Effects of Biodegradable Imidazolium-Based Ionic Liquid with Ester Group on the Structure and Properties of PLLA

Hao Guan Gui,Yun Sheng Ding,Yu Li,Shouyu Chen,Pei Xu,Bin Zheng 한국고분자학회 2014 Macromolecular Research Vol.22 No.6

Blends of poly(L-lactide) (PLLA) and a functional ionic liquid (IL), 3-methyl-1-(ethoxycarbonylethyl) imidazoliumtetrafluoroborate ([AOEMIm][BF4]) with various weight ratios were prepared by melt compounding andtheir interactions, compatibilities, processing characteristics, crystallization behaviors, mechanical properties and thermaldegradation were investigated in this study. The interaction between PLLA and [AOEMIm][BF4] was first studiedby infrared spectroscopy (IR) investigation, and then the Flory-Huggins interaction parameter between PLLA and[AOEMIm][BF4] was calculated. The compatibility was also supported by both sample appearance and scanning electronmicroscopy (SEM) results. Crystallization and melting conditions were obtained from differential scanning calorimetry(DSC), and the glass transition temperature (Tg) of PLLA showed a gradual decrease with the increasing addition of[AOEMIm][BF4]. The balancing torque data were obtained by Haaker torque rheometry, and the molecular weight data ofprocessed PLLA obtained by gel permeation chromatography (GPC) tests reflected a positive effect of [AOEMIm][BF4]on the melt-processing of PLLA. A strong increase of the mechanical parameters of PLLA, such as the elongation atbreak and the impact strength, was observed with the incorporation of [AOEMIm][BF4] up to the content of 7 phr (phris the abbreviation for parts per hundreds of resin, n phr denoted n g IL/100 g PLLA), while the tensile strength decreasedslightly. The thermal stability of PLLA took a sustained downward trend, with the increasing contents of [AOEMIm][BF4] inits matrices, as presented from thermogravimetric analysis (TGA). PLLA blended with 5 phr [AOEMIm][BF4] achievedexcellent overall performance; as well, the mechanical properties improved considerably, and damage to the thermal stabilitywas acceptable.

Refolding and Purification of Recombinant Human $Interferon-\gamma$ Expressed as Inclusion Bodies in Escherichia coli Using Size Exclusion Chromatography

Guan Yi-Xin,Pan Hai-Xue,Gao Yong-Gui,Yao Shan-Jing,Cho Man-Gi The Korean Society for Biotechnology and Bioengine 2005 Biotechnology and Bioprocess Engineering Vol.10 No.2

A size exclusion chromatography (SEC) process, in the presence of denaturant in the refolding buffer was developed to refold recombinant human $interferon-\gamma$ ($rhIFN-\gamma$) at a high concentration. The $rhlFN-\gamma$ was overexpressed in E. coli resulting in the formation of inactive inclusion bodies (IBs). The IBs were first solubilized in 8 M urea as the denaturant, and then the refolding process performed by decreasing the urea concentration on the SEC column to suppress protein aggregation. The effects of the urea concentration, protein loading mode and column height during the refolding step were investigated. The combination of the buffer-exchange effect of SEC and a moderate urea concentration in the refolding buffer resulted in an efficient route for producing correctly folded $rhIFN-\gamma$, with protein recovery of $67.1\%$ and specific activity up to $1.2\times10^7\;IU/mg$.

Improved Direct Power Control for Grid-Connected Voltage Source Converters

Gui, Yonghao,Kim, Chunghun,Chung, Chung Choo,Guerrero, Josep M.,Guan, Yajuan,Vasquez, Juan C. Institute of Electrical and Electronics Engineers 2018 IEEE transactions on industrial electronics Vol.65 No.10

<P>A novel grid voltage modulated direct power control (GVM-DPC) strategy for a grid-connected voltage source converter is proposed to control the instantaneous active and reactive powers directly. The GVM-DPC method consists of a nonlinear GVM controller, a conventional controller (feedforward and PI feedback), and nonlinear damping. The proposed control strategy shows a relationship between DPC and voltage-oriented control methods designed in <TEX>$d$</TEX>-<TEX>$q$</TEX> frame. The main advantage is that the proposed method makes the system be a linear time-invariant system, which enables us to apply various control methods easily. The GVM-DPC guarantees not only the convergence rate but also the steady-state performance of the system. Moreover, it is ensured that the closed-loop system is exponentially stable. Finally, simulation and experimental results using a 2.2-kVA VSC are provided to validate the tracking performance and robustness of the proposed control architecture. In addition, the total harmonic distortion of the current is 1.9<TEX>$\%$</TEX> which is much less than the requirement for grid operation.</P>

