This paper discusses the design of a 10 kV and 200 A hybrid dc circuit breaker suitable for the protection of the dc power systems in electric ships. The proposed hybrid dc circuit breaker employs a ...Thompson coil based ultrafast mechanical switch (MS) with the assistance of two additional solid-state power devices. A low-voltage (80 V) metal-oxide-semiconductor field-effect transistors (MOSFETs)-based commutating switch (CS) is series connected with the MS to realize the zero current turn-OFF of the MS. In this way, the arcing issue with the MS is avoided. A 15 kV SiC emitter turn-OFF thyristor-based main breaker (MB) is parallel connected with the MS and CS branch to interrupt the fault current. A stack of MOVs parallel with the MB are used to clamp the voltage across the hybrid dc circuit breaker during interruption. This paper focuses on the electronic parts of the hybrid dc circuit breaker, and a companion paper will elucidate the principle and operation of the fast acting MS and the overall operation of the hybrid dc circuit breaker. The selection and design of both the high-voltage and low-voltage electronic components in the hybrid dc circuit breaker are presented in this paper. The turn-OFF capability of the MB with and without snubber circuit is experimentally tested, validating its suitability for the hybrid dc circuit breaker application. The CSs' conduction performances are tested up to 200 A, and its current commutating during fault current interruption is also analyzed. Finally, the hybrid dc circuit breaker demonstrated a fast current interruption within 2 ms at 7 kV and 100 A.
We aimed to investigate the cytotoxicity and antibacterial properties of nano-silver-coated polyetheretherketone (PEEK) produced through magnetron sputtering and provide a theoretical basis for its ...use in clinical applications.
The surfaces of PEEKs were coated with nano-silver at varying thicknesses (3, 6, 9, and 12nm) through magnetron sputtering technology. The resulting coated PEEK samples were classified into the following groups according to the thickness of the nano-silver coating: PEEK-3 (3nm), PEEK-6 (6nm), PEEK-9 (9nm), PEEK-12 (12nm), and PEEK control group. The surface microstructure and composition of each sample were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectrum (EDS) analysis. The water contact angle of each sample was then measured by contact angle meters. A cell counting kit (CCK-8) was used to analyze the cytotoxicity of the mouse fibroblast cells (L929) in the coated groups (n=5) and group test samples (n=6), negative control (polyethylene, PE) (n=6), and positive control group (phenol) (n=6). The antibacterial properties of the samples were tested by co-culturing Streptococcus mutans and Straphylococcus aureus. The bacteria that adhered to the surface of samples were observed by SEM. The antibacterial adhesion ability of each sample was then evaluated.
SEM and AFM analysis results showed that the surfaces of control group samples were smooth but compact. Homogeneous silver nano-particles (AgNPs) and nano-silver coating were uniformly distributed on the surface of the coated group samples. Compared with the control samples, the nano-silver coated samples had a significant increase in surface roughness (P<0.05) as the thickness of their nano-silver coating increased. EDS analysis showed that not only C and O but also Ag were present on the surface of the coated samples. Moreover, the water contact angle of modified samples significantly increased after nano-silver coating modification (P<0.01). CCK-8 cytotoxicity test results showed that coated samples did not exhibit cytotoxicity. The antibacterial experimental results showed that the nano-silver coating can significantly improve the antibacterial activity and bacterial adhesion ability of the PEEK samples.
The compact and homogeneous nano-silver coating was successfully prepared on the surface of PEEK through magnetron sputtering. The nano-silver coated PEEKs demonstrated enhanced antibacterial activities and bacterial adhesion abilities and had no cytotoxic effects.
Crop diversity is crucial for sustainable farmland ecosystems and global sustainability, and thus is a popular subject of research in ecological economics, agricultural science, and geography. Many ...studies have revealed the individual impacts of government policies or market changes on crop diversity. However, research on the combined effects of both government policy interventions and market-induced substitutions on changing crop diversity remains limited. This study clarifies the underlying mechanisms leading to changes in crop diversity in light of the joint effects of policies on grain subsidy implemented by the government to encourage monocropping as well as the market-induced forces that stimulate diversified planting. We used Hubei Province, one of the main grain-producing areas in Central China, as a case study. The foremost contribution of this study is its exploration of a global understanding of policy-oriented versus market-induced forces in driving changes in crop diversity at the regional level. Policy-oriented forces played a leading role in the past decline in diversity by restraining an increase in market-induced crop diversity. This leading role was reliant on encouraging certain crops through grain subsidies provided according to the farmers' targeted land use to maximize labor productivity. On the whole, strong implementation of policies on grain subsidy have challenged sustainable farmland ecosystems because of the resulting reduction in crop diversity. We argue that the relationship between top-down food security-oriented policies and bottom-up market-induced crop substitutions for a sustainable farmland ecosystem should be immediately and completely coordinated, while regionally differentiated cropping regulations should also be considered.
