Development of lattice inversion modified embedded atom method and its applications

Xianbao Duan,Bing Zhou,Rong Chen,Huamin Zhou,YanweiWen,Bin Shan 한국물리학회 2014 Current Applied Physics Vol.14 No.12

The modified embedded atom method (MEAM) has been widely used in describing the physical properties of elemental crystals, alloys and compounds with multiple lattice structures. We report here the development of a reliable procedure to reduce the complexity of the MEAM formalism by removing the many-body screening function. In the proposed formulation, the interatomic pair potential is obtained by applying Chen-M€obius lattice inversion up to fifth nearest neighbors, so that the cohesive energy curve can be reproduced faithfully. The newly developed model (Lattice Inversion MEAM, LI-MEAM), which can be viewed as a direct extension of the embedded atom method (EAM), no longer requires the computation of many-body screen functions and has fewer adjustable parameters than MEAM. As an illustration, we optimized the potential parameters of body centered cubic iron (bcc-Fe). The values of the calculated physical properties agree well with experimental results. We further investigated the sizedependent melting behavior of bcc-Fe nanoparticles (NPs) with particle size ranging from 725-atom (~25 Å) to 22899-atom (~80 Å) using replica exchange molecular dynamics (REMD) simulations. Our simulations show advantages of LI-MEAM in modeling of the melting process and quantitatively reveals that the liquid skin melting (LSM) process of bcc-Fe NPs.

IQGAP1 is overexpressed in hepatocellular carcinoma and promotes cell proliferation by Akt activation

Chen, Feng,Zhu, Hai-Hong,Zhou, Lin-Fu,Wu, Shan-Shan,Wang, Jing,Chen, Zhi Korean Society for Biochemistry and Molecular Bion 2010 Experimental and molecular medicine Vol.42 No.7

The scaffold protein IQGAP1 shows elevated levels in several cancer types, but its expression in hepatocellular carcinoma is unknown. We found that 58% of human hepatocellular carcinoma tissue samples had increased IQGAP1 expression compared to adjacent normal tissue. Overexpressing IQGAP1 raised the in vivo tumorigenicity of hepatocellular carcinoma cells, and forced overexpression of IQGAP1 in vitro stimulated cell proliferation. Cell growth was reduced by knockdown or mutation of IQGAP1, or by treatment of cells with a phosphotidylinositol 3-kinase inhibitor. To determine the mechanism by which IQGAP1 overexpression affected hepatocellular carcinoma cells, we confirmed its interaction in these cells with mammalian target of rapamycin (mTOR), a serine/threonine kinase that integrates signals about nutrient and energy status with downstream effectors that influence cell division. In addition, we discovered a new interaction involving IQGAP1, mTOR and Akt, which is a downstream target of mTOR. Akt phosphorylation on Ser-473, which is catalyzed by mTOR and required for Akt activation, increased with increasing amounts of IQGAP1, and decreased with IQGAP1 mutation. We hypothesize that IQGAP1 is a scaffold that facilitates mTOR and Akt interaction.

Excellent Cycle Stability of Fe3O4 Nanoparticles Decorated Graphene as Anode Material for Lithium-Ion Batteries

Shan-Shan Chen,Xueqing Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.6

Fe3O4–graphene nanocomposites were prepared via a simple hydrothermal method. Ultrafine Fe3O4 nanoparticles were evenly anchored on graphene substrates. As anode material for Li-ion batteries (LIB), the nanocomposite showed high initial discharge and charge capacities of 1456 mAhg-1 and 739.9 mAhg-1 at high current density of 500 mAg-1. Additionally, the charge capacity was also retained at 698.3 mAhg-1 after 200 cycles, thereby indicating excellent cycling stability. The results suggested that the as-prepared Fe3O4–graphene nanocomposite is a promising candidate for practical application as a Li-ion battery anode material.

