Thermo- and pH-Responsive CeF3 Nanocrystals/HPC–PAA Complex Nanogel and Its Drug Release Behavior

Ben Liu,Qiusheng Song,Qiancheng Zhang,Haihong Ma,Ziwen Zhang,Dapeng Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.8

In this study, a kind of novel rare-earth nanocrystals/hydroxypropylcellulose–poly (acrylic acid) (HPC–PAA) complex fluorescent nanogel, its responsive behavior to environmental temperature and pH value were reported. For preparation, with HPC being used as template, HPC–PAA nanogel was first synthesized by polymerization and crosslinking reaction of acrylic acid (AA) in water solution. In the process, a redox initiator, which composed of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED), was used to initiate the reaction. Then, the as-prepared nanogel reacted with Ce(NO3)3 and NH4F solution successively, and a novel CeF3 nanocrystals/HPC–PAA complex nanogel was fabricated. The microstructure of the nanogel was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric (TG) and Transmission electron microscopy (TEM). The environmental sensitivity of the nanogel was investigated by photoluminescence (PL) and UV–Visible spectrophotometer (UV–Vis). The thermo- and pH-sensitive fluorescence were studied by PL at various temperatures and pH values; besides, the behavior of drug loading and release was researched by PL with a famous antibiotic of Ibuprofen as model drug. The results show that the PL intensity of the nanogel was largely affected by environmental temperature, or content of Ibuprofen loaded in the nanogel. The as-prepared nanogel can be used as useful sensitive material to detect temperature and pH value change, and drug loading or release property of Ibuprofen can be detected by PL emission of the nanogels conveniently.

In situ observation of mesophase transformation behaviour and mechanistic analysis in β-resin

Liu Ben,Yan Xi,Tao Zechao,Li Xiangfen,Lei Shiwen,Zhang Dongqing,Yang Zonghe,Liu Zhanjun 한국탄소학회 2024 Carbon Letters Vol.34 No.1

β-Resin was extracted by solvent separation of refined coal tar pitch. Several analytical methods revealed that β-resin had a better aromatic plane packing structure and a higher number of carbon residues, making it ideal for mesophase transformation. The mesophase transformation process of β-resin (the formation of liquid-crystalline spheres, the growth of mesophase spheres, and the coalescence and disintegration of mesophase spheres) was observed in situ using a polarizing microscope with a hot stage. Moreover, the mesophase transformation mechanism of β-resin was investigated at each transformation stage. The mesophase content and mesophase transformation kinetics were analyzed based on the area method and quinoline insoluble (QI) substitution method. Both methods revealed changes in the mesophase content of β-resin. However, the test results of the two methods were slightly different at the initial stage of mesophase transformation and tended to be consistent during the later stage.

Efficient Surface Display of L-glutamate Oxidase and L-amino Acid Oxidase on Pichia pastoris Using Multi-copy Expression Strains

Rao Ben,Zhou Ronghua,Dong Qing,Liao Xianqing,Liu Fang,Chen Wei,Liu Xiaoyan,Min Yong,Wang YaPing 한국생물공학회 2020 Biotechnology and Bioprocess Engineering Vol.25 No.4

L-glutamate oxidase (GLOD) and L-amino acid oxidase (AAO) were reported to be capable of convert L-glutamic acid to α-aketoglutaric acid (α-KG). These two enzymes gene have been successfully expressed by using pHBM905BDM in Pichia pastoris to produce α-aketoglutaric acid from L-glutamic acid in our previous studies. Here these two enzymes were displayed on P. pastoris to achieve the conversion. We constructed multi-copy expression plasmids using plasmid pHBM905BDM. By using this plasmid, multi-copy strains were constructed and named as PGLOD(1-3)-AGα1 and PAAO(1-3)-AGα1, respectively. The following results showed that expression of GLOD(1-3)- AGα1 and AAO(1-3)-AGα1 in multi-copy strains increased as designed and strain PGLOD3-AGα1 and PAAO3-AGα1 was chosen for high-density fermentation and enzyme activity experiments. By using a multi-copy expression approach and high-density fermentation, we achieved a GLOD expression yield of 688.5 U/g dry cell weight and AAO expression yield of 626.7 U/g dry cell weight. By using displayed GLOD, the average production rate of L-glutamic acid to α-KG was 6.22 g/L/h and the highest α-KG titer (124.5 g/L) was converted from 135 g/L L-glutamic acid. By using displayed AAO, the average production rate of L-glutamic acid to α-KG was 5.78 g/L/h and the highest α-KG titer (115.6 g/L) was converted from 135 g/L L-glutamic acid. It showed that displaying enzymes on P. pastoris are suitable for use in industrial applications.

