Overdistention Operation of Cascaded Multilevel Inverters

In the past decade, the multilevel power converter has transitioned from an experimental concept to a standard product of many medium-voltage drive manufacturers. By utilizing small voltage steps, the multilevel topology offers higher power quality, higher voltage capability, lower switching losses, and improved electromagnetic compatibility over standard topologies. Recently, several researchers have focused on the cascaded multilevel inverter whereby two multilevel inverters are series connected to a motor load by splitting the neutral connection. The resulting performance is exceptional in terms of power quality since the overall number of voltage levels is effectively the product of the two cascaded inverters. This paper demonstrates that it is possible to extend this performance to an even higher number of voltage levels referred to as overdistended operation. This further improves the power quality that is significant in applications that have stringent total harmonic distorsion requirements, such as naval ship propulsion. A new control is introduced for overdistention operation and is validated with computer simulation and laboratory measurements

Dynamic Average-Value Modeling of a Four-Level Drive System

Multilevel power converters have gained much attention in recent years due to their high power quality, low switching losses, and high-voltage capability. These advantages make the multilevel converter a candidate for the next generation of naval ship prolusion systems. Evaluation of these systems is typically assisted with a dynamic average-value models in order to rapidly predict system performance under several operating scenarios. In this paper, an average-value model is developed for the four-level diode-clamped converter which takes into account the active capacitor voltage balancing control. This model performance prediction is compared to a detailed model and laboratory measurements on an 18 kW rectifier/inverter test system

A Unique Fault-Tolerant Design for Flying Capacitor Multilevel Inverter

This paper presents a unique design for flying capacitor type multilevel inverters with fault-tolerant features. When a single-switch fault per phase occurs, the new design can still provide the same number of converting levels by shorting the fault power semiconductors and reconfiguring the gate controls. The most attractive point of the proposed design is that it can undertake the single-switch fault per phase without sacrificing power converting quality. Future more, if multiple faults occur in different phases and each phase have only one fault switch, the proposed design can still conditionally provide consistent voltage converting levels. This paper will also discuss the capacitor balancing approach under fault-conditions, which is an essential part of controlling flying capacitor type multilevel inverters. Suggested fault diagnosing methods are also discussed in this paper. Computer simulation and lab results validate the proposed controls

Data from: Differential impacts of nitrogen addition on rhizosphere and bulk-soil carbon sequestration in an alpine shrubland