Bulk Synthesis of Fe3Al Intermetallic Compound Nanoparticles by Flow-Levitation Method

Shan-Jun Chen,Song Li,Yang-En Wang,Hui Zeng,Yong-Jian Tang,Wei-Guo Sun,Yan Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.1

Metallic nanopowders have an increasing application in magnetic materials, catalysts and chemical and metallic industries. In this research, a novel bulk synthesis method for preparing high pure intermetallic Fe3Al nanoparticles was developed by flow-levitation (FL) method. The Fe and Al vapors ascending from the high-temperature levitated droplet were condensed by cryogenic argon gas under atmospheric pressure. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) were used to identify and characterize the prepared nanopowders exhibiting a Fe3Al phase. Measurement of transmission electron microscopy (TEM) indicated that the Fe3Al particles are nearly spherical, and the particle size of the compound ranges from 10 nm to 200 nm in diameter. The chemical composition of the nanoparticles were determined with energy dispersive spectrometer. The magnetic properties of the nanopowder indicate that Fe3Al intermetallic compound is a soft magnet at room temperature, with coercivity of 24.2 Oe and saturation magnetization of 173.2 emu/g. The production rate of Fe3Al nanoparticles was estimated to be about 4 g/h in a continuous manner, by using the FL method. This method as great potential in mass production of Fe3Al nanoparticles.

Microstructure Distribution and Grain Coarsening Model of GCr15 Steel in the Laser Surface Treatment

Jin‑shan Chen,Zhen‑xing Li,Ya‑jie Chu,Jie Chen, Xin‑jun Shen 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

The GCr15 steel was subjected to laser surface treatment using a diode laser with rectangular spot. Based on the simulatedtemperature field, the microstructure distribution of the laser hardened layer was analyzed, and an empirical equation wasproposed to predict the peak temperature at different depths. The results indicated that with the decrease of depth, the peaktemperature increased exponentially, and the peak temperature at different depths was approximately linear with the powerdensity and the reciprocal of square root of scanning speed. High peak temperature led to the coarsening of grain and thesignificant dissolution of cementite near the surface of hardened layer. At the deeper position of hardened layer, the prioraustenite grain size decreased slightly due to high nucleation rate. The cementite dissolution and coarsening occurred simultaneouslynear the surface, and the cementite dissolution process was postponed due to the significant enrichment of Cr nearthe interface of austenite and cementite. Additionally, an empirical model about grain coarsening was established, which canbe used to predict the prior austenite grain size near the surface during the laser surface treatment.

IQGAP1 is overexpressed in hepatocellular carcinoma and promotes cell proliferation by Akt activation

Feng Chen,Zhi Chen,Hai-Hong Zhu,Lin-Fu Zhou,Shan-Shan Wu,Jing Wang 생화학분자생물학회 2010 Experimental and molecular medicine Vol.42 No.7

The scaffold protein IQGAP1 shows elevated levels in several cancer types, but its expression in hepatocellular carcinoma is unknown. We found that 58%of human hepatocellular carcinoma tissue samples had increased IQGAP1 expression compared to adjacent normal tissue. Overexpressing IQGAP1 raised the in vivo tumorigenicity of hepatocellular carcinoma cells, and forced overexpression of IQGAP1 in vitro stimulated cell proliferation. Cell growth was reduced by knockdown or mutation of IQGAP1, or by treatment of cells with a phosphotidylinositol 3-kinase inhibitor. To determine the mechanism by which IQGAP1 overexpression affected hepatocellular carcinoma cells,we confirmed its interaction in these cells with mammalian target of rapamycin (mTOR), a serine/threonine kinase that integrates signals about nutrient and energy status with downstream effectors that influence cell division. In addition, we discovered a new interaction involving IQGAP1, mTOR and Akt, which is a downstream target of mTOR. Akt phosphorylation on Ser-473, which is catalyzed by mTOR and required for Akt activation, increased with increasing amounts of IQGAP1, and decreased with IQGAP1 mutation. We hypothesize that IQGAP1 is a scaffold that facilitates mTOR and Akt interaction.

