Modified Chaplygin gas as a unified dark matter and dark energy model and cosmic constraints

Xu, Lixin,Wang, Yuting,Noh, Hyerim Springer-Verlag 2012 European Physical Journal C Vol.72 No.3

Influences of friction and mesh misalignment on time-varying mesh stiffness of helical gears

Lin Han,Lixin Xu,Houjun Qi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7

As one of the most important excitation sources of vibration, time-varying mesh stiffness of helical gear pairs need accurately calculated. Compared with spur gears, friction in helical gears is significant. This work for the first time presents an improved calculation method for the mesh stiffness of helical gears with effect of friction incorporated. Firstly, helical gear is sliced into number of pieces along its axis direction and each piece could be regarded as spur gear. Then forces applied to each piece including friction force are analyzed. Potential energy method is employed to develop time-varying mesh stiffness of each piece pair of both kinds of helical gears with different transverse and axial contact ratios. Furthermore, influences of various working conditions and misalignment on mesh stiffness are also investigated. Results indicate that effect brought by friction on total mesh stiffness should be not neglected. The reduction amount of stiffness increases with lower speed, heavier load and rougher surface. The stiffness difference between cases with and without friction is affected by gear geometry and mounting parameters like module, helix angle and mounting misalignment. This work provides an essential tool for comprehensive dynamics analysis with consideration of the relationship between stiffness and working conditions.

Biosynthesized Au/TiO2@SBA-15 catalysts for selective oxidation of cyclohexane with O2

Fang Yao,Lixin Xu,Jili Luo,Xiao Li,Yue An,Chao Wan 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.4

A variety of TiO2@SBA-15 supporters with various TiO2 loadings were synthesized using a facile sol-gel method. Gold (Au)-based catalysts were prepared with an environmentally benign and economical bioreduction method via Cacumen Platycladi (CP) leaf extract and immobilized on various TiO2@SBA-15 supporters with different TiO2 loadings. The as-prepared biosynthesized Au catalysts were applied in the liquid-phase cyclohexane oxidation. The results showed that the Au nanoparticles were well-dispersed on TiO2@SBA-15, and the Au existed as Au0. These biosynthesized Au catalysts are promising for cyclohexane oxidation, achieving a turnover frequency up to 3,426 h1 with a 14.1% cyclohexane conversion rate.

Systematic equity risk change around convertible debt offerings

Lifang Chen,Lixin Xu 인하대학교 정석물류통상연구원 2009 인하대학교 정석물류통상연구원 학술대회 Vol.2009 No.10

This study investigates Systematic Equity Risk Change of a firm when it issues convertible bonds by studying the change in beta before and after the issuance of convertible bonds. Descriptive statistics provide the evidence that the systematic equity risk declines slightly after a firm has issued convertible debt, while the systematic equity risk was low both before and after issuance. However, both the T test and Wilcoxon signed-rank test of the paired-samples show that there appears to be no significant change in the systematic equity risk after a firm has issued convertible bonds. Although the conclusion is different from previous studies, it is consistent with and gives further support to the conjecture that firms try to stabilize the level of systematic risk of their common stock. Moreover, our results have implications for existing theories and suggest that it is important to consider possible risk changes when examining the issuance effects of offering convertible bonds.

Development of Toxoplasma gondii Chinese I genotype Wh6 Strain in Cat Intestinal Epithelial Cells

Gui-Hua Zhao,Lixin Zhang,Lisha Dai,Haozhi Xu,Chao Xu,Ting Xiao,Jin Li,Hui Sun,Beibei Zhou,Kun Yin 대한기생충학ㆍ열대의학회 2022 The Korean Journal of Parasitology Vol.60 No.4