1. Study site: The Field Research Station of Alpine Shrubland Ecosystem is located in Songpan County, Sichuan Province, China. This region belongs to a typical alpine climate. The community composition of plants was dominated by temperate and cold-temperate vegetation at our study region. The dominant shrub species was Sibiraea angustata, followed by Salix oritrepha, Spiraea alpine, and Potentilla fruticosa (Wang et al., 2017). The average coverage, basal diameter and height of Sibiraea angustata are 53%, 0.62 cm and 1.03 m, respectively. Our previous study showed that the aboveground and belowground biomasses of Sibiraea angustata were 3.71 kg m-2 and 4.39 kg m-2, respectively, accounting for 96% and 97% of the aboveground and belowground biomass (Wang et al., 2017). These results suggest that both the aboveground- and belowground-biomass of Sibiraea angustata have an overwhelming superiority within this shrub community. 2. The manipulated experiment of nitrogen addition: An experiment of nitrogen addition was initiated within this shrubland ecosystem in May 2012. A randomized block design with three replicated blocks of three treatments was established before the experiment; these treatments included the control (no N fertilizer), low-N addition (50 kg N ha-1 year-1), and HN (100 kg N ha-1 year-1). Each block included three plots in 5 m × 5 m, and each plot was surrounded by 10-m-wide buffer strips. According to the average increase of bulk N deposition across China (approximately 8 kg N ha-1 yr-1; Liu et al., 2013) and the level of N fertilizer experiments performed in neighbor sites on the QTP (10 and 350 kg N ha-1 year-1; Fu et al., 2017), we chose the doses of the N additions in our study equal to be nearly 3- and 5-times the value of the background N deposition. An ammonium nitrate (NH4NO3) solution has been sprayed onto the forest floor in 6 equal doses in the first week of every month from May to October (i.e., the growing season) since May 2012. In each N-addition event, the fertilizer was weighed, dissolved in 20 L of water, and sprayed evenly using backpack sprayers. The control plots received an equal volume of water. 3. Soil sampling protocol: We sampled the upper 15 cm of mineral soil in July 2017. After organic horizon removal, five replicate cores from each plot using a 6-cm diameter soil corer to ensure that fine roots would have a sufficient mass of adhering rhizosphere soil. The soil cores were stored on ice transported to the laboratory. The living roots of Sibiraea angustata in each core were empirically identified by features such as shape, color, and elasticity. The soil adhering to the roots was carefully separated from the roots using fine forceps; this fraction was operationally defined as rhizosphere soil, and non-adhering soil was considered to be bulk soil (Phillips et al., 2011). All soil samples were passed through a 2-mm mesh sieve and were divided into two parts: one part was used to determine the soil physicochemical properties and the soil carbon density fractionation; another part was stored at -20 °C for later analyses of microbial biomass carbon and enzymatic activity. 4. Basic physicochemical properties: For soil bulk density (SBD) determination, a bulk-density corer with 5-cm diameter stainless steel rings as an inner sleeve was manually inserted into the upper 15-cm depth of the mineral soil (three corers for each plot) (Davidson et al., 2004). The SOC was determined by dichromate oxidation and titration with ferrous ammonium sulfate (Walkley and Black, 1934). The DOC was extracted with 0.5 M K2SO4 and determined using a TOC analyzer (Vario TOC, Elementar Corp., UK). The total N concentration (SON) in soil was determined on a TOC analyzer (Vario TOC, Elementar Corp., UK). Soil NH4+ and NO3- were extracted by 2 M KCl (soil:solution = 1:5) and then determined on a continuous flow injection analyzer (SEAL Analytical, Germany). The dissolved inorganic N (DIN) was the sum of NH4+ and NO3-. The soil organic N concentration (SON) in soil was the difference between TSN and DIN. Available phosphorus (Av.P) was extracted with Bray-I solution (0.03 M NH4F - 0.025 M HCl) (Bray and Kurtz, 1945) and was determined by molybdenum antimony colorimetry. Soil pH was measured in slurry with a soil-to-water ratio of 1:2.5 using a pH meter (Mettler-Toledo Instruments Co., Ltd., Shanghai, China). 5. Soil carbon fractionations: The SOC fractions were separated using a density fraction method (McLauchlan and Hobbie, 2004). Briefly, a 15 g of air-dried rhizosphere or bulk soil (passed through 2mm-mesh sieve) was weighed and placed in a 100 mL centrifuge tube and dispersed in 50 mL of NaI (with a density of 1.8 g cm−3). The tubes were centrifuged at 3000 rpm for 20 min. The suspended materials (FLF) were decanted into a vacuum filter unit with 0.40 µm polycarbonate filter. This process was repeated 2-3 times until no floating material remained. The materials remaining at the bottom (HF) of the centrifuge tube were then rinsed into the vacuum filter unit. All samples on the filter paper were washed with 75 mL 0.01 mol L−1 CaCl2, followed by at least 75 mL of distilled water. The light and heavy materials were dried at 60°C for 48 h and weighed. All samples were passed through a 0.25 mm mesh sieve and analyzed for SOC as previously described. 