Xylitol fermentation by Candida subtropicalis WF79 immobilized in polyacrylic hydrogel films

Chee-Shan Chen,Wen-Chang Liaw,Wen-Shion Chang,Kuan-Pin Chen,Yee-Fan Chen 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.5

Polyacrylate hydrogel films were used as immobilization matrices for cell entrapment of the yeast strain, Candida subtropicalis WF79, isolated from sugarcane bagasse. The hydrogel films with immobilized viable yeast cells were employed for the bioconversion from xylose to xylitol. The hydrogel was prepared from the monomers of 2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA), and N,N-dimethyl acrylamide (DMA) with polyethylene glycol diacrylate (PEG-DA, weight-average molecular weight Mw=400 and 1,000 g/mol) as the crosslinking agent. The mechanical properties and fermentation yields of the immobilized polyacrylate hydrogel film with different monomeric formulation were investigated. Fermentation was carried out in a medium of 100 mL aqueous solution containing various amount of xylose. The conversion rate of xylose to xylitol conversion reached a maximum value of 80% after 120 h. The bioconversion activity gradually declined, after 720 h, to 65% conversion at 1,080 h

Pretreatment Serum Amyloid A and C-reactive Protein Comparing with Epstein-Barr Virus DNA as Prognostic Indicators in Patients with Nasopharyngeal Carcinoma: A Prospective Study

Qiu-Yan Chen,Qing-Nan Tang,Lin-Quan Tang,Wen-Hui Chen,Shan-Shan Guo,Li-Ting Liu,Chao-Feng Li,Yang Li,Yu-Jing Liang,Xue-Song Sun,Ling Guo,Hao-Yuan Mo,Rui Sun,Dong-Hua Luo,Yu-Ying Fan,Yan He,Ming-Yuan C 대한암학회 2018 Cancer Research and Treatment Vol.50 No.3

Purpose The measuring Epstein-Barr virus (EBV) DNA is an important predictor of nasopharyngeal carcinoma (NPC). This study evaluated the predictive value of pretreatment serum amyloid A (SAA) and C-reactive protein (CRP) comparing with EBV DNA in patients with NPC. Materials and Methods In an observational study of 419 non-metastatic NPC patients, we prospectively evaluated the prognostic effects of pretreatment SAA, CRP, and EBV DNA on survival. The primary endpoint was progress-free survival (PFS). Results The median level of SAA and CRP was 4.28 mg/L and 1.88 mg/L, respectively. For the high- SAA group (> 4.28 mg/L) versus the low-SAA ( 4.28 mg/L) group and the high-CRP group (> 1.88 mg/L) versus the low-CRP ( 1.88 mg/L) group, the 5-year PFS was 64.5% versus 73.1% (p=0.013) and 65.2% versus 73.3% (p=0.064), respectively. EBV DNA detection showed a superior predictive result, the 5-year PFS in the EBV DNA  1,500 copies/mL group was obviously different than the EBV DNA < 1,500 copies/mL group (62.2% versus 77.8%, p < 0.001). Multifactorial Cox regression analysis confirmed that in the PFS, the independent prognostic factors were including EBV DNA (hazard ratio [HR], 1.788; p=0.009), tumour stage (HR, 1.903; p=0.021), and node stage (HR, 1.498; p=0.049), but the SAA and CRP were not included in the independent prognostic factors. Conclusion The results of SAA and CRP had a certain relationship with the prognosis of NPC, and the prognosis of patients with high level of SAA and CRP were poor. However, the predictive ability of SAA and CRP was lower than that of EBV DNA.

Combination of Tumor Volume and Epstein-Barr Virus DNA Improved Prognostic Stratification of Stage II Nasopharyngeal Carcinoma in the Intensity Modulated Radiotherapy Era: A Large-Scale Cohort Study

Qiu-Yan Chen,Shao-Yan Guo,Lin-Quan Tang,Tong-Yu Lu,Bo-Lin Chen,Qi-Yu Zhong,Meng-Sha Zou,Qing-Nan Tang,Wen-Hui Chen,Shan-Shan Guo,Li-Ting Liu,Yang Li,Ling Guo,Hao-Yuan Mo,Rui Sun,Dong-Hua Luo,Chong Zha 대한암학회 2018 Cancer Research and Treatment Vol.50 No.3