Felids are the unique definitive host of Toxoplasma gondii. The intestine of felid is the only site for initiating Toxoplasma gondii sexual reproduction. T. gondii excretes millions of infectious oocysts from the intestine, which are the primary source of infection. There are many difficulties in developing vaccines and drugs to control oocyst excretion due to the lack of an appropriate experimental model. Here, we established an in vitro feline intestinal epithelial cell (IEC) infection system and an efficient animal model of T. gondii Chinese 1 genotype, Wh6 strain (TgCtwh6). The Kunming mice brain tissues containing TgCtwh6 cysts were harvested 42-day post-infection. The bradyzoites were co-cultured with cat IECs in vitro at a ratio of 1:10. Five 3-month-old domestic cats were orally inoculated with 600 cysts each. The oocysts were detected by daily observation of cat feces by microscopy and polymerase chain reaction. We found that the parasite adhered and invaded cat IECs in vitro, transformed into tachyzoites, and then divided to form rose-like structures. These parasites eventually destroyed host cells, escaped, and finished the asexual reproduction process. Schizonts associated with sexual reproduction have not been observed during development in vitro cultured cells. However, schizonts were detected in all infected cat intestinal epithelial cells, and oocysts were presented in all cat feces. Our study provides a feasible cell model and an efficient infection system for the following studies of T. gondii sexual reproduction, and also lays a foundation to develop drugs and vaccines for blocking excretion and transmission of oocysts.

DDAB-MODIFIED TPGS-b-(PCL-ran-PGA) NANOPARTICLES AS ORAL ANTICANCER DRUG CARRIER FOR LUNG CANCER CHEMOTHERAPY

TIEJUN ZHAO,HEZHONG CHEN,LIXIN YANG,HAI JIN,ZHIGANG LI,LIN HAN,FANGLIN LU,ZHIYUN XU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.2

Oral chemotherapy is a great way to cancer treatment because it is less stressful being that the patient will have less hospital visits and can still maintain a close relationship with health care professionals. In this research, three types of nanoparticle formulation from commercial PCL and self-synthesized TPGS-b-(PCL-ran-PGA) diblock copolymer were fabricated for oral delivery of antitumor agents, including DDAB-modified PCL nanoparticles, unmodified TPGS-b-(PCL-ran-PGA) nanoparticles and DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles. Firstly, the TPGS-b-(PCL-ran-PGA) diblock copolymer was synthesized and characterized. DDAB was adopted to increase retention time at the cell surface, thus increasing the chances of nanoparticle uptake by the gastrointestinal mucosa and improving drug absorption. The TPGS-b-(PCL-ran-PGA) nanoparticles were found by FESEM of spherical shape and around 200 nm in diameter. The surface charge of TPGS-b-(PCL-ran-PGA) nanoparticles was reversed from anionic to cationic after DDAB modification. The DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles have significantly higher level of the cell uptake than that of DDAB-modified PCL nanoparticles and unmodified TPGS-b-(PCL-ran-PGA) nanoparticles. In vitro cell viability studies showed advantages of the DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles over Taxotere® in terms of cytotoxicity against A549 cells. In conclusion, oral chemotherapy by DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticle formulation may provide a promising outcome for lung cancer patients.

BRAF-Activated Long Noncoding RNA Modulates Papillary Thyroid Carcinoma Cell Proliferation through Regulating Thyroid Stimulating Hormone Receptor

Haitao Zheng,Meng Wang,Lixin Jiang,Haidi Chu,Jinchen Hu,Jinyao Ning,Baoyuan Li,Dong Wang,Jie Xu 대한암학회 2016 Cancer Research and Treatment Vol.48 No.2