•Market-induced crop substitution is able to enhance crop diversity.•The national grain subsidy policy encourages large-scale farming with mono-cropping.•The effect of market-induced crop substitution is strongly constrained by the national grain subsidy policy.•The relationship between food safety-oriented grain subsidy policies and market-induced crop substitution should be urgently coordinated.
Preimplantation genetic screening (PGS) is widely used to select in vitro-fertilized embryos free of chromosomal abnormalities and to improve the clinical outcome of in vitro fertilization (IVF). A ...disadvantage of PGS is that it requires biopsy of the preimplantation human embryo, which can limit the clinical applicability of PGS due to the invasiveness and complexity of the process. Here, we present and validate a noninvasive chromosome screening (NICS) method based on sequencing the genomic DNA secreted into the culture medium from the human blastocyst. By using multiple annealing and looping-based amplification cycles (MALBAC) forwhole-genome amplification (WGA), we performed next-generation sequencing (NGS) on the spent culture medium used to culture human blastocysts (n = 42) and obtained the ploidy information of all 24 chromosomes. We validated these results by comparing each with their corresponding whole donated embryo and obtained a high correlation for identification of chromosomal abnormalities (sensitivity, 0.882, and specificity, 0.840). With this validated NICS method, we performed chromosome screening on IVF embryos from seven couples with balanced translocation, azoospermia, or recurrent pregnancy loss. Six of them achieved successful clinical pregnancies, and five have already achieved healthy live births thus far. The NICS method avoids the need for embryo biopsy and therefore substantially increases the safety of its use. The method has the potential of much wider chromosome screening applicability in clinical IVF, due to its high accuracy and noninvasiveness.
High-voltage wide bandgap semiconductor devices such as the 15 kV SiC mosfet have attracted great attention because of their potential applications in high-voltage and high-frequency power ...converters. However, these devices are not commercially available at the moment, and their high cost due to expensive material growth and fabrication may limit their widespread adoption in the future. In this paper, a 15-kV 40-A SiC three-terminal power switch, the Future Renewable Electric Energy Delivery and Management (FREEDM) supercascode, is reported for the first time, which is based on a series connection of 1.2-kV SiC power devices. Compared with the monolithic 15-kV SiC mosfet, the FREEDM supercascode demonstrates obvious advantages in cost and thermal conductivity. The design and voltage-balancing mechanism of the FREEDM supercascode are introduced, and the performance including the voltage balancing, conduction characteristics over a wide range of temperatures, and dynamic switching performance, is analyzed. The FREEDM supercascode's low cost and excellent thermal dissipation capability will facilitate early applications of SiC in very high voltage and high frequency power converters.
Alzheimer's disease (AD), also known as senile dementia, is a progressive neurodegenerative disease. The etiology and pathogenesis of AD have not yet been elucidated. We examined common ...differentially expressed genes (DEGs) from different AD tissue microarray datasets by meta-analysis and screened the AD-associated genes from the common DEGs using GCBI. Then we studied the gene expression network using the STRING database and identified the hub genes using Cytoscape. Furthermore, we analyzed the microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and single nucleotide polymorphisms (SNPs) associated with the AD-associated genes, and then identified feed-forward loops. Finally, we performed SNP analysis of the AD-associated genes. Our results identified 207 common DEGs, of which 57 have previously been reported to be associated with AD. The common DEG expression network identified eight hub genes, all of which were previously known to be associated with AD. Further study of the regulatory miRNAs associated with the AD-associated genes and other genes specific to neurodegenerative diseases revealed 65 AD-associated miRNAs. Analysis of the miRNA associated transcription factor-miRNA-gene-gene associated TF (mTF-miRNA-gene-gTF) network around the AD-associated genes revealed 131 feed-forward loops (FFLs). Among them, one important FFL was found between the gene
, hsa-miR-27a, and the transcription factor MYC. Furthermore, SNP analysis of the AD-associated genes identified 173 SNPs, and also found a role in AD for miRNAs specific to other neurodegenerative diseases, including hsa-miR-34c, hsa-miR-212, hsa-miR-34a, and hsa-miR-7. The regulatory network constructed in this study describes the mechanism of cell regulation in AD, in which miRNAs and lncRNAs can be considered AD regulatory factors.
This paper presents the test results of an ultrafast (less than 2 ms) medium-voltage hybrid dc circuit breaker prototype that consists of three switching devices: a 15-kV silicon carbide (SiC) ...emitter turn-off thyristor as the main breaker (MB), a fast acting mechanical switch, and a commutating switch (CS) to quickly divert the primary current to the MB for arcless interruption. The hybrid dc circuit breaker prototype can interrupt a circuit in less than 2 ms in dc power systems up to 10 kV, such as in electric ships. The ultrafast operations and extremely low loss can effectively limit the fault current level and switching transients in all medium-voltage systems, and can provide intelligent and fast protection function for smart power distribution and critical loads in a modernized grid. The design considerations of the three switching devices of the hybrid dc circuit breaker are presented. This paper focuses on the ultrafast mechanical switch and the testing of the hybrid dc circuit breaker, while a companion paper addresses the high-voltage solid-state main switch and the low-voltage solid-state CS.
