Common-mode voltage (CMV) is harmful to high-power converter-fed drive systems, thus actively suppressing the CMV that is of great significance. Compared with CMV reduction, CMV elimination is a ...better choice as it can totally avoid the influence of CMV. In this letter, a discrete selective harmonic elimination (SHE) formulation with CMV elimination ability is proposed, which uses output voltage levels as variables to be optimized instead of switching angles as in conventional SHE models. In this formulation, the optimization objective is low-order harmonic elimination, while CMV elimination is used as a constraint. The output result is the complete full SHE- pulsewidth modulated waveform over one fundamental period, where selected low-order harmonics and CMV have both been eliminated. Experimental results verify the effectiveness of the proposed formulation, and some comparison results are also provided.
In order to explore the minimum switching frequency required to regulate certain amount of harmonic components, a novel switching frequency minimized harmonic mitigation (SFMHM) model is proposed in ...this paper, which can regulate <inline-formula><tex-math notation="LaTeX"> \mathit{N}\mathbf{-1}</tex-math></inline-formula> harmonics with far less than N switching angles. By flexibly adjusting the threshold values, the proposed model can achieve both harmonic elimination and mitigation objectives. Based on PWM discretization and supported by quadratic programming, the switching frequency in the proposed model is expressed as a quadratic objective function of the PWM waveform. The objectives as fundamental control and selected harmonic mitigations are realized by treating the numerical approximations of the Fourier coefficients as constraints, which are finally transformed into an optimization model with binary variables and can be easily solved by some optimization toolboxes such as YALMIP. Some computing results show that, compared with the conventional selective harmonic elimination/mitigation (SHE/SHM) methods, the number of switching angles required to mitigate the same number of harmonics under the proposed method has been significantly reduced. The switching frequency can be reduced a lot compared with the conventional SHE/SHM methods, e.g., by 40% for some modulation indexes. Simulations and experiments verify the correctness of proposed SFMHM model.
Heavy metal contamination of soils has been a global environmental issue over the past decades, threatening food security and human health. Understanding the migration and transformation of heavy ...metals in soils is critical for restoring an impaired environment and developing sustainable agriculture, particularly in the face of global warming. However, little effort has been devoted to investigating the impact of elevated temperatures on the migration and distribution of exogenous heavy metals in soils. This study experimented with a 180-day incubation at 15 °C, 30 °C, and 45 °C with an arable soil (Alfisol) of Huang-Huai-Hai River Basin, China, which was initially spiked with copper (Cu). A comparison of the results revealed that the percentage of soil water-soluble Cu doubled at 45 °C compared with 15 °C. The percentage of protein-like substances in dissolved organic matter (DOM) was the highest at 45 °C, suggesting that proteinaceous components play a more significant role in controlling the dissolution of Cu into DOM. Moreover, by sequential extraction and micro-X-ray fluorescence (μ-XRF), Cu was facilitatively transformed from exchangeable, and specifically adsorbed fractions, to iron (Fe)/manganese (Mn) oxides bound species by 7.75%23.63% with the elevation of temperature from 15 °C to 45 °C. The conversion of Cu speciation is attributed to the significant release of organic carbon from Fe/Mn oxides, especially the Mn oxide components, which are available for Cu binding. The findings of this work will provide an in-depth understanding of the fate of Cu in soils, which is fundamental for the risk assessment and remediation of Cu-polluted soils in the Huang-Huai-Hai River Basin under the context of global warming.
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•Warming enhanced Cu transformation to soil solution and solid phases.•The proteinaceous components control the binding of Cu with soil DOM.•The release of OC from Fe/Mn oxides offered the binding sites for Cu.•The μ-XRF provided direct evidence for the formation of stable Cu in soil.
To obtain the optimal switching pattern with low-order harmonic mitigation capability and the optimal switching angle distribution in asymmetric cascaded H-bridge (ACHB) converters with the lowest ...switching frequency, a unified switching frequency minimized harmonic mitigation (SFMHM) model for ACHB converters is proposed in this article. Based on PWM waveform discretization, the switching frequency of each H-bridge cell can be mathematically modeled as the state change of output levels. Then, the overall switching frequency of all cells is used as the objective function to be minimized in the proposed model, while the amplitude of fundamental and low-order harmonic components to be regulated are used as constraints. To achieve an optimal switching angle distribution with fewer switching losses, the well-designed weighting factors are assigned to the switching frequency functions of different cells in the proposed formulation. The model-solving algorithm based on mixed integer programming is introduced, and various numerical results are presented and compared with the conventional selective harmonic elimination PWM (SHE-PWM) and selective harmonic mitigation PWM (SHM-PWM) for ACHB converters. Simulation and experimental results verify the effectiveness of the proposed model.