6. Microbial gene abundance: For microbial gene abundance, DNA was extracted from 0.25 g of soil using the MoBio Power Soil DNA isolation kit (Mobio Laboratories, CA, USA). DNA quality and concentration were measured using a nanodrop spectrophotometer (NanoDrop, DE, USA) and electrophoresis in agarose gels (1% w/v in TAE), then stored at -20 °C prior to amplification. Quantitative PCR (qPCR) was used to quantify the gene copy numbers of bacterial 16S rRNA and fungal ITS using the primer pairs 515F/909R and ITS7F/ITS4R, respectively (Li et al., 2014; Schulz et al., 2018). Each 10-µL reaction contained 5 µL of SybrGreen (2×) PCR Master Mix (Bio-Rad, USA), 0.5 µL of each primer (10 pM), 2 µL of DNA templates and 2.5 µL of sterilized water. Bacterial 16S rRNA and fungal ITS conditions were 5 min at 95 °C, followed by 40 cycles of 95 °C for 30 s, 30 s at 55 °C, and 30 s at 72°C, with a final extension cycle of 8 min at 72°C. The qPCR standards for quantification were prepared from PCR products of target genes from environmental DNA with each primer set using the method described by Kou et al. (2017). Four replicates were performed for each sample. The amplification efficiencies of the 16S rDNA gene and ITS gene were 90% and 92%, respectively, with R2 values higher than 0.99, and no signals were observed in the negative controls. 7. Carbon-acquisition enzyme activities: Two grams of sieved soil was suspended in 125 mL of 50 mM sodium acetate buffer (pH = 5.0) in a homogenizer for 1 min to form slurry. Black 96-well microplates were used for fluorometric analysis. The microplates were assigned to six parts, including the sample assay, sample control, quench control, reference standard, negative control, and blank wells. First, 200 μL of buffer was pipetted into the blank, reference standard and negative control wells. Second, 50 μL of buffer was pipetted into the blank and sample control wells. Third, 200 μL of the soil slurry was pipetted into the sample assay, sample control, quench control wells, and then 50 μL of 10 μM 4-methylumbelliferyl (MUB) was pipetted into the reference standard and quench standard wells. Finally, 50 μL of 200 μM fluorogenic substrate (4-methyl-umbelliferyl β-D-glucopyranoside) were pipetted into into the negative control and sample assay wells. Plates were incubated for 4 h in the dark (25°C) and then scanned on a Varioskan Flash multiplate reader (Thermo Scientific, USA) at 365 nm excitation and 450 nm emission wavelengths. The unit for BG activity was expressed as μmol MU g-1dry soil (dry weight) h-1. Phenol oxidase and peroxidase activities were measured spectrophotometrically using L-3, 4-dihydroxyphenylalanine (L-DOPA, Sigma, St. Louis, USA) as the substrate. A total of 200 μL soil suspension (see above) and 50 μL of 25 mM DOPA were added to each sample well. The wells of peroxidase assays additionally received 10 μL of a 0.3% H2O2 solution. The microplates were incubated in the dark at 20°C for up to 8 h. Absorption was measured at 450 nm and expressed in units of μmol DOPA g−1 h−1. The background absorbance of DOPA was measured, and an extinction coefficient was calculated using a standard curve of DOPA degraded with mushroom tyrosinase.,1. Due to complex root-soil interactions, the responses of carbon (C) dynamics in the rhizosphere to elevated nitrogen (N) deposition may be different from those in bulk soil. However, the potentially different response of C dynamics in the rhizosphere and bulk soils and their contributions to soil C sequestration under N deposition is still not elucidated. 2. We conducted an N addition experiment in an alpine shrubland dominated by Sibiraea angustata located on the eastern Qinghai-Tibet Plateau (QTP). We measured the soil organic C (SOC) contents and density fractions in the rhizosphere and bulk soils in the top 15 cm of mineral soil and then employed a numerical model based on the rhizosphere extent to evaluate how the rhizosphere modulates soil C sequestration under N addition. We also measured the microbial gene abundance and C-acquisition enzyme activities to assess microbial community responses to N addition. 3. The results showed that nitrogen addition had opposite effects on the rhizosphere and bulk-soil C stocks. Specifically, N addition decreased the rhizosphere SOC content through increasing bacterial abundance, β-glucosidase activity, and thus accelerating the loss of free light fraction C (FLF-C). However, N addition increased the bulk-soil C content, which was corresponding with the reduced oxidase activities and the accelerated accumulation of heavy fraction C (HF-C) under N addition. Numerical model analysis showed that the decrease induced by N addition in rhizosphere SOC stock ranged from 0.11 to 3.01 kg C m-2 as root exudation diffusion distance extended from 0.5 mm to 2 mm, while the corresponding increase in the bulk-soil C stock ranged from 1.91 to 4.08 kg C m-2. By synthesizing the dynamics of the SOC stocks in these two soil compartments under N addition, the SOC stock at the ecosystem level exhibited an increase in range of 0.73-2.44 kg C m-2. 4. Synthesis Our results suggest that alpine shrublands on the eastern QTP have great potential for soil C sequestration under N deposition, and the magnitude of the sequestration would depend closely on the responses of rhizosphere microbial C processes and the rhizosphere extent. Our results highlight the importance of integrating rhizosphere processes into land surface models to accurately predict ecosystem functions in the background of elevated N deposition