Aims/Introduction
The triglyceride–glucose (TyG) index has been proposed as a reliable and simple marker of insulin resistance. We investigated the association between TyG index and diabetic ...nephropathy (DN) in patients with type 2 diabetes.
Materials and Methods
A consecutive case series of 682 adult patients with type 2 diabetes hospitalized in the Department of Endocrinology at the Tongji Hospital (Wuhan, Hubei, China) from January 2007 to December 2009 was included in this cross‐sectional analysis. Receiver operating characteristics curve analysis, correlation analysis and multiple logistic regression analysis were carried out.
Results
A total of 232 (34.0%) participants were identified with DN. Compared with the non‐DN group, the DN group had longer disease duration, and higher bodyweight, systolic blood pressure, diastolic blood pressure, glycated hemoglobin, triglycerides, total cholesterol, serum uric acid, 24 h‐urinary albumin, TyG index and homeostasis model assessment 2 estimates for insulin resistance (HOMA2‐IR; P < 0.05 for each). The TyG index with an optimal cut‐off point >9.66 showed a higher area under the receiver operating characteristic curve of 0.67 (P = 0.002) than HOMA2‐IR (area under the curve 0.61, P = 0.029) on receiver operating characteristic curve analysis for DN identification. Additionally, the TyG index positively correlated with the levels of metabolic indicators (bodyweight, glycated hemoglobin, triglycerides, total cholesterol, serum uric acid, fasting glucose and HOMA2‐IR) and natural logarithmic 24 h‐urinary albumin (P < 0.05 for each), but not natural logarithm of estimated glomerular filtration rate. On multiple regression analysis, an increased TyG index was shown to be an independent risk factor (odds ratio 1.91, P = 0.001) for DN.
Conclusions
The TyG index was independently associated with DN in patients with type 2 diabetes, and was a better marker than HOMA2‐IR for identification of DN in type 2 diabetes patients.
The triglyceride–glucose index provides an affordable and easily interpreted biomarker for monitoring the degree of insulin resistance, and was independently associated with diabetic nephropathy in patients with type 2 diabetes. It was a better marker than homeostasis model assessment for insulin resistance for identification of diabetic nephropathy in type 2 diabetes patients.
Land function change has been the focus of scientific research and policy making worldwide. Agricultural development and land use demand at present in China shared common characteristics with the ...countries such as Japan, South Korea, USA, and European developed countries, which have undergone cultivated land function transition. Whether cultivated land function transition occurred is of significance for land change science and cultivated land protection in China. However, there has been no explicit methodology for cultivated land function change research. This paper firstly presents a methodology by integrating policy development analysis based on the normative connotation of cultivated land function or termed cultivated land function demand and quantitative assessment based on the positive connotation of cultivated land function or termed cultivated land function supply. Then, cultivated land function transition is diagnosed by analyzing cultivated land function change in 1949-2012. Results show that cultivated land function transition overall occurred in 2006. Specifically, the normative cultivated land function or cultivated land function demand fragmented into seven types in 1985 and upgraded in 2004. Total value of the positive cultivated land function or cultivated land function supply turned to rise with an increase from 2.40 to 2.45 as the coefficients of variability （CV） of the value of the seven functions decreased from 2.94 to 2.29 in 2006-2012. The two-year gap between these two aspects of transition mainly resulted from the time lag effects of policy implementation. In the process of the transition, co-ordination and malposition of supply and demand of cultivated land function coexisted with supply lag and function morphology distortion. Considering the transition experiences in the developed countries mentioned above, suggestions on multifunctional cultivated land man- agement are proposed. Moreover, route of land use transition research is discussed.
Controllable three terminal high voltage (>10 kV) power switches based on silicon carbide (SiC) material are gaining significant attentions since silicon (Si) power switches such as insulated gate ...bipolar transistors (IGBTs) are typically designed for much lower blocking voltages. After more than 30 years of commercial development, there is a fundamental limitation in designing Si IGBTs with more than 6.5 kV voltage rating. On the other hand, the voltage barrier for SiC power devices could easily exceed 10 kV. In this paper, a world record 22 kV SiC p-type emitter turn-OFF (ETO) (p-ETO) thyristor is reported and analyzed as a promising candidate for high-voltage applications, such as solid-state circuit breaker, HVdc, flexible alternating current transmission system (FACTS), and motor drives. The device is based on a 2 cm 2 22 kV p-type SiC gate turn-OFF thyristor (p-GTO) structure. Its static performances are analyzed exhibiting a high voltage (22 kV) blocking characteristic, ultralow leakage current, and a low forward voltage drop (~7 V at 100 A) for a broad range of temperatures. The dynamic performances including turn-ON and turn-OFF are studied. Key switching characteristics such as turn-OFF storage time, turn-OFF loss, dv/dt, and di/dt are presented and analyzed. In addition, the large reverse biased safe operation area (RBSOA) of the 22 kV SiC ETO is theoretically analyzed and verified by simulations and experimental tests.
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