A review of fine structures of nanoporous materials as evidenced by microscopic methods.

Liu, Zheng,Fujita, Nobuhisa,Miyasaka, Keiichi,Han, Lu,Stevens, Sam M,Suga, Mitsuo,Asahina, Shunsuke,Slater, Ben,Xiao, Changhong,Sakamoto, Yasuhiro,Anderson, Michael W,Ryoo, Ryong,Terasaki, Osamu Oxford University Press 2013 Microscopy Vol.62 No.1

<P>This paper reviews diverse capabilities offered by modern electron microscopy techniques in studying fine structures of nanoporous crystals such as zeolites, silica mesoporous crystals, metal organic frameworks and yolk-shell materials. For the case of silica mesoporous crystals, new approaches that have been developed recently to determine the three-dimensionally periodic average structure, e.g., through self-consistent analysis of electron microscope images or through consideration of accidental extinctions, are presented. Various structural deviations in nanoporous materials from their average structures including intergrowth, surface termination, incommensurate modulation, quasicrystal and defects are demonstrated. Ibidem observations of the scanning electron microscope and atomic force microscope give information about the zeolite-crystal-growth mechanism, and an energy for unstitching a building-unit from a crystal surface is directly observed by an anatomic force microscope. It is argued how these observations lead to a deeper understanding of the materials.</P>

Exergy-based Energy Efficiency Evaluation Model for Machine Tools Considering Thermal Stability

Ben-jie Li,Huajun Cao,Bernard Hon,Lei Liu,Xi Gao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.2

Machine tools, as the extensively used basic equipment of manufacturing industry, are characterized by intensive and inefficient energy consumption. With the launch and implementation of ISO 14955-1, energy efficiency has become an important criterion for machine tool evaluation. However, most ongoing research on energy efficiency evaluation of machine tools emphasizes on workpiece material removal energy efficiency and rarely considers energy consumption needed to ensure machining accuracy and accuracy consistency, especially energy consumption for thermal stability control of machine tools. In light of this, an exergy analysis based approach is presented to assess the comprehensive energy efficiency of machine tools, including energy consumption for material removal and thermal stability control. The key performance indexes of exergy efficiency, exergy destruction, and specific exergy consumption are analyzed. The feasibility of the proposed approach was demonstrated by a case study, in which the comprehensive energy efficiency of a machine tool was found to be 21.57% instead of 14.38% of material removal energy efficiency. The proposed method is more effective to evaluate the comprehensive energy efficiency, to support designers to design high-efficient machine tool and users to operate machine tool for green and precision machining.

D₂(2317) and D₂(2457) from HQET Sum Rules

Chun Liu,Chao-Shang Huang,Shi-Lin Zhu,Yuan-Ben Dai 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2

Within the framework of the heavy quark effective theory, QCD sum rules are used to calculate the masses of p-wave cs states. The results for 0+ and 1+ states with the angular momentum of the light component jl = 1=2 are consistent with the experimental values for Ds(2317) and Ds(2457), respectively.

Expression and Characterization of a New L-amino Acid Oxidase AAO Producing α-ketoglutaric Acid from L-glutamic Acid

Rao Ben,Liao Xianqing,Liu Fang,Chen Wei,Zhou Ronghua,Ma Lixin,Wang YaPing 한국생물공학회 2019 Biotechnology and Bioprocess Engineering Vol.24 No.6

