A nearest level PWM method for the MMC in DC distribution grids

For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models

Exo84c-regulated degradation is involved in the normal self-incompatible response in Brassicaceae

The self-incompatibility system evolves in angiosperms to promote cross-pollination by rejecting self-pollination. Here, we show the involvement of Exo84c in the SI response of both Brassica napus and Arabidopsis. The expression of Exo84c is specifically elevated in stigma during the SI response. Knocking out Exo84c in B.napus and SI Arabidopsis partially breaks down the SI response. The SI response inhibits both the protein secretion in papillae and the recruitment of the exocyst complex to the pollen-pistil contact sites. Interestingly, these processes can be partially restored in exo84c SI Arabidopsis. After incompatible pollination, the turnover of the exocyst-labeled compartment is enhanced in papillae. However, this process is perturbed in exo84c SI Arabidopsis. Taken together, our results suggest that Exo84c regulates the exocyst complex vacuolar degradation during the SI response. This process is likely independent of the known SI pathway in Brassicaceae to secure the SI response. [Abstract copyright: Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

Synthesis and characterization of 2-(2-benzhydrylnaphthyliminomethyl)pyridylnickel halides: formation of branched polyethylene

A series of 2-(2-benzhydrylnaphthyliminomethyl)pyridine derivatives (L1–L3) was prepared and used to synthesize the corresponding bis-ligated nickel(II) halide complexes (Ni1–Ni6) in good yield. The molecular structures of representative complexes, namely the bromide Ni3 and the chloride complex Ni6, were confirmed by single crystal X-ray diffraction, and revealed a distorted octahedral geometry at nickel. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all nickel complex pre-catalysts exhibited high activities (up to 2.02 × 10⁷ g(PE) mol⁻¹(Ni) h⁻¹) towards ethylene polymerization, producing branched polyethylene of low molecular weight and narrow polydispersity. The influence of the reaction parameters and the nature of the ligands on the catalytic behavior of the title nickel complexes were investigated

Influenza virus infection among pediatric patients reporting diarrhea and influenza-like illness

<p>Abstract</p> <p>Background</p> <p>Influenza is a major cause of morbidity and hospitalization among children. While less often reported in adults, gastrointestinal symptoms have been associated with influenza in children, including abdominal pain, nausea, vomiting, and diarrhea.</p> <p>Methods</p> <p>From September 2005 and April 2008, pediatric patients in Indonesia presenting with concurrent diarrhea and influenza-like illness were enrolled in a study to determine the frequency of influenza virus infection in young patients presenting with symptoms less commonly associated with an upper respiratory tract infection (URTI). Stool specimens and upper respiratory swabs were assayed for the presence of influenza virus.</p> <p>Results</p> <p>Seasonal influenza A or influenza B viral RNA was detected in 85 (11.6%) upper respiratory specimens and 21 (2.9%) of stool specimens. Viable influenza B virus was isolated from the stool specimen of one case. During the time of this study, human infections with highly pathogenic avian influenza A (H5N1) virus were common in the survey area. However, among 733 enrolled subjects, none had evidence of H5N1 virus infection.</p> <p>Conclusions</p> <p>The detection of influenza viral RNA and viable influenza virus from stool suggests that influenza virus may be localized in the gastrointestinal tract of children, may be associated with pediatric diarrhea and may serve as a potential mode of transmission during seasonal and epidemic influenza outbreaks.</p

Synergistic Effect of Ni and Cu on the Microstructure, Corrosion Properties and Mechanical Properties of As-Cast Biomedical Co-Based Alloy

The microstructure, phase component, corrosion resistance, microhardness, and mechanical property of the as-cast CoCrW-(0~5)Ni-(1~4)Cu alloys were investigated to reveal the synergistic effect of Ni and Cu by using X-ray diffraction, scanning electron microscopy, electron probe microanalysis, microhardness tests, and compression tests. The alloys exhibited coarse grains consisting of dendritic substructures. No precipitate was observed in the alloys, but dendritic segregation of Cu in the interdendritic regions and grain boundaries was observed. The phase component of all alloys consists of &gamma; phase and &epsilon; phase; the &epsilon; phase fraction decreased with increasing Ni or Cu content. The corrosion resistance of these alloys decreased with increasing Cu content when the Cu content was greater than 1 wt.%. The addition of Cu or Ni reduced the hardness significantly. The compressive yield strength showed an increasing tendency with increasing Cu content, but the influence of Ni content on compressive yield strength was limited. The results demonstrated that it should be feasible to fabricate a new biomedical CoCrWNiCu alloy by regulating Ni and Cu content, which should be a new development direction of Co-based alloy

Synergistic Effect of Ni and Cu on the Microstructure, Corrosion Properties and Mechanical Properties of As-Cast Biomedical Co-Based Alloy

The microstructure, phase component, corrosion resistance, microhardness, and mechanical property of the as-cast CoCrW-(0~5)Ni-(1~4)Cu alloys were investigated to reveal the synergistic effect of Ni and Cu by using X-ray diffraction, scanning electron microscopy, electron probe microanalysis, microhardness tests, and compression tests. The alloys exhibited coarse grains consisting of dendritic substructures. No precipitate was observed in the alloys, but dendritic segregation of Cu in the interdendritic regions and grain boundaries was observed. The phase component of all alloys consists of γ phase and ε phase; the ε phase fraction decreased with increasing Ni or Cu content. The corrosion resistance of these alloys decreased with increasing Cu content when the Cu content was greater than 1 wt.%. The addition of Cu or Ni reduced the hardness significantly. The compressive yield strength showed an increasing tendency with increasing Cu content, but the influence of Ni content on compressive yield strength was limited. The results demonstrated that it should be feasible to fabricate a new biomedical CoCrWNiCu alloy by regulating Ni and Cu content, which should be a new development direction of Co-based alloy