Proteasome is a multi-subunit protease complex in eukaryocytes, and plays an important role in ubiquitin-proteosome pathway. Recombinant proteasome can be used to screen proteasome inhibitors. In ...this study, recombinant plasmid of pET28a-PSMB1 was constructed by inserting human proteasome catalytic subunit (PSMB1) cDNA (726 bp) into the prokaryotic expression vector pET28a(+), and transforming the plasmid into E. coli BL21(DE3) cells for expression. After overnight induction (1 mmol/L IPTG, 20 degrees C), an expected protein band with molecular weight of 27 kDa was observed on SDS-PAGE gel. The recombinant protein was then purified through affinity chromatography, and the purity is more than 95%. The amino acid sequence of the recombinant protein was validated by NanoLC-MS/MS. The data from in vitro BIAcore analysis showed that the recombinant PSMB1 could bind to celastrol. The binding affinity between PSMB1 and 10 micromol/L celastrol was more than 27RU.
Solving the switching angles in real time is the key point to apply selective harmonic elimination (SHE) to engineering project. In this paper, a real time algorithm is presented to solve the SHE ...equations for two level inverters, which can be easily implemented on the micro-controllers and includes two computing stages, the offline computing stage and the online computing stage. In the offline stage, the SHE equations are transformed into an equivalent polynomial system which includes a set of univariate linear equations and a univariate high order equation by using symmetric polynomials and Groebner bases theory. Then, the univariate linear equations are stored into the micro-controllers and solved online according to the input modulation indices, and their solutions are used to construct a univariate high order polynomial equation whose real roots are actually the solutions for the original SHE equations. In order to find all the real roots of this constructed high order polynomial equation, the Sturm theorem is used to isolate every real root into non overlapping intervals and then the secant method is applied to every interval to find the exact real root, i.e., the final solutions for the SHE equations. Compared to the traditional numerical method, the executing efficiency is increased 20 times on STM32F407. Finally, a two-level inverter test platform is built based on the proposed algorithm, and the experimental results show that the algorithm is effective.
To seek possible effect targets of bufalin in HeLa cells by studying the impact of bufalin on cell protein expression profile after treatment on human cervical carcinoma cell lines HeLa.
Bufalin's ...ICs0was measured by MTr assay. The apoptosis of cells was observed by FCM (flow cytometry) and Hoechst 33342 staining assay. Differentiated expression protein spots were founded and identified using proteomic techniques, which could induce HeLa cell apoptosis.
Bufalin showed remarkable cytotoxic effect on HeLa cells. IC50 (154 +/- 21.5) nmol X L(-1) indicated the possibility of inducing cell apoptosis. The protein expression profile showed 11 differentiated expression protein spots. Among the 11 proteins, nudix-type motif 5, vimentin, hnRNP C1/hnRNP C2 variant, HNRPK, HNRPK isoform a variant (two spots are the same protein), heat shock protein 27, macrophage-capping protein, SELENBP1 protein were down-regulated, while ribosomal protein, large, P0 and S-adenosylmethionine synthetase 2 were up-regulated by bufalin treatment. They may be effect targets of bufalin in HeLa cells. Western blotting showed consistent results in heat shock protein 27, vimentin and HNRPK between expression after treatment with bufalin and two-dimensional electrophoresis.
Bufa-Lin can induce apoptosis in human cervical carcinoma cells HeLa and the effect of bufalin may be related to the joint intervention with multiple protein targets.
Four new prenylated bibenzyls, named aglaiabbrevins A-D (2, 4-6), were isolated from the leaves of Aglaia abbreviate, along with two known related analogues, ...3,5-dihydroxy-2-3,7-dimethyl-2(E),6-octadienyl bibenzyl (7) and 3,5-dihydroxy-2-(3-methyl-2-butenyl) bibenzyl (8). The structures of the new compounds were elucidated on the basis of extensive spectroscopic experiments, mainly one and two dimensional (1D- and 2D)-NMR, and the absolute configuration of 5 was determined by the measurement of specific rotation. The isolated compounds were evaluated for their protein tyrosine phosphatase-1B (PTP1B) inhibitory activity. The results showed that compounds 5-7 exhibited more potent PTP1B inhibitory effects with IC50 values of 2.58+-0.52, 2.44+-0.35, and 2.23+-0.14 μM, respectively, than the positive control oleanolic acid (IC50=2.74+-0.20 μM). On the basis of the data obtained, these bibenzyls with the longer C-2 prenyl groups may be considered as potential lead compounds for the development of new anti-obesity and anti-diabetic agents. Also, the PTP1B inhibitory effects for prenylated bibenzyls are being reported for the first time.
In selective harmonic elimination (SHE), if there are N switching angles, N-1 harmonics can be eliminated, however, can we use fewer switching angles to eliminate the same number of harmonics? No one ...has ever thought about this question. In this paper, based on the discrete representation of two-level PWM waveforms, a binary quadratic programming (BQP) model is proposed to minimize the switching losses and meanwhile eliminate the harmonics. In this model, the switching losses which is closely related to the jump times of the PWM waveform is formulated to a quadratic objective function, and the numerical approximation of the Fourier coefficients are treated as the constraints which control the fundamental and eliminate the harmonics. This BQP model is solved by using the optimization toolbox YALMIP and some results are given, in which the switching angles required to eliminate the same number of harmonics are significantly reduced compared to the SHE method. Experiments on a two-level inverter verify the correctness of this method.
