High-voltage DC–DC converter based on adaptive frequency conversion modulation

Lixia Zheng,Yi Zhu,Jie Ren,Changyuan Chang,Jialing Ye 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.3

With the development of electric vehicles, the demand for the high-voltage low-current DC-DC chips used in vehicle on-board equipment continues to grow. To improve the effi ciency of the switching power supply, an asynchronous buck high-voltage DC-DC converter with adaptive variable frequency modulation (AVFM) technology is designed in this paper. This work focuses on the efficiency optimization of the buck converter, and the relationship between power consumption and operating frequency under different loads. The optimal frequency range is selected during light and heavy loads, and adaptive transition of the frequency is realized during a medium load. Using a threshold voltage ( V th_cs ) circuit with an adjustable current inside the chip, the on-time of the switch is changed to realize frequency conversion. The whole chip design is based on 0.35 μm BCD process, in which the integrated LDMOS can withstand 200 V. System simulations are completed in Cadence. The results show that when the input voltage is 30–60 V and the output specifi cation is 5 V/0.5 A, the system realizes adaptive frequency conversion in the entire load range, and the efficiency reaches 88.9%. The actual performance of the chip meets the design requirements and has good EMI characteristics.

Alternative Splicing of Breast Cancer Associated Gene BRCA1 from Breast Cancer Cell Line

Lixia, Miao,Zhijian, Cao,Chao, Shen,Chaojiang, Gu,Congyi, Zheng Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.1

Breast cancer is the most common malignancy among women, and mutations in the BRCA1 gene produce increased susceptibility to these malignancies in certain families. In this study, the forward 1-13 exons of breast cancer associated gene BRCA1 were cloned from breast cancer cell line ZR-75-30 by RT-PCR method. Sequence analysis showed that nine BRCA1 splice forms were isolated and characterized, compared with wild-type BRCA1 gene, five splice forms of which were novel. These splice isoforms were produced from the molecular mechanism of 5' and 3' alternative splicing. All these splice forms deleting exon 11b and the locations of alternative splicing were focused on two parts:one was exons 2 and 3, and the other was exons 9 and 10. These splice forms accorded with GT-AG rule. Most these BRCA1 splice variants still kept the original reading frame. Western blot analysis indicated that some BRCA1 splice variants were expressed in ZR-75-30 cell line at the protein level. In addition, we confirmed the presence of these new transcripts of BRCA1 gene in MDA-MB-435S, K562, Hela, HLA, HIC, H9, Jurkat and human fetus samples by RT-PCR analysis. These results suggested that breast cancer associated gene BRCA1 may have unexpectedly a large number of splice variants. We hypothesized that alternative splicing of BRCA1 possibly plays a major role in the tumorigenesis of breast and/or ovarian cancer. Thus, the identification of cancer-specific splice forms will provide a novel source for the discovery of diagnostic or prognostic biomarkers and tumor antigens suitable as targets for therapeutic intervention.

Microstructural and Mechanical Properties of TiCX–Ni3(Al,Ti)/Ni Functionally Graded Composites Fabricated from Ti3AlC2 and Ni Powders

Guangming Zheng,Zhenying Huang,Qun Yu,Wenqiang Hu,Xingyang Qiu,A. Lixia,Yuanbo Wang,Yidan Jiao,Yang Zhou,Hongxiang Zhai 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

In this paper, a novel type of functionally graded material (FGM) was successfully fabricated from pure Ni and Ti3AlC2powder mixtures by hot-press sintering route at 1200 °C and 17 MPa. In each layer, Ti3AlC2particles transformed into TiCxphase, while the additional Al–Ti atoms decomposed from Ti3AlC2diffused into the Ni matrix, giving rise to the formationof γ′-Ni3(Al,Ti). Part of the submicron TiCxand Ni3(Al,Ti) particles were uniformly distributed in the Ni matrix, whilesome of the TiCxmaintained the original Ti3AlC2plate-like morphology. Both TiCxand Ni3(Al,Ti) content decreased from60Ti3AlC2/Ni layer to 10Ti3AlC2/Ni layer in a stepwise manner was fabricated. The microstructural analysis indicatesthat no cracks, delamination and step-type abrupt changes occured in the graded layer of the manufactured FGM. Flexuralstrength and Vickers hardness enhanced with the increasing Ti3AlC2content except for fracture strain and toughness. Theoverall fracture toughness and the flexural strength of FGM can reach 21.76 MPa m1/2 and 1329 ± 34 MPa, respectively. Theprepared FGM, herein, with a hard ceramic surface on one side to resist local plastic deformation, and a ductile metallicsurface on the other side to provide toughness.