Purpose The importance of long noncoding RNAs (lncRNAs) in tumorigenesis has recently been demonstrated. However, the role of lncRNAs in development of thyroid cancer remains largely unknown. Materials and Methods Using quantitative reverse transcription polymerase chain reaction, expression of three lncRNAs, including BRAF-activated long noncoding RNA (BANCR), papillary thyroid cancer susceptibility candidate 3 (PTCSC3), and noncoding RNA associated with mitogen-activated protein kinase pathway and growth arrest (NAMA), was investigated in the current study. Results Of the three lncRNAs (BANCR, PTCSC3, and NAMA), expression of BANCR was significantly up-regulated while PTCSC3 and NAMA were significantly down-regulated in papillary thyroid carcinoma (PTC) compared to that in normal tissue. BANCR-knockdown in a PTC-derived cell line (IHH-4) resulted in significant suppression of thyroid stimulating hormone receptor (TSHR). BANCR-knockdown also led to inhibition of cell growth and cell cycle arrest at G0/G1 phase through down-regulation of cyclin D1. In addition, BANCR was enriched by polycomb enhancer of zeste homolog 2 (EZH2), and silencing BANCR led to decreased chromatin recruitment of EZH2, which resulted significantly reduced expression of TSHR. Conclusion These findings indicate that BANCR may contribute to the tumorigenesis of PTC through regulation of cyclin D1 and TSHR.

An Iris Localization Algorithm based on Morphological Processing

Kun Yu,Zeyu Xu,Lixin Xu 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.3

To improve the speed of iris localization, an iris localization algorithm based on the morphological processing is proposed with fast speed. Firstly, pupil area is segmented from eye image by thresholding, to remove eyelash noise and other noises from binaryzation pupil area by morphological open operation. Then, a series of structure element of radius increasing is used to make morphological erode operation on pupil area to localize roughly the inner boundary of the iris. Finally, calculus operator is employed to accurately localize the inner and outer iris boundary. 108 iris images from CASIA (Version 1.0) iris database are used to do iris localization experiments. The localization accurate rate of the proposed algorithm, calculus operator and hough transform is 97.2%, 90.3% and 92.1% respectively. Experiment results have showed that the proposed algorithm has a high performance on speed and precision with strong robustness to the different quality iris images.

Protective Effect of Exogenous Spermidine on Ion and Polyamine Metabolism in Kentucky bluegrass under Salinity Stress

Xuehua Puyang,Mengying An,Lixin Xu,Liebao Han,Xunzhong Zhang 한국원예학회 2016 Horticulture, Environment, and Biotechnology Vol.57 No.1

Spermidine (Spd) acts as a plant protectant under salinity stress. The objective of this study was to determine whether exogenous Spd pre-treatment could improve the salinity tolerance of Kentucky bluegrass (Poa pratensis L.). Exogenous Spd was applied before the grass was exposed to 200 mM sodium chloride (NaCl) for 28 d in the growth chamber. Salinity stress decreased chlorophyll (Chl) content, K+/Na+ratio and K+, Ca2+, and Mg2+ contents, and increased electrolyte leakage (EL), proline, Na+, putrescine (Put), Spd and Spermine (Spm) levels and the activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC) and polyamine oxidase (PAO). Pre-treatment with 1 mM Spd effectively alleviated the decline of Chl content, K+/Na+ratio and K+, Ca2+, and Mg2+ contents under salinity stress conditions. Spd pre-treatment also reduced EL, Na+ content, Put levels and the activities of ADC and PAO, but increased proline content, endogenous Spd and Spm levels and the activities of ODC and SAMDC upon salinity stress. These results indicate that exogenous Spd pre-treatment could enhance salinity tolerance by increasing proline levels and regulating ion and polyamine metabolism.

Modified Model Free Adaptive Control for a Class of Nonlinear Systems with Multi-threshold Quantized Observations

Xiangquan Li,Zhengguang Xu,Yanrong Lu,Jiarui Cui,Lixin Zhang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.10

This paper addresses a pattern-moving-based modified model free adaptive control (PMFAC) scheme and illustrates the convergence of its tracking error for a class of nonlinear systems with unknown model and multi-threshold quantized observations. The basic idea is to consider the system’s quantization error as an external disturbance and an improved performance index function of control law is proposed from the perspective of twoplayer zero-sum game (TP-ZSG) based on the existed MFAC algorithms. The PMFAC scheme is established which mainly includes an improved tracking control law and a pseudo-partial derivative (PPD) estimation algorithm. Under certain conditions, the bounded convergence of system tracking error and the stability of PMFAC system with quantization errors can be guaranteed. The theoretical results are demonstrated by two numerical examples.