Protective Effect of Ultra Low Molecular Weight Heparin on Glutamate-Induced Apoptosis in Cortical Cells

Tian-Gui Yu,Qing-Zhu Zhang,Zhi-Guo Zhang,Wei-Wei Wang,Sheng-Li Ji,Guan-Hua Du 연세대학교의과대학 2008 Yonsei medical journal Vol.49 No.3

Purpose: To investigate the effect of ultra low molecular weight heparin (ULMWH) on glutamate induced apoptosis in rat cortical cells and to explore the possible mechanisms. Materials and Methods: Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was first analyzed with Hoechst 33258 and then confirmed by DNA fragmentation. The concentration of free intracellular calcium ([Ca²+]i) was determined with fura-2/AM fluorometry. The expression of Bcl-2 family protein and caspase-3 were evaluated with Western blot. Results: Typical apoptotic morphological change in rat cortical cells treated with 100μmol/L glutamate for 24h was detected by Hoechst 33258 staining, which was then confirmed by the DNA ladder of agarose gel electrophoresis. The apoptotic rate of the glutamate treated cells was up to 33.21%, and 24 h of treatment with glutamate increased [Ca²+]i, down-regulated Bcl-2 expression, up-regulated Bax expression, and increased caspase-3 activation in rat cortical cells. Our research demonstrated that ULMWH pretreatment can prevent the glutamate- induced apoptosis, attenuate the increase of [Ca²+]i not only in medium containing Ca²+ but also in Ca²+-free medium, up-regulate the expression of Bcl-2, down-regulate the expression of Bax, and decrease caspase-3 activation. Conclusion: ULMWH has neuroprotective capacity to antagonize glutamate-induced apoptosis in cortical cells, through decrease of Ca²+ release and modulation of apoptotic processes.

Separation Technology , Thermodynamics : Refolding of Lysozyme at High Concentration in Batch and Fed - batch Operation

(Yong Gui Gao),(Yi Xin Guan),(Shan Jing Yao),(Man Gi Cho) 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.5

한반도 식생의 녹색화에 대한 시계열적 분석

Lv, Guan Ting,ZHUYONGYAN,Liu, Wei Qi,Huang, Xiao,Li, Cheng Lei,Cui, Gui Shan 한국기후변화학회 2019 한국기후변화학회지 Vol.10 No.4

The vegetation is feedback on environmental change due to global warming. Also, the growth status of vegetation and the coverage area of vegetation are greatly affected by the environmental changes. The quantitative change of vegetation growth status is the primary task of vegetation response to environmental changes. In this study, the Global Inventory Modeling and Mapping Studies (GIMMS) based Normalized Difference Vegetation Index (NDVI) and CRU climate data are used to analyze the spatio‐temporal characteristics of vegetation greening evolution and its response to climate change from 1982 to 2015 in the Korean Peninsula by applying the partial correlation and trend analysis. The results show that the average NDVI value of the Korean Peninsula in the period 1982‐2015 was 0.68, among which the average NDVI in North Korea and South Korea was 0.69 and 0.67, respectively. The NDVI of the Korean Peninsula between 1982 and 2015 increased by 0.6x10‐3 year‐1. The increasing trend prior to and after 1998 was 2.5×10‐3 year‐1 and 0.9×10‐3 year‐1, respectively. During the 1982‐2015 years, the NDVI of DPRK and South Korea have grown mainly with the trend of 0.2×10‐3 year‐1 and 1.1×10‐3 year‐1, respectively. According to the analysis of NDVI and climatic factors, the distribution of NDVI in the three‐time series of Korean Peninsula is consistent in spatial distribution. According to the results of partial correlation analysis of climate factor and NDVI distribution in Korean Peninsula, the region has significant partial correlation with temperature change. The climate factor of temperature is the main driver of NDVI change, which plays a key role in controlling NDVI change accumulation.

Accuracy Analysis for 3D Model Measurement Based on Digital Close-range Photogrammetry Technique for the Deep Foundation Pit Deformation Monitoring

Lei-lei Guan,Yong-gui Chen,Rao-ping Liao 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