Purpose Little is known about combination of the circulating Epstein-Barr viral (EBV) DNA and tumor volume in prognosis of stage II nasopharyngeal carcinoma (NPC) patients in the intensity modulated radiotherapy (IMRT) era. We conducted this cohort study to evaluate the prognostic values of combining these two factors. Materials and Methods By Kaplan-Meier, we compare the differences of survival curves between 385 patients with different EBV DNA or tumor volume levels, or with the combination of two biomarkers mentioned above. Results Gross tumor volume of cervical lymph nodes (GTVnd, p < 0.001) and total tumor volume (GTVtotal, p < 0.001) were both closely related to pretreatment EBV DNA, while gross tumor volume of nasopharynx (GTVnx, p=0.047) was weakly related to EBV DNA. EBV DNA was significantly correlated with progress-free survival (PFS, p=0.005), locoregional-free survival (LRFS, p=0.039), and distant metastasis-free survival (DMFS, p=0.017), while GTVtotal, regardless of GTVnx and GTVnd, had a significant correlation with PFS and LRFS. The p-values of GTVtotal for PFS and LRFS were 0.008 and 0.001, respectively. According to GTVtotal and pretreatment EBV DNA level, patients were divided into a low-risk group (EBV DNA 0 copy/mL, GTVtotal < 30 cm3; EBV DNA 0 copy/mL, GTVtotal  30 cm3; or EBV DNA > 0 copy/mL, GTVtotal < 30 cm3) and a high-risk group (EBV DNA > 0 copy/mL, GTVtotal  30 cm3). When patients in the low-risk group were compared with those in the high-risk group, 3-year PFS (p=0.003), LRFS (p=0.010), and DMFS (p=0.031) rates were statistically significant. Conclusion Pretreatment plasma EBV DNA and tumor volume were both closely correlated with prognosis of stage II NPC patients in the IMRT era. Combination of EBV DNA and tumor volume can refine prognosis and indicate for clinical therapy.

Mesenchymal Stem Cell Secreted-Extracellular Vesicles are Involved in Chondrocyte Production and Reduce Adipogenesis during Stem Cell Differentiation

Tsai Yu-Chen,Cheng Tai-Shan,Liao Hsiu-Jung,Chuang Ming-Hsi,Chen Hui-Ting,Chen Chun-Hung,Zhang Kai-Ling,Chang Chih-Hung,Lin Po-Cheng,Huang Chi-Ying F. 한국조직공학과 재생의학회 2022 조직공학과 재생의학 Vol.19 No.6

BACKGROUND: Extracellular vesicles (EVs) are derived from internal cellular compartments, and have potential as a diagnostic and therapeutic tool in degenerative disease associated with aging. Mesenchymal stem cells (MSCs) have become a promising tool for functional EVs production. This study investigated the efficacy of EVs and its effect on differentiation capacity. METHODS: The characteristics of MSCs were evaluated by flow cytometry and stem cell differentiation analysis, and a production mode of functional EVs was scaled from MSCs. The concentration and size of EVs were quantitated by Nanoparticle Tracking Analysis (NTA). Western blot analysis was used to assess the protein expression of exosomespecific markers. The effects of MSC-derived EVs were assessed by chondrogenic and adipogenic differentiation analyses and histological observation. RESULTS: The range of the particle size of adipose-derived stem cells (ADSCs)- and Wharton’s jelly -MSCs-derived EVs were from 130 to 150 nm as measured by NTA, which showed positive expression of exosomal markers. The chondrogenic induction ability was weakened in the absence of EVs in vitro. Interestingly, after EV administration, type II collagen, a major component in the cartilage extracellular matrix, was upregulated compared to the EV-free condition. Moreover, EVs decreased the lipid accumulation rate during adipogenic induction. CONCLUSION: The results indicated that the production model could facilitate production of effective EVs and further demonstrated the role of MSC-derived EVs in cell differentiation. MSC-derived EVs could be successfully used in cell-free therapy to guide chondrogenic differentiation of ADSC for future clinical applications in cartilage regeneration.