BMP4 aggravates mitochondrial dysfunction of HRMECs

Mitochondria are important places for the oxidative phosphorylation of glucose and the maintenance of cell oxidation and antioxidant stability. However, mitochondrial dysfunction causes cell dysfunction. Meanwhile, retinal vascular endothelial cell dysfunction may cause vascular inflammation, hemorrhage, angiogenesis, and other manifestations. Our previous studies have shown that Bone morphogenetic protein 4 (BMP4) is an important target for the treatment of retinal neovascularization, but the mechanism remains unclear. Therefore, our study aims to observe the effects of BMP4 on vascular endothelial cells and hopes to provide a new target for diabetic retinopathy. 4-Hydroxynonenal (4HNE), a kind of lipid peroxide, was used to induce the oxidative stress model. Human retinal microvascular endothelial cells (HRMECs) were randomly divided into control, 4HNE, negative control, and siBMP4 groups. Si-BMP4 significantly reduced leukocyte adhesion and 4HNE-induced high ROS level and restored the mitochondrial membrane potential and OCR. This indicates that BMP4 plays an important role in inducing leukocyte adhesion, oxidative stress, and mitochondrial dysfunction. The relationship between BMP4 and retinal vascular endothelial cell dysfunction is preliminarily confirmed by this study. Mitochondrial dysfunction and oxidative stress may be involved in BMP4-mediated retinal vascular endothelial cell dysfunction

Versatile synthesis of dendritic mesoporous rare earth–based nanoparticles

Rare earth–based nanomaterials that have abundant optical, magnetic, and catalytic characteristics have many applications. The controllable introduction of mesoporous channels can further enhance its performance, such as exposing more active sites of rare earth and improving the loading capacity, yet remains a challenge. Here, we report a universal viscosity-mediated assembly strategy and successfully endowed rare earth–based nanoparticles with central divergent dendritic mesopores. More than 40 kinds of dendritic mesoporous rare earth–based (DM-REX) nanoparticles with desired composition (single or multiple rare earth elements, high-entropy compounds, etc.), particle diameter (80 to 500 nanometers), pore size (3 to 20 nanometers), phase (amorphous hydroxides, crystalline oxides, and fluorides), and architecture were synthesized. Theoretically, a DM-REX nanoparticle library with 393,213 kinds of possible combinations can be constructed on the basis of this versatile method, which provides a very broad platform for the application of rare earth–based nanomaterials with rational designed functions and structures.This work was supported by the National Natural Science Foundation of China (22075049, 21875043, 22088101, 21701027, 21733003, 21905052, and 51961145403), National Key R&D Program of China (2018YFA0209401 and 2017YFA0207303), Key Basic Research Program of Science and Technology Commission of Shanghai Municipality (17JC1400100), Natural Science Foundation of Shanghai (18ZR1404600, 20490710600, and 22ZR1478900), Shanghai Rising-Star Program (20QA1401200), and Qatar National Research Fund (a member of the Qatar Foundation) (NPRP grant no. NPRP 12S-0309-190268)

Cyanohydrin Phosphonate Natural Product from <i>Streptomyces regensis</i>

<i>Streptomyces regensis</i> strain WC-3744 was identified as a potential phosphonic acid producer in a large-scale screen of microorganisms for the presence of the <i>pepM</i> gene, which encodes the key phosphonate biosynthetic enzyme phosphoenolpyruvate phosphonomutase. ³¹P NMR revealed the presence of several unidentified phosphonates in spent medium after growth of <i>S. regensis</i>. These compounds were purified and structurally characterized via extensive 1D and 2D NMR spectroscopic and mass spectrometric analyses. Three new phosphonic acid metabolites, whose structures were confirmed by comparison to chemically synthesized standards, were observed: (2-acetamidoethyl)­phosphonic acid (<b>1</b>), (2-acetamido-1-hydroxyethyl)­phosphonic (<b>3</b>), and a novel cyanohydrin-containing phosphonate, (cyano­(hydroxy)­methyl)­phosphonic acid (<b>4</b>). The gene cluster responsible for synthesis of these molecules was also identified from the draft genome sequence of <i>S. regensis</i>, laying the groundwork for future investigations into the metabolic pathway leading to this unusual natural product

