Parameters Design and Optimization of SiC MOSFET Driving Circuit with Consideration of Comprehensive Loss and Voltage Stress

In conventional parameters design, the driving circuit is usually simplified as an RLC second-order circuit, and the switching characteristics are optimized by selecting parameters, but the influence of switching characteristics on the driving circuit is not considered. In this paper, the insight mechanism for the gate-source voltage changed by overshoot and ringing caused by the high switching speed of SiC MOSFET is highlighted, and we propose an optimized design method to obtain optimal parameters of the SiC MOSFET driving circuit with consideration of parasitic parameters. Based on the double-pulse circuit, we evaluated the influence of main parameters on the gate-source voltage, including driving voltage, driving resistance, gate parasitic inductance, and stray inductance of the power circuit. A SiC-based boost PFC is constructed and tested. The test results show that the switching loss can be reduced by 7.282 W by using the proposed parameter optimization method, and the over-voltage stress of SiC MOSFET is avoided

A study of 10 Rotating Radio Transients using Parkes radio telescope

Rotating Radio Transients (RRATs) are a relatively new subclass of pulsars that emit detectable radio bursts sporadically. We conducted an analysis of 10 RRATs observed using the Parkes telescope, with 8 of these observed via the Ultra-Wideband Receiver. We measured the burst rate and produced integrated profiles spanning multiple frequency bands for 3 RRATs. We also conducted a spectral analysis on both integrated pulses and individual pulses of 3 RRATs. All of their integrated pulses follow a simple power law, consistent with the known range of pulsar spectral indices. Their average spectral indices of single pulses are -0.9, -1.2, and -1.0 respectively, which are within the known range of pulsar spectral indices. Additionally, we find that the spreads of single-pulse spectral indices for these RRATs (ranging from -3.5 to +0.5) are narrower compared to what has been observed in other RRATs (Shapiro-Albert et al. 2018; Xie et al. 2022). It is notable that the average spectral index and scatter of single pulses are both relatively small. For the remaining 5 RRATs observed at the UWL receiver, we also provided the upper limits on fluence and flux density. In addition, we obtained the timing solution of PSR J1709-43. Our analysis shows that PSRs J1919+1745, J1709-43 and J1649-4653 are potentially nulling pulsars or weak pulsars with sparse strong pulses.Comment: 16 pages, 8 figures, RAA accepte

Evaluation and Suppression Method of Turn-off Current Spike for SiC/Si Hybrid Switch

SiC MOSFET/Si IGBT (SiC/Si) hybrid switch usually selects the gate control pattern that SiC MOSFET turns on earlier and turns off later than Si IGBT, with the aim of making the hybrid switch show excellent switching characteristics of SiC MOSFET and reduce switching loss. However, when SiC MOSFET turns off, the fast slew rate of drain source voltage causes the current spike in Si IGBT due to the effects of parasitic capacitance charging and carrier recombination, which will produce additional turn-off loss, thus affecting the overall efficiency and temperature rise of the converter. Based on the double pulse test circuit of SiC/Si hybrid switch, the mathematical model of the turn-off transient process is established. The effects of the remnant carrier recombination degree of Si IGBT, the turn-off speed of SiC MOSFET and the working conditions on the turn-off current spike of hybrid switch are evaluated. Although adjusting these parameters can reduce the turn-off current spike somewhat, additional losses will be introduced. Therefore, a new method to suppress the turn-off current spike is proposed to balance the power loss and current stress

