The modular multilevel converter (MMC) is very attractive in a high-voltage dc (HVdc) transmission system due to its high modularity and scalability. It is also a promising candidate for ...medium-voltage applications. An MMC has many power devices that lead to a relatively low reliability based only on a direct failure rate calculation. The reliability of an MMC can be improved by redundant designs. Lots of redundant designs and strategies have been proposed in recent years, while their reliability improvements are hardly quantified in existing literature. In practice, reliability improvement with constraint costs is a challenge. In view of these, this paper proposes a reliability and cost assessment scheme for MMC redundant designs and strategies. Reliability and cost are quantified for comparison purposes. A medium-voltage application is used to demonstrate the reliability and cost assessment scheme. The reliability analysis is based on a combinatorial model and the Poisson process model. The cost analysis focuses on capital cost and power loss cost. The proposed reliability and cost analysis scheme provides a guideline for MMC redundant design and redundant strategy selection.
Traditional Chinese medicines (TCMs) are gaining more and more attention all over the world, due to their specific theory and long historical clinical practice. But the uncontrollable quality is a ...bottleneck for its modernization and globalization. This paper reviewed the recent analytical methods in the quality control of TCMs, including screening strategies of bioactive markers from TCMs through biochromatographic methods, the traditional chromatographic methods, DNA methods, as well as the spectroscopic methods, including FT-IR, NIR and NMR. The comprehensive methods, such as fingerprint and multi-component quantification are emphasized; hyphenated techniques, like HPLC-MS, GC-MS, CE-MS, LC-NMR, chemometric methods, and combination of chemical and biological methods, such as biofingerprint, metabolic fingerprint are now more and more widely used in TCMs. In a few word, the analysis and quality control of TCMs are moving towards an integrative and comprehensive direction, in order to better address the inherent holistic nature of TCMs.
Power allocation is a major concern in hybrid energy storage system. This paper proposes an extended droop control (EDC) strategy to achieve dynamic current sharing autonomously during sudden load ...change and resource variations. The proposed method consists of a virtual resistance droop controller and a virtual capacitance droop controller for energy storages with complementary characteristics, such as battery and supercapacitor (SC). By using this method, battery provides consistent power and SC only compensates high-frequency fluctuations without the involvement of conventionally used centralized controllers. To implement the proposed EDC method, a detailed design procedure is proposed to achieve the control objectives of stable operation, voltage regulation, and dynamic current sharing. System dynamic model and relevant impedances are derived and detailed frequency domain analysis is performed. Moreover, the system level stability analysis is investigated and system expansion with the proposed method is illustrated. Both simulations and experiments are conducted to validate the effectiveness of the proposed control strategy and analytical results.
•Curcumin loaded self-assembled polymeric micelles (Cur-PMs) were developed.•The oral absorption mechanism of Cur-PMs was evaluated in vitro and in vivo.•The intestinal absorption and oral ...bioavailability of curcumin were remarkably improved by Cur-PMs.
Curcumin-loaded self-assembled polymeric micelles (Cur-PMs) were designed to increase oral bioavailability of curcumin and investigate the oral absorption mechanism in vitro and in vivo. The Cur-PMs were spherical nano-size particles 17.82±0.33nm in size, with a drug loading of 3.52±0.18%, and encapsulation efficiency as high as 93.08±2.23%. The intestinal absorption of Cur-PMs in the duodenum, jejunum, and ileum was 3.09-, 6.48-, and 1.78-fold greater than that of curcumin solution (Cur-Sol) at 0.5h. The cellular uptake of Cur-PMs in Caco-2 cells was significantly enhanced in comparison with Cur-Sol by caveolae-mediated and clathrin-mediated endocytosis. Moreover, the apparent permeability coefficient (Papp) of Cur-PMs was 3.50-fold higher than that of Cur-Sol in Caco-2 transport studies. The transport mechanism of Cur-PMs into the system circulation was not paracellular transport through opening the tight junctions, but was by energy-dependent, macropinocytic transcytosis and lymphatic transport pathways. Furthermore, the AUC(0−t) value of Cur-PMs was improved 2.87-fold compared with that of Cur-Sol after oral administration in rats. Therefore, self-assembled polymeric micelles could be a promising vehicle to efficiently improve the oral absorption of curcumin.
The traditional finite-control-set model predictive control (FCS-MPC) method for a cascaded H-bridge (CHB) rectifier has two main issues: heavy computational burden and low steady-state current ...performance. In this paper, a novel FCS-MPC method has been proposed for a single-phase CHB rectifier. The proposed method solves the optimization problem of FCS-MPC for one cell by one cell, like a "pipeline." In the proposed method, the sampling period is divided into equal intervals by the number of cells. At the beginning of the first interval, the first cell selects its switching state to be applied. Then, the following cell selects its switching state to be applied at the beginning of next interval. Finally, the selected switching state of last cell will be applied at the beginning of the last interval. A cost function presenting the control objectives of common source current error and itself dc-link voltage error is evaluated for each cell. A single-phase three-cell CHB rectifier controlled by a DSpace DS1104 is tested and the experimental results show that a significant reduction in computational time, an improved steady-state current performance, and a comparable dynamic response are achieved in the proposed method in comparison with the traditional FCS-MPC method.