TNF-α-Induced SOX5 Upregulation Is Involved in the Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells Through KLF4 Signal Pathway

Xu, Lijun,Zheng, Lili,Wang, Zhifang,Li, Chong,Li, Shan,Xia, Xuedi,Zhang, Pengyan,Li, Li,Zhang, Lixia Korean Society for Molecular and Cellular Biology 2018 Molecules and cells Vol.41 No.6

Postmenopausal osteoporosis (PMOP) is a common systemic skeletal disease characterized by reduced bone mass and microarchitecture deterioration. Although differentially expressed SOX5 has been found in bone marrow from ovariectomized mice, its role in osteogenic differentiation in human mesenchymal stem cells (hMSCs) from bone marrow in PMOP remains unknown. In this study, we investigated the biological function of SOX5 and explore its molecular mechanism in hMSCs from patients with PMOP. Our findings showed that the mRNA and protein expression levels of SOX5 were upregulated in hMSCs isolated from bone marrow samples of PMOP patients. We also found that SOX5 overexpression decreased the alkaline phosphatase (ALP) activity and the gene expression of osteoblast markers including Collagen I, Runx2 and Osterix, which were increased by SOX5 knockdown using RNA interference. Furthermore, $TNF-{\alpha}$ notably upregulated the SOX5 mRNA expression level, and SOX5 knockdown reversed the effect of $TNF-{\alpha}$ on osteogenic differentiation of hMSCs. In addition, SOX5 overexpression increased Kruppel-like factor 4 (KLF4) gene expression, which was decreased by SOX5 silencing. KLF4 knockdown abrogated the suppressive effect of SOX5 overexpression on osteogenic differentiation of hMSCs. Taken together, our results indicated that $TNF-{\alpha}$-induced SOX5 upregulation inhibited osteogenic differentiation of hMSCs through KLF4 signal pathway, suggesting that SOX5 might be a novel therapeutic target for PMOP treatment.

TNF-α-Induced SOX5 Upregulation Is Involved in the Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells Through KLF4 Signal Pathway

Lijun Xu,Lili Zheng,Zhifang Wang,Chong Li,Shan Li,Xuedi Xia,Pengyan Zhang,Li Li,Lixia Zhang 한국분자세포생물학회 2018 Molecules and cells Vol.41 No.6

Postmenopausal osteoporosis (PMOP) is a common sys-temic skeletal disease characterized by reduced bone mass and microarchitecture deterioration. Although differentially expressed SOX5 has been found in bone marrow from ovariectomized mice, its role in osteogenic differentiation in human mesenchymal stem cells (hMSCs) from bone marrow in PMOP remains unknown. In this study, we investigated the biological function of SOX5 and explore its molecular mechanism in hMSCs from patients with PMOP. Our findings showed that the mRNA and protein expression levels of SOX5 were upregulated in hMSCs isolated from bone marrow samples of PMOP patients. We also found that SOX5 overexpression decreased the alkaline phosphatase (ALP) activity and the gene expression of osteoblast markers including Collagen I, Runx2 and Osterix, which were increased by SOX5 knockdown using RNA interference. Furthermore, TNF- notably upregulated the SOX5 mRNA expression level, and SOX5 knockdown reversed the effect of TNF- on osteogenic differentiation of hMSCs. In addition, SOX5 overexpression increased Kruppel-like factor 4 (KLF4) gene expression, which was decreased by SOX5 silencing. KLF4 knockdown abrogated the suppressive effect of SOX5 overexpression on osteogenic differentiation of hMSCs. Taken together, our results indicated that TNF--induced SOX5 upregulation inhibited osteogenic differentiation of hMSCs through KLF4 signal pathway, suggesting that SOX5 might be a novel therapeutic target for PMOP treatment.

A review of the migration mechanisms of microplastics in terrestrial environments

Hui Yu,Weiqing Zhang,Lixia Zheng,Tong Li,Chunxing Hai,Yong Wang,Tao Lyu 대한환경공학회 2024 Environmental Engineering Research Vol.29 No.5

Microplastic (MP) release into the terrestrial environment has occurred since humans started manufacturing and using plastics. These tiny plastic particles can be found in various media, including the atmosphere, soil, freshwater, sediments, and organisms. MPs migrate through terrestrial environmental media due to wind, water, gravity, and biological processes. Although the variables that affect the migration process have been investigated in various settings, the mechanisms of MP migration in terrestrial environments have yet to be systematically characterized. This study classifies the migration mechanisms of MPs as physical, chemical and biological manners, and discusses the factors affecting migration mechanisms in dynamic factors, environmental factors and MP characteristics. Examining the action mechanisms of migration can establish a foundation for understanding the migration processes of MPs and provide a theoretical framework for modeling MP movement in environmental. Future research challenges include understanding the effect of MP characteristics in the migration process and simulating the migration of MPs in the environment in the long-term. Exploring the MP migration on various spatial and temporal scales, considering the life cycle of MPs is a worthy research direction.