The deformation of deep foundation pits (DFP) may pose a huge potential threat to the safety of the bracing system and the surrounding environment. A large amount of deformation data facilitates the deformation prediction of DFP and the dynamic adjustment of the bracing scheme. This study proposes and validates a 3D modeling technique based on digital close-range photogrammetry, which can obtain sufficient deformation data and enhance the understanding of deformation patterns. Two typical sets of deformation experiments, namely the vertical deformation test and the horizontal deformation test, were conducted to examine the viability and accuracy of 3D model measurement. Furthermore, the factors affecting the accuracy of the measurement were discussed in detail. The results indicate that the measurement accuracy of 3D models can reach millimeter-level or even sub-millimeter level. The measurement accuracy is affected by the coupling of the pixel resolution of CCD, focal length, photographic distance, and photographic baseline. The increase in the pixel resolution of CCD and focal length improve the measurement accuracy of 3D model measurement, but increasing photographic distance shows the opposite trend. The ratio of photographic baseline to photographic distance (BDR) has a much greater effect on accuracy than other factors. The photographic distance with a resolution of less than 1.0mm and the BDR value of 0.6 − 1.8 are recommended. Based on the results, it is found that this technique can be adopted as an effective monitoring method in DFP deformation monitoring due to the high precision and labor-saving.

Novel Adaptive Distributed Compressed Sensing Algorithm for Estimating Channels in Doubly-Selective Fading OFDM Systems

( Yuming Song ),( Xueyun He ),( Guan Gui ),( Yan Liang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

Doubly-selective (DS) fading channel is often occurred in many orthogonal frequency division multiplexing (OFDM) communication systems, such as high-speed rail communication systems and underwater acoustic (UWA) wireless networks. It is challenging to provide an accurate and fast estimation over the doubly-selective channel, due to the strong Doppler shift. This paper addresses the doubly selective channel estimation problem based on complex exponential basis expansion model (CE-BEM) in OFDM systems from the perspective of distributed compressive sensing (DCS). We propose a novel DCS-based improved sparsity adaptive matching pursuit (DCS-IMSAMP) algorithm. The advantage of the proposed algorithm is that it can exploit the joint channel sparsity information using dynamic threshold, variable step size and tailoring mechanism. Simulation results show that the proposed algorithm achieves 5dB performance gain with faster operation speed, in comparison with traditional DCS-based sparsity adaptive matching pursuit (DCS-SAMP) algorithm.

Dielectric and Conductivity Properties of Poly(L-lactide) and Poly(L-lactide)/Ionic Liquid Blends

Pei Xu,Hao Guan Gui,Shan Zhong Yang,Yun Sheng Ding,Qian Hao 한국고분자학회 2014 Macromolecular Research Vol.22 No.3

Dielectric relaxation spectroscopy (DRS) was employed to study the dielectric and conductivity propertiesof poly(L-lactide) and poly(L-lactide)/ionic liquid (IL) blends. The experimental dielectric data were analyzedwithin the formalism of complex permittivity. The results were discussed in terms of AC conductivity, αN relaxationcorresponding to the longest normal mode motion, α relaxation originating from the segmental mode motion, andDC conductivity. The results revealed that the motion of the polymer chains governs the charge carrier transport. The temperature dependence of the relaxation times follows the Vogel-Tammann-Fulcher (VTF) equation. Theincorporation of IL into the matrix accelerates the segmental (α) and normal mode (αN) motions and the conductivity,and increases the charge carrier movement of IL following the longest αN motion of chains, which led to an increasein the relaxation strength of the αN relaxation.

Optimized Medium Improves Expression and Secretion of Extremely Thermostable Bacterial Xylanase, XynB, in Kluyveromyces Lactis

( Yin Tie ),( Li Li Miao ),( Fei Fei Guan ),( Gui Li Wang ),( Qing Peng ),( Bing Xue Li ),( Guo Hua Guan ),( Ying Li ) 한국미생물 · 생명공학회 2010 Journal of microbiology and biotechnology Vol.20 No.11

An extremely thermostable xylanase gene, xynB, from the hyperthermophilic bacterium Thermotoga maritima MSB8 was successful expressed in Kluyveromyces lactis. The response surface methodology (RSM) was also applied to optimize the medium components for the production of XynB secreted by the recombinant K. lactis. The secretion level (102 mg/l) and enzyme activity (49 U/ml) of XynB in the optimized medium (yeast extract, lactose, and urea; YLU) were much higher than those (56 mg/l, 16 U/ml) in the original medium (yeast extract, lactose, and peptone; YLP). The secretory efficiency of mature XynB was also improved when using the YLU medium. When the mRNA levels of 13 characterized secretion-related genes in the K. lactis cultured in YLP and YLU were detected using a semiquantitative RT-PCR method, the unfolded protein response (UPR)-related genes, including ero1, hac1, and kar2, were found to be up-regulated in the K. lactis cultured in YLU. Therefore, the nutrient ingredients, especially the nitrogen source, were shown to have a significant influence on the XynB secretory efficiency of the host K. lactis.