Microglial-mediated neuroinflammation has been established as playing a vital role in pathogenesis of neurodegenerative disorders. Thus, rational regulation of microglia functions to inhibit ...inflammation injury may be a logical and promising approach to neurodegenerative disease therapy. The purposes of the present study were to explore the neuroprotective effects and potential molecular mechanism of Schizandrin A (Sch A), a lignin compound isolated from Schisandra chinesnesis. Our observations showed that Sch A could significantly down-regulate the increased production of nitric oxide (NO), tumor necrosis factor (TNF)-α and interleukin (IL)-6 induced by lipopolysaccharide (LPS) both in BV-2 cells and primary microglia cells. Moreover, Sch A exerted obvious neuroprotective effects against inflammatory injury in neurons when exposed to microglia-conditioned medium. Investigations of the mechanism showed the anti-inflammatory effect of Sch A involved the inhibition of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expression levels and inhibition of the LPS-induced TRAF6-IKKβ-NF-κB pathway. Furthermore, inhibition of Jak2-Stat3 pathway activation and Stat3 nuclear translocation also was observed. In conclusion, SchA can exert anti-inflammatory and neuroprotective effects by alleviating microglia-mediated neuroinflammation injury through inhibiting the TRAF6-IKKβ-NF-κB and Jak2-Stat3 signaling pathways.
•Eight novel 8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols were identified.•The metabolic pathway of theanine and catechins were clarified.•These compounds showed great antioxidant activities.
...Phytochemical investigation of the aqueous extract of pu-erh tea afforded eight novel 8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols (puerins I–VIII) by 1H, 13C, two-dimensional nuclear magnetic resonance (NMR) and high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD–ESI/MS) analysis. Comparative chemical analysis of green tea, black tea and Chinese dark teas confirmed that these compounds were the marker compounds of Chinese dark teas. Furthermore, fungal fermentation was indispensable for the biosynthesis of these novel compounds. Through single fungal fermentation, it was proved that catechins and theanine were the precursors of puerins I–VIII. HPLC-DAD-ESI/MS analysis elucidated the biosynthetic pathway for puerins I–VIII. Puerins I–IV have potential protective effects for the human micro-vascular endothelial cells (HMEC) injury induced by hydrogen dioxide compared to other tea polyphenols. 8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols could be used in the quality control and authentication of Chinese dark teas.
Acteoside, isoacteoside, and 2'-acetylacteoside are three representative phenylethanoid glycosides (PhGs), which are widely distributed in many plants and also known as the active components of ...Cistanches Herba. However, the extremely low oral bioavailability of acteoside in rats implies that these structural similar components may go through multiple sequential routes of hydrolysis in gastrointestinal tract before they are absorbed into blood. Therefore, the metabolites of these three components and other PhGs from gastrointestinal tract such as echinacoside, are supposed to be the bioactive elements. In this study, we established an approach combining ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) with MS(E) technology and MetaboLynx™ software for the rapid metabolic profiling of acteoside, isoacteoside, and 2'-acetylacteoside by human intestinal bacteria. As a result, 11 metabolites of acteoside, 7 metabolites of isoacteoside, and 11 metabolites of 2'-acetylacteoside were identified respectively. 8 metabolic pathways including deglycosylation, de-rhamnose, de-hydroxytyrosol, de-caffeoyl, deacetylation, reduction, acetylation, and sulfate conjugation were proposed to involve in the generation of these metabolites. Furthermore, we found that the degraded metabolites hydroxytyrosol (HT) and 3-hydroxyphenylpropionic (3-HPP) were transformed from acteoside, isoacteoside, and 2'-acetylacteoside by human intestinal bacteria and demonstrated similar bioactivities to their precursors. These findings are significant for our understanding of the metabolism of PhGs and the proposed metabolic pathways of bioactive components might be crucial for further pharmacokinetic evaluations of Cistanches Herba.
Since the incidence of cancer has been on the rise due to increasing exposure to various carcinogenic factors in recent years, cancer has gradually become the first killer to the health of human ...beings. A growing attention has been paid to anti-cancer effects of traditional Chinese medicine (TCM) with low toxicity and good efficacy. As a kind of TCM,
(
) has a good effect on clinical application, and its anti-tumor effects has been increasingly well studied. In this review, the research progress on the anti-tumor effects of
was summarized. The main mechanisms of its anti-tumor effects include suppression of tumor cell growth, induction of cell cycle arrest and tumor cell apoptosis, inhibition of angiogenesis, enhancement of immunity, and reversal of tumor drug resistance. This review aims to provide an overview of the research on anti-tumor effects of
and aids in its further application as an anti-tumor drug.
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A phytochemical study on the roots of Pongamia pinnata afforded five new isoflavone and isoflavanone derivatives (1–5), including two previously undescribed phenylisoflavones ...possessing an 1,2-oxetane ring, along with 21 known compounds (6–26) among which compound 18 is the first time to be isolated from nature. The structures of the isolated compounds were determined on the basis of 1D, 2D NMR, and HRESIMS. The absolute configurations of the compounds were assigned via analysis of the specific rotations and circular dichroism (CD) spectra, as well as by comparison of the calculated and experimental electronic circular dichroism (ECD) data. All the isolated compounds were evaluated for their inhibitory effects on NO production in LPS-stimulated BV-2 microglial cells. Twelve compounds exhibited different levels of inhibitory effects against NO production, and compound 1 showed the best activity with an IC50 value at 9.0 μM.
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