown pileus surface, heterogeneous context, wavy margin, and ovoid basidiospores.
Ganoderma obscuratum
is distinguished by small pores (6–9 per mm), dorsolaterally sub-stipitate basidiomata which become greyish-brown when dry, and narrow ellipsoid basidiospores.
Ganoderma yunnanense
is characterized by cream color pore surface and context, centrally to laterally stipitate basidiomata with reddish-brown to violet-brown strongly laccate pileus surface, and broadly ellipsoid basidiospores. With the help of an extensive literature survey and the results of this study, a checklist of 32
Ganoderma
species from YPC was established, which accounts for 71.11% of the known species in China. In addition, a key to the
Ganoderma
in YPC is also provided.
Laser Dispersion of Detonation Nanodiamonds Niu, Kai-Yang; Zheng, Hai-Mei; Li, Zhi-Qing ...
Angewandte Chemie (International ed.),
April 26, 2011, Letnik:
50, Številka:
18
Journal Article
Recenzirano
Laser blasting: Complete dispersion of detonation nanodiamonds was realized by laser irradiation. The infrared laser could selectively destroy the agglomerant of detonation nanodiamonds (see ...picture), resulting in well‐dispersed nanodiamonds in solution. The optical properties of nanodiamonds were modified by changing their surface ligands in situ.
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