Multi-node Acceleration for Large-scale GCNs

Limited by the memory capacity and compute power, singe-node graph convolutional neural network (GCN) accelerators cannot complete the execution of GCNs within a reasonable amount of time, due to the explosive size of graphs nowadays. Thus, large-scale GCNs call for a multi-node acceleration system (MultiAccSys) like TPU-Pod for large-scale neural networks. In this work, we aim to scale up single-node GCN accelerators to accelerate GCNs on large-scale graphs. We first identify the communication pattern and challenges of multi-node acceleration for GCNs on large-scale graphs. We observe that (1) coarse-grained communication patterns exist in the execution of GCNs in MultiAccSys, which introduces massive amount of redundant network transmissions and off-chip memory accesses; (2) overall, the acceleration of GCNs in MultiAccSys is bandwidth-bound and latency-tolerant. Guided by these two observations, we then propose MultiGCN, the first MultiAccSys for large-scale GCNs that trades network latency for network bandwidth. Specifically, by leveraging the network latency tolerance, we first propose a topology-aware multicast mechanism with a one put per multicast message-passing model to reduce transmissions and alleviate network bandwidth requirements. Second, we introduce a scatter-based round execution mechanism which cooperates with the multicast mechanism and reduces redundant off-chip memory accesses. Compared to the baseline MultiAccSys, MultiGCN achieves 4~12x speedup using only 28%~68% energy, while reducing 32% transmissions and 73% off-chip memory accesses on average. It not only achieves 2.5~8x speedup over the state-of-the-art multi-GPU solution, but also scales to large-scale graphs as opposed to single-node GCN accelerators.Comment: To appear in T

Exposure of Hyperandrogen During Pregnancy Causes Depression- and Anxiety-Like Behaviors, and Reduced Hippocampal Neurogenesis in Rat Offspring

The hippocampus is a region in which neurogenesis persists and retains substantial plasticity throughout lifespan. Accumulating evidences indicate an important role of androgens and androgenic signaling in the regulation of offspring hippocampal neurogenesis and the survival of mature or immature neurons and gliocyte. Hyperandrogenic disorders have been associated with depression and anxiety. Previous studies have found that pregnant hyperandrogenism may increase the susceptibility of the offspring to depression or anxiety and lead to abnormal hippocampal neurogenesis in rats. In this study, pregnant rats were given subcutaneous injection of aromatase inhibitor letrozole in order to establish a maternal hyperandrogenic environment for the fetal rats. The lithium chloride (LICl) was used as an intervention agent since a previous study has shown that lithium chloride could promote neurogenesis in the hippocampus. The results revealed that pregnant administration of letrozole resulted in depressive- and anxious-like behaviors in the adolescent period. A remarkable decrease in immature nerve cells marked by doublecortin and mature neurons co-expressed by Brdu and NeuN in adult years were detected in the hippocampal dentate gyrus of adolescent rats. Lithium chloride alleviated the effects on neurobehavioral and promoted the differentiation and proliferation of neural progenitor cells, while a hyperandrogenic intrauterine environment had no effects on astrocytes marked by GFAP in the dentate gyrus. Furthermore, the Wnt/β-catenin signaling pathway related to normal development of hippocampus was examined but there was no significant changes in Wnt signaling pathway members. Our study provides evidence that exposure of androgen during pregnancy leads to alterations in depressive, anxious and stereotypical behaviors and these phenotypes are possibly associated with changes in neurogenesis in the dentate gyrus

Preliminary study based on methylation and transcriptome gene sequencing of lncRNAs and immune infiltration in hypopharyngeal carcinoma