Epimedium for Osteoporosis Based on Western and Eastern Medicine: An Updated Systematic Review and Meta-analysis

Osteoporosis is a chronic bone lytic disease attributed to imbalance between bone ossification and bone resorption characterized by decreased bone mass, altered bone micro-architecture and increased bone fragility. It is related to high fracture risk, with an accident of osteoporotic fracture every 3 seconds. With a prevalence of 200 - 300 million patients worldwide, osteoporosis has become a major public health concern. However, its treatment remains a challenge around the world. Given the complications and side effects of currently available treatments,5 developing new therapeutic approaches for the prevention and interventions of osteoporosis with phytomedicine may be promising. Phytotherapy including herbs has been safely used for thousands of years, attracting great attention worldwide. Epimedium (Epimedium), also known as Yinyanghuo or Xianlingpi in Chinese, is derived from the dried leaf of the Epimedii Folium brevicornu Maxim, which has been widely used in treating bone diseases in traditional Chinese medicine. Studies have reported pharmacological activity of Epimedium extracts like icariin, flavonoids, lignins, daidzein, genistein, and many other compounds. Efficacy of Epimedium-containing herbal formula for osteoporosis has been suggested by several reviews. However, the effect of Epimedium alone or combined with conventional pharmaceutical treatment on osteoporosis remains poorly understood clinically and has not been evaluated systematically, which limits clinical application and overall recognition of Epimedium treatment. To identify the effect of Epimedium alone or combined with conventional pharmaceutical treatment with current evidence of clinical studies, and to update and improve the previous reviews, we conducted this systematic review and meta-analysis. We designed this study following Preferred Reported Items for Systematic Review and Meta-analysis (PRISMA). The search strategy aimed to identify randomized controlled trials (RCTs) comparing Epimedium alone or combined with conventional pharmaceutical treatment on osteoporosis. Systematic literature searches in Web of Science, WorldCat, Cochrane Library, EMBASE, Science Direct, Google Scholar, PubMed, SinoMed, Chongqing VIP Chinese Science and Technology Periodical Database, China National Knowledge Infrastructure (CNKI), and Wanfang Data were conducted. All the electronic databases were searched from the earliest available date to 30 March 2021 (updated September 21, 2021). In order to collect a more comprehensive data, a combination of the following English terms was used in the database searches: (“Epimedium” or “Epimediums” or “Epimedium sagittatum” or “Epimedium sagittatums” or “sagittatum, Epimedium” or “sagittatums, Epimedium” or “Epimedium grandiflorum” or “Epimedium grandiflorums” or “grandiflorum, Epimedium” or “grandiflorums, Epimedium” or “Epimedii Folium”) and (“Osteoporosis” or “Osteoporosis, Senile” or “Osteoporoses, Senile” or “Senile Osteoporoses” or “Senile Osteoporosis” or “Osteoporosis, Age Related” or “Bone Loss, Age-Related” or “Age-Related Bone Loss” or “Age-Related Bone Losses” or “Bone Loss, Age Related” or “Bone Losses, Age-Related” or “Age-Related Osteoporosis” or “Age Related Osteoporosis” or “Age-Related Osteoporoses” or “Osteoporoses, Age-Related”) and “randomized controlled trial”. No limits or restrictions were used. For the Chinese databases, the following keywords were used in combine: (“Yinyanghuo” or “Xianlingpi”) and “Osteoporosis” and “randomized controlled trial”. Furthermore, reviews and the reference lists of all the related articles were screened to check for potential eligible RCTs. Search strategies for all databases could be found in the supplementary material. Primary outcomes included BMD which was measured by dual-energy X-ray bone density analyzer before and after the treatment, clinical efficacy (effective: the clinical symptoms such as pain and fatigue were relieved, BMD increased than that before treatment, and functional activities significantly improved), and pain intensity using a VAS. Secondary outcomes included pain relief time, adverse events, plasma or serum concentrations of bone metabolic markers like alkaline phosphatase (ALP), blood phosphorus (P), blood calcium ion (Ca2+), Estradiol (E2) as well as interleukin 6 (IL-6) in osteoporosis patients. When available data in the articles were insufficient, researchers attempted to contact the corresponding authors by e-mail. No trials were excluded due to their publication status or language, thus reducing the risk of publication bias