L-amino acid oxidase (AAO) was reported to be capable of converting L-glutamic acid to α-aketoglutaric acid (α-KG). The sequence of AAO from Kitasatospora cheerisanensis was synthesized based on Pichia pastoris codon-usage preferences. AAO gene was cloned into plasmid pPICZα which was transformed into P. pastoris. Next, multi-copy expression plasmids were constructed by using plasmid pHBM905BDM. High-density fermentation was performed and the recombinant enzyme was characterized. The conversion conditions were optimized. By using Escherichia coli expression system, no soluble or active AAO was obtained from two strains after fermentation and induction. We can’t obtain high-level expression of recombinant strains by using plasmid pPICZα. Therefore, we constructed multi-copy expression plasmids using plasmid pHBM905BDM. By using this plasmid, multi-copy strains were constructed and named as PAAO1, PAAO2, PAAO3, PAAO4, and PAAO5, respectively. The following results showed that expression of AAO in multicopy strains increased as designed and strain PAAO5 was chosen for high-density fermentation and enzyme activity experiments. After high-density fermentation, we achieved an AAO-expression yield of 120.8 U/mL. After temperature and pH optimization, the highest AAO activity was observed at a temperature and pH of 20°C and 6, respectively. After optimization of the conversion conditions, the average production rate of L-glutamic acid to α-KG was 3.46 g/L/h and the highest α-KG titer (103 g/L) was converted from 120 g/L L-glutamic acid. In this study, AAO was abundantly expressed by using P. pastoris expression system. The following experiments indicated that AAO is suitable for use in industrial applications.

Numerical investigation of the rotating instability uniqueness in a MWe scale supercritical carbon dioxide centrifugal compressor

Zhiyuan Liu,Peng Wang,Ben Zhao 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.11

Flow instability attracts much attention for air compressors but little for a supercritical carbon dioxide (CO2) compressor that is a critical component in the supercritical CO2 Brayton cycle. This paper presents a numerical investigation of the rotating instability in a megawatt-scale (MWe-scale) supercritical CO2 centrifugal compressor from the Institute of Engineering Thermophysics. Unsteady full annulus simulations were carried out at different operating conditions and validated by the experimental data. According to the validated method, we analyzed the blade tip leakage flow, the rotating instability, and the propagation speed of the stalled flow cell. The findings are that (1) the blockage effects of leakage flow are responsible for rotating instability, and (2) the propagation speed of rotating cells is approximately 16.67% of the rotor speed. The novelty is that the figure is lower than that in air compressors, close to that found in water pumps.

Fault-tolerant Consensus of Leader-following Multi-agent Systems Based on Distributed Fault Estimation Observer

Pu Yang,Ben Ma,Yan Dong,Jianwei Liu 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.5

This paper is concerned with the fault-tolerant consensus control problem for leader-following multiagent systems with actuator faults and external disturbance. Firstly, by employing the relative output estimation errors with respect to the corresponding neighbours and the leader, a distributed fault estimation observer is constructed for each follower and the established global estimation error system is proven to be asymptotically stable. Secondly, based on the obtained fault estimation, the active fault-tolerant consensus control protocol for each follower is proposed with the utilization of the relative output measurements rather than the state of the systems. Under this control protocol, the actuator faults can be compensated and the influence of disturbance can be eliminated as well. Moreover, it is worth noticing that the process of designing the fault estimation observer and the fault-tolerant controller is separated and their performances are considered simultaneously to simplify the design procedures. Finally, an illustrative example is presented to demonstrate the applicability and the effectiveness of the obtained results.

Effect of Aging Precipitate on Ductility Anisotropy and Low Cycle Fatigue Behavior of AA2195 Al-Li Alloy

Gui Wang,Ben Lin,Ding‑ding Lu,San‑xi Deng,Guang‑jun Zeng,Xu‑feng Cai,Jin‑feng Li,Dan‑yang Liu 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.8

The mechanical properties and low-cycle fatigue behavior of the hot-rolled AA2195 Al-Li alloy taken along the longitudinaldirection and transverse direction were investigated. The anisotropy ductility of the alloy with the short-term naturalaging (T4-SN), long-term natural aging (T4-LN), and T6 artificial aging alloy is mainly related to the grain structure andgrain boundaries, whereas the weakened anisotropy of ductility is attributed to the appearance of PFZs. The T4-SN andT4-LN specimens present the cyclic hardening phenomenon due to the interaction of dislocations with dislocations or theGuinier–Preston zone. The cyclic softening phenomenon in T6 specimens is attributed to that the dislocations cut throughthe T1precipitates, and some dislocations bypass the non-shearable precipitates, which activates more potential slip systemsto shear the T1precipitates.