BackgroundHypopharyngeal squamous cell cancer (HSCC) is one of the most malignant tumors of the head and neck. It is not easy to detect in the early stage due to its hidden location; thus, lymph node metastasis is highly likely at diagnosis, leading to a poor prognosis. It is believed that epigenetic modification is related to cancer invasion and metastasis. However, the role of m6A-related lncRNA in the tumor microenvironment (TME) of HSCC remains unclear.MethodsThe whole transcriptome and methylation sequencing of 5 pairs of HSCC tissues and adjacent tissues were performed to identify the methylation and transcriptome profiles of lncRNAs. The biological significance of lncRNAs differentially expressing the m6A peak was analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. By constructing an m6A lncRNA-microRNA network, the mechanism of m6A lncRNAs in HSCC was analyzed. The relative expression levels of selected lncRNAs were examined by quantitative polymerase chain reaction. The CIBERSORT algorithm was used to evaluate the relative proportion of immune cell infiltration in HSCC and paracancerous tissues.ResultsBased on an in-depth analysis of the sequencing results, 14413 differentially expressed lncRNAs were revealed, including 7329 up-regulated and 7084 down-regulated lncRNAs. Additionally, 4542 up-methylated and 2253 down-methylated lncRNAs were detected. We demonstrated methylation patterns and gene expression profiles of lncRNAs of HSCC transcriptome. In the intersection analysis of lncRNAs and methylated lncRNAs, 51 lncRNAs with up-regulated transcriptome and methylation and 40 lncRNAs with down-regulated transcriptome and methylation were screened, and significantly differentiated lncRNAs were further studied. In the immune cell infiltration analysis, B cell memory was significantly elevated in cancer tissue, while γδT cell amount was significantly decreased.Conclusionm6A modification of lncRNAs might be involved in HSCC pathogenesis. Infiltration of immune cells in HSCC might provide a new direction for its treatment. This study provides new insights for exploring the possible HSCC pathogenesis and searching for new potential therapeutic targets

Bacteroides acidifaciens and its derived extracellular vesicles improve DSS-induced colitis

Introduction“Probiotic therapy” to regulate gut microbiota and intervene in intestinal diseases such as inflammatory bowel disease (IBD) has become a research hotspot. Bacteroides acidifaciens, as a new generation of probiotics, has shown beneficial effects on various diseases.MethodsIn this study, we utilized a mouse colitis model induced by dextran sodium sulfate (DSS) to investigate how B. acidifaciens positively affects IBD. We evaluated the effects ofB. acidifaciens, fecal microbiota transplantation, and bacterial extracellular vesicles (EVs) on DSS-induced colitis in mice. We monitored the phenotype of mouse colitis, detected serum inflammatory factors using ELISA, evaluated intestinal mucosal barrier function using Western blotting and tissue staining, evaluated gut microbiota using 16S rRNA sequencing, and analyzed differences in EVs protein composition derived from B. acidifaciens using proteomics to explore how B. acidifaciens has a positive impact on mouse colitis.ResultsWe confirmed that B. acidifaciens has a protective effect on colitis, including alleviating the colitis phenotype, reducing inflammatory response, and improving intestinal barrier function, accompanied by an increase in the relative abundance of B. acidifaciens and Ruminococcus callidus but a decrease in the relative abundance of B. fragilis. Further fecal bacterial transplantation or fecal filtrate transplantation confirmed the protective effect of eosinophil-regulated gut microbiota and metabolites on DSS-induced colitis. Finally, we validated that EVs derived from B. acidifaciens contain rich functional proteins that can contribute to the relief of colitis.ConclusionTherefore, B. acidifaciens and its derived EVs can alleviate DSS-induced colitis by reducing mucosal damage to colon tissue, reducing inflammatory response, promoting mucosal barrier repair, restoring gut microbiota diversity, and restoring gut microbiota balance in mice. The results of this study provide a theoretical basis for the preclinical application of the new generation of probiotics

A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms

We describe a genetic variation map for the chicken genome containing 2.8 million single-nucleotide polymorphisms ( SNPs). This map is based on a comparison of the sequences of three domestic chicken breeds ( a broiler, a layer and a Chinese silkie) with that of their wild ancestor, red jungle fowl. Subsequent experiments indicate that at least 90% of the variant sites are true SNPs, and at least 70% are common SNPs that segregate in many domestic breeds. Mean nucleotide diversity is about five SNPs per kilobase for almost every possible comparison between red jungle fowl and domestic lines, between two different domestic lines, and within domestic lines - in contrast to the notion that domestic animals are highly inbred relative to their wild ancestors. In fact, most of the SNPs originated before domestication, and there is little evidence of selective sweeps for adaptive alleles on length scales greater than 100 kilobases